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1 | /* | |
2 | * linux/fs/file.c | |
3 | * | |
4 | * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes | |
5 | * | |
6 | * Manage the dynamic fd arrays in the process files_struct. | |
7 | */ | |
8 | ||
9 | #include <linux/syscalls.h> | |
10 | #include <linux/export.h> | |
11 | #include <linux/fs.h> | |
12 | #include <linux/mm.h> | |
13 | #include <linux/mmzone.h> | |
14 | #include <linux/time.h> | |
15 | #include <linux/sched.h> | |
16 | #include <linux/slab.h> | |
17 | #include <linux/vmalloc.h> | |
18 | #include <linux/file.h> | |
19 | #include <linux/fdtable.h> | |
20 | #include <linux/bitops.h> | |
21 | #include <linux/interrupt.h> | |
22 | #include <linux/spinlock.h> | |
23 | #include <linux/rcupdate.h> | |
24 | #include <linux/workqueue.h> | |
25 | ||
26 | int sysctl_nr_open __read_mostly = 1024*1024; | |
27 | int sysctl_nr_open_min = BITS_PER_LONG; | |
28 | /* our max() is unusable in constant expressions ;-/ */ | |
29 | #define __const_max(x, y) ((x) < (y) ? (x) : (y)) | |
30 | int sysctl_nr_open_max = __const_max(INT_MAX, ~(size_t)0/sizeof(void *)) & | |
31 | -BITS_PER_LONG; | |
32 | ||
33 | static 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|__GFP_NOWARN|__GFP_NORETRY); | |
41 | if (data != NULL) | |
42 | return data; | |
43 | } | |
44 | return vmalloc(size); | |
45 | } | |
46 | ||
47 | static void __free_fdtable(struct fdtable *fdt) | |
48 | { | |
49 | kvfree(fdt->fd); | |
50 | kvfree(fdt->open_fds); | |
51 | kfree(fdt); | |
52 | } | |
53 | ||
54 | static void free_fdtable_rcu(struct rcu_head *rcu) | |
55 | { | |
56 | __free_fdtable(container_of(rcu, struct fdtable, rcu)); | |
57 | } | |
58 | ||
59 | /* | |
60 | * Expand the fdset in the files_struct. Called with the files spinlock | |
61 | * held for write. | |
62 | */ | |
63 | static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt) | |
64 | { | |
65 | unsigned int cpy, set; | |
66 | ||
67 | BUG_ON(nfdt->max_fds < ofdt->max_fds); | |
68 | ||
69 | cpy = ofdt->max_fds * sizeof(struct file *); | |
70 | set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *); | |
71 | memcpy(nfdt->fd, ofdt->fd, cpy); | |
72 | memset((char *)(nfdt->fd) + cpy, 0, set); | |
73 | ||
74 | cpy = ofdt->max_fds / BITS_PER_BYTE; | |
75 | set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE; | |
76 | memcpy(nfdt->open_fds, ofdt->open_fds, cpy); | |
77 | memset((char *)(nfdt->open_fds) + cpy, 0, set); | |
78 | memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy); | |
79 | memset((char *)(nfdt->close_on_exec) + cpy, 0, set); | |
80 | } | |
81 | ||
82 | static struct fdtable * alloc_fdtable(unsigned int nr) | |
83 | { | |
84 | struct fdtable *fdt; | |
85 | void *data; | |
86 | ||
87 | /* | |
88 | * Figure out how many fds we actually want to support in this fdtable. | |
89 | * Allocation steps are keyed to the size of the fdarray, since it | |
90 | * grows far faster than any of the other dynamic data. We try to fit | |
91 | * the fdarray into comfortable page-tuned chunks: starting at 1024B | |
92 | * and growing in powers of two from there on. | |
93 | */ | |
94 | nr /= (1024 / sizeof(struct file *)); | |
95 | nr = roundup_pow_of_two(nr + 1); | |
96 | nr *= (1024 / sizeof(struct file *)); | |
97 | /* | |
98 | * Note that this can drive nr *below* what we had passed if sysctl_nr_open | |
99 | * had been set lower between the check in expand_files() and here. Deal | |
