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1/*
2 * linux/fs/file.c
3 *
4 * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
5 *
6 * Manage the dynamic fd arrays in the process files_struct.
7 */
8
9#include <linux/syscalls.h>
10#include <linux/export.h>
11#include <linux/fs.h>
12#include <linux/mm.h>
13#include <linux/mmzone.h>
14#include <linux/time.h>
15#include <linux/sched.h>
16#include <linux/slab.h>
17#include <linux/vmalloc.h>
18#include <linux/file.h>
19#include <linux/fdtable.h>
20#include <linux/bitops.h>
21#include <linux/interrupt.h>
22#include <linux/spinlock.h>
23#include <linux/rcupdate.h>
24#include <linux/workqueue.h>
25
26int sysctl_nr_open __read_mostly = 1024*1024;
27int sysctl_nr_open_min = BITS_PER_LONG;
28/* our min() is unusable in constant expressions ;-/ */
29#define __const_min(x, y) ((x) < (y) ? (x) : (y))
30int sysctl_nr_open_max = __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) &
31 -BITS_PER_LONG;
32
33static void *alloc_fdmem(size_t size)
34{
35 /*
36 * Very large allocations can stress page reclaim, so fall back to
37 * vmalloc() if the allocation size will be considered "large" by the VM.
38 */
39 if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) {
40 void *data = kmalloc(size, GFP_KERNEL_ACCOUNT |
41 __GFP_NOWARN | __GFP_NORETRY);
42 if (data != NULL)
43 return data;
44 }
45 return __vmalloc(size, GFP_KERNEL_ACCOUNT | __GFP_HIGHMEM, PAGE_KERNEL);
46}
47
48static void __free_fdtable(struct fdtable *fdt)
49{
50 kvfree(fdt->fd);
51 kvfree(fdt->open_fds);
52 kfree(fdt);
53}
54
55static void free_fdtable_rcu(struct rcu_head *rcu)
56{
57 __free_fdtable(container_of(rcu, struct fdtable, rcu));
58}
59
60#define BITBIT_NR(nr) BITS_TO_LONGS(BITS_TO_LONGS(nr))
61#define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))
62
63/*
64 * Copy 'count' fd bits from the old table to the new table and clear the extra
65 * space if any. This does not copy the file pointers. Called with the files
66 * spinlock held for write.
67 */
68static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
69 unsigned int count)
70{
71 unsigned int cpy, set;
72
73 cpy = count / BITS_PER_BYTE;
74 set = (nfdt->max_fds - count) / BITS_PER_BYTE;
75 memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
76 memset((char *)nfdt->open_fds + cpy, 0, set);
77 memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
78 memset((char *)nfdt->close_on_exec + cpy, 0, set);
79
80 cpy = BITBIT_SIZE(count);
81 set = BITBIT_SIZE(nfdt->max_fds) - cpy;
82 memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
83 memset((char *)nfdt->full_fds_bits + cpy, 0, set);
84}
85
86/*
87 * Copy all file descriptors from the old table to the new, expanded table and
88 * clear the extra space. Called with the files spinlock held for write.
89 */
90static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
91{
92 unsigned int cpy, set;
93
94 BUG_ON(nfdt->max_fds < ofdt->max_fds);
95
96 cpy = ofdt->max_fds * sizeof(struct file *);
97 set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
98 memcpy(nfdt->fd, ofdt->fd, cpy);
99 memset((char *)nfdt->fd + cpy, 0, set);
100
101 copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
102}
103
104static struct fdtable * alloc_fdtable(unsigned int nr)
105{
106 struct fdtable *fdt;
107 void *data;
108
109 /*
110 * Figure out how many fds we actually want to support in this fdtable.
111 * Allocation steps are keyed to the size of the fdarray, since it
112 * grows far faster than any of the other dynamic data. We try to fit
113 * the fdarray into comfortable page-tuned chunks: starting at 1024B
114 * and growing in powers of two from there on.
115 */
116 nr /= (1024 / sizeof(struct file *));
117 nr = roundup_pow_of_two(nr + 1);
118 nr *= (1024 / sizeof(struct file *));
119 /*
120 * Note that this can drive nr *below* what we had passed if sysctl_nr_open
121 * had been set lower between the check in expand_files() and here. Deal
122 * with that in caller, it's cheaper that way.
123 *
124 * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
125 * bitmaps handling below becomes unpleasant, to put it mildly...
126 */
127 if (unlikely(nr > sysctl_nr_open))
128 nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
129
130 fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
131 if (!fdt)
132 goto out;
133 fdt->max_fds = nr;
134 data = alloc_fdmem(nr * sizeof(struct file *));
135 if (!data)
136 goto out_fdt;
137 fdt->fd = data;
138
139 data = alloc_fdmem(max_t(size_t,
140 2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES));
141 if (!data)
142 goto out_arr;
143 fdt->open_fds = data;
144 data += nr / BITS_PER_BYTE;
145 fdt->close_on_exec = data;
146 data += nr / BITS_PER_BYTE;
147 fdt->full_fds_bits = data;
148
149 return fdt;
150
151out_arr:
152 kvfree(fdt->fd);
153out_fdt:
154 kfree(fdt);
155out:
156 return NULL;
157}
158
159/*
160 * Expand the file descriptor table.
161 * This function will allocate a new fdtable and both fd array and fdset, of
162 * the given size.
163 * Return <0 error code on error; 1 on successful completion.
164 * The files->file_lock should be held on entry, and will be held on exit.
165 */
166static int expand_fdtable(struct files_struct *files, int nr)
167 __releases(files->file_lock)
168 __acquires(files->file_lock)
169{
170 struct fdtable *new_fdt, *cur_fdt;
171
172 spin_unlock(&files->file_lock);
173 new_fdt = alloc_fdtable(nr);
174
175 /* make sure all __fd_install() have seen resize_in_progress
176 * or have finished their rcu_read_lock_sched() section.
177 */
178 if (atomic_read(&files->count) > 1)
179 synchronize_sched();
180
181 spin_lock(&files->file_lock);
182 if (!new_fdt)
183 return -ENOMEM;
184 /*
185 * extremely unlikely race - sysctl_nr_open decreased between the check in
186 * caller and alloc_fdtable(). Cheaper to catch it here...
187 */
188 if (unlikely(new_fdt->max_fds <= nr)) {
189 __free_fdtable(new_fdt);
190 return -EMFILE;
191 }
192 cur_fdt = files_fdtable(files);
193 BUG_ON(nr < cur_fdt->max_fds);
194 copy_fdtable(new_fdt, cur_fdt);
195 rcu_assign_pointer(files->fdt, new_fdt);
196 if (cur_fdt != &files->fdtab)
197 call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
198 /* coupled with smp_rmb() in __fd_install() */
199 smp_wmb();
200 return 1;
201}
202
203/*
204 * Expand files.
205 * This function will expand the file structures, if the requested size exceeds
206 * the current capacity and there is room for expansion.
207 * Return <0 error code on error; 0 when nothing done; 1 when files were
208 * expanded and execution may have blocked.
209 * The files->file_lock should be held on entry, and will be held on exit.
210 */
211static int expand_files(struct files_struct *files, int nr)
212 __releases(files->file_lock)
213 __acquires(files->file_lock)
214{
215 struct fdtable *fdt;
216 int expanded = 0;
217
218repeat:
219 fdt = files_fdtable(files);
220
221 /* Do we need to expand? */
222 if (nr < fdt->max_fds)
223 return expanded;
224
225 /* Can we expand? */
226 if (nr >= sysctl_nr_open)
227 return -EMFILE;
228
229 if (unlikely(files->resize_in_progress)) {
230 spin_unlock(&files->file_lock);
231 expanded = 1;
232 wait_event(files->resize_wait, !files->resize_in_progress);
233 spin_lock(&files->file_lock);
234 goto repeat;
235 }
236
237 /* All good, so we try */
238 files->resize_in_progress = true;
239 expanded = expand_fdtable(files, nr);
240 files->resize_in_progress = false;
241
242 wake_up_all(&files->resize_wait);
243 return expanded;
244}
245
246static inline void __set_close_on_exec(int fd, struct fdtable *fdt)
247{
248 __set_bit(fd, fdt->close_on_exec);
249}
250
251static inline void __clear_close_on_exec(int fd, struct fdtable *fdt)
252{
253 if (test_bit(fd, fdt->close_on_exec))
254 __clear_bit(fd, fdt->close_on_exec);
255}
256
257static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
258{
259 __set_bit(fd, fdt->open_fds);
260 fd /= BITS_PER_LONG;
261 if (!~fdt->open_fds[fd])
262 __set_bit(fd, fdt->full_fds_bits);
263}
264
265static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
266{
267 __clear_bit(fd, fdt->open_fds);
268 __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
269}
270
271static int count_open_files(struct fdtable *fdt)
272{
273 int size = fdt->max_fds;
274 int i;
275
276 /* Find the last open fd */
277 for (i = size / BITS_PER_LONG; i > 0; ) {
278 if (fdt->open_fds[--i])
279 break;
280 }
281 i = (i + 1) * BITS_PER_LONG;
282 return i;
283}
284
285/*
286 * Allocate a new files structure and copy contents from the
287 * passed in files structure.
