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 runtine 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 * The special case is use_global_lock:
 209 * Setting it from non-zero to 0 is a RELEASE, this is ensured by
 210 * using smp_store_release().
 211 * Testing if it is non-zero is an ACQUIRE, this is ensured by using
 212 * smp_load_acquire().
 213 * Setting it from 0 to non-zero must be ordered with regards to
 214 * this smp_load_acquire(), this is guaranteed because the smp_load_acquire()
 215 * is inside a spin_lock() and after a write from 0 to non-zero a
 216 * spin_lock()+spin_unlock() is done.
 217 */
 218
 219#define sc_semmsl	sem_ctls[0]
 220#define sc_semmns	sem_ctls[1]
 221#define sc_semopm	sem_ctls[2]
 222#define sc_semmni	sem_ctls[3]
 223
 224void sem_init_ns(struct ipc_namespace *ns)
 225{
 226	ns->sc_semmsl = SEMMSL;
 227	ns->sc_semmns = SEMMNS;
 228	ns->sc_semopm = SEMOPM;
 229	ns->sc_semmni = SEMMNI;
 230	ns->used_sems = 0;
 231	ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
 232}
 233
 234#ifdef CONFIG_IPC_NS
 235void sem_exit_ns(struct ipc_namespace *ns)
 236{
 237	free_ipcs(ns, &sem_ids(ns), freeary);
 238	idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
 239	rhashtable_destroy(&ns->ids[IPC_SEM_IDS].key_ht);
 240}
 241#endif
 242
 243void __init sem_init(void)
 244{
 245	sem_init_ns(&init_ipc_ns);
 
 246	ipc_init_proc_interface("sysvipc/sem",
 247				"       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
 248				IPC_SEM_IDS, sysvipc_sem_proc_show);
 
 249}
 250
 251/**
 252 * unmerge_queues - unmerge queues, if possible.
 253 * @sma: semaphore array
 254 *
 255 * The function unmerges the wait queues if complex_count is 0.
 256 * It must be called prior to dropping the global semaphore array lock.
 257 */
 258static void unmerge_queues(struct sem_array *sma)
 259{
 260	struct sem_queue *q, *tq;
 261
 262	/* complex operations still around? */
 263	if (sma->complex_count)
 264		return;
 265	/*
 266	 * We will switch back to simple mode.
 267	 * Move all pending operation back into the per-semaphore
 268	 * queues.
 269	 */
 270	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
 271		struct sem *curr;
 272		curr = &sma->sems[q->sops[0].sem_num];
 273
 274		list_add_tail(&q->list, &curr->pending_alter);
 275	}
 276	INIT_LIST_HEAD(&sma->pending_alter);
 277}
 278
 279/**
 280 * merge_queues - merge single semop queues into global queue
 281 * @sma: semaphore array
 282 *
 283 * This function merges all per-semaphore queues into the global queue.
 284 * It is necessary to achieve FIFO ordering for the pending single-sop
 285 * operations when a multi-semop operation must sleep.
 286 * Only the alter operations must be moved, the const operations can stay.
 287 */
 288static void merge_queues(struct sem_array *sma)
 289{
 290	int i;
 291	for (i = 0; i < sma->sem_nsems; i++) {
 292		struct sem *sem = &sma->sems[i];
 293
 294		list_splice_init(&sem->pending_alter, &sma->pending_alter);
 295	}
 296}
 297
 298static void sem_rcu_free(struct rcu_head *head)
 299{
 300	struct kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu);
 301	struct sem_array *sma = container_of(p, struct sem_array, sem_perm);
 302
 303	security_sem_free(&sma->sem_perm);
 304	kvfree(sma);
 305}
 306
 307/*
 308 * Enter the mode suitable for non-simple operations:
 309 * Caller must own sem_perm.lock.
 310 */
 311static void complexmode_enter(struct sem_array *sma)
 312{
 313	int i;
 314	struct sem *sem;
 315
 316	if (sma->use_global_lock > 0)  {
 317		/*
 318		 * We are already in global lock mode.
 319		 * Nothing to do, just reset the
 320		 * counter until we return to simple mode.
 321		 */
 322		sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
 323		return;
 324	}
 325	sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
 326
 327	for (i = 0; i < sma->sem_nsems; i++) {
 328		sem = &sma->sems[i];
 329		spin_lock(&sem->lock);
 330		spin_unlock(&sem->lock);
 331	}
 332}
 333
 334/*
 335 * Try to leave the mode that disallows simple operations:
 336 * Caller must own sem_perm.lock.
 337 */
 338static void complexmode_tryleave(struct sem_array *sma)
 339{
 340	if (sma->complex_count)  {
 341		/* Complex ops are sleeping.
 342		 * We must stay in complex mode
 343		 */
 344		return;
 345	}
 346	if (sma->use_global_lock == 1) {
 347		/*
 348		 * Immediately after setting use_global_lock to 0,
 349		 * a simple op can start. Thus: all memory writes
 350		 * performed by the current operation must be visible
 351		 * before we set use_global_lock to 0.
 352		 */
 353		smp_store_release(&sma->use_global_lock, 0);
 354	} else {
 355		sma->use_global_lock--;
 356	}
 357}
 358
 359#define SEM_GLOBAL_LOCK	(-1)
 360/*
 361 * If the request contains only one semaphore operation, and there are
 362 * no complex transactions pending, lock only the semaphore involved.
 363 * Otherwise, lock the entire semaphore array, since we either have
 364 * multiple semaphores in our own semops, or we need to look at
 365 * semaphores from other pending complex operations.
 366 */
 367static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
 368			      int nsops)
 369{
 370	struct sem *sem;
 371	int idx;
 372
 373	if (nsops != 1) {
 374		/* Complex operation - acquire a full lock */
 375		ipc_lock_object(&sma->sem_perm);
 376
 377		/* Prevent parallel simple ops */
 378		complexmode_enter(sma);
 379		return SEM_GLOBAL_LOCK;
 380	}
 381
 382	/*
 383	 * Only one semaphore affected - try to optimize locking.
 384	 * Optimized locking is possible if no complex operation
 385	 * is either enqueued or processed right now.
 386	 *
 387	 * Both facts are tracked by use_global_mode.
 388	 */
 389	idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
 390	sem = &sma->sems[idx];
 391
 392	/*
 393	 * Initial check for use_global_lock. Just an optimization,
 394	 * no locking, no memory barrier.
 395	 */
 396	if (!sma->use_global_lock) {
 397		/*
 398		 * It appears that no complex operation is around.
 399		 * Acquire the per-semaphore lock.
 400		 */
 401		spin_lock(&sem->lock);
 402
 403		/* pairs with smp_store_release() */
 404		if (!smp_load_acquire(&sma->use_global_lock)) {
 405			/* fast path successful! */
 406			return sops->sem_num;
 407		}
 408		spin_unlock(&sem->lock);
 409	}
 410
 411	/* slow path: acquire the full lock */
 412	ipc_lock_object(&sma->sem_perm);
 413
 414	if (sma->use_global_lock == 0) {
 415		/*
 416		 * The use_global_lock mode ended while we waited for
 417		 * sma->sem_perm.lock. Thus we must switch to locking
 418		 * with sem->lock.
 419		 * Unlike in the fast path, there is no need to recheck
 420		 * sma->use_global_lock after we have acquired sem->lock:
 421		 * We own sma->sem_perm.lock, thus use_global_lock cannot
 422		 * change.
 423		 */
 424		spin_lock(&sem->lock);
 425
 426		ipc_unlock_object(&sma->sem_perm);
 427		return sops->sem_num;
 428	} else {
 429		/*
 430		 * Not a false alarm, thus continue to use the global lock
 431		 * mode. No need for complexmode_enter(), this was done by
 432		 * the caller that has set use_global_mode to non-zero.
 433		 */
 434		return SEM_GLOBAL_LOCK;
 435	}
 436}
 437
 438static inline void sem_unlock(struct sem_array *sma, int locknum)
 439{
 440	if (locknum == SEM_GLOBAL_LOCK) {
 441		unmerge_queues(sma);
 442		complexmode_tryleave(sma);
 443		ipc_unlock_object(&sma->sem_perm);
 444	} else {
 445		struct sem *sem = &sma->sems[locknum];
 446		spin_unlock(&sem->lock);
 447	}
 448}
 449
 450/*
 451 * sem_lock_(check_) routines are called in the paths where the rwsem
 452 * is not held.
 453 *
 454 * The caller holds the RCU read lock.
