Line data Source code
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 :
27 : unsigned int sysctl_nr_open __read_mostly = 1024*1024;
28 : unsigned 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))
31 : unsigned int sysctl_nr_open_max =
32 : __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
33 :
34 0 : static void __free_fdtable(struct fdtable *fdt)
35 : {
36 0 : kvfree(fdt->fd);
37 0 : kvfree(fdt->open_fds);
38 0 : kfree(fdt);
39 0 : }
40 :
41 0 : static void free_fdtable_rcu(struct rcu_head *rcu)
42 : {
43 0 : __free_fdtable(container_of(rcu, struct fdtable, rcu));
44 0 : }
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 : */
54 1 : static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
55 : unsigned int count)
56 : {
57 : unsigned int cpy, set;
58 :
59 1 : cpy = count / BITS_PER_BYTE;
60 1 : set = (nfdt->max_fds - count) / BITS_PER_BYTE;
61 1 : memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
62 1 : memset((char *)nfdt->open_fds + cpy, 0, set);
63 1 : memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
64 1 : memset((char *)nfdt->close_on_exec + cpy, 0, set);
65 :
66 1 : cpy = BITBIT_SIZE(count);
67 1 : set = BITBIT_SIZE(nfdt->max_fds) - cpy;
68 1 : memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
69 1 : memset((char *)nfdt->full_fds_bits + cpy, 0, set);
70 1 : }
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 : */
76 0 : static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
77 : {
78 : size_t cpy, set;
79 :
80 0 : BUG_ON(nfdt->max_fds < ofdt->max_fds);
81 :
82 0 : cpy = ofdt->max_fds * sizeof(struct file *);
83 0 : set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
84 0 : memcpy(nfdt->fd, ofdt->fd, cpy);
85 0 : memset((char *)nfdt->fd + cpy, 0, set);
86 :
87 0 : copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
88 0 : }
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 : */
105 0 : static 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 0 : nr /= (1024 / sizeof(struct file *));
118 0 : nr = roundup_pow_of_two(nr + 1);
119 0 : nr *= (1024 / sizeof(struct file *));
120 0 : 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 0 : if (unlikely(nr > sysctl_nr_open))
130 0 : nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
131 :
132 0 : fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
133 0 : if (!fdt)
134 : goto out;
135 0 : fdt->max_fds = nr;
136 0 : data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT);
137 0 : if (!data)
138 : goto out_fdt;
139 0 : fdt->fd = data;
140 :
141 0 : data = kvmalloc(max_t(size_t,
142 : 2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES),
143 : GFP_KERNEL_ACCOUNT);
144 0 : if (!data)
145 : goto out_arr;
146 0 : fdt->open_fds = data;
147 0 : data += nr / BITS_PER_BYTE;
148 0 : fdt->close_on_exec = data;
149 0 : data += nr / BITS_PER_BYTE;
150 0 : fdt->full_fds_bits = data;
151 :
152 0 : return fdt;
153 :
154 : out_arr:
155 0 : kvfree(fdt->fd);
156 : out_fdt:
157 0 : kfree(fdt);
158 : out:
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 : */
169 0 : static 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 0 : spin_unlock(&files->file_lock);
176 0 : 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 0 : if (atomic_read(&files->count) > 1)
182 0 : synchronize_rcu();
183 :
184 0 : spin_lock(&files->file_lock);
185 0 : 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 0 : if (unlikely(new_fdt->max_fds <= nr)) {
192 0 : __free_fdtable(new_fdt);
193 0 : return -EMFILE;
194 : }
195 0 : cur_fdt = files_fdtable(files);
196 0 : BUG_ON(nr < cur_fdt->max_fds);
197 0 : copy_fdtable(new_fdt, cur_fdt);
198 0 : rcu_assign_pointer(files->fdt, new_fdt);
199 0 : if (cur_fdt != &files->fdtab)
200 0 : call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
201 : /* coupled with smp_rmb() in fd_install() */
202 0 : smp_wmb();
203 0 : 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 : */
214 0 : static 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 0 : int expanded = 0;
220 :
221 : repeat:
222 0 : fdt = files_fdtable(files);
223 :
224 : /* Do we need to expand? */
225 0 : if (nr < fdt->max_fds)
226 : return expanded;
227 :
228 : /* Can we expand? */
229 0 : if (nr >= sysctl_nr_open)
230 : return -EMFILE;
231 :
232 0 : if (unlikely(files->resize_in_progress)) {
233 0 : spin_unlock(&files->file_lock);
234 0 : expanded = 1;
235 0 : wait_event(files->resize_wait, !files->resize_in_progress);
236 0 : spin_lock(&files->file_lock);
237 : goto repeat;
238 : }
239 :
240 : /* All good, so we try */
241 0 : files->resize_in_progress = true;
242 0 : expanded = expand_fdtable(files, nr);
243 0 : files->resize_in_progress = false;
244 :
245 0 : wake_up_all(&files->resize_wait);
246 0 : return expanded;
247 : }
248 :
249 : static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt)
250 : {
251 0 : __set_bit(fd, fdt->close_on_exec);
252 : }
253 :
254 : static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt)
255 : {
256 0 : if (test_bit(fd, fdt->close_on_exec))
257 0 : __clear_bit(fd, fdt->close_on_exec);
258 : }
259 :
260 : static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
