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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/fs/file.c
4 *
5 * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
6 *
7 * Manage the dynamic fd arrays in the process files_struct.
8 */
9
10#include <linux/syscalls.h>
11#include <linux/export.h>
12#include <linux/fs.h>
13#include <linux/kernel.h>
14#include <linux/mm.h>
15#include <linux/sched/signal.h>
16#include <linux/slab.h>
17#include <linux/file.h>
18#include <linux/fdtable.h>
19#include <linux/bitops.h>
20#include <linux/spinlock.h>
21#include <linux/rcupdate.h>
22#include <linux/close_range.h>
23#include <net/sock.h>
24
25unsigned int sysctl_nr_open __read_mostly = 1024*1024;
26unsigned int sysctl_nr_open_min = BITS_PER_LONG;
27/* our min() is unusable in constant expressions ;-/ */
28#define __const_min(x, y) ((x) < (y) ? (x) : (y))
29unsigned int sysctl_nr_open_max =
30 __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
31
32static void __free_fdtable(struct fdtable *fdt)
33{
34 kvfree(fdt->fd);
35 kvfree(fdt->open_fds);
36 kfree(fdt);
37}
38
39static void free_fdtable_rcu(struct rcu_head *rcu)
40{
41 __free_fdtable(container_of(rcu, struct fdtable, rcu));
42}
43
44#define BITBIT_NR(nr) BITS_TO_LONGS(BITS_TO_LONGS(nr))
45#define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))
46
47/*
48 * Copy 'count' fd bits from the old table to the new table and clear the extra
49 * space if any. This does not copy the file pointers. Called with the files
50 * spinlock held for write.
51 */
52static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
53 unsigned int count)
54{
55 unsigned int cpy, set;
56
57 cpy = count / BITS_PER_BYTE;
58 set = (nfdt->max_fds - count) / BITS_PER_BYTE;
59 memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
60 memset((char *)nfdt->open_fds + cpy, 0, set);
61 memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
62 memset((char *)nfdt->close_on_exec + cpy, 0, set);
63
64 cpy = BITBIT_SIZE(count);
65 set = BITBIT_SIZE(nfdt->max_fds) - cpy;
66 memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
67 memset((char *)nfdt->full_fds_bits + cpy, 0, set);
68}
69
70/*
71 * Copy all file descriptors from the old table to the new, expanded table and
72 * clear the extra space. Called with the files spinlock held for write.
73 */
74static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
75{
76 size_t cpy, set;
77
78 BUG_ON(nfdt->max_fds < ofdt->max_fds);
79
80 cpy = ofdt->max_fds * sizeof(struct file *);
81 set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
82 memcpy(nfdt->fd, ofdt->fd, cpy);
83 memset((char *)nfdt->fd + cpy, 0, set);
84
85 copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
86}
87
88static struct fdtable * alloc_fdtable(unsigned int nr)
89{
90 struct fdtable *fdt;
91 void *data;
92
93 /*
94 * Figure out how many fds we actually want to support in this fdtable.
95 * Allocation steps are keyed to the size of the fdarray, since it
96 * grows far faster than any of the other dynamic data. We try to fit
97 * the fdarray into comfortable page-tuned chunks: starting at 1024B
98 * and growing in powers of two from there on.
99 */
100 nr /= (1024 / sizeof(struct file *));
101 nr = roundup_pow_of_two(nr + 1);
102 nr *= (1024 / sizeof(struct file *));
103 /*
104 * Note that this can drive nr *below* what we had passed if sysctl_nr_open
105 * had been set lower between the check in expand_files() and here. Deal
106 * with that in caller, it's cheaper that way.
107 *
108 * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
109 * bitmaps handling below becomes unpleasant, to put it mildly...
110 */
111 if (unlikely(nr > sysctl_nr_open))
112 nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
113
114 fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
115 if (!fdt)
116 goto out;
117 fdt->max_fds = nr;
118 data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT);
119 if (!data)
120 goto out_fdt;
121 fdt->fd = data;
122
123 data = kvmalloc(max_t(size_t,
124 2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES),
125 GFP_KERNEL_ACCOUNT);
126 if (!data)
127 goto out_arr;
128 fdt->open_fds = data;
129 data += nr / BITS_PER_BYTE;
130 fdt->close_on_exec = data;
131 data += nr / BITS_PER_BYTE;
132 fdt->full_fds_bits = data;
133
134 return fdt;
135
136out_arr:
137 kvfree(fdt->fd);
138out_fdt:
139 kfree(fdt);
140out:
141 return NULL;
142}
143
144/*
145 * Expand the file descriptor table.
146 * This function will allocate a new fdtable and both fd array and fdset, of
147 * the given size.
148 * Return <0 error code on error; 1 on successful completion.
149 * The files->file_lock should be held on entry, and will be held on exit.
150 */
151static int expand_fdtable(struct files_struct *files, unsigned int nr)
152 __releases(files->file_lock)
153 __acquires(files->file_lock)
154{
155 struct fdtable *new_fdt, *cur_fdt;
156
157 spin_unlock(&files->file_lock);
158 new_fdt = alloc_fdtable(nr);
159
160 /* make sure all __fd_install() have seen resize_in_progress
161 * or have finished their rcu_read_lock_sched() section.
162 */
163 if (atomic_read(&files->count) > 1)
164 synchronize_rcu();
165
166 spin_lock(&files->file_lock);
167 if (!new_fdt)
168 return -ENOMEM;
169 /*
170 * extremely unlikely race - sysctl_nr_open decreased between the check in
171 * caller and alloc_fdtable(). Cheaper to catch it here...
172 */
173 if (unlikely(new_fdt->max_fds <= nr)) {
174 __free_fdtable(new_fdt);
175 return -EMFILE;
176 }
177 cur_fdt = files_fdtable(files);
178 BUG_ON(nr < cur_fdt->max_fds);
179 copy_fdtable(new_fdt, cur_fdt);
180 rcu_assign_pointer(files->fdt, new_fdt);
181 if (cur_fdt != &files->fdtab)
182 call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
183 /* coupled with smp_rmb() in __fd_install() */
184 smp_wmb();
185 return 1;
186}
187
188/*
189 * Expand files.
190 * This function will expand the file structures, if the requested size exceeds
191 * the current capacity and there is room for expansion.
192 * Return <0 error code on error; 0 when nothing done; 1 when files were
193 * expanded and execution may have blocked.