 455 */
 456static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
 457{
 458	struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id);
 459
 460	if (IS_ERR(ipcp))
 461		return ERR_CAST(ipcp);
 462
 463	return container_of(ipcp, struct sem_array, sem_perm);
 464}
 465
 466static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
 467							int id)
 468{
 469	struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
 470
 471	if (IS_ERR(ipcp))
 472		return ERR_CAST(ipcp);
 473
 474	return container_of(ipcp, struct sem_array, sem_perm);
 475}
 476
 477static inline void sem_lock_and_putref(struct sem_array *sma)
 478{
 479	sem_lock(sma, NULL, -1);
 480	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
 481}
 482
 483static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
 484{
 485	ipc_rmid(&sem_ids(ns), &s->sem_perm);
 486}
 487
 488static struct sem_array *sem_alloc(size_t nsems)
 489{
 490	struct sem_array *sma;
 
 491
 492	if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0]))
 493		return NULL;
 494
 495	sma = kvzalloc(struct_size(sma, sems, nsems), GFP_KERNEL);
 
 496	if (unlikely(!sma))
 497		return NULL;
 498
 
 
 499	return sma;
 500}
 501
 502/**
 503 * newary - Create a new semaphore set
 504 * @ns: namespace
 505 * @params: ptr to the structure that contains key, semflg and nsems
 506 *
 507 * Called with sem_ids.rwsem held (as a writer)
 508 */
 509static int newary(struct ipc_namespace *ns, struct ipc_params *params)
 510{
 511	int retval;
 512	struct sem_array *sma;
 513	key_t key = params->key;
 514	int nsems = params->u.nsems;
 515	int semflg = params->flg;
 516	int i;
 517
 518	if (!nsems)
 519		return -EINVAL;
 520	if (ns->used_sems + nsems > ns->sc_semmns)
 521		return -ENOSPC;
 522
 523	sma = sem_alloc(nsems);
 524	if (!sma)
 525		return -ENOMEM;
 526
 527	sma->sem_perm.mode = (semflg & S_IRWXUGO);
 528	sma->sem_perm.key = key;
 529
 530	sma->sem_perm.security = NULL;
 531	retval = security_sem_alloc(&sma->sem_perm);
 532	if (retval) {
 533		kvfree(sma);
 534		return retval;
 535	}
 536
 537	for (i = 0; i < nsems; i++) {
 538		INIT_LIST_HEAD(&sma->sems[i].pending_alter);
 539		INIT_LIST_HEAD(&sma->sems[i].pending_const);
 540		spin_lock_init(&sma->sems[i].lock);
 541	}
 542
 543	sma->complex_count = 0;
 544	sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
 545	INIT_LIST_HEAD(&sma->pending_alter);
 546	INIT_LIST_HEAD(&sma->pending_const);
 547	INIT_LIST_HEAD(&sma->list_id);
 548	sma->sem_nsems = nsems;
 549	sma->sem_ctime = ktime_get_real_seconds();
 550
 551	/* ipc_addid() locks sma upon success. */
 552	retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
 553	if (retval < 0) {
 554		ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
 555		return retval;
 556	}
 557	ns->used_sems += nsems;
 558
 559	sem_unlock(sma, -1);
 560	rcu_read_unlock();
 561
 562	return sma->sem_perm.id;
 563}
 564
 565
 566/*
 567 * Called with sem_ids.rwsem and ipcp locked.
 568 */
 569static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
 570				struct ipc_params *params)
 571{
 572	struct sem_array *sma;
 573
 574	sma = container_of(ipcp, struct sem_array, sem_perm);
 575	if (params->u.nsems > sma->sem_nsems)
 576		return -EINVAL;
 577
 578	return 0;
 579}
 580
 581long ksys_semget(key_t key, int nsems, int semflg)
 582{
 583	struct ipc_namespace *ns;
 584	static const struct ipc_ops sem_ops = {
 585		.getnew = newary,
 586		.associate = security_sem_associate,
 587		.more_checks = sem_more_checks,
 588	};
 589	struct ipc_params sem_params;
 590
 591	ns = current->nsproxy->ipc_ns;
 592
 593	if (nsems < 0 || nsems > ns->sc_semmsl)
 594		return -EINVAL;
 595
 596	sem_params.key = key;
 597	sem_params.flg = semflg;
 598	sem_params.u.nsems = nsems;
 599
 600	return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
 601}
 602
 603SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
 604{
 605	return ksys_semget(key, nsems, semflg);
 606}
 607
 608/**
 609 * perform_atomic_semop[_slow] - Attempt to perform semaphore
 610 *                               operations on a given array.
 611 * @sma: semaphore array
 612 * @q: struct sem_queue that describes the operation
 613 *
 614 * Caller blocking are as follows, based the value
 615 * indicated by the semaphore operation (sem_op):
 616 *
 617 *  (1) >0 never blocks.
 618 *  (2)  0 (wait-for-zero operation): semval is non-zero.
 619 *  (3) <0 attempting to decrement semval to a value smaller than zero.
 620 *
 621 * Returns 0 if the operation was possible.
 622 * Returns 1 if the operation is impossible, the caller must sleep.
 623 * Returns <0 for error codes.
 624 */
 625static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q)
 626{
 627	int result, sem_op, nsops;
 628	struct pid *pid;
 629	struct sembuf *sop;
 630	struct sem *curr;
 631	struct sembuf *sops;
 632	struct sem_undo *un;
 633
 634	sops = q->sops;
 635	nsops = q->nsops;
 636	un = q->undo;
 637
 638	for (sop = sops; sop < sops + nsops; sop++) {
 639		int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
 640		curr = &sma->sems[idx];
 641		sem_op = sop->sem_op;
 642		result = curr->semval;
 643
 644		if (!sem_op && result)
 645			goto would_block;
 646
 647		result += sem_op;
 648		if (result < 0)
 649			goto would_block;
 650		if (result > SEMVMX)
 651			goto out_of_range;
 652
 653		if (sop->sem_flg & SEM_UNDO) {
 654			int undo = un->semadj[sop->sem_num] - sem_op;
 655			/* Exceeding the undo range is an error. */
 656			if (undo < (-SEMAEM - 1) || undo > SEMAEM)
 657				goto out_of_range;
 658			un->semadj[sop->sem_num] = undo;
 659		}
 660
 661		curr->semval = result;
 662	}
 663
 664	sop--;
 665	pid = q->pid;
 666	while (sop >= sops) {
 667		ipc_update_pid(&sma->sems[sop->sem_num].sempid, pid);
 668		sop--;
 669	}
 670
 671	return 0;
 672
 673out_of_range:
 674	result = -ERANGE;
 675	goto undo;
 676
 677would_block:
 678	q->blocking = sop;
 679
 680	if (sop->sem_flg & IPC_NOWAIT)
 681		result = -EAGAIN;
 682	else
 683		result = 1;
 684
 685undo:
 686	sop--;
 687	while (sop >= sops) {
 688		sem_op = sop->sem_op;
 689		sma->sems[sop->sem_num].semval -= sem_op;
 690		if (sop->sem_flg & SEM_UNDO)
 691			un->semadj[sop->sem_num] += sem_op;
 692		sop--;
 693	}
 694
 695	return result;
 696}
 697
 698static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
 699{
 700	int result, sem_op, nsops;
 701	struct sembuf *sop;
 702	struct sem *curr;
 703	struct sembuf *sops;
 704	struct sem_undo *un;
 705
 706	sops = q->sops;
 707	nsops = q->nsops;
 708	un = q->undo;
 709
 710	if (unlikely(q->dupsop))
 711		return perform_atomic_semop_slow(sma, q);
 712
 713	/*
 714	 * We scan the semaphore set twice, first to ensure that the entire
 715	 * operation can succeed, therefore avoiding any pointless writes
 716	 * to shared memory and having to undo such changes in order to block
 717	 * until the operations can go through.
 718	 */
 719	for (sop = sops; sop < sops + nsops; sop++) {
 720		int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
 721
 722		curr = &sma->sems[idx];
 723		sem_op = sop->sem_op;
 724		result = curr->semval;
 725
 726		if (!sem_op && result)
 727			goto would_block; /* wait-for-zero */
 728
 729		result += sem_op;
 730		if (result < 0)
 731			goto would_block;
 732
 733		if (result > SEMVMX)
 734			return -ERANGE;
 735
 736		if (sop->sem_flg & SEM_UNDO) {
 737			int undo = un->semadj[sop->sem_num] - sem_op;
 738
 739			/* Exceeding the undo range is an error. */
 740			if (undo < (-SEMAEM - 1) || undo > SEMAEM)
 741				return -ERANGE;
 742		}
 743	}
 744
 745	for (sop = sops; sop < sops + nsops; sop++) {
 746		curr = &sma->sems[sop->sem_num];
 747		sem_op = sop->sem_op;
 748		result = curr->semval;
 749
 750		if (sop->sem_flg & SEM_UNDO) {
 751			int undo = un->semadj[sop->sem_num] - sem_op;
 752
 753			un->semadj[sop->sem_num] = undo;
 754		}
 755		curr->semval += sem_op;
 756		ipc_update_pid(&curr->sempid, q->pid);
 757	}
 758
 759	return 0;
 760
 761would_block:
 762	q->blocking = sop;
 763	return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1;
 764}
 765
 766static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error,
 767					     struct wake_q_head *wake_q)
 768{
 769	wake_q_add(wake_q, q->sleeper);
 770	/*
 771	 * Rely on the above implicit barrier, such that we can
 772	 * ensure that we hold reference to the task before setting
 773	 * q->status. Otherwise we could race with do_exit if the
 774	 * task is awoken by an external event before calling
 775	 * wake_up_process().
 776	 */
 777	WRITE_ONCE(q->status, error);
 778}
 779
 780static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
 781{
 782	list_del(&q->list);
 783	if (q->nsops > 1)
 784		sma->complex_count--;
 785}
 786
 787/** check_restart(sma, q)
 788 * @sma: semaphore array
 789 * @q: the operation that just completed
 790 *
 791 * update_queue is O(N^2) when it restarts scanning the whole queue of
 792 * waiting operations. Therefore this function checks if the restart is
 793 * really necessary. It is called after a previously waiting operation
 794 * modified the array.