261 : {
262 0 : __set_bit(fd, fdt->open_fds);
263 0 : fd /= BITS_PER_LONG;
264 0 : if (!~fdt->open_fds[fd])
265 0 : __set_bit(fd, fdt->full_fds_bits);
266 : }
267 :
268 : static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
269 : {
270 128 : __clear_bit(fd, fdt->open_fds);
271 128 : __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
272 : }
273 :
274 : static unsigned int count_open_files(struct fdtable *fdt)
275 : {
276 1 : unsigned int size = fdt->max_fds;
277 : unsigned int i;
278 :
279 : /* Find the last open fd */
280 3 : for (i = size / BITS_PER_LONG; i > 0; ) {
281 1 : if (fdt->open_fds[--i])
282 : break;
283 : }
284 1 : 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 : */
301 : static unsigned int sane_fdtable_size(struct fdtable *fdt, unsigned int max_fds)
302 : {
303 : unsigned int count;
304 :
305 2 : count = count_open_files(fdt);
306 1 : if (max_fds < NR_OPEN_DEFAULT)
307 0 : max_fds = NR_OPEN_DEFAULT;
308 1 : 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 : */
316 1 : struct 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 1 : *errorp = -ENOMEM;
324 1 : newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
325 1 : if (!newf)
326 : goto out;
327 :
328 2 : atomic_set(&newf->count, 1);
329 :
330 1 : spin_lock_init(&newf->file_lock);
331 1 : newf->resize_in_progress = false;
332 1 : init_waitqueue_head(&newf->resize_wait);
333 1 : newf->next_fd = 0;
334 1 : new_fdt = &newf->fdtab;
335 1 : new_fdt->max_fds = NR_OPEN_DEFAULT;
336 1 : new_fdt->close_on_exec = newf->close_on_exec_init;
337 1 : new_fdt->open_fds = newf->open_fds_init;
338 1 : new_fdt->full_fds_bits = newf->full_fds_bits_init;
339 1 : new_fdt->fd = &newf->fd_array[0];
340 :
341 2 : spin_lock(&oldf->file_lock);
342 1 : old_fdt = files_fdtable(oldf);
343 1 : 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 2 : while (unlikely(open_files > new_fdt->max_fds)) {
349 0 : spin_unlock(&oldf->file_lock);
350 :
351 0 : if (new_fdt != &newf->fdtab)
352 0 : __free_fdtable(new_fdt);
353 :
354 0 : new_fdt = alloc_fdtable(open_files - 1);
355 0 : if (!new_fdt) {
356 0 : *errorp = -ENOMEM;
357 0 : goto out_release;
358 : }
359 :
360 : /* beyond sysctl_nr_open; nothing to do */
361 0 : if (unlikely(new_fdt->max_fds < open_files)) {
362 0 : __free_fdtable(new_fdt);
363 0 : *errorp = -EMFILE;
364 0 : 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 0 : spin_lock(&oldf->file_lock);
373 0 : old_fdt = files_fdtable(oldf);
374 0 : open_files = sane_fdtable_size(old_fdt, max_fds);
375 : }
376 :
377 1 : copy_fd_bitmaps(new_fdt, old_fdt, open_files);
378 :
379 1 : old_fds = old_fdt->fd;
380 1 : new_fds = new_fdt->fd;
381 :
382 65 : for (i = open_files; i != 0; i--) {
383 64 : struct file *f = *old_fds++;
384 64 : 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 64 : __clear_open_fd(open_files - i, new_fdt);
394 : }
395 64 : rcu_assign_pointer(*new_fds++, f);
396 : }
397 2 : spin_unlock(&oldf->file_lock);
398 :
399 : /* clear the remainder */
400 1 : memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
401 :
402 1 : rcu_assign_pointer(newf->fdt, new_fdt);
403 :
404 1 : return newf;
405 :
406 : out_release:
407 0 : kmem_cache_free(files_cachep, newf);
408 : out:
409 : return NULL;
410 : }
411 :
412 0 : static 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 0 : struct fdtable *fdt = rcu_dereference_raw(files->fdt);
420 0 : unsigned int i, j = 0;
421 :
422 : for (;;) {
423 : unsigned long set;
424 0 : i = j * BITS_PER_LONG;
425 0 : if (i >= fdt->max_fds)
426 : break;
427 0 : set = fdt->open_fds[j++];
428 0 : while (set) {
429 0 : if (set & 1) {
430 0 : struct file * file = xchg(&fdt->fd[i], NULL);
431 0 : if (file) {
432 0 : filp_close(file, files);
433 0 : cond_resched();
434 : }
435 : }
436 0 : i++;
437 0 : set >>= 1;
438 : }
439 : }
440 :
441 0 : return fdt;
442 : }
443 :
444 93 : void put_files_struct(struct files_struct *files)
445 : {
446 186 : if (atomic_dec_and_test(&files->count)) {
447 0 : struct fdtable *fdt = close_files(files);
448 :
449 : /* free the arrays if they are not embedded */
450 0 : if (fdt != &files->fdtab)
451 0 : __free_fdtable(fdt);
452 0 : kmem_cache_free(files_cachep, files);
453 : }
454 93 : }
455 :
456 93 : void exit_files(struct task_struct *tsk)
457 : {
458 93 : struct files_struct * files = tsk->files;
459 :
460 93 : if (files) {
461 93 : task_lock(tsk);
462 93 : tsk->files = NULL;
463 93 : task_unlock(tsk);
464 93 : put_files_struct(files);
465 : }
466 93 : }
467 :
468 : struct 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 :
482 0 : static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
483 : {
484 0 : unsigned int maxfd = fdt->max_fds;
485 0 : unsigned int maxbit = maxfd / BITS_PER_LONG;
486 0 : unsigned int bitbit = start / BITS_PER_LONG;
487 :
488 0 : bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
489 0 : if (bitbit > maxfd)
490 : return maxfd;
491 0 : if (bitbit > start)
492 0 : start = bitbit;
493 0 : return find_next_zero_bit(fdt->open_fds, maxfd, start);
494 : }
495 :
496 : /*
497 : * allocate a file descriptor, mark it busy.