194 * The files->file_lock should be held on entry, and will be held on exit.
195 */
196static int expand_files(struct files_struct *files, unsigned int nr)
197 __releases(files->file_lock)
198 __acquires(files->file_lock)
199{
200 struct fdtable *fdt;
201 int expanded = 0;
202
203repeat:
204 fdt = files_fdtable(files);
205
206 /* Do we need to expand? */
207 if (nr < fdt->max_fds)
208 return expanded;
209
210 /* Can we expand? */
211 if (nr >= sysctl_nr_open)
212 return -EMFILE;
213
214 if (unlikely(files->resize_in_progress)) {
215 spin_unlock(&files->file_lock);
216 expanded = 1;
217 wait_event(files->resize_wait, !files->resize_in_progress);
218 spin_lock(&files->file_lock);
219 goto repeat;
220 }
221
222 /* All good, so we try */
223 files->resize_in_progress = true;
224 expanded = expand_fdtable(files, nr);
225 files->resize_in_progress = false;
226
227 wake_up_all(&files->resize_wait);
228 return expanded;
229}
230
231static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt)
232{
233 __set_bit(fd, fdt->close_on_exec);
234}
235
236static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt)
237{
238 if (test_bit(fd, fdt->close_on_exec))
239 __clear_bit(fd, fdt->close_on_exec);
240}
241
242static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
243{
244 __set_bit(fd, fdt->open_fds);
245 fd /= BITS_PER_LONG;
246 if (!~fdt->open_fds[fd])
247 __set_bit(fd, fdt->full_fds_bits);
248}
249
250static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
251{
252 __clear_bit(fd, fdt->open_fds);
253 __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
254}
255
256static unsigned int count_open_files(struct fdtable *fdt)
257{
258 unsigned int size = fdt->max_fds;
259 unsigned int i;
260
261 /* Find the last open fd */
262 for (i = size / BITS_PER_LONG; i > 0; ) {
263 if (fdt->open_fds[--i])
264 break;
265 }
266 i = (i + 1) * BITS_PER_LONG;
267 return i;
268}
269
270static unsigned int sane_fdtable_size(struct fdtable *fdt, unsigned int max_fds)
271{
272 unsigned int count;
273
274 count = count_open_files(fdt);
275 if (max_fds < NR_OPEN_DEFAULT)
276 max_fds = NR_OPEN_DEFAULT;
277 return min(count, max_fds);
278}
279
280/*
281 * Allocate a new files structure and copy contents from the
282 * passed in files structure.
283 * errorp will be valid only when the returned files_struct is NULL.
284 */
285struct files_struct *dup_fd(struct files_struct *oldf, unsigned int max_fds, int *errorp)
286{
287 struct files_struct *newf;
288 struct file **old_fds, **new_fds;
289 unsigned int open_files, i;
290 struct fdtable *old_fdt, *new_fdt;
291
292 *errorp = -ENOMEM;
293 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
294 if (!newf)
295 goto out;
296
297 atomic_set(&newf->count, 1);
298
299 spin_lock_init(&newf->file_lock);
300 newf->resize_in_progress = false;
301 init_waitqueue_head(&newf->resize_wait);
302 newf->next_fd = 0;
303 new_fdt = &newf->fdtab;
304 new_fdt->max_fds = NR_OPEN_DEFAULT;
305 new_fdt->close_on_exec = newf->close_on_exec_init;
306 new_fdt->open_fds = newf->open_fds_init;
307 new_fdt->full_fds_bits = newf->full_fds_bits_init;
308 new_fdt->fd = &newf->fd_array[0];
309
310 spin_lock(&oldf->file_lock);
311 old_fdt = files_fdtable(oldf);
312 open_files = sane_fdtable_size(old_fdt, max_fds);
313
314 /*
315 * Check whether we need to allocate a larger fd array and fd set.
316 */
317 while (unlikely(open_files > new_fdt->max_fds)) {
318 spin_unlock(&oldf->file_lock);
319
320 if (new_fdt != &newf->fdtab)
321 __free_fdtable(new_fdt);
322
323 new_fdt = alloc_fdtable(open_files - 1);
324 if (!new_fdt) {
325 *errorp = -ENOMEM;
326 goto out_release;
327 }
328
329 /* beyond sysctl_nr_open; nothing to do */
330 if (unlikely(new_fdt->max_fds < open_files)) {
331 __free_fdtable(new_fdt);
332 *errorp = -EMFILE;
333 goto out_release;
334 }
335
336 /*
337 * Reacquire the oldf lock and a pointer to its fd table
338 * who knows it may have a new bigger fd table. We need
339 * the latest pointer.
340 */
341 spin_lock(&oldf->file_lock);
342 old_fdt = files_fdtable(oldf);
343 open_files = sane_fdtable_size(old_fdt, max_fds);
344 }
345
346 copy_fd_bitmaps(new_fdt, old_fdt, open_files);
347
348 old_fds = old_fdt->fd;
349 new_fds = new_fdt->fd;
350
351 for (i = open_files; i != 0; i--) {
352 struct file *f = *old_fds++;
353 if (f) {
354 get_file(f);
355 } else {
356 /*
357 * The fd may be claimed in the fd bitmap but not yet
358 * instantiated in the files array if a sibling thread
359 * is partway through open(). So make sure that this
360 * fd is available to the new process.
361 */
362 __clear_open_fd(open_files - i, new_fdt);
363 }
364 rcu_assign_pointer(*new_fds++, f);
365 }
366 spin_unlock(&oldf->file_lock);
367
368 /* clear the remainder */
369 memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
370
371 rcu_assign_pointer(newf->fdt, new_fdt);
372
373 return newf;
374
375out_release:
376 kmem_cache_free(files_cachep, newf);
377out:
378 return NULL;
379}
380
381static struct fdtable *close_files(struct files_struct * files)
382{
383 /*
384 * It is safe to dereference the fd table without RCU or
385 * ->file_lock because this is the last reference to the
386 * files structure.
