Loading...
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
25#include "internal.h"
26
27unsigned int sysctl_nr_open __read_mostly = 1024*1024;
28unsigned int sysctl_nr_open_min = BITS_PER_LONG;
29/* our min() is unusable in constant expressions ;-/ */
30#define __const_min(x, y) ((x) < (y) ? (x) : (y))
31unsigned int sysctl_nr_open_max =
32 __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
33
34static void __free_fdtable(struct fdtable *fdt)
35{
36 kvfree(fdt->fd);
37 kvfree(fdt->open_fds);
38 kfree(fdt);
39}
40
41static void free_fdtable_rcu(struct rcu_head *rcu)
42{
43 __free_fdtable(container_of(rcu, struct fdtable, rcu));
44}
45
46#define BITBIT_NR(nr) BITS_TO_LONGS(BITS_TO_LONGS(nr))
47#define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))
48
49/*
50 * Copy 'count' fd bits from the old table to the new table and clear the extra
51 * space if any. This does not copy the file pointers. Called with the files
52 * spinlock held for write.
53 */
54static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
55 unsigned int count)
56{
57 unsigned int cpy, set;
58
59 cpy = count / BITS_PER_BYTE;
60 set = (nfdt->max_fds - count) / BITS_PER_BYTE;
61 memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
62 memset((char *)nfdt->open_fds + cpy, 0, set);
63 memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
64 memset((char *)nfdt->close_on_exec + cpy, 0, set);
65
66 cpy = BITBIT_SIZE(count);
67 set = BITBIT_SIZE(nfdt->max_fds) - cpy;
68 memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
69 memset((char *)nfdt->full_fds_bits + cpy, 0, set);
70}
71
72/*
73 * Copy all file descriptors from the old table to the new, expanded table and
74 * clear the extra space. Called with the files spinlock held for write.
75 */
76static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
77{
78 size_t cpy, set;
79
80 BUG_ON(nfdt->max_fds < ofdt->max_fds);
81
82 cpy = ofdt->max_fds * sizeof(struct file *);
83 set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
84 memcpy(nfdt->fd, ofdt->fd, cpy);
85 memset((char *)nfdt->fd + cpy, 0, set);
86
87 copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
88}
89
90/*
91 * Note how the fdtable bitmap allocations very much have to be a multiple of
92 * BITS_PER_LONG. This is not only because we walk those things in chunks of
93 * 'unsigned long' in some places, but simply because that is how the Linux
94 * kernel bitmaps are defined to work: they are not "bits in an array of bytes",
95 * they are very much "bits in an array of unsigned long".
96 *
97 * The ALIGN(nr, BITS_PER_LONG) here is for clarity: since we just multiplied
98 * by that "1024/sizeof(ptr)" before, we already know there are sufficient
99 * clear low bits. Clang seems to realize that, gcc ends up being confused.
100 *
101 * On a 128-bit machine, the ALIGN() would actually matter. In the meantime,
102 * let's consider it documentation (and maybe a test-case for gcc to improve
103 * its code generation ;)
104 */
105static struct fdtable * alloc_fdtable(unsigned int nr)
106{
107 struct fdtable *fdt;
108 void *data;
109
110 /*
111 * Figure out how many fds we actually want to support in this fdtable.
112 * Allocation steps are keyed to the size of the fdarray, since it
113 * grows far faster than any of the other dynamic data. We try to fit
114 * the fdarray into comfortable page-tuned chunks: starting at 1024B
115 * and growing in powers of two from there on.
116 */
117 nr /= (1024 / sizeof(struct file *));
118 nr = roundup_pow_of_two(nr + 1);
119 nr *= (1024 / sizeof(struct file *));
120 nr = ALIGN(nr, BITS_PER_LONG);
121 /*
122 * Note that this can drive nr *below* what we had passed if sysctl_nr_open
123 * had been set lower between the check in expand_files() and here. Deal
124 * with that in caller, it's cheaper that way.
125 *
126 * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
127 * bitmaps handling below becomes unpleasant, to put it mildly...
128 */
129 if (unlikely(nr > sysctl_nr_open))
130 nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
131
132 fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
133 if (!fdt)
134 goto out;
135 fdt->max_fds = nr;
136 data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT);
137 if (!data)
138 goto out_fdt;
139 fdt->fd = data;
140
141 data = kvmalloc(max_t(size_t,
142 2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES),
143 GFP_KERNEL_ACCOUNT);
144 if (!data)
145 goto out_arr;
146 fdt->open_fds = data;
147 data += nr / BITS_PER_BYTE;
148 fdt->close_on_exec = data;
149 data += nr / BITS_PER_BYTE;
150 fdt->full_fds_bits = data;
151
152 return fdt;
153
154out_arr:
155 kvfree(fdt->fd);
156out_fdt:
157 kfree(fdt);
158out:
159 return NULL;
160}
161
162/*
163 * Expand the file descriptor table.
164 * This function will allocate a new fdtable and both fd array and fdset, of
165 * the given size.
166 * Return <0 error code on error; 1 on successful completion.