 795 * Note that wait-for-zero operations are handled without restart.
 796 */
 797static inline int check_restart(struct sem_array *sma, struct sem_queue *q)
 798{
 799	/* pending complex alter operations are too difficult to analyse */
 800	if (!list_empty(&sma->pending_alter))
 801		return 1;
 802
 803	/* we were a sleeping complex operation. Too difficult */
 804	if (q->nsops > 1)
 805		return 1;
 806
 807	/* It is impossible that someone waits for the new value:
 808	 * - complex operations always restart.
 809	 * - wait-for-zero are handled seperately.
 810	 * - q is a previously sleeping simple operation that
 811	 *   altered the array. It must be a decrement, because
 812	 *   simple increments never sleep.
 813	 * - If there are older (higher priority) decrements
 814	 *   in the queue, then they have observed the original
 815	 *   semval value and couldn't proceed. The operation
 816	 *   decremented to value - thus they won't proceed either.
 817	 */
 818	return 0;
 819}
 820
 821/**
 822 * wake_const_ops - wake up non-alter tasks
 823 * @sma: semaphore array.
 824 * @semnum: semaphore that was modified.
 825 * @wake_q: lockless wake-queue head.
 826 *
 827 * wake_const_ops must be called after a semaphore in a semaphore array
 828 * was set to 0. If complex const operations are pending, wake_const_ops must
 829 * be called with semnum = -1, as well as with the number of each modified
 830 * semaphore.
 831 * The tasks that must be woken up are added to @wake_q. The return code
 832 * is stored in q->pid.
 833 * The function returns 1 if at least one operation was completed successfully.
 834 */
 835static int wake_const_ops(struct sem_array *sma, int semnum,
 836			  struct wake_q_head *wake_q)
 837{
 838	struct sem_queue *q, *tmp;
 839	struct list_head *pending_list;
 840	int semop_completed = 0;
 841
 842	if (semnum == -1)
 843		pending_list = &sma->pending_const;
 844	else
 845		pending_list = &sma->sems[semnum].pending_const;
 846
 847	list_for_each_entry_safe(q, tmp, pending_list, list) {
 848		int error = perform_atomic_semop(sma, q);
 849
 850		if (error > 0)
 851			continue;
 852		/* operation completed, remove from queue & wakeup */
 853		unlink_queue(sma, q);
 854
 855		wake_up_sem_queue_prepare(q, error, wake_q);
 856		if (error == 0)
 857			semop_completed = 1;
 858	}
 859
 860	return semop_completed;
 861}
 862
 863/**
 864 * do_smart_wakeup_zero - wakeup all wait for zero tasks
 865 * @sma: semaphore array
 866 * @sops: operations that were performed
 867 * @nsops: number of operations
 868 * @wake_q: lockless wake-queue head
 869 *
 870 * Checks all required queue for wait-for-zero operations, based
 871 * on the actual changes that were performed on the semaphore array.
 872 * The function returns 1 if at least one operation was completed successfully.
 873 */
 874static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
 875				int nsops, struct wake_q_head *wake_q)
 876{
 877	int i;
 878	int semop_completed = 0;
 879	int got_zero = 0;
 880
 881	/* first: the per-semaphore queues, if known */
 882	if (sops) {
 883		for (i = 0; i < nsops; i++) {
 884			int num = sops[i].sem_num;
 885
 886			if (sma->sems[num].semval == 0) {
 887				got_zero = 1;
 888				semop_completed |= wake_const_ops(sma, num, wake_q);
 889			}
 890		}
 891	} else {
 892		/*
 893		 * No sops means modified semaphores not known.
 894		 * Assume all were changed.
 895		 */
 896		for (i = 0; i < sma->sem_nsems; i++) {
 897			if (sma->sems[i].semval == 0) {
 898				got_zero = 1;
 899				semop_completed |= wake_const_ops(sma, i, wake_q);
 900			}
 901		}
 902	}
 903	/*
 904	 * If one of the modified semaphores got 0,
 905	 * then check the global queue, too.
 906	 */
 907	if (got_zero)
 908		semop_completed |= wake_const_ops(sma, -1, wake_q);
 909
 910	return semop_completed;
 911}
 912
 913
 914/**
 915 * update_queue - look for tasks that can be completed.
 916 * @sma: semaphore array.
 917 * @semnum: semaphore that was modified.
 918 * @wake_q: lockless wake-queue head.
 919 *
 920 * update_queue must be called after a semaphore in a semaphore array
 921 * was modified. If multiple semaphores were modified, update_queue must
 922 * be called with semnum = -1, as well as with the number of each modified
 923 * semaphore.
 924 * The tasks that must be woken up are added to @wake_q. The return code
 925 * is stored in q->pid.
 926 * The function internally checks if const operations can now succeed.
 927 *
 928 * The function return 1 if at least one semop was completed successfully.
 929 */
 930static int update_queue(struct sem_array *sma, int semnum, struct wake_q_head *wake_q)
 931{
 932	struct sem_queue *q, *tmp;
 933	struct list_head *pending_list;
 934	int semop_completed = 0;
 935
 936	if (semnum == -1)
 937		pending_list = &sma->pending_alter;
 938	else
 939		pending_list = &sma->sems[semnum].pending_alter;
 940
 941again:
 942	list_for_each_entry_safe(q, tmp, pending_list, list) {
 943		int error, restart;
 944
 945		/* If we are scanning the single sop, per-semaphore list of
 946		 * one semaphore and that semaphore is 0, then it is not
 947		 * necessary to scan further: simple increments
 948		 * that affect only one entry succeed immediately and cannot
 949		 * be in the  per semaphore pending queue, and decrements
 950		 * cannot be successful if the value is already 0.
 951		 */
 952		if (semnum != -1 && sma->sems[semnum].semval == 0)
 953			break;
 954
 955		error = perform_atomic_semop(sma, q);
 956
 957		/* Does q->sleeper still need to sleep? */
 958		if (error > 0)
 959			continue;
 960
 961		unlink_queue(sma, q);
 962
 963		if (error) {
 964			restart = 0;
 965		} else {
 966			semop_completed = 1;
 967			do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q);
 968			restart = check_restart(sma, q);
 969		}
 970
 971		wake_up_sem_queue_prepare(q, error, wake_q);
 972		if (restart)
 973			goto again;
 974	}
 975	return semop_completed;
 976}
 977
 978/**
 979 * set_semotime - set sem_otime
 980 * @sma: semaphore array
 981 * @sops: operations that modified the array, may be NULL
 982 *
 983 * sem_otime is replicated to avoid cache line trashing.
 984 * This function sets one instance to the current time.
 985 */
 986static void set_semotime(struct sem_array *sma, struct sembuf *sops)
 987{
 988	if (sops == NULL) {
 989		sma->sems[0].sem_otime = ktime_get_real_seconds();
 990	} else {
 991		sma->sems[sops[0].sem_num].sem_otime =
 992						ktime_get_real_seconds();
 993	}
 994}
 995
 996/**
 997 * do_smart_update - optimized update_queue
 998 * @sma: semaphore array
 999 * @sops: operations that were performed
1000 * @nsops: number of operations
1001 * @otime: force setting otime
1002 * @wake_q: lockless wake-queue head
1003 *
1004 * do_smart_update() does the required calls to update_queue and wakeup_zero,
1005 * based on the actual changes that were performed on the semaphore array.
1006 * Note that the function does not do the actual wake-up: the caller is
1007 * responsible for calling wake_up_q().
1008 * It is safe to perform this call after dropping all locks.
1009 */
1010static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
1011			    int otime, struct wake_q_head *wake_q)
1012{
1013	int i;
1014
1015	otime |= do_smart_wakeup_zero(sma, sops, nsops, wake_q);
1016
1017	if (!list_empty(&sma->pending_alter)) {
1018		/* semaphore array uses the global queue - just process it. */
1019		otime |= update_queue(sma, -1, wake_q);
1020	} else {
1021		if (!sops) {
1022			/*
1023			 * No sops, thus the modified semaphores are not
1024			 * known. Check all.
1025			 */
1026			for (i = 0; i < sma->sem_nsems; i++)
1027				otime |= update_queue(sma, i, wake_q);
1028		} else {
1029			/*
1030			 * Check the semaphores that were increased:
1031			 * - No complex ops, thus all sleeping ops are
1032			 *   decrease.
1033			 * - if we decreased the value, then any sleeping
1034			 *   semaphore ops wont be able to run: If the
1035			 *   previous value was too small, then the new
1036			 *   value will be too small, too.
1037			 */
1038			for (i = 0; i < nsops; i++) {
1039				if (sops[i].sem_op > 0) {
1040					otime |= update_queue(sma,
1041							      sops[i].sem_num, wake_q);
1042				}
1043			}
1044		}
1045	}
1046	if (otime)
1047		set_semotime(sma, sops);
1048}
1049
1050/*
1051 * check_qop: Test if a queued operation sleeps on the semaphore semnum
1052 */
1053static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
1054			bool count_zero)
1055{
1056	struct sembuf *sop = q->blocking;
1057
1058	/*
1059	 * Linux always (since 0.99.10) reported a task as sleeping on all
1060	 * semaphores. This violates SUS, therefore it was changed to the
1061	 * standard compliant behavior.