288 * errorp will be valid only when the returned files_struct is NULL.
289 */
290struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
291{
292 struct files_struct *newf;
293 struct file **old_fds, **new_fds;
294 int open_files, i;
295 struct fdtable *old_fdt, *new_fdt;
296
297 *errorp = -ENOMEM;
298 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
299 if (!newf)
300 goto out;
301
302 atomic_set(&newf->count, 1);
303
304 spin_lock_init(&newf->file_lock);
305 newf->resize_in_progress = false;
306 init_waitqueue_head(&newf->resize_wait);
307 newf->next_fd = 0;
308 new_fdt = &newf->fdtab;
309 new_fdt->max_fds = NR_OPEN_DEFAULT;
310 new_fdt->close_on_exec = newf->close_on_exec_init;
311 new_fdt->open_fds = newf->open_fds_init;
312 new_fdt->full_fds_bits = newf->full_fds_bits_init;
313 new_fdt->fd = &newf->fd_array[0];
314
315 spin_lock(&oldf->file_lock);
316 old_fdt = files_fdtable(oldf);
317 open_files = count_open_files(old_fdt);
318
319 /*
320 * Check whether we need to allocate a larger fd array and fd set.
321 */
322 while (unlikely(open_files > new_fdt->max_fds)) {
323 spin_unlock(&oldf->file_lock);
324
325 if (new_fdt != &newf->fdtab)
326 __free_fdtable(new_fdt);
327
328 new_fdt = alloc_fdtable(open_files - 1);
329 if (!new_fdt) {
330 *errorp = -ENOMEM;
331 goto out_release;
332 }
333
334 /* beyond sysctl_nr_open; nothing to do */
335 if (unlikely(new_fdt->max_fds < open_files)) {
336 __free_fdtable(new_fdt);
337 *errorp = -EMFILE;
338 goto out_release;
339 }
340
341 /*
342 * Reacquire the oldf lock and a pointer to its fd table
343 * who knows it may have a new bigger fd table. We need
344 * the latest pointer.
345 */
346 spin_lock(&oldf->file_lock);
347 old_fdt = files_fdtable(oldf);
348 open_files = count_open_files(old_fdt);
349 }
350
351 copy_fd_bitmaps(new_fdt, old_fdt, open_files);
352
353 old_fds = old_fdt->fd;
354 new_fds = new_fdt->fd;
355
356 for (i = open_files; i != 0; i--) {
357 struct file *f = *old_fds++;
358 if (f) {
359 get_file(f);
360 } else {
361 /*
362 * The fd may be claimed in the fd bitmap but not yet
363 * instantiated in the files array if a sibling thread
364 * is partway through open(). So make sure that this
365 * fd is available to the new process.
366 */
367 __clear_open_fd(open_files - i, new_fdt);
368 }
369 rcu_assign_pointer(*new_fds++, f);
370 }
371 spin_unlock(&oldf->file_lock);
372
373 /* clear the remainder */
374 memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
375
376 rcu_assign_pointer(newf->fdt, new_fdt);
377
378 return newf;
379
380out_release:
381 kmem_cache_free(files_cachep, newf);
382out:
383 return NULL;
384}
385
386static struct fdtable *close_files(struct files_struct * files)
387{
388 /*
389 * It is safe to dereference the fd table without RCU or
390 * ->file_lock because this is the last reference to the
391 * files structure.
392 */
393 struct fdtable *fdt = rcu_dereference_raw(files->fdt);
394 int i, j = 0;
395
396 for (;;) {
397 unsigned long set;
398 i = j * BITS_PER_LONG;
399 if (i >= fdt->max_fds)
400 break;
401 set = fdt->open_fds[j++];
402 while (set) {
403 if (set & 1) {
404 struct file * file = xchg(&fdt->fd[i], NULL);
405 if (file) {
406 filp_close(file, files);
407 cond_resched_rcu_qs();
408 }
409 }
410 i++;
411 set >>= 1;
412 }
413 }
414
415 return fdt;
416}
417
418struct files_struct *get_files_struct(struct task_struct *task)
419{
420 struct files_struct *files;
421
422 task_lock(task);
423 files = task->files;
424 if (files)
425 atomic_inc(&files->count);
426 task_unlock(task);
427
428 return files;
429}
430
431void put_files_struct(struct files_struct *files)
432{
433 if (atomic_dec_and_test(&files->count)) {
434 struct fdtable *fdt = close_files(files);
435
436 /* free the arrays if they are not embedded */
437 if (fdt != &files->fdtab)
438 __free_fdtable(fdt);
439 kmem_cache_free(files_cachep, files);
440 }
441}
442
443void reset_files_struct(struct files_struct *files)
444{
445 struct task_struct *tsk = current;
446 struct files_struct *old;
447
448 old = tsk->files;
449 task_lock(tsk);
450 tsk->files = files;
451 task_unlock(tsk);
452 put_files_struct(old);
453}
454
455void exit_files(struct task_struct *tsk)
456{
457 struct files_struct * files = tsk->files;
458
459 if (files) {
460 task_lock(tsk);
461 tsk->files = NULL;
462 task_unlock(tsk);
463 put_files_struct(files);
464 }
465}
466
467struct files_struct init_files = {
468 .count = ATOMIC_INIT(1),
469 .fdt = &init_files.fdtab,
470 .fdtab = {
471 .max_fds = NR_OPEN_DEFAULT,
472 .fd = &init_files.fd_array[0],
473 .close_on_exec = init_files.close_on_exec_init,
474 .open_fds = init_files.open_fds_init,
475 .full_fds_bits = init_files.full_fds_bits_init,
476 },
477 .file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
478};
479
480static unsigned long find_next_fd(struct fdtable *fdt, unsigned long start)
481{
482 unsigned long maxfd = fdt->max_fds;
483 unsigned long maxbit = maxfd / BITS_PER_LONG;
484 unsigned long bitbit = start / BITS_PER_LONG;
485
486 bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
487 if (bitbit > maxfd)
488 return maxfd;
489 if (bitbit > start)
490 start = bitbit;
491 return find_next_zero_bit(fdt->open_fds, maxfd, start);
492}
493
494/*
495 * allocate a file descriptor, mark it busy.
496 */
497int __alloc_fd(struct files_struct *files,
498 unsigned start, unsigned end, unsigned flags)
499{
500 unsigned int fd;
501 int error;
502 struct fdtable *fdt;
503
504 spin_lock(&files->file_lock);
505repeat:
506 fdt = files_fdtable(files);
507 fd = start;
508 if (fd < files->next_fd)
509 fd = files->next_fd;
510
511 if (fd < fdt->max_fds)
512 fd = find_next_fd(fdt, fd);
513
514 /*
515 * N.B. For clone tasks sharing a files structure, this test
516 * will limit the total number of files that can be opened.
517 */
518 error = -EMFILE;
519 if (fd >= end)
520 goto out;
521
522 error = expand_files(files, fd);
523 if (error < 0)
524 goto out;
525
526 /*
527 * If we needed to expand the fs array we
528 * might have blocked - try again.