100 | * with that in caller, it's cheaper that way. | |
101 | * | |
102 | * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise | |
103 | * bitmaps handling below becomes unpleasant, to put it mildly... | |
104 | */ | |
105 | if (unlikely(nr > sysctl_nr_open)) | |
106 | nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1; | |
107 | ||
108 | fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL); | |
109 | if (!fdt) | |
110 | goto out; | |
111 | fdt->max_fds = nr; | |
112 | data = alloc_fdmem(nr * sizeof(struct file *)); | |
113 | if (!data) | |
114 | goto out_fdt; | |
115 | fdt->fd = data; | |
116 | ||
117 | data = alloc_fdmem(max_t(size_t, | |
118 | 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES)); | |
119 | if (!data) | |
120 | goto out_arr; | |
121 | fdt->open_fds = data; | |
122 | data += nr / BITS_PER_BYTE; | |
123 | fdt->close_on_exec = data; | |
124 | ||
125 | return fdt; | |
126 | ||
127 | out_arr: | |
128 | kvfree(fdt->fd); | |
129 | out_fdt: | |
130 | kfree(fdt); | |
131 | out: | |
132 | return NULL; | |
133 | } | |
134 | ||
135 | /* | |
136 | * Expand the file descriptor table. | |
137 | * This function will allocate a new fdtable and both fd array and fdset, of | |
138 | * the given size. | |
139 | * Return <0 error code on error; 1 on successful completion. | |
140 | * The files->file_lock should be held on entry, and will be held on exit. | |
141 | */ | |
142 | static int expand_fdtable(struct files_struct *files, int nr) | |
143 | __releases(files->file_lock) | |
144 | __acquires(files->file_lock) | |
145 | { | |
146 | struct fdtable *new_fdt, *cur_fdt; | |
147 | ||
148 | spin_unlock(&files->file_lock); | |
149 | new_fdt = alloc_fdtable(nr); | |
150 | ||
151 | /* make sure all __fd_install() have seen resize_in_progress | |
152 | * or have finished their rcu_read_lock_sched() section. | |
153 | */ | |
154 | if (atomic_read(&files->count) > 1) | |
155 | synchronize_sched(); | |
156 | ||
157 | spin_lock(&files->file_lock); | |
158 | if (!new_fdt) | |
159 | return -ENOMEM; | |
160 | /* | |
161 | * extremely unlikely race - sysctl_nr_open decreased between the check in | |
162 | * caller and alloc_fdtable(). Cheaper to catch it here... | |
163 | */ | |
164 | if (unlikely(new_fdt->max_fds <= nr)) { | |
165 | __free_fdtable(new_fdt); | |
166 | return -EMFILE; | |
167 | } | |
168 | cur_fdt = files_fdtable(files); | |
169 | BUG_ON(nr < cur_fdt->max_fds); | |
170 | copy_fdtable(new_fdt, cur_fdt); | |
171 | rcu_assign_pointer(files->fdt, new_fdt); | |
172 | if (cur_fdt != &files->fdtab) | |
173 | call_rcu(&cur_fdt->rcu, free_fdtable_rcu); | |
174 | /* coupled with smp_rmb() in __fd_install() */ | |
175 | smp_wmb(); | |
176 | return 1; | |
177 | } | |
178 | ||
179 | /* | |
180 | * Expand files. | |
181 | * This function will expand the file structures, if the requested size exceeds | |
182 | * the current capacity and there is room for expansion. | |
183 | * Return <0 error code on error; 0 when nothing done; 1 when files were | |
184 | * expanded and execution may have blocked. | |
185 | * The files->file_lock should be held on entry, and will be held on exit. | |
186 | */ | |
187 | static int expand_files(struct files_struct *files, int nr) | |
188 | __releases(files->file_lock) | |
189 | __acquires(files->file_lock) | |
190 | { | |
191 | struct fdtable *fdt; | |
192 | int expanded = 0; | |
193 | ||
194 | repeat: | |
195 | fdt = files_fdtable(files); | |
196 | ||
197 | /* Do we need to expand? */ | |
