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1/*
2 * linux/ipc/sem.c
3 * Copyright (C) 1992 Krishna Balasubramanian
4 * Copyright (C) 1995 Eric Schenk, Bruno Haible
5 *
6 * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
7 *
8 * SMP-threaded, sysctl's added
9 * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
10 * Enforced range limit on SEM_UNDO
11 * (c) 2001 Red Hat Inc
12 * Lockless wakeup
13 * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
14 * Further wakeup optimizations, documentation
15 * (c) 2010 Manfred Spraul <manfred@colorfullife.com>
16 *
17 * support for audit of ipc object properties and permission changes
18 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
19 *
20 * namespaces support
21 * OpenVZ, SWsoft Inc.
22 * Pavel Emelianov <xemul@openvz.org>
23 *
24 * Implementation notes: (May 2010)
25 * This file implements System V semaphores.
26 *
27 * User space visible behavior:
28 * - FIFO ordering for semop() operations (just FIFO, not starvation
29 * protection)
30 * - multiple semaphore operations that alter the same semaphore in
31 * one semop() are handled.
32 * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and
33 * SETALL calls.
34 * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO.
35 * - undo adjustments at process exit are limited to 0..SEMVMX.
36 * - namespace are supported.
37 * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtine by writing
38 * to /proc/sys/kernel/sem.
39 * - statistics about the usage are reported in /proc/sysvipc/sem.
40 *
41 * Internals:
42 * - scalability:
43 * - all global variables are read-mostly.
44 * - semop() calls and semctl(RMID) are synchronized by RCU.
45 * - most operations do write operations (actually: spin_lock calls) to
46 * the per-semaphore array structure.
47 * Thus: Perfect SMP scaling between independent semaphore arrays.
48 * If multiple semaphores in one array are used, then cache line
49 * trashing on the semaphore array spinlock will limit the scaling.
50 * - semncnt and semzcnt are calculated on demand in count_semncnt() and
51 * count_semzcnt()
52 * - the task that performs a successful semop() scans the list of all
53 * sleeping tasks and completes any pending operations that can be fulfilled.
54 * Semaphores are actively given to waiting tasks (necessary for FIFO).
55 * (see update_queue())
56 * - To improve the scalability, the actual wake-up calls are performed after
57 * dropping all locks. (see wake_up_sem_queue_prepare(),
58 * wake_up_sem_queue_do())
59 * - All work is done by the waker, the woken up task does not have to do
60 * anything - not even acquiring a lock or dropping a refcount.
61 * - A woken up task may not even touch the semaphore array anymore, it may
62 * have been destroyed already by a semctl(RMID).
63 * - The synchronizations between wake-ups due to a timeout/signal and a
64 * wake-up due to a completed semaphore operation is achieved by using an
65 * intermediate state (IN_WAKEUP).
66 * - UNDO values are stored in an array (one per process and per
67 * semaphore array, lazily allocated). For backwards compatibility, multiple
68 * modes for the UNDO variables are supported (per process, per thread)
69 * (see copy_semundo, CLONE_SYSVSEM)
70 * - There are two lists of the pending operations: a per-array list
71 * and per-semaphore list (stored in the array). This allows to achieve FIFO
72 * ordering without always scanning all pending operations.
73 * The worst-case behavior is nevertheless O(N^2) for N wakeups.
74 */
75
76#include <linux/slab.h>
77#include <linux/spinlock.h>
78#include <linux/init.h>
79#include <linux/proc_fs.h>
80#include <linux/time.h>
81#include <linux/security.h>
82#include <linux/syscalls.h>
83#include <linux/audit.h>
84#include <linux/capability.h>
85#include <linux/seq_file.h>
86#include <linux/rwsem.h>
87#include <linux/nsproxy.h>
88#include <linux/ipc_namespace.h>
89
90#include <asm/uaccess.h>
91#include "util.h"
92
93/* One semaphore structure for each semaphore in the system. */
94struct sem {
95 int semval; /* current value */
96 int sempid; /* pid of last operation */
97 struct list_head sem_pending; /* pending single-sop operations */
98};
99
100/* One queue for each sleeping process in the system. */
101struct sem_queue {
102 struct list_head simple_list; /* queue of pending operations */
103 struct list_head list; /* queue of pending operations */
104 struct task_struct *sleeper; /* this process */
105 struct sem_undo *undo; /* undo structure */
106 int pid; /* process id of requesting process */
107 int status; /* completion status of operation */
108 struct sembuf *sops; /* array of pending operations */
109 int nsops; /* number of operations */
110 int alter; /* does *sops alter the array? */
111};
112
113/* Each task has a list of undo requests. They are executed automatically
114 * when the process exits.
115 */
116struct sem_undo {
117 struct list_head list_proc; /* per-process list: *
118 * all undos from one process
119 * rcu protected */
120 struct rcu_head rcu; /* rcu struct for sem_undo */
121 struct sem_undo_list *ulp; /* back ptr to sem_undo_list */
122 struct list_head list_id; /* per semaphore array list:
123 * all undos for one array */
124 int semid; /* semaphore set identifier */
125 short *semadj; /* array of adjustments */
126 /* one per semaphore */
127};
128
129/* sem_undo_list controls shared access to the list of sem_undo structures
130 * that may be shared among all a CLONE_SYSVSEM task group.
131 */
132struct sem_undo_list {
133 atomic_t refcnt;
134 spinlock_t lock;
135 struct list_head list_proc;
136};
137
138
139#define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS])
140
141#define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm)
142#define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid)
143
144static int newary(struct ipc_namespace *, struct ipc_params *);
145static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
146#ifdef CONFIG_PROC_FS
147static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
148#endif
149
150#define SEMMSL_FAST 256 /* 512 bytes on stack */
151#define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
152
153/*
154 * linked list protection:
155 * sem_undo.id_next,
156 * sem_array.sem_pending{,last},
157 * sem_array.sem_undo: sem_lock() for read/write
158 * sem_undo.proc_next: only "current" is allowed to read/write that field.
159 *
160 */
161
162#define sc_semmsl sem_ctls[0]
163#define sc_semmns sem_ctls[1]
164#define sc_semopm sem_ctls[2]
165#define sc_semmni sem_ctls[3]
166
167void sem_init_ns(struct ipc_namespace *ns)
168{
169 ns->sc_semmsl = SEMMSL;
170 ns->sc_semmns = SEMMNS;
171 ns->sc_semopm = SEMOPM;
172 ns->sc_semmni = SEMMNI;
173 ns->used_sems = 0;
174 ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
175}
176
177#ifdef CONFIG_IPC_NS
178void sem_exit_ns(struct ipc_namespace *ns)
179{
180 free_ipcs(ns, &sem_ids(ns), freeary);
181 idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
182}
183#endif
184
185void __init sem_init (void)
186{
187 sem_init_ns(&init_ipc_ns);
188 ipc_init_proc_interface("sysvipc/sem",
189 " key semid perms nsems uid gid cuid cgid otime ctime\n",
190 IPC_SEM_IDS, sysvipc_sem_proc_show);
191}
192
193/*
194 * sem_lock_(check_) routines are called in the paths where the rw_mutex
195 * is not held.
196 */
197static inline struct sem_array *sem_lock(struct ipc_namespace *ns, int id)
198{
199 struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id);
200
201 if (IS_ERR(ipcp))
202 return (struct sem_array *)ipcp;
203
204 return container_of(ipcp, struct sem_array, sem_perm);
205}
206
207static inline struct sem_array *sem_lock_check(struct ipc_namespace *ns,
208 int id)
209{
210 struct kern_ipc_perm *ipcp = ipc_lock_check(&sem_ids(ns), id);
211
212 if (IS_ERR(ipcp))
213 return (struct sem_array *)ipcp;
214
215 return container_of(ipcp, struct sem_array, sem_perm);
216}
217
218static inline void sem_lock_and_putref(struct sem_array *sma)
219{
220 ipc_lock_by_ptr(&sma->sem_perm);
221 ipc_rcu_putref(sma);
222}
223
224static inline void sem_getref_and_unlock(struct sem_array *sma)
225{
226 ipc_rcu_getref(sma);
227 ipc_unlock(&(sma)->sem_perm);
228}
229
230static inline void sem_putref(struct sem_array *sma)
231{
232 ipc_lock_by_ptr(&sma->sem_perm);
233 ipc_rcu_putref(sma);
234 ipc_unlock(&(sma)->sem_perm);
235}
236
237static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
238{
239 ipc_rmid(&sem_ids(ns), &s->sem_perm);
240}
241
242/*
243 * Lockless wakeup algorithm:
244 * Without the check/retry algorithm a lockless wakeup is possible:
245 * - queue.status is initialized to -EINTR before blocking.
246 * - wakeup is performed by
247 * * unlinking the queue entry from sma->sem_pending
248 * * setting queue.status to IN_WAKEUP
249 * This is the notification for the blocked thread that a
250 * result value is imminent.
251 * * call wake_up_process
252 * * set queue.status to the final value.
253 * - the previously blocked thread checks queue.status:
254 * * if it's IN_WAKEUP, then it must wait until the value changes
255 * * if it's not -EINTR, then the operation was completed by
256 * update_queue. semtimedop can return queue.status without
257 * performing any operation on the sem array.
258 * * otherwise it must acquire the spinlock and check what's up.
259 *
260 * The two-stage algorithm is necessary to protect against the following
261 * races:
262 * - if queue.status is set after wake_up_process, then the woken up idle
263 * thread could race forward and try (and fail) to acquire sma->lock
264 * before update_queue had a chance to set queue.status
265 * - if queue.status is written before wake_up_process and if the
266 * blocked process is woken up by a signal between writing
267 * queue.status and the wake_up_process, then the woken up
268 * process could return from semtimedop and die by calling
269 * sys_exit before wake_up_process is called. Then wake_up_process
270 * will oops, because the task structure is already invalid.
271 * (yes, this happened on s390 with sysv msg).
272 *
273 */
274#define IN_WAKEUP 1
275
276/**
277 * newary - Create a new semaphore set
278 * @ns: namespace
279 * @params: ptr to the structure that contains key, semflg and nsems
280 *
281 * Called with sem_ids.rw_mutex held (as a writer)
282 */
283
284static int newary(struct ipc_namespace *ns, struct ipc_params *params)
285{
286 int id;
287 int retval;
288 struct sem_array *sma;
289 int size;
290 key_t key = params->key;
291 int nsems = params->u.nsems;
292 int semflg = params->flg;
293 int i;
294
295 if (!nsems)
296 return -EINVAL;
297 if (ns->used_sems + nsems > ns->sc_semmns)
298 return -ENOSPC;
299
300 size = sizeof (*sma) + nsems * sizeof (struct sem);
301 sma = ipc_rcu_alloc(size);
302 if (!sma) {
303 return -ENOMEM;
304 }
305 memset (sma, 0, size);
306
307 sma->sem_perm.mode = (semflg & S_IRWXUGO);
308 sma->sem_perm.key = key;
309
310 sma->sem_perm.security = NULL;
311 retval = security_sem_alloc(sma);
312 if (retval) {
313 ipc_rcu_putref(sma);
314 return retval;
315 }
316
317 id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
318 if (id < 0) {
319 security_sem_free(sma);
320 ipc_rcu_putref(sma);
321 return id;
322 }
323 ns->used_sems += nsems;
324
325 sma->sem_base = (struct sem *) &sma[1];
326
327 for (i = 0; i < nsems; i++)
328 INIT_LIST_HEAD(&sma->sem_base[i].sem_pending);
329
330 sma->complex_count = 0;
331 INIT_LIST_HEAD(&sma->sem_pending);
332 INIT_LIST_HEAD(&sma->list_id);
333 sma->sem_nsems = nsems;
334 sma->sem_ctime = get_seconds();
335 sem_unlock(sma);
336
337 return sma->sem_perm.id;
338}
339
340
341/*
342 * Called with sem_ids.rw_mutex and ipcp locked.
343 */
344static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
345{
346 struct sem_array *sma;
347
348 sma = container_of(ipcp, struct sem_array, sem_perm);
349 return security_sem_associate(sma, semflg);
350}
351
352/*
353 * Called with sem_ids.rw_mutex and ipcp locked.
354 */
355static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
356 struct ipc_params *params)
357{
358 struct sem_array *sma;
359
360 sma = container_of(ipcp, struct sem_array, sem_perm);
361 if (params->u.nsems > sma->sem_nsems)
362 return -EINVAL;
363
364 return 0;
365}
366
367SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
368{
369 struct ipc_namespace *ns;
370 struct ipc_ops sem_ops;
371 struct ipc_params sem_params;
372
373 ns = current->nsproxy->ipc_ns;
374
375 if (nsems < 0 || nsems > ns->sc_semmsl)
376 return -EINVAL;
377
378 sem_ops.getnew = newary;
379 sem_ops.associate = sem_security;
380 sem_ops.more_checks = sem_more_checks;
381
382 sem_params.key = key;
383 sem_params.flg = semflg;
384 sem_params.u.nsems = nsems;
385
386 return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
387}
388
389/*
390 * Determine whether a sequence of semaphore operations would succeed
391 * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
392 */
393
394static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
395 int nsops, struct sem_undo *un, int pid)
396{
397 int result, sem_op;
398 struct sembuf *sop;
399 struct sem * curr;
400
401 for (sop = sops; sop < sops + nsops; sop++) {
402 curr = sma->sem_base + sop->sem_num;
403 sem_op = sop->sem_op;
404 result = curr->semval;
405
406 if (!sem_op && result)
407 goto would_block;
408
409 result += sem_op;
410 if (result < 0)
411 goto would_block;
412 if (result > SEMVMX)
413 goto out_of_range;
414 if (sop->sem_flg & SEM_UNDO) {
415 int undo = un->semadj[sop->sem_num] - sem_op;
416 /*
417 * Exceeding the undo range is an error.
418 */
419 if (undo < (-SEMAEM - 1) || undo > SEMAEM)
420 goto out_of_range;
421 }
422 curr->semval = result;
423 }
424
425 sop--;
426 while (sop >= sops) {
427 sma->sem_base[sop->sem_num].sempid = pid;
428 if (sop->sem_flg & SEM_UNDO)
429 un->semadj[sop->sem_num] -= sop->sem_op;
430 sop--;
431 }
432
433 return 0;
434
435out_of_range:
436 result = -ERANGE;
437 goto undo;
438
439would_block:
440 if (sop->sem_flg & IPC_NOWAIT)
441 result = -EAGAIN;
442 else
443 result = 1;
444
445undo:
446 sop--;
447 while (sop >= sops) {
448 sma->sem_base[sop->sem_num].semval -= sop->sem_op;
449 sop--;
450 }
451
452 return result;
453}
454
455/** wake_up_sem_queue_prepare(q, error): Prepare wake-up
456 * @q: queue entry that must be signaled
457 * @error: Error value for the signal
458 *
459 * Prepare the wake-up of the queue entry q.
460 */
461static void wake_up_sem_queue_prepare(struct list_head *pt,
462 struct sem_queue *q, int error)
463{
464 if (list_empty(pt)) {
465 /*
466 * Hold preempt off so that we don't get preempted and have the
467 * wakee busy-wait until we're scheduled back on.
468 */
469 preempt_disable();
470 }
471 q->status = IN_WAKEUP;
472 q->pid = error;
473
474 list_add_tail(&q->simple_list, pt);
475}
476
477/**
478 * wake_up_sem_queue_do(pt) - do the actual wake-up
479 * @pt: list of tasks to be woken up
480 *
481 * Do the actual wake-up.
482 * The function is called without any locks held, thus the semaphore array
483 * could be destroyed already and the tasks can disappear as soon as the
484 * status is set to the actual return code.
485 */
486static void wake_up_sem_queue_do(struct list_head *pt)
487{
488 struct sem_queue *q, *t;
489 int did_something;
490
491 did_something = !list_empty(pt);
492 list_for_each_entry_safe(q, t, pt, simple_list) {
493 wake_up_process(q->sleeper);
494 /* q can disappear immediately after writing q->status. */
495 smp_wmb();
496 q->status = q->pid;
497 }
498 if (did_something)
499 preempt_enable();
500}
501
502static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
503{
504 list_del(&q->list);
505 if (q->nsops == 1)
506 list_del(&q->simple_list);
507 else
508 sma->complex_count--;
509}
510
511/** check_restart(sma, q)
512 * @sma: semaphore array
513 * @q: the operation that just completed
514 *
515 * update_queue is O(N^2) when it restarts scanning the whole queue of
516 * waiting operations. Therefore this function checks if the restart is
517 * really necessary. It is called after a previously waiting operation
518 * was completed.