498 : */
499 0 : static int alloc_fd(unsigned start, unsigned end, unsigned flags)
500 : {
501 0 : struct files_struct *files = current->files;
502 : unsigned int fd;
503 : int error;
504 : struct fdtable *fdt;
505 :
506 0 : spin_lock(&files->file_lock);
507 : repeat:
508 0 : fdt = files_fdtable(files);
509 0 : fd = start;
510 0 : if (fd < files->next_fd)
511 0 : fd = files->next_fd;
512 :
513 0 : if (fd < fdt->max_fds)
514 0 : 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 0 : error = -EMFILE;
521 0 : if (fd >= end)
522 : goto out;
523 :
524 0 : error = expand_files(files, fd);
525 0 : 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 0 : if (error)
533 : goto repeat;
534 :
535 0 : if (start <= files->next_fd)
536 0 : files->next_fd = fd + 1;
537 :
538 0 : __set_open_fd(fd, fdt);
539 0 : if (flags & O_CLOEXEC)
540 0 : __set_close_on_exec(fd, fdt);
541 : else
542 0 : __clear_close_on_exec(fd, fdt);
543 0 : error = fd;
544 : #if 1
545 : /* Sanity check */
546 0 : if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
547 0 : printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
548 0 : rcu_assign_pointer(fdt->fd[fd], NULL);
549 : }
550 : #endif
551 :
552 : out:
553 0 : spin_unlock(&files->file_lock);
554 0 : return error;
555 : }
556 :
557 0 : int __get_unused_fd_flags(unsigned flags, unsigned long nofile)
558 : {
559 0 : return alloc_fd(0, nofile, flags);
560 : }
561 :
562 0 : int get_unused_fd_flags(unsigned flags)
563 : {
564 0 : return __get_unused_fd_flags(flags, rlimit(RLIMIT_NOFILE));
565 : }
566 : EXPORT_SYMBOL(get_unused_fd_flags);
567 :
568 : static void __put_unused_fd(struct files_struct *files, unsigned int fd)
569 : {
570 0 : struct fdtable *fdt = files_fdtable(files);
571 0 : __clear_open_fd(fd, fdt);
572 0 : if (fd < files->next_fd)
573 0 : files->next_fd = fd;
574 : }
575 :
576 0 : void put_unused_fd(unsigned int fd)
577 : {
578 0 : struct files_struct *files = current->files;
579 0 : spin_lock(&files->file_lock);
580 0 : __put_unused_fd(files, fd);
581 0 : spin_unlock(&files->file_lock);
582 0 : }
583 :
584 : EXPORT_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 :
602 0 : void fd_install(unsigned int fd, struct file *file)
603 : {
604 0 : struct files_struct *files = current->files;
605 : struct fdtable *fdt;
606 :
607 : rcu_read_lock_sched();
608 :
609 0 : if (unlikely(files->resize_in_progress)) {
610 : rcu_read_unlock_sched();
611 0 : spin_lock(&files->file_lock);
612 0 : fdt = files_fdtable(files);
613 0 : BUG_ON(fdt->fd[fd] != NULL);
614 0 : rcu_assign_pointer(fdt->fd[fd], file);
615 0 : spin_unlock(&files->file_lock);
616 : return;
617 : }
618 : /* coupled with smp_wmb() in expand_fdtable() */
619 0 : smp_rmb();
620 0 : fdt = rcu_dereference_sched(files->fdt);
621 0 : BUG_ON(fdt->fd[fd] != NULL);
622 0 : rcu_assign_pointer(fdt->fd[fd], file);
623 : rcu_read_unlock_sched();
624 : }
625 :
626 : EXPORT_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 : * If this functions returns an EINVAL error pointer the fd was beyond the
634 : * current maximum number of file descriptors for that fdtable.