167 * The files->file_lock should be held on entry, and will be held on exit.
168 */
169static int expand_fdtable(struct files_struct *files, unsigned int nr)
170 __releases(files->file_lock)
171 __acquires(files->file_lock)
172{
173 struct fdtable *new_fdt, *cur_fdt;
174
175 spin_unlock(&files->file_lock);
176 new_fdt = alloc_fdtable(nr);
177
178 /* make sure all fd_install() have seen resize_in_progress
179 * or have finished their rcu_read_lock_sched() section.
180 */
181 if (atomic_read(&files->count) > 1)
182 synchronize_rcu();
183
184 spin_lock(&files->file_lock);
185 if (!new_fdt)
186 return -ENOMEM;
187 /*
188 * extremely unlikely race - sysctl_nr_open decreased between the check in
189 * caller and alloc_fdtable(). Cheaper to catch it here...
190 */
191 if (unlikely(new_fdt->max_fds <= nr)) {
192 __free_fdtable(new_fdt);
193 return -EMFILE;
194 }
195 cur_fdt = files_fdtable(files);
196 BUG_ON(nr < cur_fdt->max_fds);
197 copy_fdtable(new_fdt, cur_fdt);
198 rcu_assign_pointer(files->fdt, new_fdt);
199 if (cur_fdt != &files->fdtab)
200 call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
201 /* coupled with smp_rmb() in fd_install() */
202 smp_wmb();
203 return 1;
204}
205
206/*
207 * Expand files.
208 * This function will expand the file structures, if the requested size exceeds
209 * the current capacity and there is room for expansion.
210 * Return <0 error code on error; 0 when nothing done; 1 when files were
211 * expanded and execution may have blocked.
212 * The files->file_lock should be held on entry, and will be held on exit.
213 */
214static int expand_files(struct files_struct *files, unsigned int nr)
215 __releases(files->file_lock)
216 __acquires(files->file_lock)
217{
218 struct fdtable *fdt;
219 int expanded = 0;
220
221repeat:
222 fdt = files_fdtable(files);
223
224 /* Do we need to expand? */
225 if (nr < fdt->max_fds)
226 return expanded;
227
228 /* Can we expand? */
229 if (nr >= sysctl_nr_open)
230 return -EMFILE;
231
232 if (unlikely(files->resize_in_progress)) {
233 spin_unlock(&files->file_lock);
234 expanded = 1;
235 wait_event(files->resize_wait, !files->resize_in_progress);
236 spin_lock(&files->file_lock);
237 goto repeat;
238 }
239
240 /* All good, so we try */
241 files->resize_in_progress = true;
242 expanded = expand_fdtable(files, nr);
243 files->resize_in_progress = false;
244
245 wake_up_all(&files->resize_wait);
246 return expanded;
247}
248
249static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt)
250{
251 __set_bit(fd, fdt->close_on_exec);
252}
253
254static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt)
255{
256 if (test_bit(fd, fdt->close_on_exec))
257 __clear_bit(fd, fdt->close_on_exec);
258}
259
260static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
261{
262 __set_bit(fd, fdt->open_fds);
263 fd /= BITS_PER_LONG;
264 if (!~fdt->open_fds[fd])
265 __set_bit(fd, fdt->full_fds_bits);
266}
267
268static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
269{
270 __clear_bit(fd, fdt->open_fds);
271 __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
272}
273
274static unsigned int count_open_files(struct fdtable *fdt)
275{
276 unsigned int size = fdt->max_fds;
277 unsigned int i;
278
279 /* Find the last open fd */
280 for (i = size / BITS_PER_LONG; i > 0; ) {
281 if (fdt->open_fds[--i])
282 break;
283 }
284 i = (i + 1) * BITS_PER_LONG;
285 return i;
286}
287
288/*
289 * Note that a sane fdtable size always has to be a multiple of
290 * BITS_PER_LONG, since we have bitmaps that are sized by this.
291 *
292 * 'max_fds' will normally already be properly aligned, but it
293 * turns out that in the close_range() -> __close_range() ->
294 * unshare_fd() -> dup_fd() -> sane_fdtable_size() we can end
295 * up having a 'max_fds' value that isn't already aligned.
296 *
297 * Rather than make close_range() have to worry about this,
298 * just make that BITS_PER_LONG alignment be part of a sane
299 * fdtable size. Becuase that's really what it is.
300 */
301static unsigned int sane_fdtable_size(struct fdtable *fdt, unsigned int max_fds)
302{
303 unsigned int count;
304
305 count = count_open_files(fdt);
306 if (max_fds < NR_OPEN_DEFAULT)
307 max_fds = NR_OPEN_DEFAULT;
308 return ALIGN(min(count, max_fds), BITS_PER_LONG);
309}
310
311/*
312 * Allocate a new files structure and copy contents from the
313 * passed in files structure.
314 * errorp will be valid only when the returned files_struct is NULL.