519 */
520static int check_restart(struct sem_array *sma, struct sem_queue *q)
521{
522 struct sem *curr;
523 struct sem_queue *h;
524
525 /* if the operation didn't modify the array, then no restart */
526 if (q->alter == 0)
527 return 0;
528
529 /* pending complex operations are too difficult to analyse */
530 if (sma->complex_count)
531 return 1;
532
533 /* we were a sleeping complex operation. Too difficult */
534 if (q->nsops > 1)
535 return 1;
536
537 curr = sma->sem_base + q->sops[0].sem_num;
538
539 /* No-one waits on this queue */
540 if (list_empty(&curr->sem_pending))
541 return 0;
542
543 /* the new semaphore value */
544 if (curr->semval) {
545 /* It is impossible that someone waits for the new value:
546 * - q is a previously sleeping simple operation that
547 * altered the array. It must be a decrement, because
548 * simple increments never sleep.
549 * - The value is not 0, thus wait-for-zero won't proceed.
550 * - If there are older (higher priority) decrements
551 * in the queue, then they have observed the original
552 * semval value and couldn't proceed. The operation
553 * decremented to value - thus they won't proceed either.
554 */
555 BUG_ON(q->sops[0].sem_op >= 0);
556 return 0;
557 }
558 /*
559 * semval is 0. Check if there are wait-for-zero semops.
560 * They must be the first entries in the per-semaphore simple queue
561 */
562 h = list_first_entry(&curr->sem_pending, struct sem_queue, simple_list);
563 BUG_ON(h->nsops != 1);
564 BUG_ON(h->sops[0].sem_num != q->sops[0].sem_num);
565
566 /* Yes, there is a wait-for-zero semop. Restart */
567 if (h->sops[0].sem_op == 0)
568 return 1;
569
570 /* Again - no-one is waiting for the new value. */
571 return 0;
572}
573
574
575/**
576 * update_queue(sma, semnum): Look for tasks that can be completed.
577 * @sma: semaphore array.
578 * @semnum: semaphore that was modified.
579 * @pt: list head for the tasks that must be woken up.
580 *
581 * update_queue must be called after a semaphore in a semaphore array
582 * was modified. If multiple semaphore were modified, then @semnum
583 * must be set to -1.
584 * The tasks that must be woken up are added to @pt. The return code
585 * is stored in q->pid.
586 * The function return 1 if at least one semop was completed successfully.
587 */
588static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
589{
590 struct sem_queue *q;
591 struct list_head *walk;
592 struct list_head *pending_list;
593 int offset;
594 int semop_completed = 0;
595
596 /* if there are complex operations around, then knowing the semaphore
597 * that was modified doesn't help us. Assume that multiple semaphores
598 * were modified.
599 */
600 if (sma->complex_count)
601 semnum = -1;
602
603 if (semnum == -1) {
604 pending_list = &sma->sem_pending;
605 offset = offsetof(struct sem_queue, list);
606 } else {
607 pending_list = &sma->sem_base[semnum].sem_pending;
608 offset = offsetof(struct sem_queue, simple_list);
609 }
610
611again:
612 walk = pending_list->next;
613 while (walk != pending_list) {
614 int error, restart;
615
616 q = (struct sem_queue *)((char *)walk - offset);
617 walk = walk->next;
618
619 /* If we are scanning the single sop, per-semaphore list of
620 * one semaphore and that semaphore is 0, then it is not
621 * necessary to scan the "alter" entries: simple increments
622 * that affect only one entry succeed immediately and cannot
623 * be in the per semaphore pending queue, and decrements
624 * cannot be successful if the value is already 0.
625 */
626 if (semnum != -1 && sma->sem_base[semnum].semval == 0 &&
627 q->alter)
628 break;
629
630 error = try_atomic_semop(sma, q->sops, q->nsops,
631 q->undo, q->pid);
632
633 /* Does q->sleeper still need to sleep? */
634 if (error > 0)
635 continue;
636
637 unlink_queue(sma, q);
638
639 if (error) {
640 restart = 0;
641 } else {
642 semop_completed = 1;
643 restart = check_restart(sma, q);
644 }
645
646 wake_up_sem_queue_prepare(pt, q, error);
647 if (restart)
648 goto again;
649 }
650 return semop_completed;
651}
652
653/**
654 * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
655 * @sma: semaphore array
656 * @sops: operations that were performed
657 * @nsops: number of operations
658 * @otime: force setting otime
659 * @pt: list head of the tasks that must be woken up.
660 *
661 * do_smart_update() does the required called to update_queue, based on the
662 * actual changes that were performed on the semaphore array.
663 * Note that the function does not do the actual wake-up: the caller is
664 * responsible for calling wake_up_sem_queue_do(@pt).
665 * It is safe to perform this call after dropping all locks.
666 */
667static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
668 int otime, struct list_head *pt)
669{
670 int i;
671
672 if (sma->complex_count || sops == NULL) {
673 if (update_queue(sma, -1, pt))
674 otime = 1;
675 goto done;
676 }
677
678 for (i = 0; i < nsops; i++) {
679 if (sops[i].sem_op > 0 ||
680 (sops[i].sem_op < 0 &&
681 sma->sem_base[sops[i].sem_num].semval == 0))
682 if (update_queue(sma, sops[i].sem_num, pt))
683 otime = 1;
684 }
685done:
686 if (otime)
687 sma->sem_otime = get_seconds();
688}
689
690
691/* The following counts are associated to each semaphore:
692 * semncnt number of tasks waiting on semval being nonzero
693 * semzcnt number of tasks waiting on semval being zero
694 * This model assumes that a task waits on exactly one semaphore.
695 * Since semaphore operations are to be performed atomically, tasks actually
696 * wait on a whole sequence of semaphores simultaneously.
697 * The counts we return here are a rough approximation, but still
698 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
699 */
700static int count_semncnt (struct sem_array * sma, ushort semnum)
701{
702 int semncnt;
703 struct sem_queue * q;
704
705 semncnt = 0;
706 list_for_each_entry(q, &sma->sem_pending, list) {
707 struct sembuf * sops = q->sops;
708 int nsops = q->nsops;
709 int i;
710 for (i = 0; i < nsops; i++)
711 if (sops[i].sem_num == semnum
712 && (sops[i].sem_op < 0)
713 && !(sops[i].sem_flg & IPC_NOWAIT))
714 semncnt++;
715 }
716 return semncnt;
717}
718
719static int count_semzcnt (struct sem_array * sma, ushort semnum)
720{
721 int semzcnt;
722 struct sem_queue * q;
723
724 semzcnt = 0;
725 list_for_each_entry(q, &sma->sem_pending, list) {
726 struct sembuf * sops = q->sops;
727 int nsops = q->nsops;
728 int i;
729 for (i = 0; i < nsops; i++)
730 if (sops[i].sem_num == semnum
731 && (sops[i].sem_op == 0)
732 && !(sops[i].sem_flg & IPC_NOWAIT))
733 semzcnt++;
734 }
735 return semzcnt;
736}
737
738/* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
739 * as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
740 * remains locked on exit.
741 */
742static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
743{
744 struct sem_undo *un, *tu;
745 struct sem_queue *q, *tq;
746 struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
747 struct list_head tasks;
748
749 /* Free the existing undo structures for this semaphore set. */
750 assert_spin_locked(&sma->sem_perm.lock);
751 list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
752 list_del(&un->list_id);
753 spin_lock(&un->ulp->lock);
754 un->semid = -1;
755 list_del_rcu(&un->list_proc);
756 spin_unlock(&un->ulp->lock);
757 kfree_rcu(un, rcu);
758 }
759
760 /* Wake up all pending processes and let them fail with EIDRM. */
761 INIT_LIST_HEAD(&tasks);
762 list_for_each_entry_safe(q, tq, &sma->sem_pending, list) {
763 unlink_queue(sma, q);
764 wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
765 }
766
767 /* Remove the semaphore set from the IDR */
768 sem_rmid(ns, sma);
769 sem_unlock(sma);
770
771 wake_up_sem_queue_do(&tasks);
772 ns->used_sems -= sma->sem_nsems;
773 security_sem_free(sma);
774 ipc_rcu_putref(sma);
775}
776
777static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
778{
779 switch(version) {
780 case IPC_64:
781 return copy_to_user(buf, in, sizeof(*in));
782 case IPC_OLD:
783 {
784 struct semid_ds out;
785
786 memset(&out, 0, sizeof(out));
787
788 ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
789
790 out.sem_otime = in->sem_otime;
791 out.sem_ctime = in->sem_ctime;
792 out.sem_nsems = in->sem_nsems;
793
794 return copy_to_user(buf, &out, sizeof(out));
795 }
796 default:
797 return -EINVAL;
798 }
799}
800
801static int semctl_nolock(struct ipc_namespace *ns, int semid,
802 int cmd, int version, union semun arg)
803{
804 int err;
805 struct sem_array *sma;
806
807 switch(cmd) {
808 case IPC_INFO:
809 case SEM_INFO:
810 {
811 struct seminfo seminfo;
812 int max_id;
813
814 err = security_sem_semctl(NULL, cmd);
815 if (err)
816 return err;
817
818 memset(&seminfo,0,sizeof(seminfo));
819 seminfo.semmni = ns->sc_semmni;
820 seminfo.semmns = ns->sc_semmns;
821 seminfo.semmsl = ns->sc_semmsl;
822 seminfo.semopm = ns->sc_semopm;
823 seminfo.semvmx = SEMVMX;
824 seminfo.semmnu = SEMMNU;
825 seminfo.semmap = SEMMAP;
826 seminfo.semume = SEMUME;
827 down_read(&sem_ids(ns).rw_mutex);
828 if (cmd == SEM_INFO) {
829 seminfo.semusz = sem_ids(ns).in_use;
830 seminfo.semaem = ns->used_sems;
831 } else {
832 seminfo.semusz = SEMUSZ;
833 seminfo.semaem = SEMAEM;
834 }
835 max_id = ipc_get_maxid(&sem_ids(ns));
836 up_read(&sem_ids(ns).rw_mutex);
837 if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo)))
838 return -EFAULT;
839 return (max_id < 0) ? 0: max_id;
840 }
841 case IPC_STAT:
842 case SEM_STAT:
843 {
844 struct semid64_ds tbuf;
845 int id;
846
847 if (cmd == SEM_STAT) {
848 sma = sem_lock(ns, semid);
849 if (IS_ERR(sma))
850 return PTR_ERR(sma);
851 id = sma->sem_perm.id;
852 } else {
853 sma = sem_lock_check(ns, semid);
854 if (IS_ERR(sma))
855 return PTR_ERR(sma);
856 id = 0;
857 }
858
859 err = -EACCES;
860 if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
861 goto out_unlock;
862
863 err = security_sem_semctl(sma, cmd);
864 if (err)
865 goto out_unlock;
866
867 memset(&tbuf, 0, sizeof(tbuf));
868
869 kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
870 tbuf.sem_otime = sma->sem_otime;
871 tbuf.sem_ctime = sma->sem_ctime;
872 tbuf.sem_nsems = sma->sem_nsems;
873 sem_unlock(sma);
874 if (copy_semid_to_user (arg.buf, &tbuf, version))
875 return -EFAULT;
876 return id;
877 }
878 default:
879 return -EINVAL;
880 }
881out_unlock:
882 sem_unlock(sma);
883 return err;
884}
885
886static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
887 int cmd, int version, union semun arg)
888{
889 struct sem_array *sma;
890 struct sem* curr;
891 int err;
892 ushort fast_sem_io[SEMMSL_FAST];
893 ushort* sem_io = fast_sem_io;
894 int nsems;
895 struct list_head tasks;
896
897 sma = sem_lock_check(ns, semid);
898 if (IS_ERR(sma))
899 return PTR_ERR(sma);
900
901 INIT_LIST_HEAD(&tasks);
902 nsems = sma->sem_nsems;
903
904 err = -EACCES;
905 if (ipcperms(ns, &sma->sem_perm,
906 (cmd == SETVAL || cmd == SETALL) ? S_IWUGO : S_IRUGO))
907 goto out_unlock;
908
909 err = security_sem_semctl(sma, cmd);
910 if (err)
911 goto out_unlock;
912
913 err = -EACCES;
914 switch (cmd) {
915 case GETALL:
916 {
917 ushort __user *array = arg.array;
918 int i;
919
920 if(nsems > SEMMSL_FAST) {
921 sem_getref_and_unlock(sma);
922
923 sem_io = ipc_alloc(sizeof(ushort)*nsems);
924 if(sem_io == NULL) {
925 sem_putref(sma);
926 return -ENOMEM;
927 }
928
929 sem_lock_and_putref(sma);
930 if (sma->sem_perm.deleted) {
931 sem_unlock(sma);
932 err = -EIDRM;
933 goto out_free;
934 }
935 }
936
937 for (i = 0; i < sma->sem_nsems; i++)
938 sem_io[i] = sma->sem_base[i].semval;
939 sem_unlock(sma);
940 err = 0;
941 if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
942 err = -EFAULT;
943 goto out_free;
944 }
945 case SETALL:
946 {
947 int i;
948 struct sem_undo *un;
949
950 sem_getref_and_unlock(sma);
951
952 if(nsems > SEMMSL_FAST) {
953 sem_io = ipc_alloc(sizeof(ushort)*nsems);
954 if(sem_io == NULL) {
955 sem_putref(sma);
956 return -ENOMEM;
957 }
958 }
959
960 if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {
961 sem_putref(sma);
962 err = -EFAULT;
963 goto out_free;
964 }
965
966 for (i = 0; i < nsems; i++) {
967 if (sem_io[i] > SEMVMX) {
968 sem_putref(sma);
969 err = -ERANGE;
970 goto out_free;
971 }
972 }
973 sem_lock_and_putref(sma);
974 if (sma->sem_perm.deleted) {
975 sem_unlock(sma);
976 err = -EIDRM;
977 goto out_free;
978 }
979
980 for (i = 0; i < nsems; i++)
981 sma->sem_base[i].semval = sem_io[i];
982
983 assert_spin_locked(&sma->sem_perm.lock);
984 list_for_each_entry(un, &sma->list_id, list_id) {
985 for (i = 0; i < nsems; i++)
986 un->semadj[i] = 0;
987 }
988 sma->sem_ctime = get_seconds();
989 /* maybe some queued-up processes were waiting for this */
990 do_smart_update(sma, NULL, 0, 0, &tasks);
991 err = 0;
992 goto out_unlock;
993 }
994 /* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
995 }
996 err = -EINVAL;
997 if(semnum < 0 || semnum >= nsems)
998 goto out_unlock;
999
1000 curr = &sma->sem_base[semnum];
1001
1002 switch (cmd) {
1003 case GETVAL:
1004 err = curr->semval;
1005 goto out_unlock;
1006 case GETPID:
1007 err = curr->sempid;
1008 goto out_unlock;
1009 case GETNCNT:
1010 err = count_semncnt(sma,semnum);
1011 goto out_unlock;
1012 case GETZCNT:
1013 err = count_semzcnt(sma,semnum);
1014 goto out_unlock;
1015 case SETVAL:
1016 {
1017 int val = arg.val;
1018 struct sem_undo *un;
1019
1020 err = -ERANGE;
1021 if (val > SEMVMX || val < 0)
1022 goto out_unlock;
1023
1024 assert_spin_locked(&sma->sem_perm.lock);
1025 list_for_each_entry(un, &sma->list_id, list_id)
1026 un->semadj[semnum] = 0;
1027
1028 curr->semval = val;
1029 curr->sempid = task_tgid_vnr(current);
1030 sma->sem_ctime = get_seconds();
1031 /* maybe some queued-up processes were waiting for this */
1032 do_smart_update(sma, NULL, 0, 0, &tasks);
1033 err = 0;
1034 goto out_unlock;
1035 }
1036 }
1037out_unlock:
1038 sem_unlock(sma);
1039 wake_up_sem_queue_do(&tasks);
1040
1041out_free:
1042 if(sem_io != fast_sem_io)
1043 ipc_free(sem_io, sizeof(ushort)*nsems);
1044 return err;
1045}
1046
1047static inline unsigned long
1048copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1049{
1050 switch(version) {
1051 case IPC_64:
1052 if (copy_from_user(out, buf, sizeof(*out)))
1053 return -EFAULT;
1054 return 0;
1055 case IPC_OLD:
1056 {
1057 struct semid_ds tbuf_old;
1058
1059 if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1060 return -EFAULT;
1061
1062 out->sem_perm.uid = tbuf_old.sem_perm.uid;
1063 out->sem_perm.gid = tbuf_old.sem_perm.gid;
1064 out->sem_perm.mode = tbuf_old.sem_perm.mode;
1065
1066 return 0;
1067 }
1068 default:
1069 return -EINVAL;
1070 }
1071}
1072
1073/*
1074 * This function handles some semctl commands which require the rw_mutex
1075 * to be held in write mode.