387 */
388 struct fdtable *fdt = rcu_dereference_raw(files->fdt);
389 unsigned int i, j = 0;
390
391 for (;;) {
392 unsigned long set;
393 i = j * BITS_PER_LONG;
394 if (i >= fdt->max_fds)
395 break;
396 set = fdt->open_fds[j++];
397 while (set) {
398 if (set & 1) {
399 struct file * file = xchg(&fdt->fd[i], NULL);
400 if (file) {
401 filp_close(file, files);
402 cond_resched();
403 }
404 }
405 i++;
406 set >>= 1;
407 }
408 }
409
410 return fdt;
411}
412
413struct files_struct *get_files_struct(struct task_struct *task)
414{
415 struct files_struct *files;
416
417 task_lock(task);
418 files = task->files;
419 if (files)
420 atomic_inc(&files->count);
421 task_unlock(task);
422
423 return files;
424}
425
426void put_files_struct(struct files_struct *files)
427{
428 if (atomic_dec_and_test(&files->count)) {
429 struct fdtable *fdt = close_files(files);
430
431 /* free the arrays if they are not embedded */
432 if (fdt != &files->fdtab)
433 __free_fdtable(fdt);
434 kmem_cache_free(files_cachep, files);
435 }
436}
437
438void reset_files_struct(struct files_struct *files)
439{
440 struct task_struct *tsk = current;
441 struct files_struct *old;
442
443 old = tsk->files;
444 task_lock(tsk);
445 tsk->files = files;
446 task_unlock(tsk);
447 put_files_struct(old);
448}
449
450void exit_files(struct task_struct *tsk)
451{
452 struct files_struct * files = tsk->files;
453
454 if (files) {
455 task_lock(tsk);
456 tsk->files = NULL;
457 task_unlock(tsk);
458 put_files_struct(files);
459 }
460}
461
462struct files_struct init_files = {
463 .count = ATOMIC_INIT(1),
464 .fdt = &init_files.fdtab,
465 .fdtab = {
466 .max_fds = NR_OPEN_DEFAULT,
467 .fd = &init_files.fd_array[0],
468 .close_on_exec = init_files.close_on_exec_init,
469 .open_fds = init_files.open_fds_init,
470 .full_fds_bits = init_files.full_fds_bits_init,
471 },
472 .file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
473 .resize_wait = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),
474};
475
476static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
477{
478 unsigned int maxfd = fdt->max_fds;
479 unsigned int maxbit = maxfd / BITS_PER_LONG;
480 unsigned int bitbit = start / BITS_PER_LONG;
481
482 bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
483 if (bitbit > maxfd)
484 return maxfd;
485 if (bitbit > start)
486 start = bitbit;
487 return find_next_zero_bit(fdt->open_fds, maxfd, start);
488}
489
490/*
491 * allocate a file descriptor, mark it busy.
492 */
493int __alloc_fd(struct files_struct *files,
494 unsigned start, unsigned end, unsigned flags)
495{
496 unsigned int fd;
497 int error;
498 struct fdtable *fdt;
499
500 spin_lock(&files->file_lock);
501repeat:
502 fdt = files_fdtable(files);
503 fd = start;
504 if (fd < files->next_fd)
505 fd = files->next_fd;
506
507 if (fd < fdt->max_fds)
508 fd = find_next_fd(fdt, fd);
509
510 /*
511 * N.B. For clone tasks sharing a files structure, this test
512 * will limit the total number of files that can be opened.
513 */
514 error = -EMFILE;
515 if (fd >= end)
516 goto out;
517
518 error = expand_files(files, fd);
519 if (error < 0)
520 goto out;
521
522 /*
523 * If we needed to expand the fs array we
524 * might have blocked - try again.
525 */
526 if (error)
527 goto repeat;
528
529 if (start <= files->next_fd)
530 files->next_fd = fd + 1;
531
532 __set_open_fd(fd, fdt);
533 if (flags & O_CLOEXEC)
534 __set_close_on_exec(fd, fdt);
535 else
536 __clear_close_on_exec(fd, fdt);
537 error = fd;
538#if 1
539 /* Sanity check */
540 if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
541 printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
542 rcu_assign_pointer(fdt->fd[fd], NULL);
543 }
544#endif
545
546out:
547 spin_unlock(&files->file_lock);
548 return error;
549}
550
551static int alloc_fd(unsigned start, unsigned flags)
552{
553 return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags);
554}
555
556int __get_unused_fd_flags(unsigned flags, unsigned long nofile)
557{
558 return __alloc_fd(current->files, 0, nofile, flags);
559}
560
561int get_unused_fd_flags(unsigned flags)
562{
563 return __get_unused_fd_flags(flags, rlimit(RLIMIT_NOFILE));
564}
565EXPORT_SYMBOL(get_unused_fd_flags);
566
567static void __put_unused_fd(struct files_struct *files, unsigned int fd)
568{
569 struct fdtable *fdt = files_fdtable(files);
570 __clear_open_fd(fd, fdt);
571 if (fd < files->next_fd)
572 files->next_fd = fd;
573}
574
575void put_unused_fd(unsigned int fd)
576{
577 struct files_struct *files = current->files;
578 spin_lock(&files->file_lock);
579 __put_unused_fd(files, fd);
580 spin_unlock(&files->file_lock);
581}
582
583EXPORT_SYMBOL(put_unused_fd);
584
585/*
586 * Install a file pointer in the fd array.
587 *
588 * The VFS is full of places where we drop the files lock between
589 * setting the open_fds bitmap and installing the file in the file
590 * array. At any such point, we are vulnerable to a dup2() race
591 * installing a file in the array before us. We need to detect this and
592 * fput() the struct file we are about to overwrite in this case.
593 *
594 * It should never happen - if we allow dup2() do it, _really_ bad things
595 * will follow.
596 *
597 * NOTE: __fd_install() variant is really, really low-level; don't
598 * use it unless you are forced to by truly lousy API shoved down
599 * your throat. 'files' *MUST* be either current->files or obtained
600 * by get_files_struct(current) done by whoever had given it to you,
601 * or really bad things will happen. Normally you want to use
602 * fd_install() instead.
603 */
604
605void __fd_install(struct files_struct *files, unsigned int fd,
606 struct file *file)
607{
608 struct fdtable *fdt;
609
610 rcu_read_lock_sched();
611
612 if (unlikely(files->resize_in_progress)) {
613 rcu_read_unlock_sched();
614 spin_lock(&files->file_lock);
615 fdt = files_fdtable(files);
616 BUG_ON(fdt->fd[fd] != NULL);
617 rcu_assign_pointer(fdt->fd[fd], file);
618 spin_unlock(&files->file_lock);
619 return;
620 }
621 /* coupled with smp_wmb() in expand_fdtable() */
622 smp_rmb();
623 fdt = rcu_dereference_sched(files->fdt);
624 BUG_ON(fdt->fd[fd] != NULL);
625 rcu_assign_pointer(fdt->fd[fd], file);
626 rcu_read_unlock_sched();
627}
628
629/*
630 * This consumes the "file" refcount, so callers should treat it
631 * as if they had called fput(file).