198 | if (nr < fdt->max_fds) | |
199 | return expanded; | |
200 | ||
201 | /* Can we expand? */ | |
202 | if (nr >= sysctl_nr_open) | |
203 | return -EMFILE; | |
204 | ||
205 | if (unlikely(files->resize_in_progress)) { | |
206 | spin_unlock(&files->file_lock); | |
207 | expanded = 1; | |
208 | wait_event(files->resize_wait, !files->resize_in_progress); | |
209 | spin_lock(&files->file_lock); | |
210 | goto repeat; | |
211 | } | |
212 | ||
213 | /* All good, so we try */ | |
214 | files->resize_in_progress = true; | |
215 | expanded = expand_fdtable(files, nr); | |
216 | files->resize_in_progress = false; | |
217 | ||
218 | wake_up_all(&files->resize_wait); | |
219 | return expanded; | |
220 | } | |
221 | ||
222 | static inline void __set_close_on_exec(int fd, struct fdtable *fdt) | |
223 | { | |
224 | __set_bit(fd, fdt->close_on_exec); | |
225 | } | |
226 | ||
227 | static inline void __clear_close_on_exec(int fd, struct fdtable *fdt) | |
228 | { | |
229 | __clear_bit(fd, fdt->close_on_exec); | |
230 | } | |
231 | ||
232 | static inline void __set_open_fd(int fd, struct fdtable *fdt) | |
233 | { | |
234 | __set_bit(fd, fdt->open_fds); | |
235 | } | |
236 | ||
237 | static inline void __clear_open_fd(int fd, struct fdtable *fdt) | |
238 | { | |
239 | __clear_bit(fd, fdt->open_fds); | |
240 | } | |
241 | ||
242 | static int count_open_files(struct fdtable *fdt) | |
243 | { | |
244 | int size = fdt->max_fds; | |
245 | int i; | |
246 | ||
247 | /* Find the last open fd */ | |
248 | for (i = size / BITS_PER_LONG; i > 0; ) { | |
249 | if (fdt->open_fds[--i]) | |
250 | break; | |
251 | } | |
252 | i = (i + 1) * BITS_PER_LONG; | |
253 | return i; | |
254 | } | |
255 | ||
256 | /* | |
257 | * Allocate a new files structure and copy contents from the | |
258 | * passed in files structure. | |
259 | * errorp will be valid only when the returned files_struct is NULL. | |
260 | */ | |
261 | struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) | |
262 | { | |
263 | struct files_struct *newf; | |
264 | struct file **old_fds, **new_fds; | |
265 | int open_files, size, i; | |
266 | struct fdtable *old_fdt, *new_fdt; | |
267 | ||
268 | *errorp = -ENOMEM; | |
269 | newf = kmem_cache_alloc(files_cachep, GFP_KERNEL); | |
270 | if (!newf) | |
271 | goto out; | |
272 | ||
273 | atomic_set(&newf->count, 1); | |
274 | ||
275 | spin_lock_init(&newf->file_lock); | |
276 | newf->resize_in_progress = false; | |
277 | init_waitqueue_head(&newf->resize_wait); | |
278 | newf->next_fd = 0; | |
279 | new_fdt = &newf->fdtab; | |
280 | new_fdt->max_fds = NR_OPEN_DEFAULT; | |
281 | new_fdt->close_on_exec = newf->close_on_exec_init; | |
282 | new_fdt->open_fds = newf->open_fds_init; | |
283 | new_fdt->fd = &newf->fd_array[0]; | |
284 | ||
285 | spin_lock(&oldf->file_lock); | |
286 | old_fdt = files_fdtable(oldf); | |
287 | open_files = count_open_files(old_fdt); | |
288 | ||
289 | /* | |
290 | * Check whether we need to allocate a larger fd array and fd set. | |
291 | */ | |
292 | while (unlikely(open_files > new_fdt->max_fds)) { | |
293 | spin_unlock(&oldf->file_lock); | |
294 | ||
295 | if (new_fdt != &newf->fdtab) | |
296 | __free_fdtable(new_fdt); | |
297 | ||
298 | new_fdt = alloc_fdtable(open_files - 1); | |
299 | if (!new_fdt) { | |
300 | *errorp = -ENOMEM; | |
301 | goto out_release; | |
302 | } | |
303 | ||
304 | /* beyond sysctl_nr_open; nothing to do */ | |
305 | if (unlikely(new_fdt->max_fds < open_files)) { | |