1076 * NOTE: no locks must be held, the rw_mutex is taken inside this function.
1077 */
1078static int semctl_down(struct ipc_namespace *ns, int semid,
1079 int cmd, int version, union semun arg)
1080{
1081 struct sem_array *sma;
1082 int err;
1083 struct semid64_ds semid64;
1084 struct kern_ipc_perm *ipcp;
1085
1086 if(cmd == IPC_SET) {
1087 if (copy_semid_from_user(&semid64, arg.buf, version))
1088 return -EFAULT;
1089 }
1090
1091 ipcp = ipcctl_pre_down(ns, &sem_ids(ns), semid, cmd,
1092 &semid64.sem_perm, 0);
1093 if (IS_ERR(ipcp))
1094 return PTR_ERR(ipcp);
1095
1096 sma = container_of(ipcp, struct sem_array, sem_perm);
1097
1098 err = security_sem_semctl(sma, cmd);
1099 if (err)
1100 goto out_unlock;
1101
1102 switch(cmd){
1103 case IPC_RMID:
1104 freeary(ns, ipcp);
1105 goto out_up;
1106 case IPC_SET:
1107 ipc_update_perm(&semid64.sem_perm, ipcp);
1108 sma->sem_ctime = get_seconds();
1109 break;
1110 default:
1111 err = -EINVAL;
1112 }
1113
1114out_unlock:
1115 sem_unlock(sma);
1116out_up:
1117 up_write(&sem_ids(ns).rw_mutex);
1118 return err;
1119}
1120
1121SYSCALL_DEFINE(semctl)(int semid, int semnum, int cmd, union semun arg)
1122{
1123 int err = -EINVAL;
1124 int version;
1125 struct ipc_namespace *ns;
1126
1127 if (semid < 0)
1128 return -EINVAL;
1129
1130 version = ipc_parse_version(&cmd);
1131 ns = current->nsproxy->ipc_ns;
1132
1133 switch(cmd) {
1134 case IPC_INFO:
1135 case SEM_INFO:
1136 case IPC_STAT:
1137 case SEM_STAT:
1138 err = semctl_nolock(ns, semid, cmd, version, arg);
1139 return err;
1140 case GETALL:
1141 case GETVAL:
1142 case GETPID:
1143 case GETNCNT:
1144 case GETZCNT:
1145 case SETVAL:
1146 case SETALL:
1147 err = semctl_main(ns,semid,semnum,cmd,version,arg);
1148 return err;
1149 case IPC_RMID:
1150 case IPC_SET:
1151 err = semctl_down(ns, semid, cmd, version, arg);
1152 return err;
1153 default:
1154 return -EINVAL;
1155 }
1156}
1157#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1158asmlinkage long SyS_semctl(int semid, int semnum, int cmd, union semun arg)
1159{
1160 return SYSC_semctl((int) semid, (int) semnum, (int) cmd, arg);
1161}
1162SYSCALL_ALIAS(sys_semctl, SyS_semctl);
1163#endif
1164
1165/* If the task doesn't already have a undo_list, then allocate one
1166 * here. We guarantee there is only one thread using this undo list,
1167 * and current is THE ONE
1168 *
1169 * If this allocation and assignment succeeds, but later
1170 * portions of this code fail, there is no need to free the sem_undo_list.
1171 * Just let it stay associated with the task, and it'll be freed later
1172 * at exit time.
1173 *
1174 * This can block, so callers must hold no locks.
1175 */
1176static inline int get_undo_list(struct sem_undo_list **undo_listp)
1177{
1178 struct sem_undo_list *undo_list;
1179
1180 undo_list = current->sysvsem.undo_list;
1181 if (!undo_list) {
1182 undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1183 if (undo_list == NULL)
1184 return -ENOMEM;
1185 spin_lock_init(&undo_list->lock);
1186 atomic_set(&undo_list->refcnt, 1);
1187 INIT_LIST_HEAD(&undo_list->list_proc);
1188
1189 current->sysvsem.undo_list = undo_list;
1190 }
1191 *undo_listp = undo_list;
1192 return 0;
1193}
1194
1195static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1196{
1197 struct sem_undo *un;
1198
1199 list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
1200 if (un->semid == semid)
1201 return un;
1202 }
1203 return NULL;
1204}
1205
1206static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1207{
1208 struct sem_undo *un;
1209
1210 assert_spin_locked(&ulp->lock);
1211
1212 un = __lookup_undo(ulp, semid);
1213 if (un) {
1214 list_del_rcu(&un->list_proc);
1215 list_add_rcu(&un->list_proc, &ulp->list_proc);
1216 }
1217 return un;
1218}
1219
1220/**
1221 * find_alloc_undo - Lookup (and if not present create) undo array
1222 * @ns: namespace
1223 * @semid: semaphore array id
1224 *
1225 * The function looks up (and if not present creates) the undo structure.
1226 * The size of the undo structure depends on the size of the semaphore
1227 * array, thus the alloc path is not that straightforward.
1228 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1229 * performs a rcu_read_lock().
1230 */
1231static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1232{
1233 struct sem_array *sma;
1234 struct sem_undo_list *ulp;
1235 struct sem_undo *un, *new;
1236 int nsems;
1237 int error;
1238
1239 error = get_undo_list(&ulp);
1240 if (error)
1241 return ERR_PTR(error);
1242
1243 rcu_read_lock();
1244 spin_lock(&ulp->lock);
1245 un = lookup_undo(ulp, semid);
1246 spin_unlock(&ulp->lock);
1247 if (likely(un!=NULL))
1248 goto out;
1249 rcu_read_unlock();
1250
1251 /* no undo structure around - allocate one. */
1252 /* step 1: figure out the size of the semaphore array */
1253 sma = sem_lock_check(ns, semid);
1254 if (IS_ERR(sma))
1255 return ERR_CAST(sma);
1256
1257 nsems = sma->sem_nsems;
1258 sem_getref_and_unlock(sma);
1259
1260 /* step 2: allocate new undo structure */
1261 new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1262 if (!new) {
1263 sem_putref(sma);
1264 return ERR_PTR(-ENOMEM);
1265 }
1266
1267 /* step 3: Acquire the lock on semaphore array */
1268 sem_lock_and_putref(sma);
1269 if (sma->sem_perm.deleted) {
1270 sem_unlock(sma);
1271 kfree(new);
1272 un = ERR_PTR(-EIDRM);
1273 goto out;
1274 }
1275 spin_lock(&ulp->lock);
1276
1277 /*
1278 * step 4: check for races: did someone else allocate the undo struct?
1279 */
1280 un = lookup_undo(ulp, semid);
1281 if (un) {
1282 kfree(new);
1283 goto success;
1284 }
1285 /* step 5: initialize & link new undo structure */
1286 new->semadj = (short *) &new[1];
1287 new->ulp = ulp;
1288 new->semid = semid;
1289 assert_spin_locked(&ulp->lock);
1290 list_add_rcu(&new->list_proc, &ulp->list_proc);
1291 assert_spin_locked(&sma->sem_perm.lock);
1292 list_add(&new->list_id, &sma->list_id);
1293 un = new;
1294
1295success:
1296 spin_unlock(&ulp->lock);
1297 rcu_read_lock();
1298 sem_unlock(sma);
1299out:
1300 return un;
1301}
1302
1303
1304/**
1305 * get_queue_result - Retrieve the result code from sem_queue
1306 * @q: Pointer to queue structure
1307 *
1308 * Retrieve the return code from the pending queue. If IN_WAKEUP is found in
1309 * q->status, then we must loop until the value is replaced with the final
1310 * value: This may happen if a task is woken up by an unrelated event (e.g.
1311 * signal) and in parallel the task is woken up by another task because it got
1312 * the requested semaphores.
1313 *
1314 * The function can be called with or without holding the semaphore spinlock.
1315 */
1316static int get_queue_result(struct sem_queue *q)
1317{
1318 int error;
1319
1320 error = q->status;
1321 while (unlikely(error == IN_WAKEUP)) {
1322 cpu_relax();
1323 error = q->status;
1324 }
1325
1326 return error;
1327}
1328
1329
1330SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
1331 unsigned, nsops, const struct timespec __user *, timeout)
1332{
1333 int error = -EINVAL;
1334 struct sem_array *sma;
1335 struct sembuf fast_sops[SEMOPM_FAST];
1336 struct sembuf* sops = fast_sops, *sop;
1337 struct sem_undo *un;
1338 int undos = 0, alter = 0, max;
1339 struct sem_queue queue;
1340 unsigned long jiffies_left = 0;
1341 struct ipc_namespace *ns;
1342 struct list_head tasks;
1343
1344 ns = current->nsproxy->ipc_ns;
1345
1346 if (nsops < 1 || semid < 0)
1347 return -EINVAL;
1348 if (nsops > ns->sc_semopm)
1349 return -E2BIG;
1350 if(nsops > SEMOPM_FAST) {
1351 sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
1352 if(sops==NULL)
1353 return -ENOMEM;
1354 }
1355 if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
1356 error=-EFAULT;
1357 goto out_free;
1358 }
1359 if (timeout) {
1360 struct timespec _timeout;
1361 if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1362 error = -EFAULT;
1363 goto out_free;
1364 }
1365 if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1366 _timeout.tv_nsec >= 1000000000L) {
1367 error = -EINVAL;
1368 goto out_free;
1369 }
1370 jiffies_left = timespec_to_jiffies(&_timeout);
1371 }
1372 max = 0;
1373 for (sop = sops; sop < sops + nsops; sop++) {
1374 if (sop->sem_num >= max)
1375 max = sop->sem_num;
1376 if (sop->sem_flg & SEM_UNDO)
1377 undos = 1;
1378 if (sop->sem_op != 0)
1379 alter = 1;
1380 }
1381
1382 if (undos) {
1383 un = find_alloc_undo(ns, semid);
1384 if (IS_ERR(un)) {
1385 error = PTR_ERR(un);
1386 goto out_free;
1387 }
1388 } else
1389 un = NULL;
1390
1391 INIT_LIST_HEAD(&tasks);
1392
1393 sma = sem_lock_check(ns, semid);
1394 if (IS_ERR(sma)) {
1395 if (un)
1396 rcu_read_unlock();
1397 error = PTR_ERR(sma);
1398 goto out_free;
1399 }
1400
1401 /*
1402 * semid identifiers are not unique - find_alloc_undo may have
1403 * allocated an undo structure, it was invalidated by an RMID
1404 * and now a new array with received the same id. Check and fail.
1405 * This case can be detected checking un->semid. The existence of
1406 * "un" itself is guaranteed by rcu.
1407 */
1408 error = -EIDRM;
1409 if (un) {
1410 if (un->semid == -1) {
1411 rcu_read_unlock();
1412 goto out_unlock_free;
1413 } else {
1414 /*
1415 * rcu lock can be released, "un" cannot disappear:
1416 * - sem_lock is acquired, thus IPC_RMID is
1417 * impossible.
1418 * - exit_sem is impossible, it always operates on
1419 * current (or a dead task).
1420 */
1421
1422 rcu_read_unlock();
1423 }
1424 }
1425
1426 error = -EFBIG;
1427 if (max >= sma->sem_nsems)
1428 goto out_unlock_free;
1429
1430 error = -EACCES;
1431 if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
1432 goto out_unlock_free;
1433
1434 error = security_sem_semop(sma, sops, nsops, alter);
1435 if (error)
1436 goto out_unlock_free;
1437
1438 error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current));
1439 if (error <= 0) {
1440 if (alter && error == 0)
1441 do_smart_update(sma, sops, nsops, 1, &tasks);
1442
1443 goto out_unlock_free;
1444 }
1445
1446 /* We need to sleep on this operation, so we put the current
1447 * task into the pending queue and go to sleep.
1448 */
1449
1450 queue.sops = sops;
1451 queue.nsops = nsops;
1452 queue.undo = un;
1453 queue.pid = task_tgid_vnr(current);
1454 queue.alter = alter;
1455 if (alter)
1456 list_add_tail(&queue.list, &sma->sem_pending);
1457 else
1458 list_add(&queue.list, &sma->sem_pending);
1459
1460 if (nsops == 1) {
1461 struct sem *curr;
1462 curr = &sma->sem_base[sops->sem_num];
1463
1464 if (alter)
1465 list_add_tail(&queue.simple_list, &curr->sem_pending);
1466 else
1467 list_add(&queue.simple_list, &curr->sem_pending);
1468 } else {
1469 INIT_LIST_HEAD(&queue.simple_list);
1470 sma->complex_count++;
1471 }
1472
1473 queue.status = -EINTR;
1474 queue.sleeper = current;
1475
1476sleep_again:
1477 current->state = TASK_INTERRUPTIBLE;
1478 sem_unlock(sma);
1479
1480 if (timeout)
1481 jiffies_left = schedule_timeout(jiffies_left);
1482 else
1483 schedule();
1484
1485 error = get_queue_result(&queue);
1486
1487 if (error != -EINTR) {
1488 /* fast path: update_queue already obtained all requested
1489 * resources.
1490 * Perform a smp_mb(): User space could assume that semop()
1491 * is a memory barrier: Without the mb(), the cpu could
1492 * speculatively read in user space stale data that was
1493 * overwritten by the previous owner of the semaphore.
1494 */
1495 smp_mb();
1496
1497 goto out_free;
1498 }
1499
1500 sma = sem_lock(ns, semid);
1501
1502 /*
1503 * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing.
1504 */
1505 error = get_queue_result(&queue);
1506
1507 /*
1508 * Array removed? If yes, leave without sem_unlock().
1509 */
1510 if (IS_ERR(sma)) {
1511 goto out_free;
1512 }
1513
1514
1515 /*
1516 * If queue.status != -EINTR we are woken up by another process.
1517 * Leave without unlink_queue(), but with sem_unlock().
1518 */
1519
1520 if (error != -EINTR) {
1521 goto out_unlock_free;
1522 }
1523
1524 /*
1525 * If an interrupt occurred we have to clean up the queue
1526 */
1527 if (timeout && jiffies_left == 0)
1528 error = -EAGAIN;
1529
1530 /*
1531 * If the wakeup was spurious, just retry
1532 */
1533 if (error == -EINTR && !signal_pending(current))
1534 goto sleep_again;
1535
1536 unlink_queue(sma, &queue);
1537
1538out_unlock_free:
1539 sem_unlock(sma);
1540
1541 wake_up_sem_queue_do(&tasks);
1542out_free:
1543 if(sops != fast_sops)
1544 kfree(sops);
1545 return error;
1546}
1547
1548SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
1549 unsigned, nsops)
1550{
1551 return sys_semtimedop(semid, tsops, nsops, NULL);
1552}
1553
1554/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
1555 * parent and child tasks.
1556 */
1557
1558int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
1559{
1560 struct sem_undo_list *undo_list;
1561 int error;
1562
1563 if (clone_flags & CLONE_SYSVSEM) {
1564 error = get_undo_list(&undo_list);
1565 if (error)
1566 return error;
1567 atomic_inc(&undo_list->refcnt);
1568 tsk->sysvsem.undo_list = undo_list;
1569 } else
1570 tsk->sysvsem.undo_list = NULL;
1571
1572 return 0;
1573}
1574
1575/*
1576 * add semadj values to semaphores, free undo structures.
1577 * undo structures are not freed when semaphore arrays are destroyed
1578 * so some of them may be out of date.
1579 * IMPLEMENTATION NOTE: There is some confusion over whether the
1580 * set of adjustments that needs to be done should be done in an atomic
1581 * manner or not. That is, if we are attempting to decrement the semval
1582 * should we queue up and wait until we can do so legally?
1583 * The original implementation attempted to do this (queue and wait).
1584 * The current implementation does not do so. The POSIX standard
1585 * and SVID should be consulted to determine what behavior is mandated.
1586 */
1587void exit_sem(struct task_struct *tsk)
1588{
1589 struct sem_undo_list *ulp;
1590
1591 ulp = tsk->sysvsem.undo_list;
1592 if (!ulp)
1593 return;
1594 tsk->sysvsem.undo_list = NULL;
1595
1596 if (!atomic_dec_and_test(&ulp->refcnt))
1597 return;
1598
1599 for (;;) {
1600 struct sem_array *sma;
1601 struct sem_undo *un;
1602 struct list_head tasks;
1603 int semid;
1604 int i;
1605
1606 rcu_read_lock();
1607 un = list_entry_rcu(ulp->list_proc.next,
1608 struct sem_undo, list_proc);
1609 if (&un->list_proc == &ulp->list_proc)
1610 semid = -1;
1611 else
1612 semid = un->semid;
1613 rcu_read_unlock();
1614
1615 if (semid == -1)
1616 break;
1617
1618 sma = sem_lock_check(tsk->nsproxy->ipc_ns, un->semid);
1619
1620 /* exit_sem raced with IPC_RMID, nothing to do */
1621 if (IS_ERR(sma))
1622 continue;
1623
1624 un = __lookup_undo(ulp, semid);
1625 if (un == NULL) {
1626 /* exit_sem raced with IPC_RMID+semget() that created
1627 * exactly the same semid. Nothing to do.