632 */
633void fd_install(unsigned int fd, struct file *file)
634{
635 __fd_install(current->files, fd, file);
636}
637
638EXPORT_SYMBOL(fd_install);
639
640static struct file *pick_file(struct files_struct *files, unsigned fd)
641{
642 struct file *file = NULL;
643 struct fdtable *fdt;
644
645 spin_lock(&files->file_lock);
646 fdt = files_fdtable(files);
647 if (fd >= fdt->max_fds)
648 goto out_unlock;
649 file = fdt->fd[fd];
650 if (!file)
651 goto out_unlock;
652 rcu_assign_pointer(fdt->fd[fd], NULL);
653 __put_unused_fd(files, fd);
654
655out_unlock:
656 spin_unlock(&files->file_lock);
657 return file;
658}
659
660/*
661 * The same warnings as for __alloc_fd()/__fd_install() apply here...
662 */
663int __close_fd(struct files_struct *files, unsigned fd)
664{
665 struct file *file;
666
667 file = pick_file(files, fd);
668 if (!file)
669 return -EBADF;
670
671 return filp_close(file, files);
672}
673EXPORT_SYMBOL(__close_fd); /* for ksys_close() */
674
675/**
676 * __close_range() - Close all file descriptors in a given range.
677 *
678 * @fd: starting file descriptor to close
679 * @max_fd: last file descriptor to close
680 *
681 * This closes a range of file descriptors. All file descriptors
682 * from @fd up to and including @max_fd are closed.
683 */
684int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
685{
686 unsigned int cur_max;
687 struct task_struct *me = current;
688 struct files_struct *cur_fds = me->files, *fds = NULL;
689
690 if (flags & ~CLOSE_RANGE_UNSHARE)
691 return -EINVAL;
692
693 if (fd > max_fd)
694 return -EINVAL;
695
696 rcu_read_lock();
697 cur_max = files_fdtable(cur_fds)->max_fds;
698 rcu_read_unlock();
699
700 /* cap to last valid index into fdtable */
701 cur_max--;
702
703 if (flags & CLOSE_RANGE_UNSHARE) {
704 int ret;
705 unsigned int max_unshare_fds = NR_OPEN_MAX;
706
707 /*
708 * If the requested range is greater than the current maximum,
709 * we're closing everything so only copy all file descriptors
710 * beneath the lowest file descriptor.
711 */
712 if (max_fd >= cur_max)
713 max_unshare_fds = fd;
714
715 ret = unshare_fd(CLONE_FILES, max_unshare_fds, &fds);
716 if (ret)
717 return ret;
718
719 /*
720 * We used to share our file descriptor table, and have now
721 * created a private one, make sure we're using it below.
722 */
723 if (fds)
724 swap(cur_fds, fds);
725 }
726
727 max_fd = min(max_fd, cur_max);
728 while (fd <= max_fd) {
729 struct file *file;
730
731 file = pick_file(cur_fds, fd++);
732 if (!file)
733 continue;
734
735 filp_close(file, cur_fds);
736 cond_resched();
737 }
738
739 if (fds) {
740 /*
741 * We're done closing the files we were supposed to. Time to install
742 * the new file descriptor table and drop the old one.
743 */
744 task_lock(me);
745 me->files = cur_fds;
746 task_unlock(me);
747 put_files_struct(fds);
748 }
749
750 return 0;
751}
752
753/*
754 * variant of __close_fd that gets a ref on the file for later fput.
755 * The caller must ensure that filp_close() called on the file, and then
756 * an fput().
757 */
758int __close_fd_get_file(unsigned int fd, struct file **res)
759{
760 struct files_struct *files = current->files;
761 struct file *file;
762 struct fdtable *fdt;
763
764 spin_lock(&files->file_lock);
765 fdt = files_fdtable(files);
766 if (fd >= fdt->max_fds)
767 goto out_unlock;
768 file = fdt->fd[fd];
769 if (!file)
770 goto out_unlock;
771 rcu_assign_pointer(fdt->fd[fd], NULL);
772 __put_unused_fd(files, fd);
773 spin_unlock(&files->file_lock);
774 get_file(file);
775 *res = file;
776 return 0;
777
778out_unlock:
779 spin_unlock(&files->file_lock);
780 *res = NULL;
781 return -ENOENT;
782}
783
784void do_close_on_exec(struct files_struct *files)
785{
786 unsigned i;
787 struct fdtable *fdt;
788
789 /* exec unshares first */
790 spin_lock(&files->file_lock);
791 for (i = 0; ; i++) {
792 unsigned long set;
793 unsigned fd = i * BITS_PER_LONG;
794 fdt = files_fdtable(files);
795 if (fd >= fdt->max_fds)
796 break;
797 set = fdt->close_on_exec[i];
798 if (!set)
799 continue;
800 fdt->close_on_exec[i] = 0;
801 for ( ; set ; fd++, set >>= 1) {
802 struct file *file;
803 if (!(set & 1))
804 continue;
805 file = fdt->fd[fd];
806 if (!file)
807 continue;
808 rcu_assign_pointer(fdt->fd[fd], NULL);
809 __put_unused_fd(files, fd);
810 spin_unlock(&files->file_lock);
811 filp_close(file, files);
812 cond_resched();
813 spin_lock(&files->file_lock);
814 }
815
816 }
817 spin_unlock(&files->file_lock);
818}
819
820static struct file *__fget_files(struct files_struct *files, unsigned int fd,
821 fmode_t mask, unsigned int refs)
822{
823 struct file *file;
824
825 rcu_read_lock();
826loop:
827 file = fcheck_files(files, fd);
828 if (file) {
829 /* File object ref couldn't be taken.