635 : *
636 : * Returns: The file associated with @fd, on error returns an error pointer.
637 : */
638 0 : static struct file *pick_file(struct files_struct *files, unsigned fd)
639 : {
640 : struct file *file;
641 : struct fdtable *fdt;
642 :
643 0 : spin_lock(&files->file_lock);
644 0 : fdt = files_fdtable(files);
645 0 : if (fd >= fdt->max_fds) {
646 : file = ERR_PTR(-EINVAL);
647 : goto out_unlock;
648 : }
649 0 : file = fdt->fd[fd];
650 0 : if (!file) {
651 : file = ERR_PTR(-EBADF);
652 : goto out_unlock;
653 : }
654 0 : rcu_assign_pointer(fdt->fd[fd], NULL);
655 : __put_unused_fd(files, fd);
656 :
657 : out_unlock:
658 0 : spin_unlock(&files->file_lock);
659 0 : return file;
660 : }
661 :
662 0 : int close_fd(unsigned fd)
663 : {
664 0 : struct files_struct *files = current->files;
665 : struct file *file;
666 :
667 0 : file = pick_file(files, fd);
668 0 : if (IS_ERR(file))
669 : return -EBADF;
670 :
671 0 : return filp_close(file, files);
672 : }
673 : EXPORT_SYMBOL(close_fd); /* for ksys_close() */
674 :
675 : /**
676 : * last_fd - return last valid index into fd table
677 : * @cur_fds: files struct
678 : *
679 : * Context: Either rcu read lock or files_lock must be held.
680 : *
681 : * Returns: Last valid index into fdtable.
682 : */
683 : static inline unsigned last_fd(struct fdtable *fdt)
684 : {
685 0 : return fdt->max_fds - 1;
686 : }
687 :
688 0 : static inline void __range_cloexec(struct files_struct *cur_fds,
689 : unsigned int fd, unsigned int max_fd)
690 : {
691 : struct fdtable *fdt;
692 :
693 : /* make sure we're using the correct maximum value */
694 0 : spin_lock(&cur_fds->file_lock);
695 0 : fdt = files_fdtable(cur_fds);
696 0 : max_fd = min(last_fd(fdt), max_fd);
697 0 : if (fd <= max_fd)
698 0 : bitmap_set(fdt->close_on_exec, fd, max_fd - fd + 1);
699 0 : spin_unlock(&cur_fds->file_lock);
700 0 : }
701 :
702 0 : static inline void __range_close(struct files_struct *cur_fds, unsigned int fd,
703 : unsigned int max_fd)
704 : {
705 0 : while (fd <= max_fd) {
706 : struct file *file;
707 :
708 0 : file = pick_file(cur_fds, fd++);
709 0 : if (!IS_ERR(file)) {
710 : /* found a valid file to close */
711 0 : filp_close(file, cur_fds);
712 0 : cond_resched();
713 0 : continue;
714 : }
715 :
716 : /* beyond the last fd in that table */
717 0 : if (PTR_ERR(file) == -EINVAL)
718 : return;
719 : }
720 : }
721 :
722 : /**
723 : * __close_range() - Close all file descriptors in a given range.
724 : *
725 : * @fd: starting file descriptor to close
726 : * @max_fd: last file descriptor to close
727 : *
728 : * This closes a range of file descriptors. All file descriptors
729 : * from @fd up to and including @max_fd are closed.
730 : */
731 0 : int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
732 : {
733 0 : struct task_struct *me = current;
734 0 : struct files_struct *cur_fds = me->files, *fds = NULL;
735 :
736 0 : if (flags & ~(CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC))
737 : return -EINVAL;
738 :
739 0 : if (fd > max_fd)
740 : return -EINVAL;
741 :
742 0 : if (flags & CLOSE_RANGE_UNSHARE) {
743 : int ret;
744 0 : unsigned int max_unshare_fds = NR_OPEN_MAX;
745 :
746 : /*
747 : * If the caller requested all fds to be made cloexec we always
748 : * copy all of the file descriptors since they still want to
749 : * use them.
750 : */
751 0 : if (!(flags & CLOSE_RANGE_CLOEXEC)) {
752 : /*
753 : * If the requested range is greater than the current
754 : * maximum, we're closing everything so only copy all
755 : * file descriptors beneath the lowest file descriptor.
756 : */
757 : rcu_read_lock();
758 0 : if (max_fd >= last_fd(files_fdtable(cur_fds)))
759 0 : max_unshare_fds = fd;
760 : rcu_read_unlock();
761 : }
762 :
763 0 : ret = unshare_fd(CLONE_FILES, max_unshare_fds, &fds);
764 0 : if (ret)
765 : return ret;
766 :
767 : /*
768 : * We used to share our file descriptor table, and have now
769 : * created a private one, make sure we're using it below.