306 | __free_fdtable(new_fdt); | |
307 | *errorp = -EMFILE; | |
308 | goto out_release; | |
309 | } | |
310 | ||
311 | /* | |
312 | * Reacquire the oldf lock and a pointer to its fd table | |
313 | * who knows it may have a new bigger fd table. We need | |
314 | * the latest pointer. | |
315 | */ | |
316 | spin_lock(&oldf->file_lock); | |
317 | old_fdt = files_fdtable(oldf); | |
318 | open_files = count_open_files(old_fdt); | |
319 | } | |
320 | ||
321 | old_fds = old_fdt->fd; | |
322 | new_fds = new_fdt->fd; | |
323 | ||
324 | memcpy(new_fdt->open_fds, old_fdt->open_fds, open_files / 8); | |
325 | memcpy(new_fdt->close_on_exec, old_fdt->close_on_exec, open_files / 8); | |
326 | ||
327 | for (i = open_files; i != 0; i--) { | |
328 | struct file *f = *old_fds++; | |
329 | if (f) { | |
330 | get_file(f); | |
331 | } else { | |
332 | /* | |
333 | * The fd may be claimed in the fd bitmap but not yet | |
334 | * instantiated in the files array if a sibling thread | |
335 | * is partway through open(). So make sure that this | |
336 | * fd is available to the new process. | |
337 | */ | |
338 | __clear_open_fd(open_files - i, new_fdt); | |
339 | } | |
340 | rcu_assign_pointer(*new_fds++, f); | |
341 | } | |
342 | spin_unlock(&oldf->file_lock); | |
343 | ||
344 | /* compute the remainder to be cleared */ | |
345 | size = (new_fdt->max_fds - open_files) * sizeof(struct file *); | |
346 | ||
347 | /* This is long word aligned thus could use a optimized version */ | |
348 | memset(new_fds, 0, size); | |
349 | ||
350 | if (new_fdt->max_fds > open_files) { | |
351 | int left = (new_fdt->max_fds - open_files) / 8; | |
352 | int start = open_files / BITS_PER_LONG; | |
353 | ||
354 | memset(&new_fdt->open_fds[start], 0, left); | |
355 | memset(&new_fdt->close_on_exec[start], 0, left); | |
356 | } | |
357 | ||
358 | rcu_assign_pointer(newf->fdt, new_fdt); | |
359 | ||
360 | return newf; | |
361 | ||
362 | out_release: | |
363 | kmem_cache_free(files_cachep, newf); | |
364 | out: | |
365 | return NULL; | |
366 | } | |
367 | ||
368 | static struct fdtable *close_files(struct files_struct * files) | |
369 | { | |
370 | /* | |
371 | * It is safe to dereference the fd table without RCU or | |
372 | * ->file_lock because this is the last reference to the | |
373 | * files structure. | |
374 | */ | |
375 | struct fdtable *fdt = rcu_dereference_raw(files->fdt); | |
376 | int i, j = 0; | |
377 | ||
378 | for (;;) { | |
379 | unsigned long set; | |
380 | i = j * BITS_PER_LONG; | |
381 | if (i >= fdt->max_fds) | |
382 | break; | |
383 | set = fdt->open_fds[j++]; | |
384 | while (set) { | |
385 | if (set & 1) { | |
386 | struct file * file = xchg(&fdt->fd[i], NULL); | |
387 | if (file) { | |
388 | filp_close(file, files); | |
389 | cond_resched_rcu_qs(); | |
390 | } | |
391 | } | |
392 | i++; | |
393 | set >>= 1; | |
394 | } | |
395 | } | |
396 | ||
397 | return fdt; | |
398 | } | |
399 | ||
400 | struct files_struct *get_files_struct(struct task_struct *task) | |
401 | { | |
402 | struct files_struct *files; | |
403 | ||
404 | task_lock(task); | |
405 | files = task->files; | |
406 | if (files) | |
407 | atomic_inc(&files->count); | |
408 | task_unlock(task); | |
409 | ||
410 | return files; | |
411 | } | |
412 | ||
413 | void put_files_struct(struct files_struct *files) | |
414 | { | |
415 | if (atomic_dec_and_test(&files->count)) { | |
416 | struct fdtable *fdt = close_files(files); | |
417 | ||