830 * dup2() atomicity guarantee is the reason
831 * we loop to catch the new file (or NULL pointer)
832 */
833 if (file->f_mode & mask)
834 file = NULL;
835 else if (!get_file_rcu_many(file, refs))
836 goto loop;
837 }
838 rcu_read_unlock();
839
840 return file;
841}
842
843static inline struct file *__fget(unsigned int fd, fmode_t mask,
844 unsigned int refs)
845{
846 return __fget_files(current->files, fd, mask, refs);
847}
848
849struct file *fget_many(unsigned int fd, unsigned int refs)
850{
851 return __fget(fd, FMODE_PATH, refs);
852}
853
854struct file *fget(unsigned int fd)
855{
856 return __fget(fd, FMODE_PATH, 1);
857}
858EXPORT_SYMBOL(fget);
859
860struct file *fget_raw(unsigned int fd)
861{
862 return __fget(fd, 0, 1);
863}
864EXPORT_SYMBOL(fget_raw);
865
866struct file *fget_task(struct task_struct *task, unsigned int fd)
867{
868 struct file *file = NULL;
869
870 task_lock(task);
871 if (task->files)
872 file = __fget_files(task->files, fd, 0, 1);
873 task_unlock(task);
874
875 return file;
876}
877
878/*
879 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
880 *
881 * You can use this instead of fget if you satisfy all of the following
882 * conditions:
883 * 1) You must call fput_light before exiting the syscall and returning control
884 * to userspace (i.e. you cannot remember the returned struct file * after
885 * returning to userspace).
886 * 2) You must not call filp_close on the returned struct file * in between
887 * calls to fget_light and fput_light.
888 * 3) You must not clone the current task in between the calls to fget_light
889 * and fput_light.
890 *
891 * The fput_needed flag returned by fget_light should be passed to the
892 * corresponding fput_light.
893 */
894static unsigned long __fget_light(unsigned int fd, fmode_t mask)
895{
896 struct files_struct *files = current->files;
897 struct file *file;
898
899 if (atomic_read(&files->count) == 1) {
900 file = __fcheck_files(files, fd);
901 if (!file || unlikely(file->f_mode & mask))
902 return 0;
903 return (unsigned long)file;
904 } else {
905 file = __fget(fd, mask, 1);
906 if (!file)
907 return 0;
908 return FDPUT_FPUT | (unsigned long)file;
909 }
910}
911unsigned long __fdget(unsigned int fd)
912{
913 return __fget_light(fd, FMODE_PATH);
914}
915EXPORT_SYMBOL(__fdget);
916
917unsigned long __fdget_raw(unsigned int fd)
918{
919 return __fget_light(fd, 0);
920}
921
922unsigned long __fdget_pos(unsigned int fd)
923{
924 unsigned long v = __fdget(fd);
925 struct file *file = (struct file *)(v & ~3);
926
927 if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
928 if (file_count(file) > 1) {
929 v |= FDPUT_POS_UNLOCK;
930 mutex_lock(&file->f_pos_lock);
931 }
932 }
933 return v;
934}
935
936void __f_unlock_pos(struct file *f)
937{
938 mutex_unlock(&f->f_pos_lock);
939}
940
941/*
942 * We only lock f_pos if we have threads or if the file might be
943 * shared with another process. In both cases we'll have an elevated
944 * file count (done either by fdget() or by fork()).
945 */
946
947void set_close_on_exec(unsigned int fd, int flag)
948{
949 struct files_struct *files = current->files;
950 struct fdtable *fdt;
951 spin_lock(&files->file_lock);
952 fdt = files_fdtable(files);
953 if (flag)
954 __set_close_on_exec(fd, fdt);
955 else
956 __clear_close_on_exec(fd, fdt);
957 spin_unlock(&files->file_lock);
958}
959
960bool get_close_on_exec(unsigned int fd)
961{
962 struct files_struct *files = current->files;
963 struct fdtable *fdt;
964 bool res;
965 rcu_read_lock();
966 fdt = files_fdtable(files);
967 res = close_on_exec(fd, fdt);
968 rcu_read_unlock();
969 return res;
970}
971
972static int do_dup2(struct files_struct *files,
973 struct file *file, unsigned fd, unsigned flags)
974__releases(&files->file_lock)
975{
976 struct file *tofree;
977 struct fdtable *fdt;
978
979 /*
980 * We need to detect attempts to do dup2() over allocated but still
981 * not finished descriptor. NB: OpenBSD avoids that at the price of
982 * extra work in their equivalent of fget() - they insert struct
983 * file immediately after grabbing descriptor, mark it larval if
984 * more work (e.g. actual opening) is needed and make sure that
985 * fget() treats larval files as absent. Potentially interesting,
986 * but while extra work in fget() is trivial, locking implications
987 * and amount of surgery on open()-related paths in VFS are not.
988 * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
989 * deadlocks in rather amusing ways, AFAICS. All of that is out of
990 * scope of POSIX or SUS, since neither considers shared descriptor
991 * tables and this condition does not arise without those.
992 */
993 fdt = files_fdtable(files);
994 tofree = fdt->fd[fd];
995 if (!tofree && fd_is_open(fd, fdt))
996 goto Ebusy;
997 get_file(file);
998 rcu_assign_pointer(fdt->fd[fd], file);
999 __set_open_fd(fd, fdt);
1000 if (flags & O_CLOEXEC)
1001 __set_close_on_exec(fd, fdt);
1002 else
1003 __clear_close_on_exec(fd, fdt);
1004 spin_unlock(&files->file_lock);
1005
1006 if (tofree)
1007 filp_close(tofree, files);
1008
1009 return fd;
1010
1011Ebusy:
1012 spin_unlock(&files->file_lock);
1013 return -EBUSY;
1014}
1015
1016int replace_fd(unsigned fd, struct file *file, unsigned flags)
1017{
1018 int err;
1019 struct files_struct *files = current->files;
1020
1021 if (!file)
1022 return __close_fd(files, fd);
1023
1024 if (fd >= rlimit(RLIMIT_NOFILE))
1025 return -EBADF;
1026
1027 spin_lock(&files->file_lock);
1028 err = expand_files(files, fd);
1029 if (unlikely(err < 0))
1030 goto out_unlock;
1031 return do_dup2(files, file, fd, flags);
1032
1033out_unlock:
1034 spin_unlock(&files->file_lock);
1035 return err;
1036}
1037
1038/**
1039 * __receive_fd() - Install received file into file descriptor table
1040 *
1041 * @fd: fd to install into (if negative, a new fd will be allocated)
1042 * @file: struct file that was received from another process
1043 * @ufd: __user pointer to write new fd number to
1044 * @o_flags: the O_* flags to apply to the new fd entry
1045 *
1046 * Installs a received file into the file descriptor table, with appropriate
1047 * checks and count updates. Optionally writes the fd number to userspace, if
1048 * @ufd is non-NULL.
1049 *
1050 * This helper handles its own reference counting of the incoming
1051 * struct file.