315 */
316struct files_struct *dup_fd(struct files_struct *oldf, unsigned int max_fds, int *errorp)
317{
318 struct files_struct *newf;
319 struct file **old_fds, **new_fds;
320 unsigned int open_files, i;
321 struct fdtable *old_fdt, *new_fdt;
322
323 *errorp = -ENOMEM;
324 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
325 if (!newf)
326 goto out;
327
328 atomic_set(&newf->count, 1);
329
330 spin_lock_init(&newf->file_lock);
331 newf->resize_in_progress = false;
332 init_waitqueue_head(&newf->resize_wait);
333 newf->next_fd = 0;
334 new_fdt = &newf->fdtab;
335 new_fdt->max_fds = NR_OPEN_DEFAULT;
336 new_fdt->close_on_exec = newf->close_on_exec_init;
337 new_fdt->open_fds = newf->open_fds_init;
338 new_fdt->full_fds_bits = newf->full_fds_bits_init;
339 new_fdt->fd = &newf->fd_array[0];
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 * Check whether we need to allocate a larger fd array and fd set.
347 */
348 while (unlikely(open_files > new_fdt->max_fds)) {
349 spin_unlock(&oldf->file_lock);
350
351 if (new_fdt != &newf->fdtab)
352 __free_fdtable(new_fdt);
353
354 new_fdt = alloc_fdtable(open_files - 1);
355 if (!new_fdt) {
356 *errorp = -ENOMEM;
357 goto out_release;
358 }
359
360 /* beyond sysctl_nr_open; nothing to do */
361 if (unlikely(new_fdt->max_fds < open_files)) {
362 __free_fdtable(new_fdt);
363 *errorp = -EMFILE;
364 goto out_release;
365 }
366
367 /*
368 * Reacquire the oldf lock and a pointer to its fd table
369 * who knows it may have a new bigger fd table. We need
370 * the latest pointer.
371 */
372 spin_lock(&oldf->file_lock);
373 old_fdt = files_fdtable(oldf);
374 open_files = sane_fdtable_size(old_fdt, max_fds);
375 }
376
377 copy_fd_bitmaps(new_fdt, old_fdt, open_files);
378
379 old_fds = old_fdt->fd;
380 new_fds = new_fdt->fd;
381
382 for (i = open_files; i != 0; i--) {
383 struct file *f = *old_fds++;
384 if (f) {
385 get_file(f);
386 } else {
387 /*
388 * The fd may be claimed in the fd bitmap but not yet
389 * instantiated in the files array if a sibling thread
390 * is partway through open(). So make sure that this
391 * fd is available to the new process.
392 */
393 __clear_open_fd(open_files - i, new_fdt);
394 }
395 rcu_assign_pointer(*new_fds++, f);
396 }
397 spin_unlock(&oldf->file_lock);
398
399 /* clear the remainder */
400 memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
401
402 rcu_assign_pointer(newf->fdt, new_fdt);
403
404 return newf;
405
406out_release:
407 kmem_cache_free(files_cachep, newf);
408out:
409 return NULL;
410}
411
412static struct fdtable *close_files(struct files_struct * files)
413{
414 /*
415 * It is safe to dereference the fd table without RCU or
416 * ->file_lock because this is the last reference to the
417 * files structure.
418 */
419 struct fdtable *fdt = rcu_dereference_raw(files->fdt);
420 unsigned int i, j = 0;
421
422 for (;;) {
423 unsigned long set;
424 i = j * BITS_PER_LONG;
425 if (i >= fdt->max_fds)
426 break;
427 set = fdt->open_fds[j++];
428 while (set) {
429 if (set & 1) {
430 struct file * file = xchg(&fdt->fd[i], NULL);
431 if (file) {
432 filp_close(file, files);
433 cond_resched();
434 }
435 }
436 i++;
437 set >>= 1;
438 }
439 }
440
441 return fdt;
442}
443
444void put_files_struct(struct files_struct *files)
445{
446 if (atomic_dec_and_test(&files->count)) {
447 struct fdtable *fdt = close_files(files);
448
449 /* free the arrays if they are not embedded */
450 if (fdt != &files->fdtab)
451 __free_fdtable(fdt);
452 kmem_cache_free(files_cachep, files);
453 }
454}
455
456void exit_files(struct task_struct *tsk)
457{
458 struct files_struct * files = tsk->files;
459
460 if (files) {
461 task_lock(tsk);
462 tsk->files = NULL;
463 task_unlock(tsk);
464 put_files_struct(files);
465 }
466}
467
468struct files_struct init_files = {
469 .count = ATOMIC_INIT(1),
470 .fdt = &init_files.fdtab,
471 .fdtab = {
472 .max_fds = NR_OPEN_DEFAULT,
473 .fd = &init_files.fd_array[0],
474 .close_on_exec = init_files.close_on_exec_init,
475 .open_fds = init_files.open_fds_init,
476 .full_fds_bits = init_files.full_fds_bits_init,
477 },
478 .file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
479 .resize_wait = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),
480};
481
482static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
483{
484 unsigned int maxfd = fdt->max_fds;
485 unsigned int maxbit = maxfd / BITS_PER_LONG;
486 unsigned int bitbit = start / BITS_PER_LONG;
487
488 bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
489 if (bitbit > maxfd)
490 return maxfd;
491 if (bitbit > start)
492 start = bitbit;
493 return find_next_zero_bit(fdt->open_fds, maxfd, start);
494}
495
496/*
497 * allocate a file descriptor, mark it busy.