529 */
530 if (error)
531 goto repeat;
532
533 if (start <= files->next_fd)
534 files->next_fd = fd + 1;
535
536 __set_open_fd(fd, fdt);
537 if (flags & O_CLOEXEC)
538 __set_close_on_exec(fd, fdt);
539 else
540 __clear_close_on_exec(fd, fdt);
541 error = fd;
542#if 1
543 /* Sanity check */
544 if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
545 printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
546 rcu_assign_pointer(fdt->fd[fd], NULL);
547 }
548#endif
549
550out:
551 spin_unlock(&files->file_lock);
552 return error;
553}
554
555static int alloc_fd(unsigned start, unsigned flags)
556{
557 return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags);
558}
559
560int get_unused_fd_flags(unsigned flags)
561{
562 return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags);
563}
564EXPORT_SYMBOL(get_unused_fd_flags);
565
566static void __put_unused_fd(struct files_struct *files, unsigned int fd)
567{
568 struct fdtable *fdt = files_fdtable(files);
569 __clear_open_fd(fd, fdt);
570 if (fd < files->next_fd)
571 files->next_fd = fd;
572}
573
574void put_unused_fd(unsigned int fd)
575{
576 struct files_struct *files = current->files;
577 spin_lock(&files->file_lock);
578 __put_unused_fd(files, fd);
579 spin_unlock(&files->file_lock);
580}
581
582EXPORT_SYMBOL(put_unused_fd);
583
584/*
585 * Install a file pointer in the fd array.
586 *
587 * The VFS is full of places where we drop the files lock between
588 * setting the open_fds bitmap and installing the file in the file
589 * array. At any such point, we are vulnerable to a dup2() race
590 * installing a file in the array before us. We need to detect this and
591 * fput() the struct file we are about to overwrite in this case.
592 *
593 * It should never happen - if we allow dup2() do it, _really_ bad things
594 * will follow.
595 *
596 * NOTE: __fd_install() variant is really, really low-level; don't
597 * use it unless you are forced to by truly lousy API shoved down
598 * your throat. 'files' *MUST* be either current->files or obtained
599 * by get_files_struct(current) done by whoever had given it to you,
600 * or really bad things will happen. Normally you want to use
601 * fd_install() instead.
602 */
603
604void __fd_install(struct files_struct *files, unsigned int fd,
605 struct file *file)
606{
607 struct fdtable *fdt;
608
609 might_sleep();
610 rcu_read_lock_sched();
611
612 while (unlikely(files->resize_in_progress)) {
613 rcu_read_unlock_sched();
614 wait_event(files->resize_wait, !files->resize_in_progress);
615 rcu_read_lock_sched();
616 }
617 /* coupled with smp_wmb() in expand_fdtable() */
618 smp_rmb();
619 fdt = rcu_dereference_sched(files->fdt);
620 BUG_ON(fdt->fd[fd] != NULL);
621 rcu_assign_pointer(fdt->fd[fd], file);
622 rcu_read_unlock_sched();
623}
624
625void fd_install(unsigned int fd, struct file *file)
626{
627 __fd_install(current->files, fd, file);
628}
629
630EXPORT_SYMBOL(fd_install);
631
632/*
633 * The same warnings as for __alloc_fd()/__fd_install() apply here...
634 */
635int __close_fd(struct files_struct *files, unsigned fd)
636{
637 struct file *file;
638 struct fdtable *fdt;
639
640 spin_lock(&files->file_lock);
641 fdt = files_fdtable(files);
642 if (fd >= fdt->max_fds)
643 goto out_unlock;
644 file = fdt->fd[fd];
645 if (!file)
646 goto out_unlock;
647 rcu_assign_pointer(fdt->fd[fd], NULL);
648 __clear_close_on_exec(fd, fdt);
649 __put_unused_fd(files, fd);
650 spin_unlock(&files->file_lock);
651 return filp_close(file, files);
652
653out_unlock:
654 spin_unlock(&files->file_lock);
655 return -EBADF;
656}
657
658void do_close_on_exec(struct files_struct *files)
659{
660 unsigned i;
661 struct fdtable *fdt;
662
663 /* exec unshares first */
664 spin_lock(&files->file_lock);
665 for (i = 0; ; i++) {
666 unsigned long set;
667 unsigned fd = i * BITS_PER_LONG;
668 fdt = files_fdtable(files);
669 if (fd >= fdt->max_fds)
670 break;
671 set = fdt->close_on_exec[i];
672 if (!set)
673 continue;
674 fdt->close_on_exec[i] = 0;
675 for ( ; set ; fd++, set >>= 1) {
676 struct file *file;
677 if (!(set & 1))
678 continue;
679 file = fdt->fd[fd];
680 if (!file)
681 continue;
682 rcu_assign_pointer(fdt->fd[fd], NULL);
683 __put_unused_fd(files, fd);
684 spin_unlock(&files->file_lock);
685 filp_close(file, files);
686 cond_resched();
687 spin_lock(&files->file_lock);
688 }
689
690 }
691 spin_unlock(&files->file_lock);
692}
693
694static struct file *__fget(unsigned int fd, fmode_t mask)
695{
696 struct files_struct *files = current->files;
697 struct file *file;
698
699 rcu_read_lock();
700loop:
701 file = fcheck_files(files, fd);
702 if (file) {
703 /* File object ref couldn't be taken.
704 * dup2() atomicity guarantee is the reason
705 * we loop to catch the new file (or NULL pointer)
706 */
707 if (file->f_mode & mask)
708 file = NULL;
709 else if (!get_file_rcu(file))
710 goto loop;
711 }
712 rcu_read_unlock();
713
714 return file;
715}
716
717struct file *fget(unsigned int fd)
718{
719 return __fget(fd, FMODE_PATH);
720}
721EXPORT_SYMBOL(fget);
722
723struct file *fget_raw(unsigned int fd)
724{
725 return __fget(fd, 0);
726}
727EXPORT_SYMBOL(fget_raw);
728
729/*
730 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
731 *
732 * You can use this instead of fget if you satisfy all of the following
733 * conditions:
734 * 1) You must call fput_light before exiting the syscall and returning control
735 * to userspace (i.e. you cannot remember the returned struct file * after
736 * returning to userspace).
737 * 2) You must not call filp_close on the returned struct file * in between
738 * calls to fget_light and fput_light.
739 * 3) You must not clone the current task in between the calls to fget_light
740 * and fput_light.
741 *
742 * The fput_needed flag returned by fget_light should be passed to the
743 * corresponding fput_light.
744 */
745static unsigned long __fget_light(unsigned int fd, fmode_t mask)
746{
747 struct files_struct *files = current->files;
748 struct file *file;
749
750 if (atomic_read(&files->count) == 1) {
751 file = __fcheck_files(files, fd);
752 if (!file || unlikely(file->f_mode & mask))
753 return 0;
754 return (unsigned long)file;
755 } else {
756 file = __fget(fd, mask);
757 if (!file)
758 return 0;
759 return FDPUT_FPUT | (unsigned long)file;
760 }
761}
762unsigned long __fdget(unsigned int fd)
763{
764 return __fget_light(fd, FMODE_PATH);
765}
766EXPORT_SYMBOL(__fdget);
767
768unsigned long __fdget_raw(unsigned int fd)
769{
770 return __fget_light(fd, 0);
771}
772
773unsigned long __fdget_pos(unsigned int fd)
774{
775 unsigned long v = __fdget(fd);
776 struct file *file = (struct file *)(v & ~3);
777
778 if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
779 if (file_count(file) > 1) {
780 v |= FDPUT_POS_UNLOCK;
781 mutex_lock(&file->f_pos_lock);
782 }
783 }
784 return v;
785}
786
787/*
788 * We only lock f_pos if we have threads or if the file might be
789 * shared with another process. In both cases we'll have an elevated
790 * file count (done either by fdget() or by fork()).