1052 *
1053 * Returns newly install fd or -ve on error.
1054 */
1055int __receive_fd(int fd, struct file *file, int __user *ufd, unsigned int o_flags)
1056{
1057 int new_fd;
1058 int error;
1059
1060 error = security_file_receive(file);
1061 if (error)
1062 return error;
1063
1064 if (fd < 0) {
1065 new_fd = get_unused_fd_flags(o_flags);
1066 if (new_fd < 0)
1067 return new_fd;
1068 } else {
1069 new_fd = fd;
1070 }
1071
1072 if (ufd) {
1073 error = put_user(new_fd, ufd);
1074 if (error) {
1075 if (fd < 0)
1076 put_unused_fd(new_fd);
1077 return error;
1078 }
1079 }
1080
1081 if (fd < 0) {
1082 fd_install(new_fd, get_file(file));
1083 } else {
1084 error = replace_fd(new_fd, file, o_flags);
1085 if (error)
1086 return error;
1087 }
1088
1089 /* Bump the sock usage counts, if any. */
1090 __receive_sock(file);
1091 return new_fd;
1092}
1093
1094static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
1095{
1096 int err = -EBADF;
1097 struct file *file;
1098 struct files_struct *files = current->files;
1099
1100 if ((flags & ~O_CLOEXEC) != 0)
1101 return -EINVAL;
1102
1103 if (unlikely(oldfd == newfd))
1104 return -EINVAL;
1105
1106 if (newfd >= rlimit(RLIMIT_NOFILE))
1107 return -EBADF;
1108
1109 spin_lock(&files->file_lock);
1110 err = expand_files(files, newfd);
1111 file = fcheck(oldfd);
1112 if (unlikely(!file))
1113 goto Ebadf;
1114 if (unlikely(err < 0)) {
1115 if (err == -EMFILE)
1116 goto Ebadf;
1117 goto out_unlock;
1118 }
1119 return do_dup2(files, file, newfd, flags);
1120
1121Ebadf:
1122 err = -EBADF;
1123out_unlock:
1124 spin_unlock(&files->file_lock);
1125 return err;
1126}
1127
1128SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
1129{
1130 return ksys_dup3(oldfd, newfd, flags);
1131}
1132
1133SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
1134{
1135 if (unlikely(newfd == oldfd)) { /* corner case */
1136 struct files_struct *files = current->files;
1137 int retval = oldfd;
1138
1139 rcu_read_lock();
1140 if (!fcheck_files(files, oldfd))
1141 retval = -EBADF;
1142 rcu_read_unlock();
1143 return retval;
1144 }
1145 return ksys_dup3(oldfd, newfd, 0);
1146}
1147
1148SYSCALL_DEFINE1(dup, unsigned int, fildes)
1149{
1150 int ret = -EBADF;
1151 struct file *file = fget_raw(fildes);
1152
1153 if (file) {
1154 ret = get_unused_fd_flags(0);
1155 if (ret >= 0)
1156 fd_install(ret, file);
1157 else
1158 fput(file);
1159 }
1160 return ret;
1161}
1162
1163int f_dupfd(unsigned int from, struct file *file, unsigned flags)
1164{
1165 int err;
1166 if (from >= rlimit(RLIMIT_NOFILE))
1167 return -EINVAL;
1168 err = alloc_fd(from, flags);
1169 if (err >= 0) {
1170 get_file(file);
1171 fd_install(err, file);
1172 }
1173 return err;
1174}
1175
1176int iterate_fd(struct files_struct *files, unsigned n,
1177 int (*f)(const void *, struct file *, unsigned),
1178 const void *p)
1179{
1180 struct fdtable *fdt;
1181 int res = 0;
1182 if (!files)
1183 return 0;
1184 spin_lock(&files->file_lock);
1185 for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
1186 struct file *file;
1187 file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
1188 if (!file)
1189 continue;
1190 res = f(p, file, n);
1191 if (res)
1192 break;
1193 }
1194 spin_unlock(&files->file_lock);
1195 return res;
1196}
1197EXPORT_SYMBOL(iterate_fd);
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/module.h>
10#include <linux/fs.h>
11#include <linux/mm.h>
12#include <linux/mmzone.h>
13#include <linux/time.h>
14#include <linux/sched.h>
15#include <linux/slab.h>
16#include <linux/vmalloc.h>
17#include <linux/file.h>
18#include <linux/fdtable.h>
19#include <linux/bitops.h>
20#include <linux/interrupt.h>
21#include <linux/spinlock.h>
22#include <linux/rcupdate.h>
23#include <linux/workqueue.h>
24
25struct fdtable_defer {
26 spinlock_t lock;
27 struct work_struct wq;
28 struct fdtable *next;
29};
30
31int sysctl_nr_open __read_mostly = 1024*1024;
32int sysctl_nr_open_min = BITS_PER_LONG;
33int sysctl_nr_open_max = 1024 * 1024; /* raised later */
34
35/*
36 * We use this list to defer free fdtables that have vmalloced
37 * sets/arrays. By keeping a per-cpu list, we avoid having to embed
38 * the work_struct in fdtable itself which avoids a 64 byte (i386) increase in
39 * this per-task structure.
40 */
41static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list);
42
43static void *alloc_fdmem(unsigned int size)
44{
45 /*
46 * Very large allocations can stress page reclaim, so fall back to
47 * vmalloc() if the allocation size will be considered "large" by the VM.
48 */
49 if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) {
50 void *data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN);
51 if (data != NULL)
52 return data;
53 }
54 return vmalloc(size);
55}
56
57static void free_fdmem(void *ptr)
58{
59 is_vmalloc_addr(ptr) ? vfree(ptr) : kfree(ptr);
60}
61
62static void __free_fdtable(struct fdtable *fdt)
63{
64 free_fdmem(fdt->fd);
65 free_fdmem(fdt->open_fds);
66 kfree(fdt);
67}
68
69static void free_fdtable_work(struct work_struct *work)
70{
71 struct fdtable_defer *f =
72 container_of(work, struct fdtable_defer, wq);
73 struct fdtable *fdt;
74
75 spin_lock_bh(&f->lock);
76 fdt = f->next;
77 f->next = NULL;
78 spin_unlock_bh(&f->lock);
79 while(fdt) {
80 struct fdtable *next = fdt->next;
81
82 __free_fdtable(fdt);
83 fdt = next;
84 }
85}
86
87void free_fdtable_rcu(struct rcu_head *rcu)
88{
89 struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);
90 struct fdtable_defer *fddef;
91
92 BUG_ON(!fdt);
93
94 if (fdt->max_fds <= NR_OPEN_DEFAULT) {
95 /*
96 * This fdtable is embedded in the files structure and that
97 * structure itself is getting destroyed.