1628 */
1629 sem_unlock(sma);
1630 continue;
1631 }
1632
1633 /* remove un from the linked lists */
1634 assert_spin_locked(&sma->sem_perm.lock);
1635 list_del(&un->list_id);
1636
1637 spin_lock(&ulp->lock);
1638 list_del_rcu(&un->list_proc);
1639 spin_unlock(&ulp->lock);
1640
1641 /* perform adjustments registered in un */
1642 for (i = 0; i < sma->sem_nsems; i++) {
1643 struct sem * semaphore = &sma->sem_base[i];
1644 if (un->semadj[i]) {
1645 semaphore->semval += un->semadj[i];
1646 /*
1647 * Range checks of the new semaphore value,
1648 * not defined by sus:
1649 * - Some unices ignore the undo entirely
1650 * (e.g. HP UX 11i 11.22, Tru64 V5.1)
1651 * - some cap the value (e.g. FreeBSD caps
1652 * at 0, but doesn't enforce SEMVMX)
1653 *
1654 * Linux caps the semaphore value, both at 0
1655 * and at SEMVMX.
1656 *
1657 * Manfred <manfred@colorfullife.com>
1658 */
1659 if (semaphore->semval < 0)
1660 semaphore->semval = 0;
1661 if (semaphore->semval > SEMVMX)
1662 semaphore->semval = SEMVMX;
1663 semaphore->sempid = task_tgid_vnr(current);
1664 }
1665 }
1666 /* maybe some queued-up processes were waiting for this */
1667 INIT_LIST_HEAD(&tasks);
1668 do_smart_update(sma, NULL, 0, 1, &tasks);
1669 sem_unlock(sma);
1670 wake_up_sem_queue_do(&tasks);
1671
1672 kfree_rcu(un, rcu);
1673 }
1674 kfree(ulp);
1675}
1676
1677#ifdef CONFIG_PROC_FS
1678static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
1679{
1680 struct sem_array *sma = it;
1681
1682 return seq_printf(s,
1683 "%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
1684 sma->sem_perm.key,
1685 sma->sem_perm.id,
1686 sma->sem_perm.mode,
1687 sma->sem_nsems,
1688 sma->sem_perm.uid,
1689 sma->sem_perm.gid,
1690 sma->sem_perm.cuid,
1691 sma->sem_perm.cgid,
1692 sma->sem_otime,
1693 sma->sem_ctime);
1694}
1695#endif
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/ipc/sem.c
4 * Copyright (C) 1992 Krishna Balasubramanian
5 * Copyright (C) 1995 Eric Schenk, Bruno Haible
6 *
7 * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
8 *
9 * SMP-threaded, sysctl's added
10 * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
11 * Enforced range limit on SEM_UNDO
12 * (c) 2001 Red Hat Inc
13 * Lockless wakeup
14 * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
15 * (c) 2016 Davidlohr Bueso <dave@stgolabs.net>
16 * Further wakeup optimizations, documentation
17 * (c) 2010 Manfred Spraul <manfred@colorfullife.com>
18 *
19 * support for audit of ipc object properties and permission changes
20 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
21 *
22 * namespaces support
23 * OpenVZ, SWsoft Inc.
24 * Pavel Emelianov <xemul@openvz.org>
25 *
26 * Implementation notes: (May 2010)
27 * This file implements System V semaphores.
28 *
29 * User space visible behavior:
30 * - FIFO ordering for semop() operations (just FIFO, not starvation
31 * protection)
32 * - multiple semaphore operations that alter the same semaphore in
33 * one semop() are handled.
34 * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and
35 * SETALL calls.
36 * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO.
37 * - undo adjustments at process exit are limited to 0..SEMVMX.
38 * - namespace are supported.
39 * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtime by writing
40 * to /proc/sys/kernel/sem.
41 * - statistics about the usage are reported in /proc/sysvipc/sem.
42 *
43 * Internals:
44 * - scalability:
45 * - all global variables are read-mostly.
46 * - semop() calls and semctl(RMID) are synchronized by RCU.
47 * - most operations do write operations (actually: spin_lock calls) to
48 * the per-semaphore array structure.
49 * Thus: Perfect SMP scaling between independent semaphore arrays.
50 * If multiple semaphores in one array are used, then cache line
51 * trashing on the semaphore array spinlock will limit the scaling.
52 * - semncnt and semzcnt are calculated on demand in count_semcnt()
53 * - the task that performs a successful semop() scans the list of all
54 * sleeping tasks and completes any pending operations that can be fulfilled.
55 * Semaphores are actively given to waiting tasks (necessary for FIFO).
56 * (see update_queue())
57 * - To improve the scalability, the actual wake-up calls are performed after
58 * dropping all locks. (see wake_up_sem_queue_prepare())
59 * - All work is done by the waker, the woken up task does not have to do
60 * anything - not even acquiring a lock or dropping a refcount.
61 * - A woken up task may not even touch the semaphore array anymore, it may
62 * have been destroyed already by a semctl(RMID).
63 * - UNDO values are stored in an array (one per process and per
64 * semaphore array, lazily allocated). For backwards compatibility, multiple
65 * modes for the UNDO variables are supported (per process, per thread)
66 * (see copy_semundo, CLONE_SYSVSEM)
67 * - There are two lists of the pending operations: a per-array list
68 * and per-semaphore list (stored in the array). This allows to achieve FIFO
69 * ordering without always scanning all pending operations.
70 * The worst-case behavior is nevertheless O(N^2) for N wakeups.
71 */
72
73#include <linux/compat.h>
74#include <linux/slab.h>
75#include <linux/spinlock.h>
76#include <linux/init.h>
77#include <linux/proc_fs.h>
78#include <linux/time.h>
79#include <linux/security.h>
80#include <linux/syscalls.h>
81#include <linux/audit.h>
82#include <linux/capability.h>
83#include <linux/seq_file.h>
84#include <linux/rwsem.h>
85#include <linux/nsproxy.h>
86#include <linux/ipc_namespace.h>
87#include <linux/sched/wake_q.h>
88#include <linux/nospec.h>
89#include <linux/rhashtable.h>
90
91#include <linux/uaccess.h>
92#include "util.h"
93
94/* One semaphore structure for each semaphore in the system. */
95struct sem {
96 int semval; /* current value */
97 /*
98 * PID of the process that last modified the semaphore. For
99 * Linux, specifically these are:
100 * - semop
101 * - semctl, via SETVAL and SETALL.
102 * - at task exit when performing undo adjustments (see exit_sem).
103 */
104 struct pid *sempid;
105 spinlock_t lock; /* spinlock for fine-grained semtimedop */
106 struct list_head pending_alter; /* pending single-sop operations */
107 /* that alter the semaphore */
108 struct list_head pending_const; /* pending single-sop operations */
109 /* that do not alter the semaphore*/
110 time64_t sem_otime; /* candidate for sem_otime */
111} ____cacheline_aligned_in_smp;
112
113/* One sem_array data structure for each set of semaphores in the system. */
114struct sem_array {
115 struct kern_ipc_perm sem_perm; /* permissions .. see ipc.h */
116 time64_t sem_ctime; /* create/last semctl() time */
117 struct list_head pending_alter; /* pending operations */
118 /* that alter the array */
119 struct list_head pending_const; /* pending complex operations */
120 /* that do not alter semvals */
121 struct list_head list_id; /* undo requests on this array */
122 int sem_nsems; /* no. of semaphores in array */
123 int complex_count; /* pending complex operations */
124 unsigned int use_global_lock;/* >0: global lock required */
125
126 struct sem sems[];
127} __randomize_layout;
128
129/* One queue for each sleeping process in the system. */
130struct sem_queue {
131 struct list_head list; /* queue of pending operations */
132 struct task_struct *sleeper; /* this process */
133 struct sem_undo *undo; /* undo structure */
134 struct pid *pid; /* process id of requesting process */
135 int status; /* completion status of operation */
136 struct sembuf *sops; /* array of pending operations */
137 struct sembuf *blocking; /* the operation that blocked */
138 int nsops; /* number of operations */
139 bool alter; /* does *sops alter the array? */
140 bool dupsop; /* sops on more than one sem_num */
141};
142
143/* Each task has a list of undo requests. They are executed automatically
144 * when the process exits.
145 */
146struct sem_undo {
147 struct list_head list_proc; /* per-process list: *
148 * all undos from one process
149 * rcu protected */
150 struct rcu_head rcu; /* rcu struct for sem_undo */
151 struct sem_undo_list *ulp; /* back ptr to sem_undo_list */
152 struct list_head list_id; /* per semaphore array list:
153 * all undos for one array */
154 int semid; /* semaphore set identifier */
155 short semadj[]; /* array of adjustments */
156 /* one per semaphore */
157};
158
159/* sem_undo_list controls shared access to the list of sem_undo structures
160 * that may be shared among all a CLONE_SYSVSEM task group.
161 */
162struct sem_undo_list {
163 refcount_t refcnt;
164 spinlock_t lock;
165 struct list_head list_proc;
166};
167
168
169#define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS])
170
171static int newary(struct ipc_namespace *, struct ipc_params *);
172static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
173#ifdef CONFIG_PROC_FS
174static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
175#endif
176
177#define SEMMSL_FAST 256 /* 512 bytes on stack */
178#define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
179
180/*
181 * Switching from the mode suitable for simple ops
182 * to the mode for complex ops is costly. Therefore:
183 * use some hysteresis
184 */
185#define USE_GLOBAL_LOCK_HYSTERESIS 10
186
187/*
188 * Locking:
189 * a) global sem_lock() for read/write
190 * sem_undo.id_next,
191 * sem_array.complex_count,
192 * sem_array.pending{_alter,_const},
193 * sem_array.sem_undo
194 *
195 * b) global or semaphore sem_lock() for read/write:
196 * sem_array.sems[i].pending_{const,alter}:
197 *
198 * c) special:
199 * sem_undo_list.list_proc:
200 * * undo_list->lock for write
201 * * rcu for read
202 * use_global_lock:
203 * * global sem_lock() for write
204 * * either local or global sem_lock() for read.
205 *
206 * Memory ordering:
207 * Most ordering is enforced by using spin_lock() and spin_unlock().
208 *
209 * Exceptions:
210 * 1) use_global_lock: (SEM_BARRIER_1)
211 * Setting it from non-zero to 0 is a RELEASE, this is ensured by
212 * using smp_store_release(): Immediately after setting it to 0,
213 * a simple op can start.
214 * Testing if it is non-zero is an ACQUIRE, this is ensured by using
215 * smp_load_acquire().
216 * Setting it from 0 to non-zero must be ordered with regards to
217 * this smp_load_acquire(), this is guaranteed because the smp_load_acquire()
218 * is inside a spin_lock() and after a write from 0 to non-zero a
219 * spin_lock()+spin_unlock() is done.
220 * To prevent the compiler/cpu temporarily writing 0 to use_global_lock,
221 * READ_ONCE()/WRITE_ONCE() is used.
222 *
223 * 2) queue.status: (SEM_BARRIER_2)
224 * Initialization is done while holding sem_lock(), so no further barrier is
225 * required.
226 * Setting it to a result code is a RELEASE, this is ensured by both a
227 * smp_store_release() (for case a) and while holding sem_lock()
228 * (for case b).
229 * The ACQUIRE when reading the result code without holding sem_lock() is
230 * achieved by using READ_ONCE() + smp_acquire__after_ctrl_dep().
231 * (case a above).
232 * Reading the result code while holding sem_lock() needs no further barriers,
233 * the locks inside sem_lock() enforce ordering (case b above)
234 *
235 * 3) current->state:
236 * current->state is set to TASK_INTERRUPTIBLE while holding sem_lock().
237 * The wakeup is handled using the wake_q infrastructure. wake_q wakeups may
238 * happen immediately after calling wake_q_add. As wake_q_add_safe() is called
239 * when holding sem_lock(), no further barriers are required.
240 *
241 * See also ipc/mqueue.c for more details on the covered races.
242 */
243
244#define sc_semmsl sem_ctls[0]
245#define sc_semmns sem_ctls[1]
246#define sc_semopm sem_ctls[2]
247#define sc_semmni sem_ctls[3]
248
249void sem_init_ns(struct ipc_namespace *ns)
250{
251 ns->sc_semmsl = SEMMSL;
252 ns->sc_semmns = SEMMNS;
253 ns->sc_semopm = SEMOPM;
254 ns->sc_semmni = SEMMNI;
255 ns->used_sems = 0;
256 ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
257}
258
259#ifdef CONFIG_IPC_NS
260void sem_exit_ns(struct ipc_namespace *ns)
261{
262 free_ipcs(ns, &sem_ids(ns), freeary);
263 idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
264 rhashtable_destroy(&ns->ids[IPC_SEM_IDS].key_ht);
265}
266#endif
267
268void __init sem_init(void)
269{
270 sem_init_ns(&init_ipc_ns);
271 ipc_init_proc_interface("sysvipc/sem",
272 " key semid perms nsems uid gid cuid cgid otime ctime\n",
273 IPC_SEM_IDS, sysvipc_sem_proc_show);
274}
275
276/**
277 * unmerge_queues - unmerge queues, if possible.
278 * @sma: semaphore array
279 *
280 * The function unmerges the wait queues if complex_count is 0.
281 * It must be called prior to dropping the global semaphore array lock.
282 */
283static void unmerge_queues(struct sem_array *sma)
284{
285 struct sem_queue *q, *tq;
286
287 /* complex operations still around? */
288 if (sma->complex_count)
289 return;
290 /*
291 * We will switch back to simple mode.
292 * Move all pending operation back into the per-semaphore
293 * queues.
294 */
295 list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
296 struct sem *curr;
297 curr = &sma->sems[q->sops[0].sem_num];
298
299 list_add_tail(&q->list, &curr->pending_alter);
300 }
301 INIT_LIST_HEAD(&sma->pending_alter);
302}
303
304/**
305 * merge_queues - merge single semop queues into global queue
306 * @sma: semaphore array
307 *
308 * This function merges all per-semaphore queues into the global queue.
309 * It is necessary to achieve FIFO ordering for the pending single-sop
310 * operations when a multi-semop operation must sleep.
311 * Only the alter operations must be moved, the const operations can stay.
312 */
313static void merge_queues(struct sem_array *sma)
314{
315 int i;
316 for (i = 0; i < sma->sem_nsems; i++) {
317 struct sem *sem = &sma->sems[i];
318
319 list_splice_init(&sem->pending_alter, &sma->pending_alter);
320 }
321}
322
323static void sem_rcu_free(struct rcu_head *head)
324{
325 struct kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu);
326 struct sem_array *sma = container_of(p, struct sem_array, sem_perm);
327
328 security_sem_free(&sma->sem_perm);
329 kvfree(sma);
330}
331
332/*
333 * Enter the mode suitable for non-simple operations:
334 * Caller must own sem_perm.lock.
335 */
336static void complexmode_enter(struct sem_array *sma)
337{
338 int i;
339 struct sem *sem;
340
341 if (sma->use_global_lock > 0) {
342 /*
343 * We are already in global lock mode.
344 * Nothing to do, just reset the
345 * counter until we return to simple mode.
346 */
347 WRITE_ONCE(sma->use_global_lock, USE_GLOBAL_LOCK_HYSTERESIS);
348 return;
349 }
350 WRITE_ONCE(sma->use_global_lock, USE_GLOBAL_LOCK_HYSTERESIS);
351
352 for (i = 0; i < sma->sem_nsems; i++) {
353 sem = &sma->sems[i];
354 spin_lock(&sem->lock);
355 spin_unlock(&sem->lock);
356 }
357}
358
359/*
360 * Try to leave the mode that disallows simple operations:
361 * Caller must own sem_perm.lock.
362 */
363static void complexmode_tryleave(struct sem_array *sma)
364{
365 if (sma->complex_count) {
366 /* Complex ops are sleeping.
367 * We must stay in complex mode
368 */
369 return;
370 }
371 if (sma->use_global_lock == 1) {
372
373 /* See SEM_BARRIER_1 for purpose/pairing */
374 smp_store_release(&sma->use_global_lock, 0);
375 } else {
376 WRITE_ONCE(sma->use_global_lock,
377 sma->use_global_lock-1);
378 }
379}
380
381#define SEM_GLOBAL_LOCK (-1)
382/*
383 * If the request contains only one semaphore operation, and there are
384 * no complex transactions pending, lock only the semaphore involved.