791 */
792
793void set_close_on_exec(unsigned int fd, int flag)
794{
795 struct files_struct *files = current->files;
796 struct fdtable *fdt;
797 spin_lock(&files->file_lock);
798 fdt = files_fdtable(files);
799 if (flag)
800 __set_close_on_exec(fd, fdt);
801 else
802 __clear_close_on_exec(fd, fdt);
803 spin_unlock(&files->file_lock);
804}
805
806bool get_close_on_exec(unsigned int fd)
807{
808 struct files_struct *files = current->files;
809 struct fdtable *fdt;
810 bool res;
811 rcu_read_lock();
812 fdt = files_fdtable(files);
813 res = close_on_exec(fd, fdt);
814 rcu_read_unlock();
815 return res;
816}
817
818static int do_dup2(struct files_struct *files,
819 struct file *file, unsigned fd, unsigned flags)
820__releases(&files->file_lock)
821{
822 struct file *tofree;
823 struct fdtable *fdt;
824
825 /*
826 * We need to detect attempts to do dup2() over allocated but still
827 * not finished descriptor. NB: OpenBSD avoids that at the price of
828 * extra work in their equivalent of fget() - they insert struct
829 * file immediately after grabbing descriptor, mark it larval if
830 * more work (e.g. actual opening) is needed and make sure that
831 * fget() treats larval files as absent. Potentially interesting,
832 * but while extra work in fget() is trivial, locking implications
833 * and amount of surgery on open()-related paths in VFS are not.
834 * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
835 * deadlocks in rather amusing ways, AFAICS. All of that is out of
836 * scope of POSIX or SUS, since neither considers shared descriptor
837 * tables and this condition does not arise without those.
838 */
839 fdt = files_fdtable(files);
840 tofree = fdt->fd[fd];
841 if (!tofree && fd_is_open(fd, fdt))
842 goto Ebusy;
843 get_file(file);
844 rcu_assign_pointer(fdt->fd[fd], file);
845 __set_open_fd(fd, fdt);
846 if (flags & O_CLOEXEC)
847 __set_close_on_exec(fd, fdt);
848 else
849 __clear_close_on_exec(fd, fdt);
850 spin_unlock(&files->file_lock);
851
852 if (tofree)
853 filp_close(tofree, files);
854
855 return fd;
856
857Ebusy:
858 spin_unlock(&files->file_lock);
859 return -EBUSY;
860}
861
862int replace_fd(unsigned fd, struct file *file, unsigned flags)
863{
864 int err;
865 struct files_struct *files = current->files;
866
867 if (!file)
868 return __close_fd(files, fd);
869
870 if (fd >= rlimit(RLIMIT_NOFILE))
871 return -EBADF;
872
873 spin_lock(&files->file_lock);
874 err = expand_files(files, fd);
875 if (unlikely(err < 0))
876 goto out_unlock;
877 return do_dup2(files, file, fd, flags);
878
879out_unlock:
880 spin_unlock(&files->file_lock);
881 return err;
882}
883
884SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
885{
886 int err = -EBADF;
887 struct file *file;
888 struct files_struct *files = current->files;
889
890 if ((flags & ~O_CLOEXEC) != 0)
891 return -EINVAL;
892
893 if (unlikely(oldfd == newfd))
894 return -EINVAL;
895
896 if (newfd >= rlimit(RLIMIT_NOFILE))
897 return -EBADF;
898
899 spin_lock(&files->file_lock);
900 err = expand_files(files, newfd);
901 file = fcheck(oldfd);
902 if (unlikely(!file))
903 goto Ebadf;
904 if (unlikely(err < 0)) {
905 if (err == -EMFILE)
906 goto Ebadf;
907 goto out_unlock;
908 }
909 return do_dup2(files, file, newfd, flags);
910
911Ebadf:
912 err = -EBADF;
913out_unlock:
914 spin_unlock(&files->file_lock);
915 return err;
916}
917
918SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
919{
920 if (unlikely(newfd == oldfd)) { /* corner case */
921 struct files_struct *files = current->files;
922 int retval = oldfd;
923
924 rcu_read_lock();
925 if (!fcheck_files(files, oldfd))
926 retval = -EBADF;
927 rcu_read_unlock();
928 return retval;
929 }
930 return sys_dup3(oldfd, newfd, 0);
931}
932
933SYSCALL_DEFINE1(dup, unsigned int, fildes)
934{
935 int ret = -EBADF;
936 struct file *file = fget_raw(fildes);
937
938 if (file) {
939 ret = get_unused_fd_flags(0);
940 if (ret >= 0)
941 fd_install(ret, file);
942 else
943 fput(file);
944 }
945 return ret;
946}
947
948int f_dupfd(unsigned int from, struct file *file, unsigned flags)
949{
950 int err;
951 if (from >= rlimit(RLIMIT_NOFILE))
952 return -EINVAL;
953 err = alloc_fd(from, flags);
954 if (err >= 0) {
955 get_file(file);
956 fd_install(err, file);
957 }
958 return err;
959}
960
961int iterate_fd(struct files_struct *files, unsigned n,
962 int (*f)(const void *, struct file *, unsigned),
963 const void *p)
964{
965 struct fdtable *fdt;
966 int res = 0;
967 if (!files)
968 return 0;
969 spin_lock(&files->file_lock);
970 for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
971 struct file *file;
972 file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
973 if (!file)
974 continue;
975 res = f(p, file, n);
976 if (res)
977 break;
978 }
979 spin_unlock(&files->file_lock);
980 return res;
981}
982EXPORT_SYMBOL(iterate_fd);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/fs/file.c
4 *
5 * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
6 *
7 * Manage the dynamic fd arrays in the process files_struct.
8 */
9
10#include <linux/syscalls.h>
11#include <linux/export.h>
12#include <linux/fs.h>
13#include <linux/kernel.h>
14#include <linux/mm.h>
15#include <linux/sched/signal.h>
16#include <linux/slab.h>
17#include <linux/file.h>
18#include <linux/fdtable.h>
19#include <linux/bitops.h>
20#include <linux/spinlock.h>
21#include <linux/rcupdate.h>
22#include <linux/close_range.h>
23#include <net/sock.h>
24
25unsigned int sysctl_nr_open __read_mostly = 1024*1024;
26unsigned int sysctl_nr_open_min = BITS_PER_LONG;
27/* our min() is unusable in constant expressions ;-/ */
28#define __const_min(x, y) ((x) < (y) ? (x) : (y))
29unsigned int sysctl_nr_open_max =
30 __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
31
32static void __free_fdtable(struct fdtable *fdt)
33{
34 kvfree(fdt->fd);
35 kvfree(fdt->open_fds);
36 kfree(fdt);
37}
38
39static void free_fdtable_rcu(struct rcu_head *rcu)
40{
41 __free_fdtable(container_of(rcu, struct fdtable, rcu));
42}
43
44#define BITBIT_NR(nr) BITS_TO_LONGS(BITS_TO_LONGS(nr))
45#define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))
46
47/*
48 * Copy 'count' fd bits from the old table to the new table and clear the extra
49 * space if any. This does not copy the file pointers. Called with the files
50 * spinlock held for write.
51 */
52static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
53 unsigned int count)
54{
55 unsigned int cpy, set;
56
57 cpy = count / BITS_PER_BYTE;
58 set = (nfdt->max_fds - count) / BITS_PER_BYTE;
59 memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
60 memset((char *)nfdt->open_fds + cpy, 0, set);
61 memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
62 memset((char *)nfdt->close_on_exec + cpy, 0, set);
63
64 cpy = BITBIT_SIZE(count);
65 set = BITBIT_SIZE(nfdt->max_fds) - cpy;
66 memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
67 memset((char *)nfdt->full_fds_bits + cpy, 0, set);
68}
69
70/*
71 * Copy all file descriptors from the old table to the new, expanded table and
72 * clear the extra space. Called with the files spinlock held for write.
73 */
74static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
75{
76 size_t cpy, set;
77
78 BUG_ON(nfdt->max_fds < ofdt->max_fds);
79
80 cpy = ofdt->max_fds * sizeof(struct file *);
81 set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
82 memcpy(nfdt->fd, ofdt->fd, cpy);
83 memset((char *)nfdt->fd + cpy, 0, set);
84
85 copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
86}
87
88static struct fdtable * alloc_fdtable(unsigned int nr)
89{
90 struct fdtable *fdt;
91 void *data;
92
93 /*
94 * Figure out how many fds we actually want to support in this fdtable.
95 * Allocation steps are keyed to the size of the fdarray, since it
96 * grows far faster than any of the other dynamic data. We try to fit
97 * the fdarray into comfortable page-tuned chunks: starting at 1024B
98 * and growing in powers of two from there on.