498 */
499static int alloc_fd(unsigned start, unsigned end, unsigned flags)
500{
501 struct files_struct *files = current->files;
502 unsigned int fd;
503 int error;
504 struct fdtable *fdt;
505
506 spin_lock(&files->file_lock);
507repeat:
508 fdt = files_fdtable(files);
509 fd = start;
510 if (fd < files->next_fd)
511 fd = files->next_fd;
512
513 if (fd < fdt->max_fds)
514 fd = find_next_fd(fdt, fd);
515
516 /*
517 * N.B. For clone tasks sharing a files structure, this test
518 * will limit the total number of files that can be opened.
519 */
520 error = -EMFILE;
521 if (fd >= end)
522 goto out;
523
524 error = expand_files(files, fd);
525 if (error < 0)
526 goto out;
527
528 /*
529 * If we needed to expand the fs array we
530 * might have blocked - try again.
531 */
532 if (error)
533 goto repeat;
534
535 if (start <= files->next_fd)
536 files->next_fd = fd + 1;
537
538 __set_open_fd(fd, fdt);
539 if (flags & O_CLOEXEC)
540 __set_close_on_exec(fd, fdt);
541 else
542 __clear_close_on_exec(fd, fdt);
543 error = fd;
544#if 1
545 /* Sanity check */
546 if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
547 printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
548 rcu_assign_pointer(fdt->fd[fd], NULL);
549 }
550#endif
551
552out:
553 spin_unlock(&files->file_lock);
554 return error;
555}
556
557int __get_unused_fd_flags(unsigned flags, unsigned long nofile)
558{
559 return alloc_fd(0, nofile, flags);
560}
561
562int get_unused_fd_flags(unsigned flags)
563{
564 return __get_unused_fd_flags(flags, rlimit(RLIMIT_NOFILE));
565}
566EXPORT_SYMBOL(get_unused_fd_flags);
567
568static void __put_unused_fd(struct files_struct *files, unsigned int fd)
569{
570 struct fdtable *fdt = files_fdtable(files);
571 __clear_open_fd(fd, fdt);
572 if (fd < files->next_fd)
573 files->next_fd = fd;
574}
575
576void put_unused_fd(unsigned int fd)
577{
578 struct files_struct *files = current->files;
579 spin_lock(&files->file_lock);
580 __put_unused_fd(files, fd);
581 spin_unlock(&files->file_lock);
582}
583
584EXPORT_SYMBOL(put_unused_fd);
585
586/*
587 * Install a file pointer in the fd array.
588 *
589 * The VFS is full of places where we drop the files lock between
590 * setting the open_fds bitmap and installing the file in the file
591 * array. At any such point, we are vulnerable to a dup2() race
592 * installing a file in the array before us. We need to detect this and
593 * fput() the struct file we are about to overwrite in this case.
594 *
595 * It should never happen - if we allow dup2() do it, _really_ bad things
596 * will follow.
597 *
598 * This consumes the "file" refcount, so callers should treat it
599 * as if they had called fput(file).
600 */
601
602void fd_install(unsigned int fd, struct file *file)
603{
604 struct files_struct *files = current->files;
605 struct fdtable *fdt;
606
607 rcu_read_lock_sched();
608
609 if (unlikely(files->resize_in_progress)) {
610 rcu_read_unlock_sched();
611 spin_lock(&files->file_lock);
612 fdt = files_fdtable(files);
613 BUG_ON(fdt->fd[fd] != NULL);
614 rcu_assign_pointer(fdt->fd[fd], file);
615 spin_unlock(&files->file_lock);
616 return;
617 }
618 /* coupled with smp_wmb() in expand_fdtable() */
619 smp_rmb();
620 fdt = rcu_dereference_sched(files->fdt);
621 BUG_ON(fdt->fd[fd] != NULL);
622 rcu_assign_pointer(fdt->fd[fd], file);
623 rcu_read_unlock_sched();
624}
625
626EXPORT_SYMBOL(fd_install);
627
628/**
629 * pick_file - return file associatd with fd
630 * @files: file struct to retrieve file from
631 * @fd: file descriptor to retrieve file for
632 *
633 * Context: files_lock must be held.
634 *
635 * Returns: The file associated with @fd (NULL if @fd is not open)
636 */
637static struct file *pick_file(struct files_struct *files, unsigned fd)
638{
639 struct fdtable *fdt = files_fdtable(files);
640 struct file *file;
641
642 if (fd >= fdt->max_fds)
643 return NULL;
644
645 file = fdt->fd[fd];
646 if (file) {
647 rcu_assign_pointer(fdt->fd[fd], NULL);
648 __put_unused_fd(files, fd);
649 }
650 return file;
651}
652
653int close_fd(unsigned fd)
654{
655 struct files_struct *files = current->files;
656 struct file *file;
657
658 spin_lock(&files->file_lock);
659 file = pick_file(files, fd);
660 spin_unlock(&files->file_lock);
661 if (!file)
662 return -EBADF;
663
664 return filp_close(file, files);
665}
666EXPORT_SYMBOL(close_fd); /* for ksys_close() */
667
668/**
669 * last_fd - return last valid index into fd table
670 * @cur_fds: files struct
671 *
672 * Context: Either rcu read lock or files_lock must be held.