1062	 * Give the administrators a chance to notice that an application
1063	 * might misbehave because it relies on the Linux behavior.
1064	 */
1065	pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
1066			"The task %s (%d) triggered the difference, watch for misbehavior.\n",
1067			current->comm, task_pid_nr(current));
1068
1069	if (sop->sem_num != semnum)
1070		return 0;
1071
1072	if (count_zero && sop->sem_op == 0)
1073		return 1;
1074	if (!count_zero && sop->sem_op < 0)
1075		return 1;
1076
1077	return 0;
1078}
1079
1080/* The following counts are associated to each semaphore:
1081 *   semncnt        number of tasks waiting on semval being nonzero
1082 *   semzcnt        number of tasks waiting on semval being zero
1083 *
1084 * Per definition, a task waits only on the semaphore of the first semop
1085 * that cannot proceed, even if additional operation would block, too.
1086 */
1087static int count_semcnt(struct sem_array *sma, ushort semnum,
1088			bool count_zero)
1089{
1090	struct list_head *l;
1091	struct sem_queue *q;
1092	int semcnt;
1093
1094	semcnt = 0;
1095	/* First: check the simple operations. They are easy to evaluate */
1096	if (count_zero)
1097		l = &sma->sems[semnum].pending_const;
1098	else
1099		l = &sma->sems[semnum].pending_alter;
1100
1101	list_for_each_entry(q, l, list) {
1102		/* all task on a per-semaphore list sleep on exactly
1103		 * that semaphore
1104		 */
1105		semcnt++;
1106	}
1107
1108	/* Then: check the complex operations. */
1109	list_for_each_entry(q, &sma->pending_alter, list) {
1110		semcnt += check_qop(sma, semnum, q, count_zero);
1111	}
1112	if (count_zero) {
1113		list_for_each_entry(q, &sma->pending_const, list) {
1114			semcnt += check_qop(sma, semnum, q, count_zero);
1115		}
1116	}
1117	return semcnt;
1118}
1119
1120/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1121 * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1122 * remains locked on exit.
1123 */
1124static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
1125{
1126	struct sem_undo *un, *tu;
1127	struct sem_queue *q, *tq;
1128	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1129	int i;
1130	DEFINE_WAKE_Q(wake_q);
1131
1132	/* Free the existing undo structures for this semaphore set.  */
1133	ipc_assert_locked_object(&sma->sem_perm);
1134	list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1135		list_del(&un->list_id);
1136		spin_lock(&un->ulp->lock);
1137		un->semid = -1;
1138		list_del_rcu(&un->list_proc);
1139		spin_unlock(&un->ulp->lock);
1140		kfree_rcu(un, rcu);
1141	}
1142
1143	/* Wake up all pending processes and let them fail with EIDRM. */
1144	list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1145		unlink_queue(sma, q);
1146		wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1147	}
1148
1149	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1150		unlink_queue(sma, q);
1151		wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1152	}
1153	for (i = 0; i < sma->sem_nsems; i++) {
1154		struct sem *sem = &sma->sems[i];
1155		list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1156			unlink_queue(sma, q);
1157			wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1158		}
1159		list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1160			unlink_queue(sma, q);
1161			wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1162		}
1163		ipc_update_pid(&sem->sempid, NULL);
1164	}
1165
1166	/* Remove the semaphore set from the IDR */
1167	sem_rmid(ns, sma);
1168	sem_unlock(sma, -1);
1169	rcu_read_unlock();
1170
1171	wake_up_q(&wake_q);
1172	ns->used_sems -= sma->sem_nsems;
1173	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1174}
1175
1176static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1177{
1178	switch (version) {
1179	case IPC_64:
1180		return copy_to_user(buf, in, sizeof(*in));
1181	case IPC_OLD:
1182	    {
1183		struct semid_ds out;
1184
1185		memset(&out, 0, sizeof(out));
1186
1187		ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1188
1189		out.sem_otime	= in->sem_otime;
1190		out.sem_ctime	= in->sem_ctime;
1191		out.sem_nsems	= in->sem_nsems;
1192
1193		return copy_to_user(buf, &out, sizeof(out));
1194	    }
1195	default:
1196		return -EINVAL;
1197	}
1198}
1199
1200static time64_t get_semotime(struct sem_array *sma)
1201{
1202	int i;
1203	time64_t res;
1204
1205	res = sma->sems[0].sem_otime;
1206	for (i = 1; i < sma->sem_nsems; i++) {
1207		time64_t to = sma->sems[i].sem_otime;
1208
1209		if (to > res)
1210			res = to;
1211	}
1212	return res;
1213}
1214
1215static int semctl_stat(struct ipc_namespace *ns, int semid,
1216			 int cmd, struct semid64_ds *semid64)
1217{
1218	struct sem_array *sma;
1219	time64_t semotime;
1220	int err;
1221
1222	memset(semid64, 0, sizeof(*semid64));
1223
1224	rcu_read_lock();
1225	if (cmd == SEM_STAT || cmd == SEM_STAT_ANY) {
1226		sma = sem_obtain_object(ns, semid);
1227		if (IS_ERR(sma)) {
1228			err = PTR_ERR(sma);
1229			goto out_unlock;
1230		}
 
1231	} else { /* IPC_STAT */
1232		sma = sem_obtain_object_check(ns, semid);
1233		if (IS_ERR(sma)) {
1234			err = PTR_ERR(sma);
1235			goto out_unlock;
1236		}
1237	}
1238
1239	/* see comment for SHM_STAT_ANY */
1240	if (cmd == SEM_STAT_ANY)
1241		audit_ipc_obj(&sma->sem_perm);
1242	else {
1243		err = -EACCES;
1244		if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1245			goto out_unlock;
1246	}
1247
1248	err = security_sem_semctl(&sma->sem_perm, cmd);
1249	if (err)
1250		goto out_unlock;
1251
1252	ipc_lock_object(&sma->sem_perm);
1253
1254	if (!ipc_valid_object(&sma->sem_perm)) {
1255		ipc_unlock_object(&sma->sem_perm);
1256		err = -EIDRM;
1257		goto out_unlock;
1258	}
1259
1260	kernel_to_ipc64_perm(&sma->sem_perm, &semid64->sem_perm);
1261	semotime = get_semotime(sma);
1262	semid64->sem_otime = semotime;
1263	semid64->sem_ctime = sma->sem_ctime;
1264#ifndef CONFIG_64BIT
1265	semid64->sem_otime_high = semotime >> 32;
1266	semid64->sem_ctime_high = sma->sem_ctime >> 32;
1267#endif
1268	semid64->sem_nsems = sma->sem_nsems;
1269
1270	if (cmd == IPC_STAT) {
1271		/*
1272		 * As defined in SUS:
1273		 * Return 0 on success
1274		 */
1275		err = 0;
1276	} else {
1277		/*
1278		 * SEM_STAT and SEM_STAT_ANY (both Linux specific)
1279		 * Return the full id, including the sequence number
1280		 */
1281		err = sma->sem_perm.id;
1282	}
1283	ipc_unlock_object(&sma->sem_perm);
 
 
 
1284out_unlock:
1285	rcu_read_unlock();
1286	return err;
1287}
1288
1289static int semctl_info(struct ipc_namespace *ns, int semid,
1290			 int cmd, void __user *p)
1291{
1292	struct seminfo seminfo;
1293	int max_idx;
1294	int err;
1295
1296	err = security_sem_semctl(NULL, cmd);
1297	if (err)
1298		return err;
1299
1300	memset(&seminfo, 0, sizeof(seminfo));
1301	seminfo.semmni = ns->sc_semmni;
1302	seminfo.semmns = ns->sc_semmns;
1303	seminfo.semmsl = ns->sc_semmsl;
1304	seminfo.semopm = ns->sc_semopm;
1305	seminfo.semvmx = SEMVMX;
1306	seminfo.semmnu = SEMMNU;
1307	seminfo.semmap = SEMMAP;
1308	seminfo.semume = SEMUME;