99 */
100 nr /= (1024 / sizeof(struct file *));
101 nr = roundup_pow_of_two(nr + 1);
102 nr *= (1024 / sizeof(struct file *));
103 /*
104 * Note that this can drive nr *below* what we had passed if sysctl_nr_open
105 * had been set lower between the check in expand_files() and here. Deal
106 * with that in caller, it's cheaper that way.
107 *
108 * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
109 * bitmaps handling below becomes unpleasant, to put it mildly...
110 */
111 if (unlikely(nr > sysctl_nr_open))
112 nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
113
114 fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
115 if (!fdt)
116 goto out;
117 fdt->max_fds = nr;
118 data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT);
119 if (!data)
120 goto out_fdt;
121 fdt->fd = data;
122
123 data = kvmalloc(max_t(size_t,
124 2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES),
125 GFP_KERNEL_ACCOUNT);
126 if (!data)
127 goto out_arr;
128 fdt->open_fds = data;
129 data += nr / BITS_PER_BYTE;
130 fdt->close_on_exec = data;
131 data += nr / BITS_PER_BYTE;
132 fdt->full_fds_bits = data;
133
134 return fdt;
135
136out_arr:
137 kvfree(fdt->fd);
138out_fdt:
139 kfree(fdt);
140out:
141 return NULL;
142}
143
144/*
145 * Expand the file descriptor table.
146 * This function will allocate a new fdtable and both fd array and fdset, of
147 * the given size.
148 * Return <0 error code on error; 1 on successful completion.
149 * The files->file_lock should be held on entry, and will be held on exit.
150 */
151static int expand_fdtable(struct files_struct *files, unsigned int nr)
152 __releases(files->file_lock)
153 __acquires(files->file_lock)
154{
155 struct fdtable *new_fdt, *cur_fdt;
156
157 spin_unlock(&files->file_lock);
158 new_fdt = alloc_fdtable(nr);
159
160 /* make sure all __fd_install() have seen resize_in_progress
161 * or have finished their rcu_read_lock_sched() section.
162 */
163 if (atomic_read(&files->count) > 1)
164 synchronize_rcu();
165
166 spin_lock(&files->file_lock);
167 if (!new_fdt)
168 return -ENOMEM;
169 /*
170 * extremely unlikely race - sysctl_nr_open decreased between the check in
171 * caller and alloc_fdtable(). Cheaper to catch it here...
172 */
173 if (unlikely(new_fdt->max_fds <= nr)) {
174 __free_fdtable(new_fdt);
175 return -EMFILE;
176 }
177 cur_fdt = files_fdtable(files);
178 BUG_ON(nr < cur_fdt->max_fds);
179 copy_fdtable(new_fdt, cur_fdt);
180 rcu_assign_pointer(files->fdt, new_fdt);
181 if (cur_fdt != &files->fdtab)
182 call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
183 /* coupled with smp_rmb() in __fd_install() */
184 smp_wmb();
185 return 1;
186}
187
188/*
189 * Expand files.
190 * This function will expand the file structures, if the requested size exceeds
191 * the current capacity and there is room for expansion.
192 * Return <0 error code on error; 0 when nothing done; 1 when files were
193 * expanded and execution may have blocked.
194 * The files->file_lock should be held on entry, and will be held on exit.
195 */
196static int expand_files(struct files_struct *files, unsigned int nr)
197 __releases(files->file_lock)
198 __acquires(files->file_lock)
199{
200 struct fdtable *fdt;
201 int expanded = 0;
202
203repeat:
204 fdt = files_fdtable(files);
205
206 /* Do we need to expand? */
207 if (nr < fdt->max_fds)
208 return expanded;
209
210 /* Can we expand? */
211 if (nr >= sysctl_nr_open)
212 return -EMFILE;
213
214 if (unlikely(files->resize_in_progress)) {
215 spin_unlock(&files->file_lock);
216 expanded = 1;
217 wait_event(files->resize_wait, !files->resize_in_progress);
218 spin_lock(&files->file_lock);
219 goto repeat;
220 }
221
222 /* All good, so we try */
223 files->resize_in_progress = true;
224 expanded = expand_fdtable(files, nr);
225 files->resize_in_progress = false;
226
227 wake_up_all(&files->resize_wait);
228 return expanded;
229}
230
231static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt)
232{
233 __set_bit(fd, fdt->close_on_exec);
234}
235
236static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt)
237{
238 if (test_bit(fd, fdt->close_on_exec))
239 __clear_bit(fd, fdt->close_on_exec);
240}
241
242static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
243{
244 __set_bit(fd, fdt->open_fds);
245 fd /= BITS_PER_LONG;
246 if (!~fdt->open_fds[fd])
247 __set_bit(fd, fdt->full_fds_bits);
248}
249
250static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
251{
252 __clear_bit(fd, fdt->open_fds);
253 __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
254}
255
256static unsigned int count_open_files(struct fdtable *fdt)
257{
258 unsigned int size = fdt->max_fds;
259 unsigned int i;
260
261 /* Find the last open fd */
262 for (i = size / BITS_PER_LONG; i > 0; ) {
263 if (fdt->open_fds[--i])
264 break;
265 }
266 i = (i + 1) * BITS_PER_LONG;
267 return i;
268}
269
270static unsigned int sane_fdtable_size(struct fdtable *fdt, unsigned int max_fds)
271{
272 unsigned int count;
273
274 count = count_open_files(fdt);
275 if (max_fds < NR_OPEN_DEFAULT)
276 max_fds = NR_OPEN_DEFAULT;
277 return min(count, max_fds);
278}
279
280/*
281 * Allocate a new files structure and copy contents from the
282 * passed in files structure.
283 * errorp will be valid only when the returned files_struct is NULL.
284 */
285struct files_struct *dup_fd(struct files_struct *oldf, unsigned int max_fds, int *errorp)
286{
287 struct files_struct *newf;
288 struct file **old_fds, **new_fds;
289 unsigned int open_files, i;
290 struct fdtable *old_fdt, *new_fdt;
291
292 *errorp = -ENOMEM;
293 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
294 if (!newf)
295 goto out;
296
297 atomic_set(&newf->count, 1);
298
299 spin_lock_init(&newf->file_lock);
300 newf->resize_in_progress = false;
301 init_waitqueue_head(&newf->resize_wait);
302 newf->next_fd = 0;
303 new_fdt = &newf->fdtab;
304 new_fdt->max_fds = NR_OPEN_DEFAULT;
305 new_fdt->close_on_exec = newf->close_on_exec_init;
306 new_fdt->open_fds = newf->open_fds_init;
307 new_fdt->full_fds_bits = newf->full_fds_bits_init;
308 new_fdt->fd = &newf->fd_array[0];
309
310 spin_lock(&oldf->file_lock);
311 old_fdt = files_fdtable(oldf);
312 open_files = sane_fdtable_size(old_fdt, max_fds);
313
314 /*
315 * Check whether we need to allocate a larger fd array and fd set.
316 */
317 while (unlikely(open_files > new_fdt->max_fds)) {
318 spin_unlock(&oldf->file_lock);
319
320 if (new_fdt != &newf->fdtab)
321 __free_fdtable(new_fdt);
322
323 new_fdt = alloc_fdtable(open_files - 1);
324 if (!new_fdt) {
325 *errorp = -ENOMEM;
326 goto out_release;
327 }
328
329 /* beyond sysctl_nr_open; nothing to do */
330 if (unlikely(new_fdt->max_fds < open_files)) {
331 __free_fdtable(new_fdt);
332 *errorp = -EMFILE;
333 goto out_release;
334 }
335
336 /*
337 * Reacquire the oldf lock and a pointer to its fd table
338 * who knows it may have a new bigger fd table. We need
339 * the latest pointer.
340 */
341 spin_lock(&oldf->file_lock);
342 old_fdt = files_fdtable(oldf);
343 open_files = sane_fdtable_size(old_fdt, max_fds);
344 }
345
346 copy_fd_bitmaps(new_fdt, old_fdt, open_files);
347
348 old_fds = old_fdt->fd;
349 new_fds = new_fdt->fd;
350
351 for (i = open_files; i != 0; i--) {
352 struct file *f = *old_fds++;
353 if (f) {
354 get_file(f);
355 } else {
356 /*
357 * The fd may be claimed in the fd bitmap but not yet
358 * instantiated in the files array if a sibling thread
359 * is partway through open(). So make sure that this
360 * fd is available to the new process.