385 * Otherwise, lock the entire semaphore array, since we either have
386 * multiple semaphores in our own semops, or we need to look at
387 * semaphores from other pending complex operations.
388 */
389static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
390 int nsops)
391{
392 struct sem *sem;
393 int idx;
394
395 if (nsops != 1) {
396 /* Complex operation - acquire a full lock */
397 ipc_lock_object(&sma->sem_perm);
398
399 /* Prevent parallel simple ops */
400 complexmode_enter(sma);
401 return SEM_GLOBAL_LOCK;
402 }
403
404 /*
405 * Only one semaphore affected - try to optimize locking.
406 * Optimized locking is possible if no complex operation
407 * is either enqueued or processed right now.
408 *
409 * Both facts are tracked by use_global_mode.
410 */
411 idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
412 sem = &sma->sems[idx];
413
414 /*
415 * Initial check for use_global_lock. Just an optimization,
416 * no locking, no memory barrier.
417 */
418 if (!READ_ONCE(sma->use_global_lock)) {
419 /*
420 * It appears that no complex operation is around.
421 * Acquire the per-semaphore lock.
422 */
423 spin_lock(&sem->lock);
424
425 /* see SEM_BARRIER_1 for purpose/pairing */
426 if (!smp_load_acquire(&sma->use_global_lock)) {
427 /* fast path successful! */
428 return sops->sem_num;
429 }
430 spin_unlock(&sem->lock);
431 }
432
433 /* slow path: acquire the full lock */
434 ipc_lock_object(&sma->sem_perm);
435
436 if (sma->use_global_lock == 0) {
437 /*
438 * The use_global_lock mode ended while we waited for
439 * sma->sem_perm.lock. Thus we must switch to locking
440 * with sem->lock.
441 * Unlike in the fast path, there is no need to recheck
442 * sma->use_global_lock after we have acquired sem->lock:
443 * We own sma->sem_perm.lock, thus use_global_lock cannot
444 * change.
445 */
446 spin_lock(&sem->lock);
447
448 ipc_unlock_object(&sma->sem_perm);
449 return sops->sem_num;
450 } else {
451 /*
452 * Not a false alarm, thus continue to use the global lock
453 * mode. No need for complexmode_enter(), this was done by
454 * the caller that has set use_global_mode to non-zero.
455 */
456 return SEM_GLOBAL_LOCK;
457 }
458}
459
460static inline void sem_unlock(struct sem_array *sma, int locknum)
461{
462 if (locknum == SEM_GLOBAL_LOCK) {
463 unmerge_queues(sma);
464 complexmode_tryleave(sma);
465 ipc_unlock_object(&sma->sem_perm);
466 } else {
467 struct sem *sem = &sma->sems[locknum];
468 spin_unlock(&sem->lock);
469 }
470}
471
472/*
473 * sem_lock_(check_) routines are called in the paths where the rwsem
474 * is not held.
475 *
476 * The caller holds the RCU read lock.
477 */
478static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
479{
480 struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id);
481
482 if (IS_ERR(ipcp))
483 return ERR_CAST(ipcp);
484
485 return container_of(ipcp, struct sem_array, sem_perm);
486}
487
488static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
489 int id)
490{
491 struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
492
493 if (IS_ERR(ipcp))
494 return ERR_CAST(ipcp);
495
496 return container_of(ipcp, struct sem_array, sem_perm);
497}
498
499static inline void sem_lock_and_putref(struct sem_array *sma)
500{
501 sem_lock(sma, NULL, -1);
502 ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
503}
504
505static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
506{
507 ipc_rmid(&sem_ids(ns), &s->sem_perm);
508}
509
510static struct sem_array *sem_alloc(size_t nsems)
511{
512 struct sem_array *sma;
513
514 if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0]))
515 return NULL;
516
517 sma = kvzalloc(struct_size(sma, sems, nsems), GFP_KERNEL_ACCOUNT);
518 if (unlikely(!sma))
519 return NULL;
520
521 return sma;
522}
523
524/**
525 * newary - Create a new semaphore set
526 * @ns: namespace
527 * @params: ptr to the structure that contains key, semflg and nsems
528 *
529 * Called with sem_ids.rwsem held (as a writer)
530 */
531static int newary(struct ipc_namespace *ns, struct ipc_params *params)
532{
533 int retval;
534 struct sem_array *sma;
535 key_t key = params->key;
536 int nsems = params->u.nsems;
537 int semflg = params->flg;
538 int i;
539
540 if (!nsems)
541 return -EINVAL;
542 if (ns->used_sems + nsems > ns->sc_semmns)
543 return -ENOSPC;
544
545 sma = sem_alloc(nsems);
546 if (!sma)
547 return -ENOMEM;
548
549 sma->sem_perm.mode = (semflg & S_IRWXUGO);
550 sma->sem_perm.key = key;
551
552 sma->sem_perm.security = NULL;
553 retval = security_sem_alloc(&sma->sem_perm);
554 if (retval) {
555 kvfree(sma);
556 return retval;
557 }
558
559 for (i = 0; i < nsems; i++) {
560 INIT_LIST_HEAD(&sma->sems[i].pending_alter);
561 INIT_LIST_HEAD(&sma->sems[i].pending_const);
562 spin_lock_init(&sma->sems[i].lock);
563 }
564
565 sma->complex_count = 0;
566 sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
567 INIT_LIST_HEAD(&sma->pending_alter);
568 INIT_LIST_HEAD(&sma->pending_const);
569 INIT_LIST_HEAD(&sma->list_id);
570 sma->sem_nsems = nsems;
571 sma->sem_ctime = ktime_get_real_seconds();
572
573 /* ipc_addid() locks sma upon success. */
574 retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
575 if (retval < 0) {
576 ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
577 return retval;
578 }
579 ns->used_sems += nsems;
580
581 sem_unlock(sma, -1);
582 rcu_read_unlock();
583
584 return sma->sem_perm.id;
585}
586
587
588/*
589 * Called with sem_ids.rwsem and ipcp locked.
590 */
591static int sem_more_checks(struct kern_ipc_perm *ipcp, struct ipc_params *params)
592{
593 struct sem_array *sma;
594
595 sma = container_of(ipcp, struct sem_array, sem_perm);
596 if (params->u.nsems > sma->sem_nsems)
597 return -EINVAL;
598
599 return 0;
600}
601
602long ksys_semget(key_t key, int nsems, int semflg)
603{
604 struct ipc_namespace *ns;
605 static const struct ipc_ops sem_ops = {
606 .getnew = newary,
607 .associate = security_sem_associate,
608 .more_checks = sem_more_checks,
609 };
610 struct ipc_params sem_params;
611
612 ns = current->nsproxy->ipc_ns;
613
614 if (nsems < 0 || nsems > ns->sc_semmsl)
615 return -EINVAL;
616
617 sem_params.key = key;
618 sem_params.flg = semflg;
619 sem_params.u.nsems = nsems;
620
621 return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
622}
623
624SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
625{
626 return ksys_semget(key, nsems, semflg);
627}
628
629/**
630 * perform_atomic_semop[_slow] - Attempt to perform semaphore
631 * operations on a given array.
632 * @sma: semaphore array
633 * @q: struct sem_queue that describes the operation
634 *
635 * Caller blocking are as follows, based the value
636 * indicated by the semaphore operation (sem_op):
637 *
638 * (1) >0 never blocks.
639 * (2) 0 (wait-for-zero operation): semval is non-zero.
640 * (3) <0 attempting to decrement semval to a value smaller than zero.
641 *
642 * Returns 0 if the operation was possible.
643 * Returns 1 if the operation is impossible, the caller must sleep.
644 * Returns <0 for error codes.
645 */
646static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q)
647{
648 int result, sem_op, nsops;
649 struct pid *pid;
650 struct sembuf *sop;
651 struct sem *curr;
652 struct sembuf *sops;
653 struct sem_undo *un;
654
655 sops = q->sops;
656 nsops = q->nsops;
657 un = q->undo;
658
659 for (sop = sops; sop < sops + nsops; sop++) {
660 int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
661 curr = &sma->sems[idx];
662 sem_op = sop->sem_op;
663 result = curr->semval;
664
665 if (!sem_op && result)
666 goto would_block;
667
668 result += sem_op;
669 if (result < 0)
670 goto would_block;
671 if (result > SEMVMX)
672 goto out_of_range;
673
674 if (sop->sem_flg & SEM_UNDO) {
675 int undo = un->semadj[sop->sem_num] - sem_op;
676 /* Exceeding the undo range is an error. */
677 if (undo < (-SEMAEM - 1) || undo > SEMAEM)
678 goto out_of_range;
679 un->semadj[sop->sem_num] = undo;
680 }
681
682 curr->semval = result;
683 }
684
685 sop--;
686 pid = q->pid;
687 while (sop >= sops) {
688 ipc_update_pid(&sma->sems[sop->sem_num].sempid, pid);
689 sop--;
690 }
691
692 return 0;
693
694out_of_range:
695 result = -ERANGE;
696 goto undo;
697
698would_block:
699 q->blocking = sop;
700
701 if (sop->sem_flg & IPC_NOWAIT)
702 result = -EAGAIN;
703 else
704 result = 1;
705
706undo:
707 sop--;
708 while (sop >= sops) {
709 sem_op = sop->sem_op;
710 sma->sems[sop->sem_num].semval -= sem_op;
711 if (sop->sem_flg & SEM_UNDO)
712 un->semadj[sop->sem_num] += sem_op;
713 sop--;
714 }
715
716 return result;
717}
718
719static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
720{
721 int result, sem_op, nsops;
722 struct sembuf *sop;
723 struct sem *curr;
724 struct sembuf *sops;
725 struct sem_undo *un;
726
727 sops = q->sops;
728 nsops = q->nsops;
729 un = q->undo;
730
731 if (unlikely(q->dupsop))
732 return perform_atomic_semop_slow(sma, q);
733
734 /*
735 * We scan the semaphore set twice, first to ensure that the entire
736 * operation can succeed, therefore avoiding any pointless writes
737 * to shared memory and having to undo such changes in order to block
738 * until the operations can go through.
739 */
740 for (sop = sops; sop < sops + nsops; sop++) {
741 int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
742
743 curr = &sma->sems[idx];
744 sem_op = sop->sem_op;
745 result = curr->semval;
746
747 if (!sem_op && result)
748 goto would_block; /* wait-for-zero */
749
750 result += sem_op;
751 if (result < 0)
752 goto would_block;
753
754 if (result > SEMVMX)
755 return -ERANGE;
756
757 if (sop->sem_flg & SEM_UNDO) {
758 int undo = un->semadj[sop->sem_num] - sem_op;
759
760 /* Exceeding the undo range is an error. */
761 if (undo < (-SEMAEM - 1) || undo > SEMAEM)
762 return -ERANGE;
763 }
764 }
765
766 for (sop = sops; sop < sops + nsops; sop++) {
767 curr = &sma->sems[sop->sem_num];
768 sem_op = sop->sem_op;
769
770 if (sop->sem_flg & SEM_UNDO) {
771 int undo = un->semadj[sop->sem_num] - sem_op;
772
773 un->semadj[sop->sem_num] = undo;
774 }
775 curr->semval += sem_op;
776 ipc_update_pid(&curr->sempid, q->pid);
777 }
778
779 return 0;
780
781would_block:
782 q->blocking = sop;
783 return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1;
784}
785
786static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error,
787 struct wake_q_head *wake_q)
788{
789 struct task_struct *sleeper;
790
791 sleeper = get_task_struct(q->sleeper);
792
793 /* see SEM_BARRIER_2 for purpose/pairing */
794 smp_store_release(&q->status, error);
795
796 wake_q_add_safe(wake_q, sleeper);
797}
798
799static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
800{
801 list_del(&q->list);
802 if (q->nsops > 1)
803 sma->complex_count--;
804}
805
806/** check_restart(sma, q)
807 * @sma: semaphore array
808 * @q: the operation that just completed
809 *
810 * update_queue is O(N^2) when it restarts scanning the whole queue of
811 * waiting operations. Therefore this function checks if the restart is
812 * really necessary. It is called after a previously waiting operation
813 * modified the array.
814 * Note that wait-for-zero operations are handled without restart.
815 */
816static inline int check_restart(struct sem_array *sma, struct sem_queue *q)
817{
818 /* pending complex alter operations are too difficult to analyse */
819 if (!list_empty(&sma->pending_alter))
820 return 1;
821
822 /* we were a sleeping complex operation. Too difficult */
823 if (q->nsops > 1)
824 return 1;
825
826 /* It is impossible that someone waits for the new value:
827 * - complex operations always restart.
828 * - wait-for-zero are handled separately.
829 * - q is a previously sleeping simple operation that
830 * altered the array. It must be a decrement, because
831 * simple increments never sleep.
832 * - If there are older (higher priority) decrements
833 * in the queue, then they have observed the original
834 * semval value and couldn't proceed. The operation
835 * decremented to value - thus they won't proceed either.
836 */
837 return 0;
838}
839
840/**
841 * wake_const_ops - wake up non-alter tasks
842 * @sma: semaphore array.
843 * @semnum: semaphore that was modified.
844 * @wake_q: lockless wake-queue head.
845 *
846 * wake_const_ops must be called after a semaphore in a semaphore array
847 * was set to 0. If complex const operations are pending, wake_const_ops must
848 * be called with semnum = -1, as well as with the number of each modified
849 * semaphore.
850 * The tasks that must be woken up are added to @wake_q. The return code
851 * is stored in q->pid.
852 * The function returns 1 if at least one operation was completed successfully.
853 */
854static int wake_const_ops(struct sem_array *sma, int semnum,
855 struct wake_q_head *wake_q)
856{
857 struct sem_queue *q, *tmp;
858 struct list_head *pending_list;
859 int semop_completed = 0;
860
861 if (semnum == -1)
862 pending_list = &sma->pending_const;
863 else
864 pending_list = &sma->sems[semnum].pending_const;
865
866 list_for_each_entry_safe(q, tmp, pending_list, list) {
867 int error = perform_atomic_semop(sma, q);
868
869 if (error > 0)
870 continue;
871 /* operation completed, remove from queue & wakeup */
872 unlink_queue(sma, q);
873
874 wake_up_sem_queue_prepare(q, error, wake_q);
875 if (error == 0)
876 semop_completed = 1;
877 }
878
879 return semop_completed;
880}
881
882/**
883 * do_smart_wakeup_zero - wakeup all wait for zero tasks
884 * @sma: semaphore array
885 * @sops: operations that were performed
886 * @nsops: number of operations
887 * @wake_q: lockless wake-queue head
888 *
889 * Checks all required queue for wait-for-zero operations, based
890 * on the actual changes that were performed on the semaphore array.
891 * The function returns 1 if at least one operation was completed successfully.
892 */
893static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
894 int nsops, struct wake_q_head *wake_q)
895{
896 int i;
897 int semop_completed = 0;
898 int got_zero = 0;
899
900 /* first: the per-semaphore queues, if known */
901 if (sops) {
902 for (i = 0; i < nsops; i++) {
903 int num = sops[i].sem_num;
904
905 if (sma->sems[num].semval == 0) {
906 got_zero = 1;
907 semop_completed |= wake_const_ops(sma, num, wake_q);
908 }
909 }
910 } else {
911 /*
912 * No sops means modified semaphores not known.
913 * Assume all were changed.
914 */
915 for (i = 0; i < sma->sem_nsems; i++) {
916 if (sma->sems[i].semval == 0) {
917 got_zero = 1;
918 semop_completed |= wake_const_ops(sma, i, wake_q);
919 }
920 }
921 }
922 /*
923 * If one of the modified semaphores got 0,
924 * then check the global queue, too.
925 */
926 if (got_zero)
927 semop_completed |= wake_const_ops(sma, -1, wake_q);
928
929 return semop_completed;
930}
931
932
933/**
934 * update_queue - look for tasks that can be completed.
935 * @sma: semaphore array.
936 * @semnum: semaphore that was modified.
937 * @wake_q: lockless wake-queue head.
938 *
939 * update_queue must be called after a semaphore in a semaphore array
940 * was modified. If multiple semaphores were modified, update_queue must
941 * be called with semnum = -1, as well as with the number of each modified
942 * semaphore.
943 * The tasks that must be woken up are added to @wake_q. The return code
944 * is stored in q->pid.
945 * The function internally checks if const operations can now succeed.
946 *
947 * The function return 1 if at least one semop was completed successfully.