673 *
674 * Returns: Last valid index into fdtable.
675 */
676static inline unsigned last_fd(struct fdtable *fdt)
677{
678 return fdt->max_fds - 1;
679}
680
681static inline void __range_cloexec(struct files_struct *cur_fds,
682 unsigned int fd, unsigned int max_fd)
683{
684 struct fdtable *fdt;
685
686 /* make sure we're using the correct maximum value */
687 spin_lock(&cur_fds->file_lock);
688 fdt = files_fdtable(cur_fds);
689 max_fd = min(last_fd(fdt), max_fd);
690 if (fd <= max_fd)
691 bitmap_set(fdt->close_on_exec, fd, max_fd - fd + 1);
692 spin_unlock(&cur_fds->file_lock);
693}
694
695static inline void __range_close(struct files_struct *cur_fds, unsigned int fd,
696 unsigned int max_fd)
697{
698 unsigned n;
699
700 rcu_read_lock();
701 n = last_fd(files_fdtable(cur_fds));
702 rcu_read_unlock();
703 max_fd = min(max_fd, n);
704
705 while (fd <= max_fd) {
706 struct file *file;
707
708 spin_lock(&cur_fds->file_lock);
709 file = pick_file(cur_fds, fd++);
710 spin_unlock(&cur_fds->file_lock);
711
712 if (file) {
713 /* found a valid file to close */
714 filp_close(file, cur_fds);
715 cond_resched();
716 }
717 }
718}
719
720/**
721 * __close_range() - Close all file descriptors in a given range.
722 *
723 * @fd: starting file descriptor to close
724 * @max_fd: last file descriptor to close
725 *
726 * This closes a range of file descriptors. All file descriptors
727 * from @fd up to and including @max_fd are closed.
728 */
729int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
730{
731 struct task_struct *me = current;
732 struct files_struct *cur_fds = me->files, *fds = NULL;
733
734 if (flags & ~(CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC))
735 return -EINVAL;
736
737 if (fd > max_fd)
738 return -EINVAL;
739
740 if (flags & CLOSE_RANGE_UNSHARE) {
741 int ret;
742 unsigned int max_unshare_fds = NR_OPEN_MAX;
743
744 /*
745 * If the caller requested all fds to be made cloexec we always
746 * copy all of the file descriptors since they still want to
747 * use them.
748 */
749 if (!(flags & CLOSE_RANGE_CLOEXEC)) {
750 /*
751 * If the requested range is greater than the current
752 * maximum, we're closing everything so only copy all
753 * file descriptors beneath the lowest file descriptor.
754 */
755 rcu_read_lock();
756 if (max_fd >= last_fd(files_fdtable(cur_fds)))
757 max_unshare_fds = fd;
758 rcu_read_unlock();
759 }
760
761 ret = unshare_fd(CLONE_FILES, max_unshare_fds, &fds);
762 if (ret)
763 return ret;
764
765 /*
766 * We used to share our file descriptor table, and have now
767 * created a private one, make sure we're using it below.
768 */
769 if (fds)
770 swap(cur_fds, fds);
771 }
772
773 if (flags & CLOSE_RANGE_CLOEXEC)
774 __range_cloexec(cur_fds, fd, max_fd);
775 else
776 __range_close(cur_fds, fd, max_fd);
777
778 if (fds) {
779 /*
780 * We're done closing the files we were supposed to. Time to install
781 * the new file descriptor table and drop the old one.
782 */
783 task_lock(me);
784 me->files = cur_fds;
785 task_unlock(me);
786 put_files_struct(fds);
787 }
788
789 return 0;
790}
791
792/*
793 * See close_fd_get_file() below, this variant assumes current->files->file_lock
794 * is held.
795 */
796struct file *__close_fd_get_file(unsigned int fd)
797{
798 return pick_file(current->files, fd);
799}
800
801/*
802 * variant of close_fd that gets a ref on the file for later fput.
803 * The caller must ensure that filp_close() called on the file.