418 | /* free the arrays if they are not embedded */ | |
419 | if (fdt != &files->fdtab) | |
420 | __free_fdtable(fdt); | |
421 | kmem_cache_free(files_cachep, files); | |
422 | } | |
423 | } | |
424 | ||
425 | void reset_files_struct(struct files_struct *files) | |
426 | { | |
427 | struct task_struct *tsk = current; | |
428 | struct files_struct *old; | |
429 | ||
430 | old = tsk->files; | |
431 | task_lock(tsk); | |
432 | tsk->files = files; | |
433 | task_unlock(tsk); | |
434 | put_files_struct(old); | |
435 | } | |
436 | ||
437 | void exit_files(struct task_struct *tsk) | |
438 | { | |
439 | struct files_struct * files = tsk->files; | |
440 | ||
441 | if (files) { | |
442 | task_lock(tsk); | |
443 | tsk->files = NULL; | |
444 | task_unlock(tsk); | |
445 | put_files_struct(files); | |
446 | } | |
447 | } | |
448 | ||
449 | struct files_struct init_files = { | |
450 | .count = ATOMIC_INIT(1), | |
451 | .fdt = &init_files.fdtab, | |
452 | .fdtab = { | |
453 | .max_fds = NR_OPEN_DEFAULT, | |
454 | .fd = &init_files.fd_array[0], | |
455 | .close_on_exec = init_files.close_on_exec_init, | |
456 | .open_fds = init_files.open_fds_init, | |
457 | }, | |
458 | .file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock), | |
459 | }; | |
460 | ||
461 | /* | |
462 | * allocate a file descriptor, mark it busy. | |
463 | */ | |
464 | int __alloc_fd(struct files_struct *files, | |
465 | unsigned start, unsigned end, unsigned flags) | |
466 | { | |
467 | unsigned int fd; | |
468 | int error; | |
469 | struct fdtable *fdt; | |
470 | ||
471 | spin_lock(&files->file_lock); | |
472 | repeat: | |
473 | fdt = files_fdtable(files); | |
474 | fd = start; | |
475 | if (fd < files->next_fd) | |
476 | fd = files->next_fd; | |
477 | ||
478 | if (fd < fdt->max_fds) | |
479 | fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd); | |
480 | ||
481 | /* | |
482 | * N.B. For clone tasks sharing a files structure, this test | |
483 | * will limit the total number of files that can be opened. | |
484 | */ | |
485 | error = -EMFILE; | |
486 | if (fd >= end) | |
487 | goto out; | |
488 | ||
489 | error = expand_files(files, fd); | |
490 | if (error < 0) | |
491 | goto out; | |
492 | ||
493 | /* | |
494 | * If we needed to expand the fs array we | |
495 | * might have blocked - try again. | |
496 | */ | |
497 | if (error) | |
498 | goto repeat; | |
499 | ||
500 | if (start <= files->next_fd) | |
501 | files->next_fd = fd + 1; | |
502 | ||
503 | __set_open_fd(fd, fdt); | |
504 | if (flags & O_CLOEXEC) | |
505 | __set_close_on_exec(fd, fdt); | |
506 | else | |
507 | __clear_close_on_exec(fd, fdt); | |
508 | error = fd; | |
509 | #if 1 | |
510 | /* Sanity check */ | |
511 | if (rcu_access_pointer(fdt->fd[fd]) != NULL) { | |
512 | printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd); | |
513 | rcu_assign_pointer(fdt->fd[fd], NULL); | |
514 | } | |
515 | #endif | |
516 | ||
517 | out: | |
518 | spin_unlock(&files->file_lock); | |
519 | return error; | |
520 | } | |
521 | ||
522 | static int alloc_fd(unsigned start, unsigned flags) | |
523 | { | |
524 | return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags); | |
525 | } | |
526 | ||
527 | int get_unused_fd_flags(unsigned flags) | |
528 | { | |
529 | return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags); | |
530 | } | |
531 | EXPORT_SYMBOL(get_unused_fd_flags); | |
532 | ||
533 | static void __put_unused_fd(struct files_struct *files, unsigned int fd) | |
534 | { | |