770 : */
771 0 : if (fds)
772 0 : swap(cur_fds, fds);
773 : }
774 :
775 0 : if (flags & CLOSE_RANGE_CLOEXEC)
776 0 : __range_cloexec(cur_fds, fd, max_fd);
777 : else
778 0 : __range_close(cur_fds, fd, max_fd);
779 :
780 0 : if (fds) {
781 : /*
782 : * We're done closing the files we were supposed to. Time to install
783 : * the new file descriptor table and drop the old one.
784 : */
785 0 : task_lock(me);
786 0 : me->files = cur_fds;
787 0 : task_unlock(me);
788 0 : put_files_struct(fds);
789 : }
790 :
791 : return 0;
792 : }
793 :
794 : /*
795 : * See close_fd_get_file() below, this variant assumes current->files->file_lock
796 : * is held.
797 : */
798 0 : int __close_fd_get_file(unsigned int fd, struct file **res)
799 : {
800 0 : struct files_struct *files = current->files;
801 : struct file *file;
802 : struct fdtable *fdt;
803 :
804 0 : fdt = files_fdtable(files);
805 0 : if (fd >= fdt->max_fds)
806 : goto out_err;
807 0 : file = fdt->fd[fd];
808 0 : if (!file)
809 : goto out_err;
810 0 : rcu_assign_pointer(fdt->fd[fd], NULL);
811 0 : __put_unused_fd(files, fd);
812 0 : get_file(file);
813 0 : *res = file;
814 0 : return 0;
815 : out_err:
816 0 : *res = NULL;
817 0 : return -ENOENT;
818 : }
819 :
820 : /*
821 : * variant of close_fd that gets a ref on the file for later fput.
822 : * The caller must ensure that filp_close() called on the file, and then
823 : * an fput().
824 : */
825 0 : int close_fd_get_file(unsigned int fd, struct file **res)
826 : {
827 0 : struct files_struct *files = current->files;
828 : int ret;
829 :
830 0 : spin_lock(&files->file_lock);
831 0 : ret = __close_fd_get_file(fd, res);
832 0 : spin_unlock(&files->file_lock);
833 :
834 0 : return ret;
835 : }
836 :
837 0 : void do_close_on_exec(struct files_struct *files)
838 : {
839 : unsigned i;
840 : struct fdtable *fdt;
841 :
842 : /* exec unshares first */
843 0 : spin_lock(&files->file_lock);
844 0 : for (i = 0; ; i++) {
845 : unsigned long set;
846 0 : unsigned fd = i * BITS_PER_LONG;
847 0 : fdt = files_fdtable(files);
848 0 : if (fd >= fdt->max_fds)
849 : break;
850 0 : set = fdt->close_on_exec[i];
851 0 : if (!set)
852 0 : continue;
853 0 : fdt->close_on_exec[i] = 0;
854 0 : for ( ; set ; fd++, set >>= 1) {
855 : struct file *file;
856 0 : if (!(set & 1))
857 0 : continue;
858 0 : file = fdt->fd[fd];
859 0 : if (!file)
860 0 : continue;
861 0 : rcu_assign_pointer(fdt->fd[fd], NULL);
862 0 : __put_unused_fd(files, fd);
863 0 : spin_unlock(&files->file_lock);
864 0 : filp_close(file, files);
865 0 : cond_resched();
866 0 : spin_lock(&files->file_lock);
867 : }
868 :
869 : }
870 0 : spin_unlock(&files->file_lock);
871 0 : }
872 :
873 0 : static inline struct file *__fget_files_rcu(struct files_struct *files,
874 : unsigned int fd, fmode_t mask, unsigned int refs)
875 : {
876 : for (;;) {
877 : struct file *file;
878 0 : struct fdtable *fdt = rcu_dereference_raw(files->fdt);
879 : struct file __rcu **fdentry;
880 :
881 0 : if (unlikely(fd >= fdt->max_fds))
882 : return NULL;
883 :
884 0 : fdentry = fdt->fd + array_index_nospec(fd, fdt->max_fds);
885 0 : file = rcu_dereference_raw(*fdentry);
886 0 : if (unlikely(!file))
887 : return NULL;
888 :
889 0 : if (unlikely(file->f_mode & mask))
890 : return NULL;
891 :
892 : /*
893 : * Ok, we have a file pointer. However, because we do
894 : * this all locklessly under RCU, we may be racing with
895 : * that file being closed.
896 : *
897 : * Such a race can take two forms:
898 : *
899 : * (a) the file ref already went down to zero,
900 : * and get_file_rcu_many() fails. Just try
901 : * again:
902 : */
903 0 : if (unlikely(!get_file_rcu_many(file, refs)))
904 0 : continue;
905 :
906 : /*
907 : * (b) the file table entry has changed under us.
908 : * Note that we don't need to re-check the 'fdt->fd'
909 : * pointer having changed, because it always goes
910 : * hand-in-hand with 'fdt'.
911 : *
912 : * If so, we need to put our refs and try again.
913 : */
914 0 : if (unlikely(rcu_dereference_raw(files->fdt) != fdt) ||
915 0 : unlikely(rcu_dereference_raw(*fdentry) != file)) {
916 0 : fput_many(file, refs);
917 0 : continue;
918 : }
919 :
920 : /*
921 : * Ok, we have a ref to the file, and checked that it
922 : * still exists.