804 */
805struct file *close_fd_get_file(unsigned int fd)
806{
807 struct files_struct *files = current->files;
808 struct file *file;
809
810 spin_lock(&files->file_lock);
811 file = pick_file(files, fd);
812 spin_unlock(&files->file_lock);
813
814 return file;
815}
816
817void do_close_on_exec(struct files_struct *files)
818{
819 unsigned i;
820 struct fdtable *fdt;
821
822 /* exec unshares first */
823 spin_lock(&files->file_lock);
824 for (i = 0; ; i++) {
825 unsigned long set;
826 unsigned fd = i * BITS_PER_LONG;
827 fdt = files_fdtable(files);
828 if (fd >= fdt->max_fds)
829 break;
830 set = fdt->close_on_exec[i];
831 if (!set)
832 continue;
833 fdt->close_on_exec[i] = 0;
834 for ( ; set ; fd++, set >>= 1) {
835 struct file *file;
836 if (!(set & 1))
837 continue;
838 file = fdt->fd[fd];
839 if (!file)
840 continue;
841 rcu_assign_pointer(fdt->fd[fd], NULL);
842 __put_unused_fd(files, fd);
843 spin_unlock(&files->file_lock);
844 filp_close(file, files);
845 cond_resched();
846 spin_lock(&files->file_lock);
847 }
848
849 }
850 spin_unlock(&files->file_lock);
851}
852
853static inline struct file *__fget_files_rcu(struct files_struct *files,
854 unsigned int fd, fmode_t mask)
855{
856 for (;;) {
857 struct file *file;
858 struct fdtable *fdt = rcu_dereference_raw(files->fdt);
859 struct file __rcu **fdentry;
860
861 if (unlikely(fd >= fdt->max_fds))
862 return NULL;
863
864 fdentry = fdt->fd + array_index_nospec(fd, fdt->max_fds);
865 file = rcu_dereference_raw(*fdentry);
866 if (unlikely(!file))
867 return NULL;
868
869 if (unlikely(file->f_mode & mask))
870 return NULL;
871
872 /*
873 * Ok, we have a file pointer. However, because we do
874 * this all locklessly under RCU, we may be racing with
875 * that file being closed.
876 *
877 * Such a race can take two forms:
878 *
879 * (a) the file ref already went down to zero,
880 * and get_file_rcu() fails. Just try again:
881 */
882 if (unlikely(!get_file_rcu(file)))
883 continue;
884
885 /*
886 * (b) the file table entry has changed under us.
887 * Note that we don't need to re-check the 'fdt->fd'
888 * pointer having changed, because it always goes
889 * hand-in-hand with 'fdt'.
890 *
891 * If so, we need to put our ref and try again.
892 */
893 if (unlikely(rcu_dereference_raw(files->fdt) != fdt) ||
894 unlikely(rcu_dereference_raw(*fdentry) != file)) {
895 fput(file);
896 continue;
897 }
898
899 /*
900 * Ok, we have a ref to the file, and checked that it
901 * still exists.
902 */
903 return file;
904 }
905}
906
907static struct file *__fget_files(struct files_struct *files, unsigned int fd,
908 fmode_t mask)
909{
910 struct file *file;
911
912 rcu_read_lock();
913 file = __fget_files_rcu(files, fd, mask);
914 rcu_read_unlock();
915
916 return file;
917}
918
919static inline struct file *__fget(unsigned int fd, fmode_t mask)
920{
921 return __fget_files(current->files, fd, mask);
922}
923
924struct file *fget(unsigned int fd)
925{
926 return __fget(fd, FMODE_PATH);
927}
928EXPORT_SYMBOL(fget);
929
930struct file *fget_raw(unsigned int fd)
931{
932 return __fget(fd, 0);
933}
934EXPORT_SYMBOL(fget_raw);
935
936struct file *fget_task(struct task_struct *task, unsigned int fd)
937{
938 struct file *file = NULL;
939
940 task_lock(task);
941 if (task->files)
942 file = __fget_files(task->files, fd, 0);
943 task_unlock(task);
944
945 return file;
946}
947
948struct file *task_lookup_fd_rcu(struct task_struct *task, unsigned int fd)
949{
950 /* Must be called with rcu_read_lock held */
951 struct files_struct *files;
952 struct file *file = NULL;
953
954 task_lock(task);
955 files = task->files;
956 if (files)
957 file = files_lookup_fd_rcu(files, fd);
958 task_unlock(task);
959
960 return file;
961}
962
963struct file *task_lookup_next_fd_rcu(struct task_struct *task, unsigned int *ret_fd)
964{
965 /* Must be called with rcu_read_lock held */
966 struct files_struct *files;
967 unsigned int fd = *ret_fd;
968 struct file *file = NULL;
969
970 task_lock(task);
971 files = task->files;
972 if (files) {
973 for (; fd < files_fdtable(files)->max_fds; fd++) {
974 file = files_lookup_fd_rcu(files, fd);
975 if (file)
976 break;
977 }
978 }
979 task_unlock(task);
980 *ret_fd = fd;
981 return file;
982}
983EXPORT_SYMBOL(task_lookup_next_fd_rcu);
984
985/*
986 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
987 *
988 * You can use this instead of fget if you satisfy all of the following
989 * conditions:
990 * 1) You must call fput_light before exiting the syscall and returning control
991 * to userspace (i.e. you cannot remember the returned struct file * after
992 * returning to userspace).
993 * 2) You must not call filp_close on the returned struct file * in between
994 * calls to fget_light and fput_light.
995 * 3) You must not clone the current task in between the calls to fget_light
996 * and fput_light.
997 *
998 * The fput_needed flag returned by fget_light should be passed to the
999 * corresponding fput_light.