535 | struct fdtable *fdt = files_fdtable(files); | |
536 | __clear_open_fd(fd, fdt); | |
537 | if (fd < files->next_fd) | |
538 | files->next_fd = fd; | |
539 | } | |
540 | ||
541 | void put_unused_fd(unsigned int fd) | |
542 | { | |
543 | struct files_struct *files = current->files; | |
544 | spin_lock(&files->file_lock); | |
545 | __put_unused_fd(files, fd); | |
546 | spin_unlock(&files->file_lock); | |
547 | } | |
548 | ||
549 | EXPORT_SYMBOL(put_unused_fd); | |
550 | ||
551 | /* | |
552 | * Install a file pointer in the fd array. | |
553 | * | |
554 | * The VFS is full of places where we drop the files lock between | |
555 | * setting the open_fds bitmap and installing the file in the file | |
556 | * array. At any such point, we are vulnerable to a dup2() race | |
557 | * installing a file in the array before us. We need to detect this and | |
558 | * fput() the struct file we are about to overwrite in this case. | |
559 | * | |
560 | * It should never happen - if we allow dup2() do it, _really_ bad things | |
561 | * will follow. | |
562 | * | |
563 | * NOTE: __fd_install() variant is really, really low-level; don't | |
564 | * use it unless you are forced to by truly lousy API shoved down | |
565 | * your throat. 'files' *MUST* be either current->files or obtained | |
566 | * by get_files_struct(current) done by whoever had given it to you, | |
567 | * or really bad things will happen. Normally you want to use | |
568 | * fd_install() instead. | |
569 | */ | |
570 | ||
571 | void __fd_install(struct files_struct *files, unsigned int fd, | |
572 | struct file *file) | |
573 | { | |
574 | struct fdtable *fdt; | |
575 | ||
576 | might_sleep(); | |
577 | rcu_read_lock_sched(); | |
578 | ||
579 | while (unlikely(files->resize_in_progress)) { | |
580 | rcu_read_unlock_sched(); | |
581 | wait_event(files->resize_wait, !files->resize_in_progress); | |
582 | rcu_read_lock_sched(); | |
583 | } | |
584 | /* coupled with smp_wmb() in expand_fdtable() */ | |
585 | smp_rmb(); | |
586 | fdt = rcu_dereference_sched(files->fdt); | |
587 | BUG_ON(fdt->fd[fd] != NULL); | |
588 | rcu_assign_pointer(fdt->fd[fd], file); | |
589 | rcu_read_unlock_sched(); | |
590 | } | |
591 | ||
592 | void fd_install(unsigned int fd, struct file *file) | |
593 | { | |
594 | __fd_install(current->files, fd, file); | |
595 | } | |
596 | ||
597 | EXPORT_SYMBOL(fd_install); | |
598 | ||
599 | /* | |
600 | * The same warnings as for __alloc_fd()/__fd_install() apply here... | |
601 | */ | |
602 | int __close_fd(struct files_struct *files, unsigned fd) | |
603 | { | |
604 | struct file *file; | |
605 | struct fdtable *fdt; | |
606 | ||
607 | spin_lock(&files->file_lock); | |
608 | fdt = files_fdtable(files); | |
609 | if (fd >= fdt->max_fds) | |
610 | goto out_unlock; | |
611 | file = fdt->fd[fd]; | |
612 | if (!file) | |
613 | goto out_unlock; | |
614 | rcu_assign_pointer(fdt->fd[fd], NULL); | |
615 | __clear_close_on_exec(fd, fdt); | |
616 | __put_unused_fd(files, fd); | |
617 | spin_unlock(&files->file_lock); | |
618 | return filp_close(file, files); | |
619 | ||
620 | out_unlock: | |
621 | spin_unlock(&files->file_lock); | |
622 | return -EBADF; | |
623 | } | |
624 | ||
625 | void do_close_on_exec(struct files_struct *files) | |
626 | { | |
627 | unsigned i; | |
628 | struct fdtable *fdt; | |
629 | ||
630 | /* exec unshares first */ | |
631 | spin_lock(&files->file_lock); | |
632 | for (i = 0; ; i++) { | |
633 | unsigned long set; | |