361 */
362 __clear_open_fd(open_files - i, new_fdt);
363 }
364 rcu_assign_pointer(*new_fds++, f);
365 }
366 spin_unlock(&oldf->file_lock);
367
368 /* clear the remainder */
369 memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
370
371 rcu_assign_pointer(newf->fdt, new_fdt);
372
373 return newf;
374
375out_release:
376 kmem_cache_free(files_cachep, newf);
377out:
378 return NULL;
379}
380
381static struct fdtable *close_files(struct files_struct * files)
382{
383 /*
384 * It is safe to dereference the fd table without RCU or
385 * ->file_lock because this is the last reference to the
386 * files structure.
387 */
388 struct fdtable *fdt = rcu_dereference_raw(files->fdt);
389 unsigned int i, j = 0;
390
391 for (;;) {
392 unsigned long set;
393 i = j * BITS_PER_LONG;
394 if (i >= fdt->max_fds)
395 break;
396 set = fdt->open_fds[j++];
397 while (set) {
398 if (set & 1) {
399 struct file * file = xchg(&fdt->fd[i], NULL);
400 if (file) {
401 filp_close(file, files);
402 cond_resched();
403 }
404 }
405 i++;
406 set >>= 1;
407 }
408 }
409
410 return fdt;
411}
412
413struct files_struct *get_files_struct(struct task_struct *task)
414{
415 struct files_struct *files;
416
417 task_lock(task);
418 files = task->files;
419 if (files)
420 atomic_inc(&files->count);
421 task_unlock(task);
422
423 return files;
424}
425
426void put_files_struct(struct files_struct *files)
427{
428 if (atomic_dec_and_test(&files->count)) {
429 struct fdtable *fdt = close_files(files);
430
431 /* free the arrays if they are not embedded */
432 if (fdt != &files->fdtab)
433 __free_fdtable(fdt);
434 kmem_cache_free(files_cachep, files);
435 }
436}
437
438void reset_files_struct(struct files_struct *files)
439{
440 struct task_struct *tsk = current;
441 struct files_struct *old;
442
443 old = tsk->files;
444 task_lock(tsk);
445 tsk->files = files;
446 task_unlock(tsk);
447 put_files_struct(old);
448}
449
450void exit_files(struct task_struct *tsk)
451{
452 struct files_struct * files = tsk->files;
453
454 if (files) {
455 task_lock(tsk);
456 tsk->files = NULL;
457 task_unlock(tsk);
458 put_files_struct(files);
459 }
460}
461
462struct files_struct init_files = {
463 .count = ATOMIC_INIT(1),
464 .fdt = &init_files.fdtab,
465 .fdtab = {
466 .max_fds = NR_OPEN_DEFAULT,
467 .fd = &init_files.fd_array[0],
468 .close_on_exec = init_files.close_on_exec_init,
469 .open_fds = init_files.open_fds_init,
470 .full_fds_bits = init_files.full_fds_bits_init,
471 },
472 .file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
473 .resize_wait = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),
474};
475
476static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
477{
478 unsigned int maxfd = fdt->max_fds;
479 unsigned int maxbit = maxfd / BITS_PER_LONG;
480 unsigned int bitbit = start / BITS_PER_LONG;
481
482 bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
483 if (bitbit > maxfd)
484 return maxfd;
485 if (bitbit > start)
486 start = bitbit;
487 return find_next_zero_bit(fdt->open_fds, maxfd, start);
488}
489
490/*
491 * allocate a file descriptor, mark it busy.
492 */
493int __alloc_fd(struct files_struct *files,
494 unsigned start, unsigned end, unsigned flags)
495{
496 unsigned int fd;
497 int error;
498 struct fdtable *fdt;
499
500 spin_lock(&files->file_lock);
501repeat:
502 fdt = files_fdtable(files);
503 fd = start;
504 if (fd < files->next_fd)
505 fd = files->next_fd;
506
507 if (fd < fdt->max_fds)
508 fd = find_next_fd(fdt, fd);
509
510 /*
511 * N.B. For clone tasks sharing a files structure, this test
512 * will limit the total number of files that can be opened.
513 */
514 error = -EMFILE;
515 if (fd >= end)
516 goto out;
517
518 error = expand_files(files, fd);
519 if (error < 0)
520 goto out;
521
522 /*
523 * If we needed to expand the fs array we
524 * might have blocked - try again.
525 */
526 if (error)
527 goto repeat;
528
529 if (start <= files->next_fd)
530 files->next_fd = fd + 1;
531
532 __set_open_fd(fd, fdt);
533 if (flags & O_CLOEXEC)
534 __set_close_on_exec(fd, fdt);
535 else
536 __clear_close_on_exec(fd, fdt);
537 error = fd;
538#if 1
539 /* Sanity check */
540 if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
541 printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
542 rcu_assign_pointer(fdt->fd[fd], NULL);
543 }
544#endif
545
546out:
547 spin_unlock(&files->file_lock);
548 return error;
549}
550
551static int alloc_fd(unsigned start, unsigned flags)
552{
553 return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags);
554}
555
556int __get_unused_fd_flags(unsigned flags, unsigned long nofile)
557{
558 return __alloc_fd(current->files, 0, nofile, flags);
559}
560
561int get_unused_fd_flags(unsigned flags)
562{
563 return __get_unused_fd_flags(flags, rlimit(RLIMIT_NOFILE));
564}
565EXPORT_SYMBOL(get_unused_fd_flags);
566
567static void __put_unused_fd(struct files_struct *files, unsigned int fd)
568{
569 struct fdtable *fdt = files_fdtable(files);
570 __clear_open_fd(fd, fdt);
571 if (fd < files->next_fd)
572 files->next_fd = fd;
573}
574
575void put_unused_fd(unsigned int fd)
576{
577 struct files_struct *files = current->files;
578 spin_lock(&files->file_lock);
579 __put_unused_fd(files, fd);
580 spin_unlock(&files->file_lock);
581}
582
583EXPORT_SYMBOL(put_unused_fd);
584
585/*
586 * Install a file pointer in the fd array.
587 *
588 * The VFS is full of places where we drop the files lock between
589 * setting the open_fds bitmap and installing the file in the file
590 * array. At any such point, we are vulnerable to a dup2() race
591 * installing a file in the array before us. We need to detect this and
592 * fput() the struct file we are about to overwrite in this case.
593 *
594 * It should never happen - if we allow dup2() do it, _really_ bad things
595 * will follow.
596 *
597 * NOTE: __fd_install() variant is really, really low-level; don't
598 * use it unless you are forced to by truly lousy API shoved down
599 * your throat. 'files' *MUST* be either current->files or obtained
600 * by get_files_struct(current) done by whoever had given it to you,
601 * or really bad things will happen. Normally you want to use
602 * fd_install() instead.
603 */
604
605void __fd_install(struct files_struct *files, unsigned int fd,
606 struct file *file)
607{
608 struct fdtable *fdt;
609
610 rcu_read_lock_sched();
611
612 if (unlikely(files->resize_in_progress)) {
613 rcu_read_unlock_sched();
614 spin_lock(&files->file_lock);
615 fdt = files_fdtable(files);
616 BUG_ON(fdt->fd[fd] != NULL);
617 rcu_assign_pointer(fdt->fd[fd], file);
618 spin_unlock(&files->file_lock);
619 return;
620 }
621 /* coupled with smp_wmb() in expand_fdtable() */
622 smp_rmb();
623 fdt = rcu_dereference_sched(files->fdt);
624 BUG_ON(fdt->fd[fd] != NULL);
625 rcu_assign_pointer(fdt->fd[fd], file);
626 rcu_read_unlock_sched();
627}
628
629/*
630 * This consumes the "file" refcount, so callers should treat it
631 * as if they had called fput(file).