923 : */
924 : return file;
925 : }
926 : }
927 :
928 : static struct file *__fget_files(struct files_struct *files, unsigned int fd,
929 : fmode_t mask, unsigned int refs)
930 : {
931 : struct file *file;
932 :
933 : rcu_read_lock();
934 0 : file = __fget_files_rcu(files, fd, mask, refs);
935 : rcu_read_unlock();
936 :
937 : return file;
938 : }
939 :
940 : static inline struct file *__fget(unsigned int fd, fmode_t mask,
941 : unsigned int refs)
942 : {
943 0 : return __fget_files(current->files, fd, mask, refs);
944 : }
945 :
946 0 : struct file *fget_many(unsigned int fd, unsigned int refs)
947 : {
948 0 : return __fget(fd, FMODE_PATH, refs);
949 : }
950 :
951 0 : struct file *fget(unsigned int fd)
952 : {
953 0 : return __fget(fd, FMODE_PATH, 1);
954 : }
955 : EXPORT_SYMBOL(fget);
956 :
957 0 : struct file *fget_raw(unsigned int fd)
958 : {
959 0 : return __fget(fd, 0, 1);
960 : }
961 : EXPORT_SYMBOL(fget_raw);
962 :
963 0 : struct file *fget_task(struct task_struct *task, unsigned int fd)
964 : {
965 0 : struct file *file = NULL;
966 :
967 0 : task_lock(task);
968 0 : if (task->files)
969 0 : file = __fget_files(task->files, fd, 0, 1);
970 0 : task_unlock(task);
971 :
972 0 : return file;
973 : }
974 :
975 0 : struct file *task_lookup_fd_rcu(struct task_struct *task, unsigned int fd)
976 : {
977 : /* Must be called with rcu_read_lock held */
978 : struct files_struct *files;
979 0 : struct file *file = NULL;
980 :
981 0 : task_lock(task);
982 0 : files = task->files;
983 0 : if (files)
984 : file = files_lookup_fd_rcu(files, fd);
985 0 : task_unlock(task);
986 :
987 0 : return file;
988 : }
989 :
990 0 : struct file *task_lookup_next_fd_rcu(struct task_struct *task, unsigned int *ret_fd)
991 : {
992 : /* Must be called with rcu_read_lock held */
993 : struct files_struct *files;
994 0 : unsigned int fd = *ret_fd;
995 0 : struct file *file = NULL;
996 :
997 0 : task_lock(task);
998 0 : files = task->files;
999 0 : if (files) {
1000 0 : for (; fd < files_fdtable(files)->max_fds; fd++) {
1001 0 : file = files_lookup_fd_rcu(files, fd);
1002 0 : if (file)
1003 : break;
1004 : }
1005 : }
1006 0 : task_unlock(task);
1007 0 : *ret_fd = fd;
1008 0 : return file;
1009 : }
1010 :
1011 : /*
1012 : * Lightweight file lookup - no refcnt increment if fd table isn't shared.
1013 : *
1014 : * You can use this instead of fget if you satisfy all of the following
1015 : * conditions:
1016 : * 1) You must call fput_light before exiting the syscall and returning control
1017 : * to userspace (i.e. you cannot remember the returned struct file * after
1018 : * returning to userspace).
1019 : * 2) You must not call filp_close on the returned struct file * in between
1020 : * calls to fget_light and fput_light.
1021 : * 3) You must not clone the current task in between the calls to fget_light
1022 : * and fput_light.
1023 : *
1024 : * The fput_needed flag returned by fget_light should be passed to the
1025 : * corresponding fput_light.
1026 : */
1027 0 : static unsigned long __fget_light(unsigned int fd, fmode_t mask)
1028 : {
1029 0 : struct files_struct *files = current->files;
1030 : struct file *file;
1031 :
1032 0 : if (atomic_read(&files->count) == 1) {
1033 0 : file = files_lookup_fd_raw(files, fd);
1034 0 : if (!file || unlikely(file->f_mode & mask))
1035 : return 0;
1036 0 : return (unsigned long)file;
1037 : } else {
1038 0 : file = __fget(fd, mask, 1);
1039 0 : if (!file)
1040 : return 0;
1041 0 : return FDPUT_FPUT | (unsigned long)file;
1042 : }
1043 : }
1044 0 : unsigned long __fdget(unsigned int fd)
1045 : {
1046 0 : return __fget_light(fd, FMODE_PATH);
1047 : }
1048 : EXPORT_SYMBOL(__fdget);
1049 :
1050 0 : unsigned long __fdget_raw(unsigned int fd)
1051 : {
1052 0 : return __fget_light(fd, 0);
1053 : }
1054 :
1055 0 : unsigned long __fdget_pos(unsigned int fd)
1056 : {
1057 0 : unsigned long v = __fdget(fd);
1058 0 : struct file *file = (struct file *)(v & ~3);
1059 :
1060 0 : if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
1061 0 : if (file_count(file) > 1) {
1062 0 : v |= FDPUT_POS_UNLOCK;
1063 0 : mutex_lock(&file->f_pos_lock);
1064 : }
1065 : }
1066 0 : return v;
1067 : }
1068 :
1069 0 : void __f_unlock_pos(struct file *f)
1070 : {
1071 0 : mutex_unlock(&f->f_pos_lock);
1072 0 : }
1073 :
1074 : /*
1075 : * We only lock f_pos if we have threads or if the file might be
1076 : * shared with another process. In both cases we'll have an elevated
1077 : * file count (done either by fdget() or by fork()).