634 | unsigned fd = i * BITS_PER_LONG; | |
635 | fdt = files_fdtable(files); | |
636 | if (fd >= fdt->max_fds) | |
637 | break; | |
638 | set = fdt->close_on_exec[i]; | |
639 | if (!set) | |
640 | continue; | |
641 | fdt->close_on_exec[i] = 0; | |
642 | for ( ; set ; fd++, set >>= 1) { | |
643 | struct file *file; | |
644 | if (!(set & 1)) | |
645 | continue; | |
646 | file = fdt->fd[fd]; | |
647 | if (!file) | |
648 | continue; | |
649 | rcu_assign_pointer(fdt->fd[fd], NULL); | |
650 | __put_unused_fd(files, fd); | |
651 | spin_unlock(&files->file_lock); | |
652 | filp_close(file, files); | |
653 | cond_resched(); | |
654 | spin_lock(&files->file_lock); | |
655 | } | |
656 | ||
657 | } | |
658 | spin_unlock(&files->file_lock); | |
659 | } | |
660 | ||
661 | static struct file *__fget(unsigned int fd, fmode_t mask) | |
662 | { | |
663 | struct files_struct *files = current->files; | |
664 | struct file *file; | |
665 | ||
666 | rcu_read_lock(); | |
667 | loop: | |
668 | file = fcheck_files(files, fd); | |
669 | if (file) { | |
670 | /* File object ref couldn't be taken. | |
671 | * dup2() atomicity guarantee is the reason | |
672 | * we loop to catch the new file (or NULL pointer) | |
673 | */ | |
674 | if (file->f_mode & mask) | |
675 | file = NULL; | |
676 | else if (!get_file_rcu(file)) | |
677 | goto loop; | |
678 | } | |
679 | rcu_read_unlock(); | |
680 | ||
681 | return file; | |
682 | } | |
683 | ||
684 | struct file *fget(unsigned int fd) | |
685 | { | |
686 | return __fget(fd, FMODE_PATH); | |
687 | } | |
688 | EXPORT_SYMBOL(fget); | |
689 | ||
690 | struct file *fget_raw(unsigned int fd) | |
691 | { | |
692 | return __fget(fd, 0); | |
693 | } | |
694 | EXPORT_SYMBOL(fget_raw); | |
695 | ||
696 | /* | |
697 | * Lightweight file lookup - no refcnt increment if fd table isn't shared. | |
698 | * | |
699 | * You can use this instead of fget if you satisfy all of the following | |
700 | * conditions: | |
701 | * 1) You must call fput_light before exiting the syscall and returning control | |
702 | * to userspace (i.e. you cannot remember the returned struct file * after | |
703 | * returning to userspace). | |
704 | * 2) You must not call filp_close on the returned struct file * in between | |
705 | * calls to fget_light and fput_light. | |
706 | * 3) You must not clone the current task in between the calls to fget_light | |
707 | * and fput_light. | |
708 | * | |
709 | * The fput_needed flag returned by fget_light should be passed to the | |
710 | * corresponding fput_light. | |
711 | */ | |
712 | static unsigned long __fget_light(unsigned int fd, fmode_t mask) | |
713 | { | |
714 | struct files_struct *files = current->files; | |
715 | struct file *file; | |
716 | ||
717 | if (atomic_read(&files->count) == 1) { | |
718 | file = __fcheck_files(files, fd); | |
719 | if (!file || unlikely(file->f_mode & mask)) | |
720 | return 0; | |
721 | return (unsigned long)file; | |
722 | } else { | |
723 | file = __fget(fd, mask); | |
724 | if (!file) | |
725 | return 0; | |
726 | return FDPUT_FPUT | (unsigned long)file; | |
727 | } | |
728 | } | |
729 | unsigned long __fdget(unsigned int fd) | |
730 | { | |
731 | return __fget_light(fd, FMODE_PATH); | |
732 | } | |
733 | EXPORT_SYMBOL(__fdget); | |
734 | ||
735 | unsigned long __fdget_raw(unsigned int fd) | |
736 | { | |
737 | return __fget_light(fd, 0); | |
738 | } | |
739 | ||
740 | unsigned long __fdget_pos(unsigned int fd) | |
741 | { | |