632 */
633void fd_install(unsigned int fd, struct file *file)
634{
635 __fd_install(current->files, fd, file);
636}
637
638EXPORT_SYMBOL(fd_install);
639
640static struct file *pick_file(struct files_struct *files, unsigned fd)
641{
642 struct file *file = NULL;
643 struct fdtable *fdt;
644
645 spin_lock(&files->file_lock);
646 fdt = files_fdtable(files);
647 if (fd >= fdt->max_fds)
648 goto out_unlock;
649 file = fdt->fd[fd];
650 if (!file)
651 goto out_unlock;
652 rcu_assign_pointer(fdt->fd[fd], NULL);
653 __put_unused_fd(files, fd);
654
655out_unlock:
656 spin_unlock(&files->file_lock);
657 return file;
658}
659
660/*
661 * The same warnings as for __alloc_fd()/__fd_install() apply here...
662 */
663int __close_fd(struct files_struct *files, unsigned fd)
664{
665 struct file *file;
666
667 file = pick_file(files, fd);
668 if (!file)
669 return -EBADF;
670
671 return filp_close(file, files);
672}
673EXPORT_SYMBOL(__close_fd); /* for ksys_close() */
674
675/**
676 * __close_range() - Close all file descriptors in a given range.
677 *
678 * @fd: starting file descriptor to close
679 * @max_fd: last file descriptor to close
680 *
681 * This closes a range of file descriptors. All file descriptors
682 * from @fd up to and including @max_fd are closed.
683 */
684int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
685{
686 unsigned int cur_max;
687 struct task_struct *me = current;
688 struct files_struct *cur_fds = me->files, *fds = NULL;
689
690 if (flags & ~CLOSE_RANGE_UNSHARE)
691 return -EINVAL;
692
693 if (fd > max_fd)
694 return -EINVAL;
695
696 rcu_read_lock();
697 cur_max = files_fdtable(cur_fds)->max_fds;
698 rcu_read_unlock();
699
700 /* cap to last valid index into fdtable */
701 cur_max--;
702
703 if (flags & CLOSE_RANGE_UNSHARE) {
704 int ret;
705 unsigned int max_unshare_fds = NR_OPEN_MAX;
706
707 /*
708 * If the requested range is greater than the current maximum,
709 * we're closing everything so only copy all file descriptors
710 * beneath the lowest file descriptor.
711 */
712 if (max_fd >= cur_max)
713 max_unshare_fds = fd;
714
715 ret = unshare_fd(CLONE_FILES, max_unshare_fds, &fds);
716 if (ret)
717 return ret;
718
719 /*
720 * We used to share our file descriptor table, and have now
721 * created a private one, make sure we're using it below.
722 */
723 if (fds)
724 swap(cur_fds, fds);
725 }
726
727 max_fd = min(max_fd, cur_max);
728 while (fd <= max_fd) {
729 struct file *file;
730
731 file = pick_file(cur_fds, fd++);
732 if (!file)
733 continue;
734
735 filp_close(file, cur_fds);
736 cond_resched();
737 }
738
739 if (fds) {
740 /*
741 * We're done closing the files we were supposed to. Time to install
742 * the new file descriptor table and drop the old one.
743 */
744 task_lock(me);
745 me->files = cur_fds;
746 task_unlock(me);
747 put_files_struct(fds);
748 }
749
750 return 0;
751}
752
753/*
754 * variant of __close_fd that gets a ref on the file for later fput.
755 * The caller must ensure that filp_close() called on the file, and then
756 * an fput().
757 */
758int __close_fd_get_file(unsigned int fd, struct file **res)
759{
760 struct files_struct *files = current->files;
761 struct file *file;
762 struct fdtable *fdt;
763
764 spin_lock(&files->file_lock);
765 fdt = files_fdtable(files);
766 if (fd >= fdt->max_fds)
767 goto out_unlock;
768 file = fdt->fd[fd];
769 if (!file)
770 goto out_unlock;
771 rcu_assign_pointer(fdt->fd[fd], NULL);
772 __put_unused_fd(files, fd);
773 spin_unlock(&files->file_lock);
774 get_file(file);
775 *res = file;
776 return 0;
777
778out_unlock:
779 spin_unlock(&files->file_lock);
780 *res = NULL;
781 return -ENOENT;
782}
783
784void do_close_on_exec(struct files_struct *files)
785{
786 unsigned i;
787 struct fdtable *fdt;
788
789 /* exec unshares first */
790 spin_lock(&files->file_lock);
791 for (i = 0; ; i++) {
792 unsigned long set;
793 unsigned fd = i * BITS_PER_LONG;
794 fdt = files_fdtable(files);
795 if (fd >= fdt->max_fds)
796 break;
797 set = fdt->close_on_exec[i];
798 if (!set)
799 continue;
800 fdt->close_on_exec[i] = 0;
801 for ( ; set ; fd++, set >>= 1) {
802 struct file *file;
803 if (!(set & 1))
804 continue;
805 file = fdt->fd[fd];
806 if (!file)
807 continue;
808 rcu_assign_pointer(fdt->fd[fd], NULL);
809 __put_unused_fd(files, fd);
810 spin_unlock(&files->file_lock);
811 filp_close(file, files);
812 cond_resched();
813 spin_lock(&files->file_lock);
814 }
815
816 }
817 spin_unlock(&files->file_lock);
818}
819
820static struct file *__fget_files(struct files_struct *files, unsigned int fd,
821 fmode_t mask, unsigned int refs)
822{
823 struct file *file;
824
825 rcu_read_lock();
826loop:
827 file = fcheck_files(files, fd);
828 if (file) {
829 /* File object ref couldn't be taken.
830 * dup2() atomicity guarantee is the reason
831 * we loop to catch the new file (or NULL pointer)
832 */
833 if (file->f_mode & mask)
834 file = NULL;
835 else if (!get_file_rcu_many(file, refs))
836 goto loop;
837 }
838 rcu_read_unlock();
839
840 return file;
841}
842
843static inline struct file *__fget(unsigned int fd, fmode_t mask,
844 unsigned int refs)
845{
846 return __fget_files(current->files, fd, mask, refs);
847}
848
849struct file *fget_many(unsigned int fd, unsigned int refs)
850{
851 return __fget(fd, FMODE_PATH, refs);
852}
853
854struct file *fget(unsigned int fd)
855{
856 return __fget(fd, FMODE_PATH, 1);
857}
858EXPORT_SYMBOL(fget);
859
860struct file *fget_raw(unsigned int fd)
861{
862 return __fget(fd, 0, 1);
863}
864EXPORT_SYMBOL(fget_raw);
865
866struct file *fget_task(struct task_struct *task, unsigned int fd)
867{
868 struct file *file = NULL;
869
870 task_lock(task);
871 if (task->files)
872 file = __fget_files(task->files, fd, 0, 1);
873 task_unlock(task);
874
875 return file;
876}
877
878/*
879 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
880 *
881 * You can use this instead of fget if you satisfy all of the following
882 * conditions:
883 * 1) You must call fput_light before exiting the syscall and returning control
884 * to userspace (i.e. you cannot remember the returned struct file * after
885 * returning to userspace).
886 * 2) You must not call filp_close on the returned struct file * in between
887 * calls to fget_light and fput_light.
888 * 3) You must not clone the current task in between the calls to fget_light
889 * and fput_light.
890 *
891 * The fput_needed flag returned by fget_light should be passed to the
892 * corresponding fput_light.
893 */
894static unsigned long __fget_light(unsigned int fd, fmode_t mask)
895{
896 struct files_struct *files = current->files;
897 struct file *file;
898
899 if (atomic_read(&files->count) == 1) {
900 file = __fcheck_files(files, fd);
901 if (!file || unlikely(file->f_mode & mask))
902 return 0;
903 return (unsigned long)file;
904 } else {
905 file = __fget(fd, mask, 1);
906 if (!file)
907 return 0;
908 return FDPUT_FPUT | (unsigned long)file;
909 }
910}
911unsigned long __fdget(unsigned int fd)
912{
913 return __fget_light(fd, FMODE_PATH);
914}
915EXPORT_SYMBOL(__fdget);
916
917unsigned long __fdget_raw(unsigned int fd)
918{
919 return __fget_light(fd, 0);
920}
921
922unsigned long __fdget_pos(unsigned int fd)
923{
924 unsigned long v = __fdget(fd);
925 struct file *file = (struct file *)(v & ~3);
926
927 if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
928 if (file_count(file) > 1) {
929 v |= FDPUT_POS_UNLOCK;
930 mutex_lock(&file->f_pos_lock);
931 }
932 }
933 return v;
934}
935
936void __f_unlock_pos(struct file *f)
937{
938 mutex_unlock(&f->f_pos_lock);
939}
940
941/*
942 * We only lock f_pos if we have threads or if the file might be
943 * shared with another process. In both cases we'll have an elevated
944 * file count (done either by fdget() or by fork()).