98 */
99 kmem_cache_free(files_cachep,
100 container_of(fdt, struct files_struct, fdtab));
101 return;
102 }
103 if (!is_vmalloc_addr(fdt->fd) && !is_vmalloc_addr(fdt->open_fds)) {
104 kfree(fdt->fd);
105 kfree(fdt->open_fds);
106 kfree(fdt);
107 } else {
108 fddef = &get_cpu_var(fdtable_defer_list);
109 spin_lock(&fddef->lock);
110 fdt->next = fddef->next;
111 fddef->next = fdt;
112 /* vmallocs are handled from the workqueue context */
113 schedule_work(&fddef->wq);
114 spin_unlock(&fddef->lock);
115 put_cpu_var(fdtable_defer_list);
116 }
117}
118
119/*
120 * Expand the fdset in the files_struct. Called with the files spinlock
121 * held for write.
122 */
123static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
124{
125 unsigned int cpy, set;
126
127 BUG_ON(nfdt->max_fds < ofdt->max_fds);
128
129 cpy = ofdt->max_fds * sizeof(struct file *);
130 set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
131 memcpy(nfdt->fd, ofdt->fd, cpy);
132 memset((char *)(nfdt->fd) + cpy, 0, set);
133
134 cpy = ofdt->max_fds / BITS_PER_BYTE;
135 set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE;
136 memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
137 memset((char *)(nfdt->open_fds) + cpy, 0, set);
138 memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
139 memset((char *)(nfdt->close_on_exec) + cpy, 0, set);
140}
141
142static struct fdtable * alloc_fdtable(unsigned int nr)
143{
144 struct fdtable *fdt;
145 char *data;
146
147 /*
148 * Figure out how many fds we actually want to support in this fdtable.
149 * Allocation steps are keyed to the size of the fdarray, since it
150 * grows far faster than any of the other dynamic data. We try to fit
151 * the fdarray into comfortable page-tuned chunks: starting at 1024B
152 * and growing in powers of two from there on.
153 */
154 nr /= (1024 / sizeof(struct file *));
155 nr = roundup_pow_of_two(nr + 1);
156 nr *= (1024 / sizeof(struct file *));
157 /*
158 * Note that this can drive nr *below* what we had passed if sysctl_nr_open
159 * had been set lower between the check in expand_files() and here. Deal
160 * with that in caller, it's cheaper that way.
161 *
162 * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
163 * bitmaps handling below becomes unpleasant, to put it mildly...
164 */
165 if (unlikely(nr > sysctl_nr_open))
166 nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
167
168 fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL);
169 if (!fdt)
170 goto out;
171 fdt->max_fds = nr;
172 data = alloc_fdmem(nr * sizeof(struct file *));
173 if (!data)
174 goto out_fdt;
175 fdt->fd = (struct file **)data;
176 data = alloc_fdmem(max_t(unsigned int,
177 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES));
178 if (!data)
179 goto out_arr;
180 fdt->open_fds = (fd_set *)data;
181 data += nr / BITS_PER_BYTE;
182 fdt->close_on_exec = (fd_set *)data;
183 fdt->next = NULL;
184
185 return fdt;
186
187out_arr:
188 free_fdmem(fdt->fd);
189out_fdt:
190 kfree(fdt);
191out:
192 return NULL;
193}
194
195/*
196 * Expand the file descriptor table.
197 * This function will allocate a new fdtable and both fd array and fdset, of
198 * the given size.
199 * Return <0 error code on error; 1 on successful completion.
200 * The files->file_lock should be held on entry, and will be held on exit.
201 */
202static int expand_fdtable(struct files_struct *files, int nr)
203 __releases(files->file_lock)
204 __acquires(files->file_lock)
205{
206 struct fdtable *new_fdt, *cur_fdt;
207
208 spin_unlock(&files->file_lock);
209 new_fdt = alloc_fdtable(nr);
210 spin_lock(&files->file_lock);
211 if (!new_fdt)
212 return -ENOMEM;
213 /*
214 * extremely unlikely race - sysctl_nr_open decreased between the check in
215 * caller and alloc_fdtable(). Cheaper to catch it here...
216 */
217 if (unlikely(new_fdt->max_fds <= nr)) {
218 __free_fdtable(new_fdt);
219 return -EMFILE;
220 }
221 /*
222 * Check again since another task may have expanded the fd table while
223 * we dropped the lock
224 */
225 cur_fdt = files_fdtable(files);
226 if (nr >= cur_fdt->max_fds) {
227 /* Continue as planned */
228 copy_fdtable(new_fdt, cur_fdt);
229 rcu_assign_pointer(files->fdt, new_fdt);
230 if (cur_fdt->max_fds > NR_OPEN_DEFAULT)
231 free_fdtable(cur_fdt);
232 } else {
233 /* Somebody else expanded, so undo our attempt */
234 __free_fdtable(new_fdt);
235 }
236 return 1;
237}
238
239/*
240 * Expand files.
241 * This function will expand the file structures, if the requested size exceeds
242 * the current capacity and there is room for expansion.
243 * Return <0 error code on error; 0 when nothing done; 1 when files were
244 * expanded and execution may have blocked.
245 * The files->file_lock should be held on entry, and will be held on exit.
246 */
247int expand_files(struct files_struct *files, int nr)
248{
249 struct fdtable *fdt;
250
251 fdt = files_fdtable(files);
252
253 /*
254 * N.B. For clone tasks sharing a files structure, this test
255 * will limit the total number of files that can be opened.
256 */
257 if (nr >= rlimit(RLIMIT_NOFILE))
258 return -EMFILE;
259
260 /* Do we need to expand? */
261 if (nr < fdt->max_fds)
262 return 0;
263
264 /* Can we expand? */
265 if (nr >= sysctl_nr_open)
266 return -EMFILE;
267
268 /* All good, so we try */
269 return expand_fdtable(files, nr);
270}
271
272static int count_open_files(struct fdtable *fdt)
273{
274 int size = fdt->max_fds;
275 int i;
276
277 /* Find the last open fd */
278 for (i = size/(8*sizeof(long)); i > 0; ) {
279 if (fdt->open_fds->fds_bits[--i])
280 break;
281 }
282 i = (i+1) * 8 * sizeof(long);
283 return i;
284}
285
286/*
287 * Allocate a new files structure and copy contents from the
288 * passed in files structure.