1000 */
1001static unsigned long __fget_light(unsigned int fd, fmode_t mask)
1002{
1003 struct files_struct *files = current->files;
1004 struct file *file;
1005
1006 /*
1007 * If another thread is concurrently calling close_fd() followed
1008 * by put_files_struct(), we must not observe the old table
1009 * entry combined with the new refcount - otherwise we could
1010 * return a file that is concurrently being freed.
1011 *
1012 * atomic_read_acquire() pairs with atomic_dec_and_test() in
1013 * put_files_struct().
1014 */
1015 if (atomic_read_acquire(&files->count) == 1) {
1016 file = files_lookup_fd_raw(files, fd);
1017 if (!file || unlikely(file->f_mode & mask))
1018 return 0;
1019 return (unsigned long)file;
1020 } else {
1021 file = __fget(fd, mask);
1022 if (!file)
1023 return 0;
1024 return FDPUT_FPUT | (unsigned long)file;
1025 }
1026}
1027unsigned long __fdget(unsigned int fd)
1028{
1029 return __fget_light(fd, FMODE_PATH);
1030}
1031EXPORT_SYMBOL(__fdget);
1032
1033unsigned long __fdget_raw(unsigned int fd)
1034{
1035 return __fget_light(fd, 0);
1036}
1037
1038unsigned long __fdget_pos(unsigned int fd)
1039{
1040 unsigned long v = __fdget(fd);
1041 struct file *file = (struct file *)(v & ~3);
1042
1043 if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
1044 if (file_count(file) > 1) {
1045 v |= FDPUT_POS_UNLOCK;
1046 mutex_lock(&file->f_pos_lock);
1047 }
1048 }
1049 return v;
1050}
1051
1052void __f_unlock_pos(struct file *f)
1053{
1054 mutex_unlock(&f->f_pos_lock);
1055}
1056
1057/*
1058 * We only lock f_pos if we have threads or if the file might be
1059 * shared with another process. In both cases we'll have an elevated
1060 * file count (done either by fdget() or by fork()).
1061 */
1062
1063void set_close_on_exec(unsigned int fd, int flag)
1064{
1065 struct files_struct *files = current->files;
1066 struct fdtable *fdt;
1067 spin_lock(&files->file_lock);
1068 fdt = files_fdtable(files);
1069 if (flag)
1070 __set_close_on_exec(fd, fdt);
1071 else
1072 __clear_close_on_exec(fd, fdt);
1073 spin_unlock(&files->file_lock);
1074}
1075
1076bool get_close_on_exec(unsigned int fd)
1077{
1078 struct files_struct *files = current->files;
1079 struct fdtable *fdt;
1080 bool res;
1081 rcu_read_lock();
1082 fdt = files_fdtable(files);
1083 res = close_on_exec(fd, fdt);
1084 rcu_read_unlock();
1085 return res;
1086}
1087
1088static int do_dup2(struct files_struct *files,
1089 struct file *file, unsigned fd, unsigned flags)
1090__releases(&files->file_lock)
1091{
1092 struct file *tofree;
1093 struct fdtable *fdt;
1094
1095 /*
1096 * We need to detect attempts to do dup2() over allocated but still
1097 * not finished descriptor. NB: OpenBSD avoids that at the price of
1098 * extra work in their equivalent of fget() - they insert struct
1099 * file immediately after grabbing descriptor, mark it larval if
1100 * more work (e.g. actual opening) is needed and make sure that
1101 * fget() treats larval files as absent. Potentially interesting,
1102 * but while extra work in fget() is trivial, locking implications
1103 * and amount of surgery on open()-related paths in VFS are not.
1104 * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
1105 * deadlocks in rather amusing ways, AFAICS. All of that is out of
1106 * scope of POSIX or SUS, since neither considers shared descriptor
1107 * tables and this condition does not arise without those.
1108 */
1109 fdt = files_fdtable(files);
1110 tofree = fdt->fd[fd];
1111 if (!tofree && fd_is_open(fd, fdt))
1112 goto Ebusy;
1113 get_file(file);
1114 rcu_assign_pointer(fdt->fd[fd], file);
1115 __set_open_fd(fd, fdt);
1116 if (flags & O_CLOEXEC)
1117 __set_close_on_exec(fd, fdt);
1118 else
1119 __clear_close_on_exec(fd, fdt);
1120 spin_unlock(&files->file_lock);
1121
1122 if (tofree)
1123 filp_close(tofree, files);
1124
1125 return fd;
1126
1127Ebusy:
1128 spin_unlock(&files->file_lock);
1129 return -EBUSY;
1130}
1131
1132int replace_fd(unsigned fd, struct file *file, unsigned flags)
1133{
1134 int err;
1135 struct files_struct *files = current->files;
1136
1137 if (!file)
1138 return close_fd(fd);
1139
1140 if (fd >= rlimit(RLIMIT_NOFILE))
1141 return -EBADF;
1142
1143 spin_lock(&files->file_lock);
1144 err = expand_files(files, fd);
1145 if (unlikely(err < 0))
1146 goto out_unlock;
1147 return do_dup2(files, file, fd, flags);
1148
1149out_unlock:
1150 spin_unlock(&files->file_lock);
1151 return err;
1152}
1153
1154/**
1155 * __receive_fd() - Install received file into file descriptor table
1156 * @file: struct file that was received from another process
1157 * @ufd: __user pointer to write new fd number to
1158 * @o_flags: the O_* flags to apply to the new fd entry
1159 *
1160 * Installs a received file into the file descriptor table, with appropriate
1161 * checks and count updates. Optionally writes the fd number to userspace, if
1162 * @ufd is non-NULL.