948 */
949static int update_queue(struct sem_array *sma, int semnum, struct wake_q_head *wake_q)
950{
951 struct sem_queue *q, *tmp;
952 struct list_head *pending_list;
953 int semop_completed = 0;
954
955 if (semnum == -1)
956 pending_list = &sma->pending_alter;
957 else
958 pending_list = &sma->sems[semnum].pending_alter;
959
960again:
961 list_for_each_entry_safe(q, tmp, pending_list, list) {
962 int error, restart;
963
964 /* If we are scanning the single sop, per-semaphore list of
965 * one semaphore and that semaphore is 0, then it is not
966 * necessary to scan further: simple increments
967 * that affect only one entry succeed immediately and cannot
968 * be in the per semaphore pending queue, and decrements
969 * cannot be successful if the value is already 0.
970 */
971 if (semnum != -1 && sma->sems[semnum].semval == 0)
972 break;
973
974 error = perform_atomic_semop(sma, q);
975
976 /* Does q->sleeper still need to sleep? */
977 if (error > 0)
978 continue;
979
980 unlink_queue(sma, q);
981
982 if (error) {
983 restart = 0;
984 } else {
985 semop_completed = 1;
986 do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q);
987 restart = check_restart(sma, q);
988 }
989
990 wake_up_sem_queue_prepare(q, error, wake_q);
991 if (restart)
992 goto again;
993 }
994 return semop_completed;
995}
996
997/**
998 * set_semotime - set sem_otime
999 * @sma: semaphore array
1000 * @sops: operations that modified the array, may be NULL
1001 *
1002 * sem_otime is replicated to avoid cache line trashing.
1003 * This function sets one instance to the current time.
1004 */
1005static void set_semotime(struct sem_array *sma, struct sembuf *sops)
1006{
1007 if (sops == NULL) {
1008 sma->sems[0].sem_otime = ktime_get_real_seconds();
1009 } else {
1010 sma->sems[sops[0].sem_num].sem_otime =
1011 ktime_get_real_seconds();
1012 }
1013}
1014
1015/**
1016 * do_smart_update - optimized update_queue
1017 * @sma: semaphore array
1018 * @sops: operations that were performed
1019 * @nsops: number of operations
1020 * @otime: force setting otime
1021 * @wake_q: lockless wake-queue head
1022 *
1023 * do_smart_update() does the required calls to update_queue and wakeup_zero,
1024 * based on the actual changes that were performed on the semaphore array.
1025 * Note that the function does not do the actual wake-up: the caller is
1026 * responsible for calling wake_up_q().
1027 * It is safe to perform this call after dropping all locks.
1028 */
1029static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
1030 int otime, struct wake_q_head *wake_q)
1031{
1032 int i;
1033
1034 otime |= do_smart_wakeup_zero(sma, sops, nsops, wake_q);
1035
1036 if (!list_empty(&sma->pending_alter)) {
1037 /* semaphore array uses the global queue - just process it. */
1038 otime |= update_queue(sma, -1, wake_q);
1039 } else {
1040 if (!sops) {
1041 /*
1042 * No sops, thus the modified semaphores are not
1043 * known. Check all.
1044 */
1045 for (i = 0; i < sma->sem_nsems; i++)
1046 otime |= update_queue(sma, i, wake_q);
1047 } else {
1048 /*
1049 * Check the semaphores that were increased:
1050 * - No complex ops, thus all sleeping ops are
1051 * decrease.
1052 * - if we decreased the value, then any sleeping
1053 * semaphore ops won't be able to run: If the
1054 * previous value was too small, then the new
1055 * value will be too small, too.
1056 */
1057 for (i = 0; i < nsops; i++) {
1058 if (sops[i].sem_op > 0) {
1059 otime |= update_queue(sma,
1060 sops[i].sem_num, wake_q);
1061 }
1062 }
1063 }
1064 }
1065 if (otime)
1066 set_semotime(sma, sops);
1067}
1068
1069/*
1070 * check_qop: Test if a queued operation sleeps on the semaphore semnum
1071 */
1072static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
1073 bool count_zero)
1074{
1075 struct sembuf *sop = q->blocking;
1076
1077 /*
1078 * Linux always (since 0.99.10) reported a task as sleeping on all
1079 * semaphores. This violates SUS, therefore it was changed to the
1080 * standard compliant behavior.
1081 * Give the administrators a chance to notice that an application
1082 * might misbehave because it relies on the Linux behavior.
1083 */
1084 pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
1085 "The task %s (%d) triggered the difference, watch for misbehavior.\n",
1086 current->comm, task_pid_nr(current));
1087
1088 if (sop->sem_num != semnum)
1089 return 0;
1090
1091 if (count_zero && sop->sem_op == 0)
1092 return 1;
1093 if (!count_zero && sop->sem_op < 0)
1094 return 1;
1095
1096 return 0;
1097}
1098
1099/* The following counts are associated to each semaphore:
1100 * semncnt number of tasks waiting on semval being nonzero
1101 * semzcnt number of tasks waiting on semval being zero
1102 *
1103 * Per definition, a task waits only on the semaphore of the first semop
1104 * that cannot proceed, even if additional operation would block, too.
1105 */
1106static int count_semcnt(struct sem_array *sma, ushort semnum,
1107 bool count_zero)
1108{
1109 struct list_head *l;
1110 struct sem_queue *q;
1111 int semcnt;
1112
1113 semcnt = 0;
1114 /* First: check the simple operations. They are easy to evaluate */
1115 if (count_zero)
1116 l = &sma->sems[semnum].pending_const;
1117 else
1118 l = &sma->sems[semnum].pending_alter;
1119
1120 list_for_each_entry(q, l, list) {
1121 /* all task on a per-semaphore list sleep on exactly
1122 * that semaphore
1123 */
1124 semcnt++;
1125 }
1126
1127 /* Then: check the complex operations. */
1128 list_for_each_entry(q, &sma->pending_alter, list) {
1129 semcnt += check_qop(sma, semnum, q, count_zero);
1130 }
1131 if (count_zero) {
1132 list_for_each_entry(q, &sma->pending_const, list) {
1133 semcnt += check_qop(sma, semnum, q, count_zero);
1134 }
1135 }
1136 return semcnt;
1137}
1138
1139/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1140 * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1141 * remains locked on exit.
1142 */
1143static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
1144{
1145 struct sem_undo *un, *tu;
1146 struct sem_queue *q, *tq;
1147 struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1148 int i;
1149 DEFINE_WAKE_Q(wake_q);
1150
1151 /* Free the existing undo structures for this semaphore set. */
1152 ipc_assert_locked_object(&sma->sem_perm);
1153 list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1154 list_del(&un->list_id);
1155 spin_lock(&un->ulp->lock);
1156 un->semid = -1;
1157 list_del_rcu(&un->list_proc);
1158 spin_unlock(&un->ulp->lock);
1159 kvfree_rcu(un, rcu);
1160 }
1161
1162 /* Wake up all pending processes and let them fail with EIDRM. */
1163 list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1164 unlink_queue(sma, q);
1165 wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1166 }
1167
1168 list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1169 unlink_queue(sma, q);
1170 wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1171 }
1172 for (i = 0; i < sma->sem_nsems; i++) {
1173 struct sem *sem = &sma->sems[i];
1174 list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1175 unlink_queue(sma, q);
1176 wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1177 }
1178 list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1179 unlink_queue(sma, q);
1180 wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1181 }
1182 ipc_update_pid(&sem->sempid, NULL);
1183 }
1184
1185 /* Remove the semaphore set from the IDR */
1186 sem_rmid(ns, sma);
1187 sem_unlock(sma, -1);
1188 rcu_read_unlock();
1189
1190 wake_up_q(&wake_q);
1191 ns->used_sems -= sma->sem_nsems;
1192 ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1193}
1194
1195static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1196{
1197 switch (version) {
1198 case IPC_64:
1199 return copy_to_user(buf, in, sizeof(*in));
1200 case IPC_OLD:
1201 {
1202 struct semid_ds out;
1203
1204 memset(&out, 0, sizeof(out));
1205
1206 ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1207
1208 out.sem_otime = in->sem_otime;
1209 out.sem_ctime = in->sem_ctime;
1210 out.sem_nsems = in->sem_nsems;
1211
1212 return copy_to_user(buf, &out, sizeof(out));
1213 }
1214 default:
1215 return -EINVAL;
1216 }
1217}
1218
1219static time64_t get_semotime(struct sem_array *sma)
1220{
1221 int i;
1222 time64_t res;
1223
1224 res = sma->sems[0].sem_otime;
1225 for (i = 1; i < sma->sem_nsems; i++) {
1226 time64_t to = sma->sems[i].sem_otime;
1227
1228 if (to > res)
1229 res = to;
1230 }
1231 return res;
1232}
1233
1234static int semctl_stat(struct ipc_namespace *ns, int semid,
1235 int cmd, struct semid64_ds *semid64)
1236{
1237 struct sem_array *sma;
1238 time64_t semotime;
1239 int err;
1240
1241 memset(semid64, 0, sizeof(*semid64));
1242
1243 rcu_read_lock();
1244 if (cmd == SEM_STAT || cmd == SEM_STAT_ANY) {
1245 sma = sem_obtain_object(ns, semid);
1246 if (IS_ERR(sma)) {
1247 err = PTR_ERR(sma);
1248 goto out_unlock;
1249 }
1250 } else { /* IPC_STAT */
1251 sma = sem_obtain_object_check(ns, semid);
1252 if (IS_ERR(sma)) {
1253 err = PTR_ERR(sma);
1254 goto out_unlock;
1255 }
1256 }
1257
1258 /* see comment for SHM_STAT_ANY */
1259 if (cmd == SEM_STAT_ANY)
1260 audit_ipc_obj(&sma->sem_perm);
1261 else {
1262 err = -EACCES;
1263 if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1264 goto out_unlock;
1265 }
1266
1267 err = security_sem_semctl(&sma->sem_perm, cmd);
1268 if (err)
1269 goto out_unlock;
1270
1271 ipc_lock_object(&sma->sem_perm);
1272
1273 if (!ipc_valid_object(&sma->sem_perm)) {
1274 ipc_unlock_object(&sma->sem_perm);
1275 err = -EIDRM;
1276 goto out_unlock;
1277 }
1278
1279 kernel_to_ipc64_perm(&sma->sem_perm, &semid64->sem_perm);
1280 semotime = get_semotime(sma);
1281 semid64->sem_otime = semotime;
1282 semid64->sem_ctime = sma->sem_ctime;
1283#ifndef CONFIG_64BIT
1284 semid64->sem_otime_high = semotime >> 32;
1285 semid64->sem_ctime_high = sma->sem_ctime >> 32;
1286#endif
1287 semid64->sem_nsems = sma->sem_nsems;
1288
1289 if (cmd == IPC_STAT) {
1290 /*
1291 * As defined in SUS:
1292 * Return 0 on success
1293 */
1294 err = 0;
1295 } else {
1296 /*
1297 * SEM_STAT and SEM_STAT_ANY (both Linux specific)
1298 * Return the full id, including the sequence number
1299 */
1300 err = sma->sem_perm.id;
1301 }
1302 ipc_unlock_object(&sma->sem_perm);
1303out_unlock:
1304 rcu_read_unlock();
1305 return err;
1306}
1307
1308static int semctl_info(struct ipc_namespace *ns, int semid,
1309 int cmd, void __user *p)
1310{
1311 struct seminfo seminfo;
1312 int max_idx;
1313 int err;
1314
1315 err = security_sem_semctl(NULL, cmd);
1316 if (err)
1317 return err;
1318
1319 memset(&seminfo, 0, sizeof(seminfo));
1320 seminfo.semmni = ns->sc_semmni;
1321 seminfo.semmns = ns->sc_semmns;
1322 seminfo.semmsl = ns->sc_semmsl;
1323 seminfo.semopm = ns->sc_semopm;
1324 seminfo.semvmx = SEMVMX;
1325 seminfo.semmnu = SEMMNU;
1326 seminfo.semmap = SEMMAP;
1327 seminfo.semume = SEMUME;
1328 down_read(&sem_ids(ns).rwsem);
1329 if (cmd == SEM_INFO) {
1330 seminfo.semusz = sem_ids(ns).in_use;
1331 seminfo.semaem = ns->used_sems;
1332 } else {
1333 seminfo.semusz = SEMUSZ;
1334 seminfo.semaem = SEMAEM;
1335 }
1336 max_idx = ipc_get_maxidx(&sem_ids(ns));
1337 up_read(&sem_ids(ns).rwsem);
1338 if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1339 return -EFAULT;
1340 return (max_idx < 0) ? 0 : max_idx;
1341}
1342
1343static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1344 int val)
1345{
1346 struct sem_undo *un;
1347 struct sem_array *sma;
1348 struct sem *curr;
1349 int err;
1350 DEFINE_WAKE_Q(wake_q);
1351
1352 if (val > SEMVMX || val < 0)
1353 return -ERANGE;
1354
1355 rcu_read_lock();
1356 sma = sem_obtain_object_check(ns, semid);
1357 if (IS_ERR(sma)) {
1358 rcu_read_unlock();
1359 return PTR_ERR(sma);
1360 }
1361
1362 if (semnum < 0 || semnum >= sma->sem_nsems) {
1363 rcu_read_unlock();
1364 return -EINVAL;
1365 }
1366
1367
1368 if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1369 rcu_read_unlock();
1370 return -EACCES;
1371 }
1372
1373 err = security_sem_semctl(&sma->sem_perm, SETVAL);
1374 if (err) {
1375 rcu_read_unlock();
1376 return -EACCES;
1377 }
1378
1379 sem_lock(sma, NULL, -1);
1380
1381 if (!ipc_valid_object(&sma->sem_perm)) {
1382 sem_unlock(sma, -1);
1383 rcu_read_unlock();
1384 return -EIDRM;
1385 }
1386
1387 semnum = array_index_nospec(semnum, sma->sem_nsems);
1388 curr = &sma->sems[semnum];
1389
1390 ipc_assert_locked_object(&sma->sem_perm);
1391 list_for_each_entry(un, &sma->list_id, list_id)
1392 un->semadj[semnum] = 0;
1393
1394 curr->semval = val;
1395 ipc_update_pid(&curr->sempid, task_tgid(current));
1396 sma->sem_ctime = ktime_get_real_seconds();
1397 /* maybe some queued-up processes were waiting for this */
1398 do_smart_update(sma, NULL, 0, 0, &wake_q);
1399 sem_unlock(sma, -1);
1400 rcu_read_unlock();
1401 wake_up_q(&wake_q);
1402 return 0;
1403}
1404
1405static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1406 int cmd, void __user *p)
1407{
1408 struct sem_array *sma;
1409 struct sem *curr;
1410 int err, nsems;
1411 ushort fast_sem_io[SEMMSL_FAST];
1412 ushort *sem_io = fast_sem_io;
1413 DEFINE_WAKE_Q(wake_q);
1414
1415 rcu_read_lock();
1416 sma = sem_obtain_object_check(ns, semid);
1417 if (IS_ERR(sma)) {
1418 rcu_read_unlock();
1419 return PTR_ERR(sma);
1420 }
1421
1422 nsems = sma->sem_nsems;
1423
1424 err = -EACCES;
1425 if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1426 goto out_rcu_wakeup;
1427
1428 err = security_sem_semctl(&sma->sem_perm, cmd);
1429 if (err)
1430 goto out_rcu_wakeup;
1431
1432 switch (cmd) {
1433 case GETALL:
1434 {
1435 ushort __user *array = p;
1436 int i;
1437
1438 sem_lock(sma, NULL, -1);
1439 if (!ipc_valid_object(&sma->sem_perm)) {
1440 err = -EIDRM;
1441 goto out_unlock;
1442 }
1443 if (nsems > SEMMSL_FAST) {
1444 if (!ipc_rcu_getref(&sma->sem_perm)) {
1445 err = -EIDRM;
1446 goto out_unlock;
1447 }
1448 sem_unlock(sma, -1);
1449 rcu_read_unlock();
1450 sem_io = kvmalloc_array(nsems, sizeof(ushort),
1451 GFP_KERNEL);
1452 if (sem_io == NULL) {
1453 ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1454 return -ENOMEM;
1455 }
1456
1457 rcu_read_lock();
1458 sem_lock_and_putref(sma);
1459 if (!ipc_valid_object(&sma->sem_perm)) {
1460 err = -EIDRM;
1461 goto out_unlock;
1462 }
1463 }
1464 for (i = 0; i < sma->sem_nsems; i++)
1465 sem_io[i] = sma->sems[i].semval;
1466 sem_unlock(sma, -1);
1467 rcu_read_unlock();
1468 err = 0;
1469 if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1470 err = -EFAULT;
1471 goto out_free;
1472 }
1473 case SETALL:
1474 {
1475 int i;
1476 struct sem_undo *un;
1477
1478 if (!ipc_rcu_getref(&sma->sem_perm)) {
1479 err = -EIDRM;
1480 goto out_rcu_wakeup;
1481 }
1482 rcu_read_unlock();
1483
1484 if (nsems > SEMMSL_FAST) {
1485 sem_io = kvmalloc_array(nsems, sizeof(ushort),
1486 GFP_KERNEL);
1487 if (sem_io == NULL) {
1488 ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1489 return -ENOMEM;
1490 }
1491 }
1492
1493 if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
1494 ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1495 err = -EFAULT;
1496 goto out_free;
1497 }
1498
1499 for (i = 0; i < nsems; i++) {
1500 if (sem_io[i] > SEMVMX) {
1501 ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1502 err = -ERANGE;
1503 goto out_free;
1504 }
1505 }
1506 rcu_read_lock();
1507 sem_lock_and_putref(sma);
1508 if (!ipc_valid_object(&sma->sem_perm)) {
1509 err = -EIDRM;
1510 goto out_unlock;
1511 }
1512
1513 for (i = 0; i < nsems; i++) {
1514 sma->sems[i].semval = sem_io[i];
1515 ipc_update_pid(&sma->sems[i].sempid, task_tgid(current));
1516 }
1517
1518 ipc_assert_locked_object(&sma->sem_perm);
1519 list_for_each_entry(un, &sma->list_id, list_id) {
1520 for (i = 0; i < nsems; i++)
1521 un->semadj[i] = 0;
1522 }
1523 sma->sem_ctime = ktime_get_real_seconds();
1524 /* maybe some queued-up processes were waiting for this */
1525 do_smart_update(sma, NULL, 0, 0, &wake_q);
1526 err = 0;
1527 goto out_unlock;
1528 }
1529 /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1530 }
1531 err = -EINVAL;
1532 if (semnum < 0 || semnum >= nsems)
1533 goto out_rcu_wakeup;
1534
1535 sem_lock(sma, NULL, -1);
1536 if (!ipc_valid_object(&sma->sem_perm)) {
1537 err = -EIDRM;
1538 goto out_unlock;
1539 }
1540
1541 semnum = array_index_nospec(semnum, nsems);
1542 curr = &sma->sems[semnum];
1543
1544 switch (cmd) {
1545 case GETVAL:
1546 err = curr->semval;
1547 goto out_unlock;
1548 case GETPID:
1549 err = pid_vnr(curr->sempid);
1550 goto out_unlock;
1551 case GETNCNT:
1552 err = count_semcnt(sma, semnum, 0);
1553 goto out_unlock;
1554 case GETZCNT:
1555 err = count_semcnt(sma, semnum, 1);
1556 goto out_unlock;
1557 }
1558
1559out_unlock:
1560 sem_unlock(sma, -1);
1561out_rcu_wakeup:
1562 rcu_read_unlock();
1563 wake_up_q(&wake_q);
1564out_free:
1565 if (sem_io != fast_sem_io)
1566 kvfree(sem_io);
1567 return err;
1568}
1569
1570static inline unsigned long
1571copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1572{
1573 switch (version) {
1574 case IPC_64:
1575 if (copy_from_user(out, buf, sizeof(*out)))
1576 return -EFAULT;
1577 return 0;
1578 case IPC_OLD:
1579 {
1580 struct semid_ds tbuf_old;
1581
1582 if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1583 return -EFAULT;
1584
1585 out->sem_perm.uid = tbuf_old.sem_perm.uid;
1586 out->sem_perm.gid = tbuf_old.sem_perm.gid;
1587 out->sem_perm.mode = tbuf_old.sem_perm.mode;
1588
1589 return 0;
1590 }
1591 default:
1592 return -EINVAL;
1593 }
1594}
1595
1596/*
1597 * This function handles some semctl commands which require the rwsem
1598 * to be held in write mode.