289 * errorp will be valid only when the returned files_struct is NULL.
290 */
291struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
292{
293 struct files_struct *newf;
294 struct file **old_fds, **new_fds;
295 int open_files, size, i;
296 struct fdtable *old_fdt, *new_fdt;
297
298 *errorp = -ENOMEM;
299 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
300 if (!newf)
301 goto out;
302
303 atomic_set(&newf->count, 1);
304
305 spin_lock_init(&newf->file_lock);
306 newf->next_fd = 0;
307 new_fdt = &newf->fdtab;
308 new_fdt->max_fds = NR_OPEN_DEFAULT;
309 new_fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
310 new_fdt->open_fds = (fd_set *)&newf->open_fds_init;
311 new_fdt->fd = &newf->fd_array[0];
312 new_fdt->next = NULL;
313
314 spin_lock(&oldf->file_lock);
315 old_fdt = files_fdtable(oldf);
316 open_files = count_open_files(old_fdt);
317
318 /*
319 * Check whether we need to allocate a larger fd array and fd set.
320 */
321 while (unlikely(open_files > new_fdt->max_fds)) {
322 spin_unlock(&oldf->file_lock);
323
324 if (new_fdt != &newf->fdtab)
325 __free_fdtable(new_fdt);
326
327 new_fdt = alloc_fdtable(open_files - 1);
328 if (!new_fdt) {
329 *errorp = -ENOMEM;
330 goto out_release;
331 }
332
333 /* beyond sysctl_nr_open; nothing to do */
334 if (unlikely(new_fdt->max_fds < open_files)) {
335 __free_fdtable(new_fdt);
336 *errorp = -EMFILE;
337 goto out_release;
338 }
339
340 /*
341 * Reacquire the oldf lock and a pointer to its fd table
342 * who knows it may have a new bigger fd table. We need
343 * the latest pointer.
344 */
345 spin_lock(&oldf->file_lock);
346 old_fdt = files_fdtable(oldf);
347 open_files = count_open_files(old_fdt);
348 }
349
350 old_fds = old_fdt->fd;
351 new_fds = new_fdt->fd;
352
353 memcpy(new_fdt->open_fds->fds_bits,
354 old_fdt->open_fds->fds_bits, open_files/8);
355 memcpy(new_fdt->close_on_exec->fds_bits,
356 old_fdt->close_on_exec->fds_bits, open_files/8);
357
358 for (i = open_files; i != 0; i--) {
359 struct file *f = *old_fds++;
360 if (f) {
361 get_file(f);
362 } else {
363 /*
364 * The fd may be claimed in the fd bitmap but not yet
365 * instantiated in the files array if a sibling thread
366 * is partway through open(). So make sure that this
367 * fd is available to the new process.
368 */
369 FD_CLR(open_files - i, new_fdt->open_fds);
370 }
371 rcu_assign_pointer(*new_fds++, f);
372 }
373 spin_unlock(&oldf->file_lock);
374
375 /* compute the remainder to be cleared */
376 size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
377
378 /* This is long word aligned thus could use a optimized version */
379 memset(new_fds, 0, size);
380
381 if (new_fdt->max_fds > open_files) {
382 int left = (new_fdt->max_fds-open_files)/8;
383 int start = open_files / (8 * sizeof(unsigned long));
384
385 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
386 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
387 }
388
389 rcu_assign_pointer(newf->fdt, new_fdt);
390
391 return newf;
392
393out_release:
394 kmem_cache_free(files_cachep, newf);
395out:
396 return NULL;
397}
398
399static void __devinit fdtable_defer_list_init(int cpu)
400{
401 struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
402 spin_lock_init(&fddef->lock);
403 INIT_WORK(&fddef->wq, free_fdtable_work);
404 fddef->next = NULL;
405}
406
407void __init files_defer_init(void)
408{
409 int i;
410 for_each_possible_cpu(i)
411 fdtable_defer_list_init(i);
412 sysctl_nr_open_max = min((size_t)INT_MAX, ~(size_t)0/sizeof(void *)) &
413 -BITS_PER_LONG;
414}
415
416struct files_struct init_files = {
417 .count = ATOMIC_INIT(1),
418 .fdt = &init_files.fdtab,
419 .fdtab = {
420 .max_fds = NR_OPEN_DEFAULT,
421 .fd = &init_files.fd_array[0],
422 .close_on_exec = (fd_set *)&init_files.close_on_exec_init,
423 .open_fds = (fd_set *)&init_files.open_fds_init,
424 },
425 .file_lock = __SPIN_LOCK_UNLOCKED(init_task.file_lock),
426};
427
428/*
429 * allocate a file descriptor, mark it busy.
430 */
431int alloc_fd(unsigned start, unsigned flags)
432{
433 struct files_struct *files = current->files;
434 unsigned int fd;
435 int error;
436 struct fdtable *fdt;
437
438 spin_lock(&files->file_lock);
439repeat:
440 fdt = files_fdtable(files);
441 fd = start;
442 if (fd < files->next_fd)
443 fd = files->next_fd;
444
445 if (fd < fdt->max_fds)
446 fd = find_next_zero_bit(fdt->open_fds->fds_bits,
447 fdt->max_fds, fd);
448
449 error = expand_files(files, fd);
450 if (error < 0)
451 goto out;
452
453 /*
454 * If we needed to expand the fs array we
455 * might have blocked - try again.
456 */
457 if (error)
458 goto repeat;
459
460 if (start <= files->next_fd)
461 files->next_fd = fd + 1;
462
463 FD_SET(fd, fdt->open_fds);
464 if (flags & O_CLOEXEC)
465 FD_SET(fd, fdt->close_on_exec);
466 else
467 FD_CLR(fd, fdt->close_on_exec);
468 error = fd;
469#if 1
470 /* Sanity check */
471 if (rcu_dereference_raw(fdt->fd[fd]) != NULL) {
472 printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
473 rcu_assign_pointer(fdt->fd[fd], NULL);
474 }
475#endif
476
477out:
478 spin_unlock(&files->file_lock);
479 return error;
480}
481
482int get_unused_fd(void)
483{
484 return alloc_fd(0, 0);
485}
486EXPORT_SYMBOL(get_unused_fd);