1078 : */
1079 :
1080 0 : void set_close_on_exec(unsigned int fd, int flag)
1081 : {
1082 0 : struct files_struct *files = current->files;
1083 : struct fdtable *fdt;
1084 0 : spin_lock(&files->file_lock);
1085 0 : fdt = files_fdtable(files);
1086 0 : if (flag)
1087 0 : __set_close_on_exec(fd, fdt);
1088 : else
1089 0 : __clear_close_on_exec(fd, fdt);
1090 0 : spin_unlock(&files->file_lock);
1091 0 : }
1092 :
1093 0 : bool get_close_on_exec(unsigned int fd)
1094 : {
1095 0 : struct files_struct *files = current->files;
1096 : struct fdtable *fdt;
1097 : bool res;
1098 : rcu_read_lock();
1099 0 : fdt = files_fdtable(files);
1100 0 : res = close_on_exec(fd, fdt);
1101 : rcu_read_unlock();
1102 0 : return res;
1103 : }
1104 :
1105 0 : static int do_dup2(struct files_struct *files,
1106 : struct file *file, unsigned fd, unsigned flags)
1107 : __releases(&files->file_lock)
1108 : {
1109 : struct file *tofree;
1110 : struct fdtable *fdt;
1111 :
1112 : /*
1113 : * We need to detect attempts to do dup2() over allocated but still
1114 : * not finished descriptor. NB: OpenBSD avoids that at the price of
1115 : * extra work in their equivalent of fget() - they insert struct
1116 : * file immediately after grabbing descriptor, mark it larval if
1117 : * more work (e.g. actual opening) is needed and make sure that
1118 : * fget() treats larval files as absent. Potentially interesting,
1119 : * but while extra work in fget() is trivial, locking implications
1120 : * and amount of surgery on open()-related paths in VFS are not.
1121 : * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
1122 : * deadlocks in rather amusing ways, AFAICS. All of that is out of
1123 : * scope of POSIX or SUS, since neither considers shared descriptor
1124 : * tables and this condition does not arise without those.
1125 : */
1126 0 : fdt = files_fdtable(files);
1127 0 : tofree = fdt->fd[fd];
1128 0 : if (!tofree && fd_is_open(fd, fdt))
1129 : goto Ebusy;
1130 0 : get_file(file);
1131 0 : rcu_assign_pointer(fdt->fd[fd], file);
1132 0 : __set_open_fd(fd, fdt);
1133 0 : if (flags & O_CLOEXEC)
1134 0 : __set_close_on_exec(fd, fdt);
1135 : else
1136 0 : __clear_close_on_exec(fd, fdt);
1137 0 : spin_unlock(&files->file_lock);
1138 :
1139 0 : if (tofree)
1140 0 : filp_close(tofree, files);
1141 :
1142 0 : return fd;
1143 :
1144 : Ebusy:
1145 0 : spin_unlock(&files->file_lock);
1146 0 : return -EBUSY;
1147 : }
1148 :
1149 0 : int replace_fd(unsigned fd, struct file *file, unsigned flags)
1150 : {
1151 : int err;
1152 0 : struct files_struct *files = current->files;
1153 :
1154 0 : if (!file)
1155 0 : return close_fd(fd);
1156 :
1157 0 : if (fd >= rlimit(RLIMIT_NOFILE))
1158 : return -EBADF;
1159 :
1160 0 : spin_lock(&files->file_lock);
1161 0 : err = expand_files(files, fd);
1162 0 : if (unlikely(err < 0))
1163 : goto out_unlock;
1164 0 : return do_dup2(files, file, fd, flags);
1165 :
1166 : out_unlock:
1167 0 : spin_unlock(&files->file_lock);
1168 0 : return err;
1169 : }
1170 :
1171 : /**
1172 : * __receive_fd() - Install received file into file descriptor table
1173 : * @file: struct file that was received from another process
1174 : * @ufd: __user pointer to write new fd number to
1175 : * @o_flags: the O_* flags to apply to the new fd entry
1176 : *
1177 : * Installs a received file into the file descriptor table, with appropriate
1178 : * checks and count updates. Optionally writes the fd number to userspace, if
1179 : * @ufd is non-NULL.
1180 : *
1181 : * This helper handles its own reference counting of the incoming
1182 : * struct file.
1183 : *
1184 : * Returns newly install fd or -ve on error.