1309	down_read(&sem_ids(ns).rwsem);
1310	if (cmd == SEM_INFO) {
1311		seminfo.semusz = sem_ids(ns).in_use;
1312		seminfo.semaem = ns->used_sems;
1313	} else {
1314		seminfo.semusz = SEMUSZ;
1315		seminfo.semaem = SEMAEM;
1316	}
1317	max_idx = ipc_get_maxidx(&sem_ids(ns));
1318	up_read(&sem_ids(ns).rwsem);
1319	if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1320		return -EFAULT;
1321	return (max_idx < 0) ? 0 : max_idx;
1322}
1323
1324static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1325		int val)
1326{
1327	struct sem_undo *un;
1328	struct sem_array *sma;
1329	struct sem *curr;
1330	int err;
1331	DEFINE_WAKE_Q(wake_q);
1332
1333	if (val > SEMVMX || val < 0)
1334		return -ERANGE;
1335
1336	rcu_read_lock();
1337	sma = sem_obtain_object_check(ns, semid);
1338	if (IS_ERR(sma)) {
1339		rcu_read_unlock();
1340		return PTR_ERR(sma);
1341	}
1342
1343	if (semnum < 0 || semnum >= sma->sem_nsems) {
1344		rcu_read_unlock();
1345		return -EINVAL;
1346	}
1347
1348
1349	if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1350		rcu_read_unlock();
1351		return -EACCES;
1352	}
1353
1354	err = security_sem_semctl(&sma->sem_perm, SETVAL);
1355	if (err) {
1356		rcu_read_unlock();
1357		return -EACCES;
1358	}
1359
1360	sem_lock(sma, NULL, -1);
1361
1362	if (!ipc_valid_object(&sma->sem_perm)) {
1363		sem_unlock(sma, -1);
1364		rcu_read_unlock();
1365		return -EIDRM;
1366	}
1367
1368	semnum = array_index_nospec(semnum, sma->sem_nsems);
1369	curr = &sma->sems[semnum];
1370
1371	ipc_assert_locked_object(&sma->sem_perm);
1372	list_for_each_entry(un, &sma->list_id, list_id)
1373		un->semadj[semnum] = 0;
1374
1375	curr->semval = val;
1376	ipc_update_pid(&curr->sempid, task_tgid(current));
1377	sma->sem_ctime = ktime_get_real_seconds();
1378	/* maybe some queued-up processes were waiting for this */
1379	do_smart_update(sma, NULL, 0, 0, &wake_q);
1380	sem_unlock(sma, -1);
1381	rcu_read_unlock();
1382	wake_up_q(&wake_q);
1383	return 0;
1384}
1385
1386static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1387		int cmd, void __user *p)
1388{
1389	struct sem_array *sma;
1390	struct sem *curr;
1391	int err, nsems;
1392	ushort fast_sem_io[SEMMSL_FAST];
1393	ushort *sem_io = fast_sem_io;
1394	DEFINE_WAKE_Q(wake_q);
1395
1396	rcu_read_lock();
1397	sma = sem_obtain_object_check(ns, semid);
1398	if (IS_ERR(sma)) {
1399		rcu_read_unlock();
1400		return PTR_ERR(sma);
1401	}
1402
1403	nsems = sma->sem_nsems;
1404
1405	err = -EACCES;
1406	if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1407		goto out_rcu_wakeup;
1408
1409	err = security_sem_semctl(&sma->sem_perm, cmd);
1410	if (err)
1411		goto out_rcu_wakeup;
1412
1413	err = -EACCES;
1414	switch (cmd) {
1415	case GETALL:
1416	{
1417		ushort __user *array = p;
1418		int i;
1419
1420		sem_lock(sma, NULL, -1);
1421		if (!ipc_valid_object(&sma->sem_perm)) {
1422			err = -EIDRM;
1423			goto out_unlock;
1424		}
1425		if (nsems > SEMMSL_FAST) {
1426			if (!ipc_rcu_getref(&sma->sem_perm)) {
1427				err = -EIDRM;
1428				goto out_unlock;
1429			}
1430			sem_unlock(sma, -1);
1431			rcu_read_unlock();
1432			sem_io = kvmalloc_array(nsems, sizeof(ushort),
1433						GFP_KERNEL);
1434			if (sem_io == NULL) {
1435				ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1436				return -ENOMEM;
1437			}
1438
1439			rcu_read_lock();
1440			sem_lock_and_putref(sma);
1441			if (!ipc_valid_object(&sma->sem_perm)) {
1442				err = -EIDRM;
1443				goto out_unlock;
1444			}
1445		}
1446		for (i = 0; i < sma->sem_nsems; i++)
1447			sem_io[i] = sma->sems[i].semval;
1448		sem_unlock(sma, -1);
1449		rcu_read_unlock();
1450		err = 0;
1451		if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1452			err = -EFAULT;
1453		goto out_free;
1454	}
1455	case SETALL:
1456	{
1457		int i;
1458		struct sem_undo *un;
1459
1460		if (!ipc_rcu_getref(&sma->sem_perm)) {
1461			err = -EIDRM;
1462			goto out_rcu_wakeup;
1463		}
1464		rcu_read_unlock();
1465
1466		if (nsems > SEMMSL_FAST) {
1467			sem_io = kvmalloc_array(nsems, sizeof(ushort),
1468						GFP_KERNEL);
1469			if (sem_io == NULL) {
1470				ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1471				return -ENOMEM;
1472			}
1473		}
1474
1475		if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
1476			ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1477			err = -EFAULT;
1478			goto out_free;
1479		}
1480
1481		for (i = 0; i < nsems; i++) {
1482			if (sem_io[i] > SEMVMX) {
1483				ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1484				err = -ERANGE;
1485				goto out_free;
1486			}
1487		}
1488		rcu_read_lock();
1489		sem_lock_and_putref(sma);
1490		if (!ipc_valid_object(&sma->sem_perm)) {
1491			err = -EIDRM;
1492			goto out_unlock;
1493		}
1494
1495		for (i = 0; i < nsems; i++) {
1496			sma->sems[i].semval = sem_io[i];
1497			ipc_update_pid(&sma->sems[i].sempid, task_tgid(current));
1498		}
1499
1500		ipc_assert_locked_object(&sma->sem_perm);
1501		list_for_each_entry(un, &sma->list_id, list_id) {
1502			for (i = 0; i < nsems; i++)
1503				un->semadj[i] = 0;
1504		}
1505		sma->sem_ctime = ktime_get_real_seconds();
1506		/* maybe some queued-up processes were waiting for this */
1507		do_smart_update(sma, NULL, 0, 0, &wake_q);
1508		err = 0;
1509		goto out_unlock;
1510	}
1511	/* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1512	}
1513	err = -EINVAL;
1514	if (semnum < 0 || semnum >= nsems)
1515		goto out_rcu_wakeup;
1516
1517	sem_lock(sma, NULL, -1);
1518	if (!ipc_valid_object(&sma->sem_perm)) {
1519		err = -EIDRM;
1520		goto out_unlock;
1521	}
1522
1523	semnum = array_index_nospec(semnum, nsems);
1524	curr = &sma->sems[semnum];
1525
1526	switch (cmd) {
1527	case GETVAL:
1528		err = curr->semval;
1529		goto out_unlock;
1530	case GETPID:
1531		err = pid_vnr(curr->sempid);
1532		goto out_unlock;
1533	case GETNCNT:
1534		err = count_semcnt(sma, semnum, 0);
1535		goto out_unlock;
1536	case GETZCNT:
1537		err = count_semcnt(sma, semnum, 1);
1538		goto out_unlock;
1539	}
1540
1541out_unlock:
1542	sem_unlock(sma, -1);
1543out_rcu_wakeup:
1544	rcu_read_unlock();
1545	wake_up_q(&wake_q);
1546out_free:
1547	if (sem_io != fast_sem_io)
1548		kvfree(sem_io);
1549	return err;
1550}
1551
1552static inline unsigned long
1553copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1554{
1555	switch (version) {
1556	case IPC_64:
1557		if (copy_from_user(out, buf, sizeof(*out)))
1558			return -EFAULT;
1559		return 0;
1560	case IPC_OLD:
1561	    {
1562		struct semid_ds tbuf_old;
1563
1564		if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1565			return -EFAULT;
1566
1567		out->sem_perm.uid	= tbuf_old.sem_perm.uid;
1568		out->sem_perm.gid	= tbuf_old.sem_perm.gid;
1569		out->sem_perm.mode	= tbuf_old.sem_perm.mode;
1570
1571		return 0;
1572	    }
1573	default:
1574		return -EINVAL;
1575	}
1576}
1577
1578/*
1579 * This function handles some semctl commands which require the rwsem
1580 * to be held in write mode.
1581 * NOTE: no locks must be held, the rwsem is taken inside this function.