945 */
946
947void set_close_on_exec(unsigned int fd, int flag)
948{
949 struct files_struct *files = current->files;
950 struct fdtable *fdt;
951 spin_lock(&files->file_lock);
952 fdt = files_fdtable(files);
953 if (flag)
954 __set_close_on_exec(fd, fdt);
955 else
956 __clear_close_on_exec(fd, fdt);
957 spin_unlock(&files->file_lock);
958}
959
960bool get_close_on_exec(unsigned int fd)
961{
962 struct files_struct *files = current->files;
963 struct fdtable *fdt;
964 bool res;
965 rcu_read_lock();
966 fdt = files_fdtable(files);
967 res = close_on_exec(fd, fdt);
968 rcu_read_unlock();
969 return res;
970}
971
972static int do_dup2(struct files_struct *files,
973 struct file *file, unsigned fd, unsigned flags)
974__releases(&files->file_lock)
975{
976 struct file *tofree;
977 struct fdtable *fdt;
978
979 /*
980 * We need to detect attempts to do dup2() over allocated but still
981 * not finished descriptor. NB: OpenBSD avoids that at the price of
982 * extra work in their equivalent of fget() - they insert struct
983 * file immediately after grabbing descriptor, mark it larval if
984 * more work (e.g. actual opening) is needed and make sure that
985 * fget() treats larval files as absent. Potentially interesting,
986 * but while extra work in fget() is trivial, locking implications
987 * and amount of surgery on open()-related paths in VFS are not.
988 * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
989 * deadlocks in rather amusing ways, AFAICS. All of that is out of
990 * scope of POSIX or SUS, since neither considers shared descriptor
991 * tables and this condition does not arise without those.
992 */
993 fdt = files_fdtable(files);
994 tofree = fdt->fd[fd];
995 if (!tofree && fd_is_open(fd, fdt))
996 goto Ebusy;
997 get_file(file);
998 rcu_assign_pointer(fdt->fd[fd], file);
999 __set_open_fd(fd, fdt);
1000 if (flags & O_CLOEXEC)
1001 __set_close_on_exec(fd, fdt);
1002 else
1003 __clear_close_on_exec(fd, fdt);
1004 spin_unlock(&files->file_lock);
1005
1006 if (tofree)
1007 filp_close(tofree, files);
1008
1009 return fd;
1010
1011Ebusy:
1012 spin_unlock(&files->file_lock);
1013 return -EBUSY;
1014}
1015
1016int replace_fd(unsigned fd, struct file *file, unsigned flags)
1017{
1018 int err;
1019 struct files_struct *files = current->files;
1020
1021 if (!file)
1022 return __close_fd(files, fd);
1023
1024 if (fd >= rlimit(RLIMIT_NOFILE))
1025 return -EBADF;
1026
1027 spin_lock(&files->file_lock);
1028 err = expand_files(files, fd);
1029 if (unlikely(err < 0))
1030 goto out_unlock;
1031 return do_dup2(files, file, fd, flags);
1032
1033out_unlock:
1034 spin_unlock(&files->file_lock);
1035 return err;
1036}
1037
1038/**
1039 * __receive_fd() - Install received file into file descriptor table
1040 *
1041 * @fd: fd to install into (if negative, a new fd will be allocated)
1042 * @file: struct file that was received from another process
1043 * @ufd: __user pointer to write new fd number to
1044 * @o_flags: the O_* flags to apply to the new fd entry
1045 *
1046 * Installs a received file into the file descriptor table, with appropriate
1047 * checks and count updates. Optionally writes the fd number to userspace, if
1048 * @ufd is non-NULL.
1049 *
1050 * This helper handles its own reference counting of the incoming
1051 * struct file.
1052 *
1053 * Returns newly install fd or -ve on error.
1054 */
1055int __receive_fd(int fd, struct file *file, int __user *ufd, unsigned int o_flags)
1056{
1057 int new_fd;
1058 int error;
1059
1060 error = security_file_receive(file);
1061 if (error)
1062 return error;
1063
1064 if (fd < 0) {
1065 new_fd = get_unused_fd_flags(o_flags);
1066 if (new_fd < 0)
1067 return new_fd;
1068 } else {
1069 new_fd = fd;
1070 }
1071
1072 if (ufd) {
1073 error = put_user(new_fd, ufd);
1074 if (error) {
1075 if (fd < 0)
1076 put_unused_fd(new_fd);
1077 return error;
1078 }
1079 }
1080
1081 if (fd < 0) {
1082 fd_install(new_fd, get_file(file));
1083 } else {
1084 error = replace_fd(new_fd, file, o_flags);
1085 if (error)
1086 return error;
1087 }
1088
1089 /* Bump the sock usage counts, if any. */
1090 __receive_sock(file);
1091 return new_fd;
1092}
1093
1094static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
1095{
1096 int err = -EBADF;
1097 struct file *file;
1098 struct files_struct *files = current->files;
1099
1100 if ((flags & ~O_CLOEXEC) != 0)
1101 return -EINVAL;
1102
1103 if (unlikely(oldfd == newfd))
1104 return -EINVAL;
1105
1106 if (newfd >= rlimit(RLIMIT_NOFILE))
1107 return -EBADF;
1108
1109 spin_lock(&files->file_lock);
1110 err = expand_files(files, newfd);
1111 file = fcheck(oldfd);
1112 if (unlikely(!file))
1113 goto Ebadf;
1114 if (unlikely(err < 0)) {
1115 if (err == -EMFILE)
1116 goto Ebadf;
1117 goto out_unlock;
1118 }
1119 return do_dup2(files, file, newfd, flags);
1120
1121Ebadf:
1122 err = -EBADF;
1123out_unlock:
1124 spin_unlock(&files->file_lock);
1125 return err;
1126}
1127
1128SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
1129{
1130 return ksys_dup3(oldfd, newfd, flags);
1131}
1132
1133SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
1134{
1135 if (unlikely(newfd == oldfd)) { /* corner case */
1136 struct files_struct *files = current->files;
1137 int retval = oldfd;
1138
1139 rcu_read_lock();
1140 if (!fcheck_files(files, oldfd))
1141 retval = -EBADF;
1142 rcu_read_unlock();
1143 return retval;
1144 }
1145 return ksys_dup3(oldfd, newfd, 0);
1146}
1147
1148SYSCALL_DEFINE1(dup, unsigned int, fildes)
1149{
1150 int ret = -EBADF;
1151 struct file *file = fget_raw(fildes);
1152
1153 if (file) {
1154 ret = get_unused_fd_flags(0);
1155 if (ret >= 0)
1156 fd_install(ret, file);
1157 else
1158 fput(file);
1159 }
1160 return ret;
1161}
1162
1163int f_dupfd(unsigned int from, struct file *file, unsigned flags)
1164{
1165 int err;
1166 if (from >= rlimit(RLIMIT_NOFILE))
1167 return -EINVAL;
1168 err = alloc_fd(from, flags);
1169 if (err >= 0) {
1170 get_file(file);
1171 fd_install(err, file);
1172 }
1173 return err;
1174}
1175
1176int iterate_fd(struct files_struct *files, unsigned n,
1177 int (*f)(const void *, struct file *, unsigned),
1178 const void *p)
1179{
1180 struct fdtable *fdt;
1181 int res = 0;
1182 if (!files)
1183 return 0;
1184 spin_lock(&files->file_lock);
1185 for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
1186 struct file *file;
1187 file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
1188 if (!file)
1189 continue;
1190 res = f(p, file, n);
1191 if (res)
1192 break;
1193 }
1194 spin_unlock(&files->file_lock);
1195 return res;
1196}
1197EXPORT_SYMBOL(iterate_fd);