1599 * NOTE: no locks must be held, the rwsem is taken inside this function.
1600 */
1601static int semctl_down(struct ipc_namespace *ns, int semid,
1602 int cmd, struct semid64_ds *semid64)
1603{
1604 struct sem_array *sma;
1605 int err;
1606 struct kern_ipc_perm *ipcp;
1607
1608 down_write(&sem_ids(ns).rwsem);
1609 rcu_read_lock();
1610
1611 ipcp = ipcctl_obtain_check(ns, &sem_ids(ns), semid, cmd,
1612 &semid64->sem_perm, 0);
1613 if (IS_ERR(ipcp)) {
1614 err = PTR_ERR(ipcp);
1615 goto out_unlock1;
1616 }
1617
1618 sma = container_of(ipcp, struct sem_array, sem_perm);
1619
1620 err = security_sem_semctl(&sma->sem_perm, cmd);
1621 if (err)
1622 goto out_unlock1;
1623
1624 switch (cmd) {
1625 case IPC_RMID:
1626 sem_lock(sma, NULL, -1);
1627 /* freeary unlocks the ipc object and rcu */
1628 freeary(ns, ipcp);
1629 goto out_up;
1630 case IPC_SET:
1631 sem_lock(sma, NULL, -1);
1632 err = ipc_update_perm(&semid64->sem_perm, ipcp);
1633 if (err)
1634 goto out_unlock0;
1635 sma->sem_ctime = ktime_get_real_seconds();
1636 break;
1637 default:
1638 err = -EINVAL;
1639 goto out_unlock1;
1640 }
1641
1642out_unlock0:
1643 sem_unlock(sma, -1);
1644out_unlock1:
1645 rcu_read_unlock();
1646out_up:
1647 up_write(&sem_ids(ns).rwsem);
1648 return err;
1649}
1650
1651static long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg, int version)
1652{
1653 struct ipc_namespace *ns;
1654 void __user *p = (void __user *)arg;
1655 struct semid64_ds semid64;
1656 int err;
1657
1658 if (semid < 0)
1659 return -EINVAL;
1660
1661 ns = current->nsproxy->ipc_ns;
1662
1663 switch (cmd) {
1664 case IPC_INFO:
1665 case SEM_INFO:
1666 return semctl_info(ns, semid, cmd, p);
1667 case IPC_STAT:
1668 case SEM_STAT:
1669 case SEM_STAT_ANY:
1670 err = semctl_stat(ns, semid, cmd, &semid64);
1671 if (err < 0)
1672 return err;
1673 if (copy_semid_to_user(p, &semid64, version))
1674 err = -EFAULT;
1675 return err;
1676 case GETALL:
1677 case GETVAL:
1678 case GETPID:
1679 case GETNCNT:
1680 case GETZCNT:
1681 case SETALL:
1682 return semctl_main(ns, semid, semnum, cmd, p);
1683 case SETVAL: {
1684 int val;
1685#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1686 /* big-endian 64bit */
1687 val = arg >> 32;
1688#else
1689 /* 32bit or little-endian 64bit */
1690 val = arg;
1691#endif
1692 return semctl_setval(ns, semid, semnum, val);
1693 }
1694 case IPC_SET:
1695 if (copy_semid_from_user(&semid64, p, version))
1696 return -EFAULT;
1697 fallthrough;
1698 case IPC_RMID:
1699 return semctl_down(ns, semid, cmd, &semid64);
1700 default:
1701 return -EINVAL;
1702 }
1703}
1704
1705SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1706{
1707 return ksys_semctl(semid, semnum, cmd, arg, IPC_64);
1708}
1709
1710#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
1711long ksys_old_semctl(int semid, int semnum, int cmd, unsigned long arg)
1712{
1713 int version = ipc_parse_version(&cmd);
1714
1715 return ksys_semctl(semid, semnum, cmd, arg, version);
1716}
1717
1718SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1719{
1720 return ksys_old_semctl(semid, semnum, cmd, arg);
1721}
1722#endif
1723
1724#ifdef CONFIG_COMPAT
1725
1726struct compat_semid_ds {
1727 struct compat_ipc_perm sem_perm;
1728 old_time32_t sem_otime;
1729 old_time32_t sem_ctime;
1730 compat_uptr_t sem_base;
1731 compat_uptr_t sem_pending;
1732 compat_uptr_t sem_pending_last;
1733 compat_uptr_t undo;
1734 unsigned short sem_nsems;
1735};
1736
1737static int copy_compat_semid_from_user(struct semid64_ds *out, void __user *buf,
1738 int version)
1739{
1740 memset(out, 0, sizeof(*out));
1741 if (version == IPC_64) {
1742 struct compat_semid64_ds __user *p = buf;
1743 return get_compat_ipc64_perm(&out->sem_perm, &p->sem_perm);
1744 } else {
1745 struct compat_semid_ds __user *p = buf;
1746 return get_compat_ipc_perm(&out->sem_perm, &p->sem_perm);
1747 }
1748}
1749
1750static int copy_compat_semid_to_user(void __user *buf, struct semid64_ds *in,
1751 int version)
1752{
1753 if (version == IPC_64) {
1754 struct compat_semid64_ds v;
1755 memset(&v, 0, sizeof(v));
1756 to_compat_ipc64_perm(&v.sem_perm, &in->sem_perm);
1757 v.sem_otime = lower_32_bits(in->sem_otime);
1758 v.sem_otime_high = upper_32_bits(in->sem_otime);
1759 v.sem_ctime = lower_32_bits(in->sem_ctime);
1760 v.sem_ctime_high = upper_32_bits(in->sem_ctime);
1761 v.sem_nsems = in->sem_nsems;
1762 return copy_to_user(buf, &v, sizeof(v));
1763 } else {
1764 struct compat_semid_ds v;
1765 memset(&v, 0, sizeof(v));
1766 to_compat_ipc_perm(&v.sem_perm, &in->sem_perm);
1767 v.sem_otime = in->sem_otime;
1768 v.sem_ctime = in->sem_ctime;
1769 v.sem_nsems = in->sem_nsems;
1770 return copy_to_user(buf, &v, sizeof(v));
1771 }
1772}
1773
1774static long compat_ksys_semctl(int semid, int semnum, int cmd, int arg, int version)
1775{
1776 void __user *p = compat_ptr(arg);
1777 struct ipc_namespace *ns;
1778 struct semid64_ds semid64;
1779 int err;
1780
1781 ns = current->nsproxy->ipc_ns;
1782
1783 if (semid < 0)
1784 return -EINVAL;
1785
1786 switch (cmd & (~IPC_64)) {
1787 case IPC_INFO:
1788 case SEM_INFO:
1789 return semctl_info(ns, semid, cmd, p);
1790 case IPC_STAT:
1791 case SEM_STAT:
1792 case SEM_STAT_ANY:
1793 err = semctl_stat(ns, semid, cmd, &semid64);
1794 if (err < 0)
1795 return err;
1796 if (copy_compat_semid_to_user(p, &semid64, version))
1797 err = -EFAULT;
1798 return err;
1799 case GETVAL:
1800 case GETPID:
1801 case GETNCNT:
1802 case GETZCNT:
1803 case GETALL:
1804 case SETALL:
1805 return semctl_main(ns, semid, semnum, cmd, p);
1806 case SETVAL:
1807 return semctl_setval(ns, semid, semnum, arg);
1808 case IPC_SET:
1809 if (copy_compat_semid_from_user(&semid64, p, version))
1810 return -EFAULT;
1811 fallthrough;
1812 case IPC_RMID:
1813 return semctl_down(ns, semid, cmd, &semid64);
1814 default:
1815 return -EINVAL;
1816 }
1817}
1818
1819COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg)
1820{
1821 return compat_ksys_semctl(semid, semnum, cmd, arg, IPC_64);
1822}
1823
1824#ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION
1825long compat_ksys_old_semctl(int semid, int semnum, int cmd, int arg)
1826{
1827 int version = compat_ipc_parse_version(&cmd);
1828
1829 return compat_ksys_semctl(semid, semnum, cmd, arg, version);
1830}
1831
1832COMPAT_SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, int, arg)
1833{
1834 return compat_ksys_old_semctl(semid, semnum, cmd, arg);
1835}
1836#endif
1837#endif
1838
1839/* If the task doesn't already have a undo_list, then allocate one
1840 * here. We guarantee there is only one thread using this undo list,
1841 * and current is THE ONE
1842 *
1843 * If this allocation and assignment succeeds, but later
1844 * portions of this code fail, there is no need to free the sem_undo_list.
1845 * Just let it stay associated with the task, and it'll be freed later
1846 * at exit time.
1847 *
1848 * This can block, so callers must hold no locks.
1849 */
1850static inline int get_undo_list(struct sem_undo_list **undo_listp)
1851{
1852 struct sem_undo_list *undo_list;
1853
1854 undo_list = current->sysvsem.undo_list;
1855 if (!undo_list) {
1856 undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL_ACCOUNT);
1857 if (undo_list == NULL)
1858 return -ENOMEM;
1859 spin_lock_init(&undo_list->lock);
1860 refcount_set(&undo_list->refcnt, 1);
1861 INIT_LIST_HEAD(&undo_list->list_proc);
1862
1863 current->sysvsem.undo_list = undo_list;
1864 }
1865 *undo_listp = undo_list;
1866 return 0;
1867}
1868
1869static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1870{
1871 struct sem_undo *un;
1872
1873 list_for_each_entry_rcu(un, &ulp->list_proc, list_proc,
1874 spin_is_locked(&ulp->lock)) {
1875 if (un->semid == semid)
1876 return un;
1877 }
1878 return NULL;
1879}
1880
1881static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1882{
1883 struct sem_undo *un;
1884
1885 assert_spin_locked(&ulp->lock);
1886
1887 un = __lookup_undo(ulp, semid);
1888 if (un) {
1889 list_del_rcu(&un->list_proc);
1890 list_add_rcu(&un->list_proc, &ulp->list_proc);
1891 }
1892 return un;
1893}
1894
1895/**
1896 * find_alloc_undo - lookup (and if not present create) undo array
1897 * @ns: namespace
1898 * @semid: semaphore array id
1899 *
1900 * The function looks up (and if not present creates) the undo structure.
1901 * The size of the undo structure depends on the size of the semaphore
1902 * array, thus the alloc path is not that straightforward.
1903 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1904 * performs a rcu_read_lock().
1905 */
1906static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1907{
1908 struct sem_array *sma;
1909 struct sem_undo_list *ulp;
1910 struct sem_undo *un, *new;
1911 int nsems, error;
1912
1913 error = get_undo_list(&ulp);
1914 if (error)
1915 return ERR_PTR(error);
1916
1917 rcu_read_lock();
1918 spin_lock(&ulp->lock);
1919 un = lookup_undo(ulp, semid);
1920 spin_unlock(&ulp->lock);
1921 if (likely(un != NULL))
1922 goto out;
1923
1924 /* no undo structure around - allocate one. */
1925 /* step 1: figure out the size of the semaphore array */
1926 sma = sem_obtain_object_check(ns, semid);
1927 if (IS_ERR(sma)) {
1928 rcu_read_unlock();
1929 return ERR_CAST(sma);
1930 }
1931
1932 nsems = sma->sem_nsems;
1933 if (!ipc_rcu_getref(&sma->sem_perm)) {
1934 rcu_read_unlock();
1935 un = ERR_PTR(-EIDRM);
1936 goto out;
1937 }
1938 rcu_read_unlock();
1939
1940 /* step 2: allocate new undo structure */
1941 new = kvzalloc(struct_size(new, semadj, nsems), GFP_KERNEL_ACCOUNT);
1942 if (!new) {
1943 ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1944 return ERR_PTR(-ENOMEM);
1945 }
1946
1947 /* step 3: Acquire the lock on semaphore array */
1948 rcu_read_lock();
1949 sem_lock_and_putref(sma);
1950 if (!ipc_valid_object(&sma->sem_perm)) {
1951 sem_unlock(sma, -1);
1952 rcu_read_unlock();
1953 kvfree(new);
1954 un = ERR_PTR(-EIDRM);
1955 goto out;
1956 }
1957 spin_lock(&ulp->lock);
1958
1959 /*
1960 * step 4: check for races: did someone else allocate the undo struct?