1582 */
1583static int semctl_down(struct ipc_namespace *ns, int semid,
1584		       int cmd, struct semid64_ds *semid64)
1585{
1586	struct sem_array *sma;
1587	int err;
1588	struct kern_ipc_perm *ipcp;
1589
1590	down_write(&sem_ids(ns).rwsem);
1591	rcu_read_lock();
1592
1593	ipcp = ipcctl_obtain_check(ns, &sem_ids(ns), semid, cmd,
1594				      &semid64->sem_perm, 0);
1595	if (IS_ERR(ipcp)) {
1596		err = PTR_ERR(ipcp);
1597		goto out_unlock1;
1598	}
1599
1600	sma = container_of(ipcp, struct sem_array, sem_perm);
1601
1602	err = security_sem_semctl(&sma->sem_perm, cmd);
1603	if (err)
1604		goto out_unlock1;
1605
1606	switch (cmd) {
1607	case IPC_RMID:
1608		sem_lock(sma, NULL, -1);
1609		/* freeary unlocks the ipc object and rcu */
1610		freeary(ns, ipcp);
1611		goto out_up;
1612	case IPC_SET:
1613		sem_lock(sma, NULL, -1);
1614		err = ipc_update_perm(&semid64->sem_perm, ipcp);
1615		if (err)
1616			goto out_unlock0;
1617		sma->sem_ctime = ktime_get_real_seconds();
1618		break;
1619	default:
1620		err = -EINVAL;
1621		goto out_unlock1;
1622	}
1623
1624out_unlock0:
1625	sem_unlock(sma, -1);
1626out_unlock1:
1627	rcu_read_unlock();
1628out_up:
1629	up_write(&sem_ids(ns).rwsem);
1630	return err;
1631}
1632
1633static long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg, int version)
1634{
 
1635	struct ipc_namespace *ns;
1636	void __user *p = (void __user *)arg;
1637	struct semid64_ds semid64;
1638	int err;
1639
1640	if (semid < 0)
1641		return -EINVAL;
1642
 
1643	ns = current->nsproxy->ipc_ns;
1644
1645	switch (cmd) {
1646	case IPC_INFO:
1647	case SEM_INFO:
1648		return semctl_info(ns, semid, cmd, p);
1649	case IPC_STAT:
1650	case SEM_STAT:
1651	case SEM_STAT_ANY:
1652		err = semctl_stat(ns, semid, cmd, &semid64);
1653		if (err < 0)
1654			return err;
1655		if (copy_semid_to_user(p, &semid64, version))
1656			err = -EFAULT;
1657		return err;
1658	case GETALL:
1659	case GETVAL:
1660	case GETPID:
1661	case GETNCNT:
1662	case GETZCNT:
1663	case SETALL:
1664		return semctl_main(ns, semid, semnum, cmd, p);
1665	case SETVAL: {
1666		int val;
1667#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1668		/* big-endian 64bit */
1669		val = arg >> 32;
1670#else
1671		/* 32bit or little-endian 64bit */
1672		val = arg;
1673#endif
1674		return semctl_setval(ns, semid, semnum, val);
1675	}
1676	case IPC_SET:
1677		if (copy_semid_from_user(&semid64, p, version))
1678			return -EFAULT;
1679		/* fall through */
1680	case IPC_RMID:
1681		return semctl_down(ns, semid, cmd, &semid64);
1682	default:
1683		return -EINVAL;
1684	}
1685}
1686
1687SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1688{
1689	return ksys_semctl(semid, semnum, cmd, arg, IPC_64);
1690}
1691
1692#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
1693long ksys_old_semctl(int semid, int semnum, int cmd, unsigned long arg)
1694{
1695	int version = ipc_parse_version(&cmd);
1696
1697	return ksys_semctl(semid, semnum, cmd, arg, version);
1698}
1699
1700SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1701{
1702	return ksys_old_semctl(semid, semnum, cmd, arg);
1703}
1704#endif
1705
1706#ifdef CONFIG_COMPAT
1707
1708struct compat_semid_ds {
1709	struct compat_ipc_perm sem_perm;
1710	old_time32_t sem_otime;
1711	old_time32_t sem_ctime;
1712	compat_uptr_t sem_base;
1713	compat_uptr_t sem_pending;
1714	compat_uptr_t sem_pending_last;
1715	compat_uptr_t undo;
1716	unsigned short sem_nsems;
1717};
1718
1719static int copy_compat_semid_from_user(struct semid64_ds *out, void __user *buf,
1720					int version)
1721{
1722	memset(out, 0, sizeof(*out));
1723	if (version == IPC_64) {
1724		struct compat_semid64_ds __user *p = buf;
1725		return get_compat_ipc64_perm(&out->sem_perm, &p->sem_perm);
1726	} else {
1727		struct compat_semid_ds __user *p = buf;
1728		return get_compat_ipc_perm(&out->sem_perm, &p->sem_perm);
1729	}
1730}
1731
1732static int copy_compat_semid_to_user(void __user *buf, struct semid64_ds *in,
1733					int version)
1734{
1735	if (version == IPC_64) {
1736		struct compat_semid64_ds v;
1737		memset(&v, 0, sizeof(v));
1738		to_compat_ipc64_perm(&v.sem_perm, &in->sem_perm);
1739		v.sem_otime	 = lower_32_bits(in->sem_otime);
1740		v.sem_otime_high = upper_32_bits(in->sem_otime);
1741		v.sem_ctime	 = lower_32_bits(in->sem_ctime);
1742		v.sem_ctime_high = upper_32_bits(in->sem_ctime);
1743		v.sem_nsems = in->sem_nsems;
1744		return copy_to_user(buf, &v, sizeof(v));
1745	} else {
1746		struct compat_semid_ds v;
1747		memset(&v, 0, sizeof(v));
1748		to_compat_ipc_perm(&v.sem_perm, &in->sem_perm);
1749		v.sem_otime = in->sem_otime;
1750		v.sem_ctime = in->sem_ctime;
1751		v.sem_nsems = in->sem_nsems;
1752		return copy_to_user(buf, &v, sizeof(v));
1753	}
1754}
1755
1756static long compat_ksys_semctl(int semid, int semnum, int cmd, int arg, int version)
1757{
1758	void __user *p = compat_ptr(arg);
1759	struct ipc_namespace *ns;
1760	struct semid64_ds semid64;
 
1761	int err;
1762
1763	ns = current->nsproxy->ipc_ns;
1764
1765	if (semid < 0)
1766		return -EINVAL;
1767
1768	switch (cmd & (~IPC_64)) {
1769	case IPC_INFO:
1770	case SEM_INFO:
1771		return semctl_info(ns, semid, cmd, p);
1772	case IPC_STAT:
1773	case SEM_STAT:
1774	case SEM_STAT_ANY:
1775		err = semctl_stat(ns, semid, cmd, &semid64);
1776		if (err < 0)
1777			return err;
1778		if (copy_compat_semid_to_user(p, &semid64, version))
1779			err = -EFAULT;
1780		return err;
1781	case GETVAL:
1782	case GETPID:
1783	case GETNCNT:
1784	case GETZCNT:
1785	case GETALL:
1786	case SETALL:
1787		return semctl_main(ns, semid, semnum, cmd, p);
1788	case SETVAL:
1789		return semctl_setval(ns, semid, semnum, arg);
1790	case IPC_SET:
1791		if (copy_compat_semid_from_user(&semid64, p, version))
1792			return -EFAULT;
1793		/* fallthru */
1794	case IPC_RMID:
1795		return semctl_down(ns, semid, cmd, &semid64);
1796	default:
1797		return -EINVAL;
1798	}
1799}
1800
1801COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg)
1802{
1803	return compat_ksys_semctl(semid, semnum, cmd, arg, IPC_64);
1804}
1805
1806#ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION
1807long compat_ksys_old_semctl(int semid, int semnum, int cmd, int arg)
1808{
1809	int version = compat_ipc_parse_version(&cmd);
1810
1811	return compat_ksys_semctl(semid, semnum, cmd, arg, version);
1812}
1813
1814COMPAT_SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, int, arg)
1815{
1816	return compat_ksys_old_semctl(semid, semnum, cmd, arg);
1817}
1818#endif
1819#endif
1820
1821/* If the task doesn't already have a undo_list, then allocate one
1822 * here.  We guarantee there is only one thread using this undo list,
1823 * and current is THE ONE
1824 *
1825 * If this allocation and assignment succeeds, but later
1826 * portions of this code fail, there is no need to free the sem_undo_list.
1827 * Just let it stay associated with the task, and it'll be freed later
1828 * at exit time.
1829 *
1830 * This can block, so callers must hold no locks.
1831 */
1832static inline int get_undo_list(struct sem_undo_list **undo_listp)
1833{
1834	struct sem_undo_list *undo_list;
1835
1836	undo_list = current->sysvsem.undo_list;
1837	if (!undo_list) {
1838		undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1839		if (undo_list == NULL)
1840			return -ENOMEM;
1841		spin_lock_init(&undo_list->lock);
1842		refcount_set(&undo_list->refcnt, 1);
1843		INIT_LIST_HEAD(&undo_list->list_proc);
1844
1845		current->sysvsem.undo_list = undo_list;
1846	}
1847	*undo_listp = undo_list;
1848	return 0;
1849}
1850
1851static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1852{
1853	struct sem_undo *un;
1854
1855	list_for_each_entry_rcu(un, &ulp->list_proc, list_proc,
1856				spin_is_locked(&ulp->lock)) {
1857		if (un->semid == semid)
1858			return un;
1859	}
1860	return NULL;
1861}
1862
1863static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1864{
1865	struct sem_undo *un;
1866
1867	assert_spin_locked(&ulp->lock);
1868
1869	un = __lookup_undo(ulp, semid);
1870	if (un) {
1871		list_del_rcu(&un->list_proc);
1872		list_add_rcu(&un->list_proc, &ulp->list_proc);
1873	}
1874	return un;
1875}
1876
1877/**
1878 * find_alloc_undo - lookup (and if not present create) undo array
1879 * @ns: namespace
1880 * @semid: semaphore array id
1881 *
1882 * The function looks up (and if not present creates) the undo structure.
1883 * The size of the undo structure depends on the size of the semaphore
1884 * array, thus the alloc path is not that straightforward.
1885 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1886 * performs a rcu_read_lock().