1185 : */
1186 0 : int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags)
1187 : {
1188 : int new_fd;
1189 : int error;
1190 :
1191 0 : error = security_file_receive(file);
1192 : if (error)
1193 : return error;
1194 :
1195 0 : new_fd = get_unused_fd_flags(o_flags);
1196 0 : if (new_fd < 0)
1197 : return new_fd;
1198 :
1199 0 : if (ufd) {
1200 0 : error = put_user(new_fd, ufd);
1201 0 : if (error) {
1202 0 : put_unused_fd(new_fd);
1203 0 : return error;
1204 : }
1205 : }
1206 :
1207 0 : fd_install(new_fd, get_file(file));
1208 0 : __receive_sock(file);
1209 0 : return new_fd;
1210 : }
1211 :
1212 0 : int receive_fd_replace(int new_fd, struct file *file, unsigned int o_flags)
1213 : {
1214 : int error;
1215 :
1216 0 : error = security_file_receive(file);
1217 : if (error)
1218 : return error;
1219 0 : error = replace_fd(new_fd, file, o_flags);
1220 0 : if (error)
1221 : return error;
1222 0 : __receive_sock(file);
1223 0 : return new_fd;
1224 : }
1225 :
1226 0 : int receive_fd(struct file *file, unsigned int o_flags)
1227 : {
1228 0 : return __receive_fd(file, NULL, o_flags);
1229 : }
1230 : EXPORT_SYMBOL_GPL(receive_fd);
1231 :
1232 0 : static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
1233 : {
1234 0 : int err = -EBADF;
1235 : struct file *file;
1236 0 : struct files_struct *files = current->files;
1237 :
1238 0 : if ((flags & ~O_CLOEXEC) != 0)
1239 : return -EINVAL;
1240 :
1241 0 : if (unlikely(oldfd == newfd))
1242 : return -EINVAL;
1243 :
1244 0 : if (newfd >= rlimit(RLIMIT_NOFILE))
1245 : return -EBADF;
1246 :
1247 0 : spin_lock(&files->file_lock);
1248 0 : err = expand_files(files, newfd);
1249 0 : file = files_lookup_fd_locked(files, oldfd);
1250 0 : if (unlikely(!file))
1251 : goto Ebadf;
1252 0 : if (unlikely(err < 0)) {
1253 0 : if (err == -EMFILE)
1254 : goto Ebadf;
1255 : goto out_unlock;
1256 : }
1257 0 : return do_dup2(files, file, newfd, flags);
1258 :
1259 : Ebadf:
1260 0 : err = -EBADF;
1261 : out_unlock:
1262 0 : spin_unlock(&files->file_lock);
1263 0 : return err;
1264 : }
1265 :
1266 0 : SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
1267 : {
1268 0 : return ksys_dup3(oldfd, newfd, flags);
1269 : }
1270 :
1271 0 : SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
1272 : {
1273 0 : if (unlikely(newfd == oldfd)) { /* corner case */
1274 0 : struct files_struct *files = current->files;
1275 0 : int retval = oldfd;
1276 :
1277 : rcu_read_lock();
1278 0 : if (!files_lookup_fd_rcu(files, oldfd))
1279 0 : retval = -EBADF;
1280 : rcu_read_unlock();
1281 0 : return retval;
1282 : }
1283 0 : return ksys_dup3(oldfd, newfd, 0);
1284 : }
1285 :
1286 0 : SYSCALL_DEFINE1(dup, unsigned int, fildes)
1287 : {
1288 0 : int ret = -EBADF;
1289 0 : struct file *file = fget_raw(fildes);
1290 :
1291 0 : if (file) {
1292 0 : ret = get_unused_fd_flags(0);
1293 0 : if (ret >= 0)
1294 0 : fd_install(ret, file);
1295 : else
1296 0 : fput(file);
1297 : }
1298 0 : return ret;
1299 : }
1300 :
1301 0 : int f_dupfd(unsigned int from, struct file *file, unsigned flags)
1302 : {
1303 0 : unsigned long nofile = rlimit(RLIMIT_NOFILE);
1304 : int err;
1305 0 : if (from >= nofile)
1306 : return -EINVAL;
1307 0 : err = alloc_fd(from, nofile, flags);
1308 0 : if (err >= 0) {
1309 0 : get_file(file);
1310 0 : fd_install(err, file);
1311 : }
1312 : return err;
1313 : }
1314 :
1315 0 : int iterate_fd(struct files_struct *files, unsigned n,
1316 : int (*f)(const void *, struct file *, unsigned),
1317 : const void *p)
1318 : {
1319 : struct fdtable *fdt;
1320 0 : int res = 0;
1321 0 : if (!files)
1322 : return 0;
1323 0 : spin_lock(&files->file_lock);
1324 0 : for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
1325 : struct file *file;
1326 0 : file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
1327 0 : if (!file)
1328 0 : continue;
1329 0 : res = f(p, file, n);
1330 0 : if (res)
1331 : break;
1332 : }
1333 0 : spin_unlock(&files->file_lock);
1334 0 : return res;
1335 : }
1336 : EXPORT_SYMBOL(iterate_fd);
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