1961 */
1962 un = lookup_undo(ulp, semid);
1963 if (un) {
1964 spin_unlock(&ulp->lock);
1965 kvfree(new);
1966 goto success;
1967 }
1968 /* step 5: initialize & link new undo structure */
1969 new->ulp = ulp;
1970 new->semid = semid;
1971 assert_spin_locked(&ulp->lock);
1972 list_add_rcu(&new->list_proc, &ulp->list_proc);
1973 ipc_assert_locked_object(&sma->sem_perm);
1974 list_add(&new->list_id, &sma->list_id);
1975 un = new;
1976 spin_unlock(&ulp->lock);
1977success:
1978 sem_unlock(sma, -1);
1979out:
1980 return un;
1981}
1982
1983long __do_semtimedop(int semid, struct sembuf *sops,
1984 unsigned nsops, const struct timespec64 *timeout,
1985 struct ipc_namespace *ns)
1986{
1987 int error = -EINVAL;
1988 struct sem_array *sma;
1989 struct sembuf *sop;
1990 struct sem_undo *un;
1991 int max, locknum;
1992 bool undos = false, alter = false, dupsop = false;
1993 struct sem_queue queue;
1994 unsigned long dup = 0;
1995 ktime_t expires, *exp = NULL;
1996 bool timed_out = false;
1997
1998 if (nsops < 1 || semid < 0)
1999 return -EINVAL;
2000 if (nsops > ns->sc_semopm)
2001 return -E2BIG;
2002
2003 if (timeout) {
2004 if (!timespec64_valid(timeout))
2005 return -EINVAL;
2006 expires = ktime_add_safe(ktime_get(),
2007 timespec64_to_ktime(*timeout));
2008 exp = &expires;
2009 }
2010
2011
2012 max = 0;
2013 for (sop = sops; sop < sops + nsops; sop++) {
2014 unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG);
2015
2016 if (sop->sem_num >= max)
2017 max = sop->sem_num;
2018 if (sop->sem_flg & SEM_UNDO)
2019 undos = true;
2020 if (dup & mask) {
2021 /*
2022 * There was a previous alter access that appears
2023 * to have accessed the same semaphore, thus use
2024 * the dupsop logic. "appears", because the detection
2025 * can only check % BITS_PER_LONG.
2026 */
2027 dupsop = true;
2028 }
2029 if (sop->sem_op != 0) {
2030 alter = true;
2031 dup |= mask;
2032 }
2033 }
2034
2035 if (undos) {
2036 /* On success, find_alloc_undo takes the rcu_read_lock */
2037 un = find_alloc_undo(ns, semid);
2038 if (IS_ERR(un)) {
2039 error = PTR_ERR(un);
2040 goto out;
2041 }
2042 } else {
2043 un = NULL;
2044 rcu_read_lock();
2045 }
2046
2047 sma = sem_obtain_object_check(ns, semid);
2048 if (IS_ERR(sma)) {
2049 rcu_read_unlock();
2050 error = PTR_ERR(sma);
2051 goto out;
2052 }
2053
2054 error = -EFBIG;
2055 if (max >= sma->sem_nsems) {
2056 rcu_read_unlock();
2057 goto out;
2058 }
2059
2060 error = -EACCES;
2061 if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) {
2062 rcu_read_unlock();
2063 goto out;
2064 }
2065
2066 error = security_sem_semop(&sma->sem_perm, sops, nsops, alter);
2067 if (error) {
2068 rcu_read_unlock();
2069 goto out;
2070 }
2071
2072 error = -EIDRM;
2073 locknum = sem_lock(sma, sops, nsops);
2074 /*
2075 * We eventually might perform the following check in a lockless
2076 * fashion, considering ipc_valid_object() locking constraints.
2077 * If nsops == 1 and there is no contention for sem_perm.lock, then
2078 * only a per-semaphore lock is held and it's OK to proceed with the
2079 * check below. More details on the fine grained locking scheme
2080 * entangled here and why it's RMID race safe on comments at sem_lock()
2081 */
2082 if (!ipc_valid_object(&sma->sem_perm))
2083 goto out_unlock;
2084 /*
2085 * semid identifiers are not unique - find_alloc_undo may have
2086 * allocated an undo structure, it was invalidated by an RMID
2087 * and now a new array with received the same id. Check and fail.
2088 * This case can be detected checking un->semid. The existence of
2089 * "un" itself is guaranteed by rcu.
2090 */
2091 if (un && un->semid == -1)
2092 goto out_unlock;
2093
2094 queue.sops = sops;
2095 queue.nsops = nsops;
2096 queue.undo = un;
2097 queue.pid = task_tgid(current);
2098 queue.alter = alter;
2099 queue.dupsop = dupsop;
2100
2101 error = perform_atomic_semop(sma, &queue);
2102 if (error == 0) { /* non-blocking successful path */
2103 DEFINE_WAKE_Q(wake_q);
2104
2105 /*
2106 * If the operation was successful, then do
2107 * the required updates.
2108 */
2109 if (alter)
2110 do_smart_update(sma, sops, nsops, 1, &wake_q);
2111 else
2112 set_semotime(sma, sops);
2113
2114 sem_unlock(sma, locknum);
2115 rcu_read_unlock();
2116 wake_up_q(&wake_q);
2117
2118 goto out;
2119 }
2120 if (error < 0) /* non-blocking error path */
2121 goto out_unlock;
2122
2123 /*
2124 * We need to sleep on this operation, so we put the current
2125 * task into the pending queue and go to sleep.
2126 */
2127 if (nsops == 1) {
2128 struct sem *curr;
2129 int idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
2130 curr = &sma->sems[idx];
2131
2132 if (alter) {
2133 if (sma->complex_count) {
2134 list_add_tail(&queue.list,
2135 &sma->pending_alter);
2136 } else {
2137
2138 list_add_tail(&queue.list,
2139 &curr->pending_alter);
2140 }
2141 } else {
2142 list_add_tail(&queue.list, &curr->pending_const);
2143 }
2144 } else {
2145 if (!sma->complex_count)
2146 merge_queues(sma);
2147
2148 if (alter)
2149 list_add_tail(&queue.list, &sma->pending_alter);
2150 else
2151 list_add_tail(&queue.list, &sma->pending_const);
2152
2153 sma->complex_count++;
2154 }
2155
2156 do {
2157 /* memory ordering ensured by the lock in sem_lock() */
2158 WRITE_ONCE(queue.status, -EINTR);
2159 queue.sleeper = current;
2160
2161 /* memory ordering is ensured by the lock in sem_lock() */
2162 __set_current_state(TASK_INTERRUPTIBLE);
2163 sem_unlock(sma, locknum);
2164 rcu_read_unlock();
2165
2166 timed_out = !schedule_hrtimeout_range(exp,
2167 current->timer_slack_ns, HRTIMER_MODE_ABS);
2168
2169 /*
2170 * fastpath: the semop has completed, either successfully or
2171 * not, from the syscall pov, is quite irrelevant to us at this
2172 * point; we're done.
2173 *
2174 * We _do_ care, nonetheless, about being awoken by a signal or
2175 * spuriously. The queue.status is checked again in the
2176 * slowpath (aka after taking sem_lock), such that we can detect
2177 * scenarios where we were awakened externally, during the
2178 * window between wake_q_add() and wake_up_q().
2179 */
2180 rcu_read_lock();
2181 error = READ_ONCE(queue.status);
2182 if (error != -EINTR) {
2183 /* see SEM_BARRIER_2 for purpose/pairing */
2184 smp_acquire__after_ctrl_dep();
2185 rcu_read_unlock();
2186 goto out;
2187 }
2188
2189 locknum = sem_lock(sma, sops, nsops);
2190
2191 if (!ipc_valid_object(&sma->sem_perm))
2192 goto out_unlock;
2193
2194 /*
2195 * No necessity for any barrier: We are protect by sem_lock()
2196 */
2197 error = READ_ONCE(queue.status);
2198
2199 /*
2200 * If queue.status != -EINTR we are woken up by another process.
2201 * Leave without unlink_queue(), but with sem_unlock().
2202 */
2203 if (error != -EINTR)
2204 goto out_unlock;
2205
2206 /*
2207 * If an interrupt occurred we have to clean up the queue.
2208 */
2209 if (timed_out)
2210 error = -EAGAIN;
2211 } while (error == -EINTR && !signal_pending(current)); /* spurious */
2212
2213 unlink_queue(sma, &queue);
2214
2215out_unlock:
2216 sem_unlock(sma, locknum);
2217 rcu_read_unlock();
2218out:
2219 return error;
2220}
2221
2222static long do_semtimedop(int semid, struct sembuf __user *tsops,
2223 unsigned nsops, const struct timespec64 *timeout)
2224{
2225 struct sembuf fast_sops[SEMOPM_FAST];
2226 struct sembuf *sops = fast_sops;
2227 struct ipc_namespace *ns;
2228 int ret;
2229
2230 ns = current->nsproxy->ipc_ns;
2231 if (nsops > ns->sc_semopm)
2232 return -E2BIG;
2233 if (nsops < 1)
2234 return -EINVAL;
2235
2236 if (nsops > SEMOPM_FAST) {
2237 sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL);
2238 if (sops == NULL)
2239 return -ENOMEM;
2240 }
2241
2242 if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
2243 ret = -EFAULT;
2244 goto out_free;
2245 }
2246
2247 ret = __do_semtimedop(semid, sops, nsops, timeout, ns);
2248
2249out_free:
2250 if (sops != fast_sops)
2251 kvfree(sops);
2252
2253 return ret;
2254}
2255
2256long ksys_semtimedop(int semid, struct sembuf __user *tsops,
2257 unsigned int nsops, const struct __kernel_timespec __user *timeout)
2258{
2259 if (timeout) {
2260 struct timespec64 ts;
2261 if (get_timespec64(&ts, timeout))
2262 return -EFAULT;
2263 return do_semtimedop(semid, tsops, nsops, &ts);
2264 }
2265 return do_semtimedop(semid, tsops, nsops, NULL);
2266}
2267
2268SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
2269 unsigned int, nsops, const struct __kernel_timespec __user *, timeout)
2270{
2271 return ksys_semtimedop(semid, tsops, nsops, timeout);
2272}
2273
2274#ifdef CONFIG_COMPAT_32BIT_TIME
2275long compat_ksys_semtimedop(int semid, struct sembuf __user *tsems,
2276 unsigned int nsops,
2277 const struct old_timespec32 __user *timeout)
2278{
2279 if (timeout) {
2280 struct timespec64 ts;
2281 if (get_old_timespec32(&ts, timeout))
2282 return -EFAULT;
2283 return do_semtimedop(semid, tsems, nsops, &ts);
2284 }
2285 return do_semtimedop(semid, tsems, nsops, NULL);
2286}
2287
2288SYSCALL_DEFINE4(semtimedop_time32, int, semid, struct sembuf __user *, tsems,
2289 unsigned int, nsops,
2290 const struct old_timespec32 __user *, timeout)
2291{
2292 return compat_ksys_semtimedop(semid, tsems, nsops, timeout);
2293}
2294#endif
2295
2296SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
2297 unsigned, nsops)
2298{
2299 return do_semtimedop(semid, tsops, nsops, NULL);
2300}
2301
2302/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
2303 * parent and child tasks.
2304 */
2305
2306int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
2307{
2308 struct sem_undo_list *undo_list;
2309 int error;
2310
2311 if (clone_flags & CLONE_SYSVSEM) {
2312 error = get_undo_list(&undo_list);
2313 if (error)
2314 return error;
2315 refcount_inc(&undo_list->refcnt);
2316 tsk->sysvsem.undo_list = undo_list;
2317 } else
2318 tsk->sysvsem.undo_list = NULL;
2319
2320 return 0;
2321}
2322
2323/*
2324 * add semadj values to semaphores, free undo structures.
2325 * undo structures are not freed when semaphore arrays are destroyed
2326 * so some of them may be out of date.
2327 * IMPLEMENTATION NOTE: There is some confusion over whether the
2328 * set of adjustments that needs to be done should be done in an atomic
2329 * manner or not. That is, if we are attempting to decrement the semval
2330 * should we queue up and wait until we can do so legally?
2331 * The original implementation attempted to do this (queue and wait).
2332 * The current implementation does not do so. The POSIX standard
2333 * and SVID should be consulted to determine what behavior is mandated.
2334 */
2335void exit_sem(struct task_struct *tsk)
2336{
2337 struct sem_undo_list *ulp;
2338
2339 ulp = tsk->sysvsem.undo_list;
2340 if (!ulp)
2341 return;
2342 tsk->sysvsem.undo_list = NULL;
2343
2344 if (!refcount_dec_and_test(&ulp->refcnt))
2345 return;
2346
2347 for (;;) {
2348 struct sem_array *sma;
2349 struct sem_undo *un;
2350 int semid, i;
2351 DEFINE_WAKE_Q(wake_q);
2352
2353 cond_resched();
2354
2355 rcu_read_lock();
2356 un = list_entry_rcu(ulp->list_proc.next,
2357 struct sem_undo, list_proc);
2358 if (&un->list_proc == &ulp->list_proc) {
2359 /*
2360 * We must wait for freeary() before freeing this ulp,
2361 * in case we raced with last sem_undo. There is a small
2362 * possibility where we exit while freeary() didn't
2363 * finish unlocking sem_undo_list.
2364 */
2365 spin_lock(&ulp->lock);
2366 spin_unlock(&ulp->lock);
2367 rcu_read_unlock();
2368 break;
2369 }
2370 spin_lock(&ulp->lock);
2371 semid = un->semid;
2372 spin_unlock(&ulp->lock);
2373
2374 /* exit_sem raced with IPC_RMID, nothing to do */
2375 if (semid == -1) {
2376 rcu_read_unlock();
2377 continue;
2378 }
2379
2380 sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid);
2381 /* exit_sem raced with IPC_RMID, nothing to do */
2382 if (IS_ERR(sma)) {
2383 rcu_read_unlock();
2384 continue;
2385 }
2386
2387 sem_lock(sma, NULL, -1);
2388 /* exit_sem raced with IPC_RMID, nothing to do */
2389 if (!ipc_valid_object(&sma->sem_perm)) {
2390 sem_unlock(sma, -1);
2391 rcu_read_unlock();
2392 continue;
2393 }
2394 un = __lookup_undo(ulp, semid);
2395 if (un == NULL) {
2396 /* exit_sem raced with IPC_RMID+semget() that created
2397 * exactly the same semid. Nothing to do.
2398 */
2399 sem_unlock(sma, -1);
2400 rcu_read_unlock();
2401 continue;
2402 }
2403
2404 /* remove un from the linked lists */
2405 ipc_assert_locked_object(&sma->sem_perm);
2406 list_del(&un->list_id);
2407
2408 spin_lock(&ulp->lock);
2409 list_del_rcu(&un->list_proc);
2410 spin_unlock(&ulp->lock);
2411
2412 /* perform adjustments registered in un */
2413 for (i = 0; i < sma->sem_nsems; i++) {
2414 struct sem *semaphore = &sma->sems[i];
2415 if (un->semadj[i]) {
2416 semaphore->semval += un->semadj[i];
2417 /*
2418 * Range checks of the new semaphore value,
2419 * not defined by sus:
2420 * - Some unices ignore the undo entirely
2421 * (e.g. HP UX 11i 11.22, Tru64 V5.1)
2422 * - some cap the value (e.g. FreeBSD caps
2423 * at 0, but doesn't enforce SEMVMX)
2424 *
2425 * Linux caps the semaphore value, both at 0
2426 * and at SEMVMX.
2427 *
2428 * Manfred <manfred@colorfullife.com>
2429 */
2430 if (semaphore->semval < 0)
2431 semaphore->semval = 0;
2432 if (semaphore->semval > SEMVMX)
2433 semaphore->semval = SEMVMX;
2434 ipc_update_pid(&semaphore->sempid, task_tgid(current));
2435 }
2436 }
2437 /* maybe some queued-up processes were waiting for this */
2438 do_smart_update(sma, NULL, 0, 1, &wake_q);
2439 sem_unlock(sma, -1);
2440 rcu_read_unlock();
2441 wake_up_q(&wake_q);
2442
2443 kvfree_rcu(un, rcu);
2444 }
2445 kfree(ulp);
2446}
2447
2448#ifdef CONFIG_PROC_FS
2449static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2450{
2451 struct user_namespace *user_ns = seq_user_ns(s);
2452 struct kern_ipc_perm *ipcp = it;
2453 struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
2454 time64_t sem_otime;
2455
2456 /*
2457 * The proc interface isn't aware of sem_lock(), it calls
2458 * ipc_lock_object(), i.e. spin_lock(&sma->sem_perm.lock).
2459 * (in sysvipc_find_ipc)
2460 * In order to stay compatible with sem_lock(), we must
2461 * enter / leave complex_mode.
2462 */
2463 complexmode_enter(sma);
2464
2465 sem_otime = get_semotime(sma);
2466
2467 seq_printf(s,
2468 "%10d %10d %4o %10u %5u %5u %5u %5u %10llu %10llu\n",
2469 sma->sem_perm.key,
2470 sma->sem_perm.id,
2471 sma->sem_perm.mode,
2472 sma->sem_nsems,
2473 from_kuid_munged(user_ns, sma->sem_perm.uid),
2474 from_kgid_munged(user_ns, sma->sem_perm.gid),
2475 from_kuid_munged(user_ns, sma->sem_perm.cuid),
2476 from_kgid_munged(user_ns, sma->sem_perm.cgid),
2477 sem_otime,
2478 sma->sem_ctime);
2479
2480 complexmode_tryleave(sma);
2481
2482 return 0;
2483}
2484#endif