1887 */
1888static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1889{
1890	struct sem_array *sma;
1891	struct sem_undo_list *ulp;
1892	struct sem_undo *un, *new;
1893	int nsems, error;
1894
1895	error = get_undo_list(&ulp);
1896	if (error)
1897		return ERR_PTR(error);
1898
1899	rcu_read_lock();
1900	spin_lock(&ulp->lock);
1901	un = lookup_undo(ulp, semid);
1902	spin_unlock(&ulp->lock);
1903	if (likely(un != NULL))
1904		goto out;
1905
1906	/* no undo structure around - allocate one. */
1907	/* step 1: figure out the size of the semaphore array */
1908	sma = sem_obtain_object_check(ns, semid);
1909	if (IS_ERR(sma)) {
1910		rcu_read_unlock();
1911		return ERR_CAST(sma);
1912	}
1913
1914	nsems = sma->sem_nsems;
1915	if (!ipc_rcu_getref(&sma->sem_perm)) {
1916		rcu_read_unlock();
1917		un = ERR_PTR(-EIDRM);
1918		goto out;
1919	}
1920	rcu_read_unlock();
1921
1922	/* step 2: allocate new undo structure */
1923	new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1924	if (!new) {
1925		ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1926		return ERR_PTR(-ENOMEM);
1927	}
1928
1929	/* step 3: Acquire the lock on semaphore array */
1930	rcu_read_lock();
1931	sem_lock_and_putref(sma);
1932	if (!ipc_valid_object(&sma->sem_perm)) {
1933		sem_unlock(sma, -1);
1934		rcu_read_unlock();
1935		kfree(new);
1936		un = ERR_PTR(-EIDRM);
1937		goto out;
1938	}
1939	spin_lock(&ulp->lock);
1940
1941	/*
1942	 * step 4: check for races: did someone else allocate the undo struct?
1943	 */
1944	un = lookup_undo(ulp, semid);
1945	if (un) {
1946		kfree(new);
1947		goto success;
1948	}
1949	/* step 5: initialize & link new undo structure */
1950	new->semadj = (short *) &new[1];
1951	new->ulp = ulp;
1952	new->semid = semid;
1953	assert_spin_locked(&ulp->lock);
1954	list_add_rcu(&new->list_proc, &ulp->list_proc);
1955	ipc_assert_locked_object(&sma->sem_perm);
1956	list_add(&new->list_id, &sma->list_id);
1957	un = new;
1958
1959success:
1960	spin_unlock(&ulp->lock);
1961	sem_unlock(sma, -1);
1962out:
1963	return un;
1964}
1965
1966static long do_semtimedop(int semid, struct sembuf __user *tsops,
1967		unsigned nsops, const struct timespec64 *timeout)
1968{
1969	int error = -EINVAL;
1970	struct sem_array *sma;
1971	struct sembuf fast_sops[SEMOPM_FAST];
1972	struct sembuf *sops = fast_sops, *sop;
1973	struct sem_undo *un;
1974	int max, locknum;
1975	bool undos = false, alter = false, dupsop = false;
1976	struct sem_queue queue;
1977	unsigned long dup = 0, jiffies_left = 0;
1978	struct ipc_namespace *ns;
1979
1980	ns = current->nsproxy->ipc_ns;
1981
1982	if (nsops < 1 || semid < 0)
1983		return -EINVAL;
1984	if (nsops > ns->sc_semopm)
1985		return -E2BIG;
1986	if (nsops > SEMOPM_FAST) {
1987		sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL);
1988		if (sops == NULL)
1989			return -ENOMEM;
1990	}
1991
1992	if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
1993		error =  -EFAULT;
1994		goto out_free;
1995	}
1996
1997	if (timeout) {
1998		if (timeout->tv_sec < 0 || timeout->tv_nsec < 0 ||
1999			timeout->tv_nsec >= 1000000000L) {
2000			error = -EINVAL;
2001			goto out_free;
2002		}
2003		jiffies_left = timespec64_to_jiffies(timeout);
2004	}
2005
2006	max = 0;
2007	for (sop = sops; sop < sops + nsops; sop++) {
2008		unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG);
2009
2010		if (sop->sem_num >= max)
2011			max = sop->sem_num;
2012		if (sop->sem_flg & SEM_UNDO)
2013			undos = true;
2014		if (dup & mask) {
2015			/*
2016			 * There was a previous alter access that appears
2017			 * to have accessed the same semaphore, thus use
2018			 * the dupsop logic. "appears", because the detection
2019			 * can only check % BITS_PER_LONG.
2020			 */
2021			dupsop = true;
2022		}
2023		if (sop->sem_op != 0) {
2024			alter = true;
2025			dup |= mask;
2026		}
2027	}
2028
2029	if (undos) {
2030		/* On success, find_alloc_undo takes the rcu_read_lock */
2031		un = find_alloc_undo(ns, semid);
2032		if (IS_ERR(un)) {
2033			error = PTR_ERR(un);
2034			goto out_free;
2035		}
2036	} else {
2037		un = NULL;
2038		rcu_read_lock();
2039	}
2040
2041	sma = sem_obtain_object_check(ns, semid);
2042	if (IS_ERR(sma)) {
2043		rcu_read_unlock();
2044		error = PTR_ERR(sma);
2045		goto out_free;
2046	}
2047
2048	error = -EFBIG;
2049	if (max >= sma->sem_nsems) {
2050		rcu_read_unlock();
2051		goto out_free;
2052	}
2053
2054	error = -EACCES;
2055	if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) {
2056		rcu_read_unlock();
2057		goto out_free;
2058	}
2059
2060	error = security_sem_semop(&sma->sem_perm, sops, nsops, alter);
2061	if (error) {
2062		rcu_read_unlock();
2063		goto out_free;
2064	}
2065
2066	error = -EIDRM;
2067	locknum = sem_lock(sma, sops, nsops);
2068	/*
2069	 * We eventually might perform the following check in a lockless
2070	 * fashion, considering ipc_valid_object() locking constraints.
2071	 * If nsops == 1 and there is no contention for sem_perm.lock, then
2072	 * only a per-semaphore lock is held and it's OK to proceed with the
2073	 * check below. More details on the fine grained locking scheme
2074	 * entangled here and why it's RMID race safe on comments at sem_lock()
2075	 */
2076	if (!ipc_valid_object(&sma->sem_perm))
2077		goto out_unlock_free;
2078	/*
2079	 * semid identifiers are not unique - find_alloc_undo may have
2080	 * allocated an undo structure, it was invalidated by an RMID
2081	 * and now a new array with received the same id. Check and fail.
2082	 * This case can be detected checking un->semid. The existence of
2083	 * "un" itself is guaranteed by rcu.
2084	 */
2085	if (un && un->semid == -1)
2086		goto out_unlock_free;
2087
2088	queue.sops = sops;
2089	queue.nsops = nsops;
2090	queue.undo = un;
2091	queue.pid = task_tgid(current);
2092	queue.alter = alter;
2093	queue.dupsop = dupsop;
2094
2095	error = perform_atomic_semop(sma, &queue);
2096	if (error == 0) { /* non-blocking succesfull path */
2097		DEFINE_WAKE_Q(wake_q);
2098
2099		/*
2100		 * If the operation was successful, then do
2101		 * the required updates.
2102		 */
2103		if (alter)
2104			do_smart_update(sma, sops, nsops, 1, &wake_q);
2105		else
2106			set_semotime(sma, sops);
2107
2108		sem_unlock(sma, locknum);
2109		rcu_read_unlock();
2110		wake_up_q(&wake_q);
2111
2112		goto out_free;
2113	}
2114	if (error < 0) /* non-blocking error path */
2115		goto out_unlock_free;
2116
2117	/*
2118	 * We need to sleep on this operation, so we put the current
2119	 * task into the pending queue and go to sleep.
2120	 */
2121	if (nsops == 1) {
2122		struct sem *curr;
2123		int idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
2124		curr = &sma->sems[idx];
2125
2126		if (alter) {
2127			if (sma->complex_count) {
2128				list_add_tail(&queue.list,
2129						&sma->pending_alter);
2130			} else {
2131
2132				list_add_tail(&queue.list,
2133						&curr->pending_alter);
2134			}
2135		} else {
2136			list_add_tail(&queue.list, &curr->pending_const);
2137		}
2138	} else {
2139		if (!sma->complex_count)
2140			merge_queues(sma);
2141
2142		if (alter)
2143			list_add_tail(&queue.list, &sma->pending_alter);
2144		else
2145			list_add_tail(&queue.list, &sma->pending_const);
2146
2147		sma->complex_count++;
2148	}
2149
2150	do {
2151		WRITE_ONCE(queue.status, -EINTR);
2152		queue.sleeper = current;
2153
2154		__set_current_state(TASK_INTERRUPTIBLE);
2155		sem_unlock(sma, locknum);
2156		rcu_read_unlock();
2157
2158		if (timeout)
2159			jiffies_left = schedule_timeout(jiffies_left);
2160		else
2161			schedule();
2162
2163		/*
2164		 * fastpath: the semop has completed, either successfully or
2165		 * not, from the syscall pov, is quite irrelevant to us at this
2166		 * point; we're done.
2167		 *
2168		 * We _do_ care, nonetheless, about being awoken by a signal or
2169		 * spuriously.  The queue.status is checked again in the
2170		 * slowpath (aka after taking sem_lock), such that we can detect
2171		 * scenarios where we were awakened externally, during the
2172		 * window between wake_q_add() and wake_up_q().
2173		 */
2174		error = READ_ONCE(queue.status);
2175		if (error != -EINTR) {
2176			/*
2177			 * User space could assume that semop() is a memory
2178			 * barrier: Without the mb(), the cpu could
2179			 * speculatively read in userspace stale data that was
2180			 * overwritten by the previous owner of the semaphore.