1163 *
1164 * This helper handles its own reference counting of the incoming
1165 * struct file.
1166 *
1167 * Returns newly install fd or -ve on error.
1168 */
1169int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags)
1170{
1171 int new_fd;
1172 int error;
1173
1174 error = security_file_receive(file);
1175 if (error)
1176 return error;
1177
1178 new_fd = get_unused_fd_flags(o_flags);
1179 if (new_fd < 0)
1180 return new_fd;
1181
1182 if (ufd) {
1183 error = put_user(new_fd, ufd);
1184 if (error) {
1185 put_unused_fd(new_fd);
1186 return error;
1187 }
1188 }
1189
1190 fd_install(new_fd, get_file(file));
1191 __receive_sock(file);
1192 return new_fd;
1193}
1194
1195int receive_fd_replace(int new_fd, struct file *file, unsigned int o_flags)
1196{
1197 int error;
1198
1199 error = security_file_receive(file);
1200 if (error)
1201 return error;
1202 error = replace_fd(new_fd, file, o_flags);
1203 if (error)
1204 return error;
1205 __receive_sock(file);
1206 return new_fd;
1207}
1208
1209int receive_fd(struct file *file, unsigned int o_flags)
1210{
1211 return __receive_fd(file, NULL, o_flags);
1212}
1213EXPORT_SYMBOL_GPL(receive_fd);
1214
1215static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
1216{
1217 int err = -EBADF;
1218 struct file *file;
1219 struct files_struct *files = current->files;
1220
1221 if ((flags & ~O_CLOEXEC) != 0)
1222 return -EINVAL;
1223
1224 if (unlikely(oldfd == newfd))
1225 return -EINVAL;
1226
1227 if (newfd >= rlimit(RLIMIT_NOFILE))
1228 return -EBADF;
1229
1230 spin_lock(&files->file_lock);
1231 err = expand_files(files, newfd);
1232 file = files_lookup_fd_locked(files, oldfd);
1233 if (unlikely(!file))
1234 goto Ebadf;
1235 if (unlikely(err < 0)) {
1236 if (err == -EMFILE)
1237 goto Ebadf;
1238 goto out_unlock;
1239 }
1240 return do_dup2(files, file, newfd, flags);
1241
1242Ebadf:
1243 err = -EBADF;
1244out_unlock:
1245 spin_unlock(&files->file_lock);
1246 return err;
1247}
1248
1249SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
1250{
1251 return ksys_dup3(oldfd, newfd, flags);
1252}
1253
1254SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
1255{
1256 if (unlikely(newfd == oldfd)) { /* corner case */
1257 struct files_struct *files = current->files;
1258 int retval = oldfd;
1259
1260 rcu_read_lock();
1261 if (!files_lookup_fd_rcu(files, oldfd))
1262 retval = -EBADF;
1263 rcu_read_unlock();
1264 return retval;
1265 }
1266 return ksys_dup3(oldfd, newfd, 0);
1267}
1268
1269SYSCALL_DEFINE1(dup, unsigned int, fildes)
1270{
1271 int ret = -EBADF;
1272 struct file *file = fget_raw(fildes);
1273
1274 if (file) {
1275 ret = get_unused_fd_flags(0);
1276 if (ret >= 0)
1277 fd_install(ret, file);
1278 else
1279 fput(file);
1280 }
1281 return ret;
1282}
1283
1284int f_dupfd(unsigned int from, struct file *file, unsigned flags)
1285{
1286 unsigned long nofile = rlimit(RLIMIT_NOFILE);
1287 int err;
1288 if (from >= nofile)
1289 return -EINVAL;
1290 err = alloc_fd(from, nofile, flags);
1291 if (err >= 0) {
1292 get_file(file);
1293 fd_install(err, file);
1294 }
1295 return err;
1296}
1297
1298int iterate_fd(struct files_struct *files, unsigned n,
1299 int (*f)(const void *, struct file *, unsigned),
1300 const void *p)
1301{
1302 struct fdtable *fdt;
1303 int res = 0;
1304 if (!files)
1305 return 0;
1306 spin_lock(&files->file_lock);
1307 for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
1308 struct file *file;
1309 file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
1310 if (!file)
1311 continue;
1312 res = f(p, file, n);
1313 if (res)
1314 break;
1315 }
1316 spin_unlock(&files->file_lock);
1317 return res;
1318}
1319EXPORT_SYMBOL(iterate_fd);