2181			 */
2182			smp_mb();
2183			goto out_free;
2184		}
2185
2186		rcu_read_lock();
2187		locknum = sem_lock(sma, sops, nsops);
2188
2189		if (!ipc_valid_object(&sma->sem_perm))
2190			goto out_unlock_free;
2191
2192		error = READ_ONCE(queue.status);
2193
2194		/*
2195		 * If queue.status != -EINTR we are woken up by another process.
2196		 * Leave without unlink_queue(), but with sem_unlock().
2197		 */
2198		if (error != -EINTR)
2199			goto out_unlock_free;
2200
2201		/*
2202		 * If an interrupt occurred we have to clean up the queue.
2203		 */
2204		if (timeout && jiffies_left == 0)
2205			error = -EAGAIN;
2206	} while (error == -EINTR && !signal_pending(current)); /* spurious */
2207
2208	unlink_queue(sma, &queue);
2209
2210out_unlock_free:
2211	sem_unlock(sma, locknum);
2212	rcu_read_unlock();
2213out_free:
2214	if (sops != fast_sops)
2215		kvfree(sops);
2216	return error;
2217}
2218
2219long ksys_semtimedop(int semid, struct sembuf __user *tsops,
2220		     unsigned int nsops, const struct __kernel_timespec __user *timeout)
2221{
2222	if (timeout) {
2223		struct timespec64 ts;
2224		if (get_timespec64(&ts, timeout))
2225			return -EFAULT;
2226		return do_semtimedop(semid, tsops, nsops, &ts);
2227	}
2228	return do_semtimedop(semid, tsops, nsops, NULL);
2229}
2230
2231SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
2232		unsigned int, nsops, const struct __kernel_timespec __user *, timeout)
2233{
2234	return ksys_semtimedop(semid, tsops, nsops, timeout);
2235}
2236
2237#ifdef CONFIG_COMPAT_32BIT_TIME
2238long compat_ksys_semtimedop(int semid, struct sembuf __user *tsems,
2239			    unsigned int nsops,
2240			    const struct old_timespec32 __user *timeout)
2241{
2242	if (timeout) {
2243		struct timespec64 ts;
2244		if (get_old_timespec32(&ts, timeout))
2245			return -EFAULT;
2246		return do_semtimedop(semid, tsems, nsops, &ts);
2247	}
2248	return do_semtimedop(semid, tsems, nsops, NULL);
2249}
2250
2251SYSCALL_DEFINE4(semtimedop_time32, int, semid, struct sembuf __user *, tsems,
2252		       unsigned int, nsops,
2253		       const struct old_timespec32 __user *, timeout)
2254{
2255	return compat_ksys_semtimedop(semid, tsems, nsops, timeout);
2256}
2257#endif
2258
2259SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
2260		unsigned, nsops)
2261{
2262	return do_semtimedop(semid, tsops, nsops, NULL);
2263}
2264
2265/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
2266 * parent and child tasks.
2267 */
2268
2269int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
2270{
2271	struct sem_undo_list *undo_list;
2272	int error;
2273
2274	if (clone_flags & CLONE_SYSVSEM) {
2275		error = get_undo_list(&undo_list);
2276		if (error)
2277			return error;
2278		refcount_inc(&undo_list->refcnt);
2279		tsk->sysvsem.undo_list = undo_list;
2280	} else
2281		tsk->sysvsem.undo_list = NULL;
2282
2283	return 0;
2284}
2285
2286/*
2287 * add semadj values to semaphores, free undo structures.
2288 * undo structures are not freed when semaphore arrays are destroyed
2289 * so some of them may be out of date.
2290 * IMPLEMENTATION NOTE: There is some confusion over whether the
2291 * set of adjustments that needs to be done should be done in an atomic
2292 * manner or not. That is, if we are attempting to decrement the semval
2293 * should we queue up and wait until we can do so legally?
2294 * The original implementation attempted to do this (queue and wait).
2295 * The current implementation does not do so. The POSIX standard
2296 * and SVID should be consulted to determine what behavior is mandated.
2297 */
2298void exit_sem(struct task_struct *tsk)
2299{
2300	struct sem_undo_list *ulp;
2301
2302	ulp = tsk->sysvsem.undo_list;
2303	if (!ulp)
2304		return;
2305	tsk->sysvsem.undo_list = NULL;
2306
2307	if (!refcount_dec_and_test(&ulp->refcnt))
2308		return;
2309
2310	for (;;) {
2311		struct sem_array *sma;
2312		struct sem_undo *un;
2313		int semid, i;
2314		DEFINE_WAKE_Q(wake_q);
2315
2316		cond_resched();
2317
2318		rcu_read_lock();
2319		un = list_entry_rcu(ulp->list_proc.next,
2320				    struct sem_undo, list_proc);
2321		if (&un->list_proc == &ulp->list_proc) {
2322			/*
2323			 * We must wait for freeary() before freeing this ulp,
2324			 * in case we raced with last sem_undo. There is a small
2325			 * possibility where we exit while freeary() didn't
2326			 * finish unlocking sem_undo_list.
2327			 */
2328			spin_lock(&ulp->lock);
2329			spin_unlock(&ulp->lock);
2330			rcu_read_unlock();
2331			break;
2332		}
2333		spin_lock(&ulp->lock);
2334		semid = un->semid;
2335		spin_unlock(&ulp->lock);
2336
2337		/* exit_sem raced with IPC_RMID, nothing to do */
2338		if (semid == -1) {
2339			rcu_read_unlock();
2340			continue;
2341		}
2342
2343		sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid);
2344		/* exit_sem raced with IPC_RMID, nothing to do */
2345		if (IS_ERR(sma)) {
2346			rcu_read_unlock();
2347			continue;
2348		}
2349
2350		sem_lock(sma, NULL, -1);
2351		/* exit_sem raced with IPC_RMID, nothing to do */
2352		if (!ipc_valid_object(&sma->sem_perm)) {
2353			sem_unlock(sma, -1);
2354			rcu_read_unlock();
2355			continue;
2356		}
2357		un = __lookup_undo(ulp, semid);
2358		if (un == NULL) {
2359			/* exit_sem raced with IPC_RMID+semget() that created
2360			 * exactly the same semid. Nothing to do.
2361			 */
2362			sem_unlock(sma, -1);
2363			rcu_read_unlock();
2364			continue;
2365		}
2366
2367		/* remove un from the linked lists */
2368		ipc_assert_locked_object(&sma->sem_perm);
2369		list_del(&un->list_id);
2370
2371		/* we are the last process using this ulp, acquiring ulp->lock
2372		 * isn't required. Besides that, we are also protected against
2373		 * IPC_RMID as we hold sma->sem_perm lock now
2374		 */
2375		list_del_rcu(&un->list_proc);
2376
2377		/* perform adjustments registered in un */
2378		for (i = 0; i < sma->sem_nsems; i++) {
2379			struct sem *semaphore = &sma->sems[i];
2380			if (un->semadj[i]) {
2381				semaphore->semval += un->semadj[i];
2382				/*
2383				 * Range checks of the new semaphore value,
2384				 * not defined by sus:
2385				 * - Some unices ignore the undo entirely
2386				 *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
2387				 * - some cap the value (e.g. FreeBSD caps
2388				 *   at 0, but doesn't enforce SEMVMX)
2389				 *
2390				 * Linux caps the semaphore value, both at 0
2391				 * and at SEMVMX.
2392				 *
2393				 *	Manfred <manfred@colorfullife.com>
2394				 */
2395				if (semaphore->semval < 0)
2396					semaphore->semval = 0;
2397				if (semaphore->semval > SEMVMX)
2398					semaphore->semval = SEMVMX;
2399				ipc_update_pid(&semaphore->sempid, task_tgid(current));
2400			}
2401		}
2402		/* maybe some queued-up processes were waiting for this */
2403		do_smart_update(sma, NULL, 0, 1, &wake_q);
2404		sem_unlock(sma, -1);
2405		rcu_read_unlock();
2406		wake_up_q(&wake_q);
2407
2408		kfree_rcu(un, rcu);
2409	}
2410	kfree(ulp);
2411}
2412
2413#ifdef CONFIG_PROC_FS
2414static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2415{
2416	struct user_namespace *user_ns = seq_user_ns(s);
2417	struct kern_ipc_perm *ipcp = it;
2418	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
2419	time64_t sem_otime;
2420
2421	/*
2422	 * The proc interface isn't aware of sem_lock(), it calls
2423	 * ipc_lock_object() directly (in sysvipc_find_ipc).
2424	 * In order to stay compatible with sem_lock(), we must
2425	 * enter / leave complex_mode.
2426	 */
2427	complexmode_enter(sma);
2428
2429	sem_otime = get_semotime(sma);
2430
2431	seq_printf(s,
2432		   "%10d %10d  %4o %10u %5u %5u %5u %5u %10llu %10llu\n",
2433		   sma->sem_perm.key,
2434		   sma->sem_perm.id,
2435		   sma->sem_perm.mode,
2436		   sma->sem_nsems,
2437		   from_kuid_munged(user_ns, sma->sem_perm.uid),
2438		   from_kgid_munged(user_ns, sma->sem_perm.gid),
2439		   from_kuid_munged(user_ns, sma->sem_perm.cuid),
2440		   from_kgid_munged(user_ns, sma->sem_perm.cgid),
2441		   sem_otime,
2442		   sma->sem_ctime);
2443
2444	complexmode_tryleave(sma);
2445
2446	return 0;
2447}
2448#endif