742 | unsigned long v = __fdget(fd); | |
743 | struct file *file = (struct file *)(v & ~3); | |
744 | ||
745 | if (file && (file->f_mode & FMODE_ATOMIC_POS)) { | |
746 | if (file_count(file) > 1) { | |
747 | v |= FDPUT_POS_UNLOCK; | |
748 | mutex_lock(&file->f_pos_lock); | |
749 | } | |
750 | } | |
751 | return v; | |
752 | } | |
753 | ||
754 | /* | |
755 | * We only lock f_pos if we have threads or if the file might be | |
756 | * shared with another process. In both cases we'll have an elevated | |
757 | * file count (done either by fdget() or by fork()). | |
758 | */ | |
759 | ||
760 | void set_close_on_exec(unsigned int fd, int flag) | |
761 | { | |
762 | struct files_struct *files = current->files; | |
763 | struct fdtable *fdt; | |
764 | spin_lock(&files->file_lock); | |
765 | fdt = files_fdtable(files); | |
766 | if (flag) | |
767 | __set_close_on_exec(fd, fdt); | |
768 | else | |
769 | __clear_close_on_exec(fd, fdt); | |
770 | spin_unlock(&files->file_lock); | |
771 | } | |
772 | ||
773 | bool get_close_on_exec(unsigned int fd) | |
774 | { | |
775 | struct files_struct *files = current->files; | |
776 | struct fdtable *fdt; | |
777 | bool res; | |
778 | rcu_read_lock(); | |
779 | fdt = files_fdtable(files); | |
780 | res = close_on_exec(fd, fdt); | |
781 | rcu_read_unlock(); | |
782 | return res; | |
783 | } | |
784 | ||
785 | static int do_dup2(struct files_struct *files, | |
786 | struct file *file, unsigned fd, unsigned flags) | |
787 | __releases(&files->file_lock) | |
788 | { | |
789 | struct file *tofree; | |
790 | struct fdtable *fdt; | |
791 | ||
792 | /* | |
793 | * We need to detect attempts to do dup2() over allocated but still | |
794 | * not finished descriptor. NB: OpenBSD avoids that at the price of | |
795 | * extra work in their equivalent of fget() - they insert struct | |
796 | * file immediately after grabbing descriptor, mark it larval if | |
797 | * more work (e.g. actual opening) is needed and make sure that | |
798 | * fget() treats larval files as absent. Potentially interesting, | |
799 | * but while extra work in fget() is trivial, locking implications | |
800 | * and amount of surgery on open()-related paths in VFS are not. | |
801 | * FreeBSD fails with -EBADF in the same situation, NetBSD "solution" | |
802 | * deadlocks in rather amusing ways, AFAICS. All of that is out of | |
803 | * scope of POSIX or SUS, since neither considers shared descriptor | |
804 | * tables and this condition does not arise without those. | |
805 | */ | |
806 | fdt = files_fdtable(files); | |
807 | tofree = fdt->fd[fd]; | |
808 | if (!tofree && fd_is_open(fd, fdt)) | |
809 | goto Ebusy; | |
810 | get_file(file); | |
811 | rcu_assign_pointer(fdt->fd[fd], file); | |
812 | __set_open_fd(fd, fdt); | |
813 | if (flags & O_CLOEXEC) | |
814 | __set_close_on_exec(fd, fdt); | |
815 | else | |
816 | __clear_close_on_exec(fd, fdt); | |
817 | spin_unlock(&files->file_lock); | |
818 | ||
819 | if (tofree) | |
820 | filp_close(tofree, files); | |
821 | ||
822 | return fd; | |
823 | ||
824 | Ebusy: | |
825 | spin_unlock(&files->file_lock); | |
826 | return -EBUSY; | |
827 | } | |
828 | ||
829 | int replace_fd(unsigned fd, struct file *file, unsigned flags) | |
830 | { | |
831 | int err; | |
832 | struct files_struct *files = current->files; | |
833 | ||
834 | if (!file) | |
835 | return __close_fd(files, fd); | |
836 | ||
837 | if (fd >= rlimit(RLIMIT_NOFILE)) | |
838 | return -EBADF; | |
839 | ||
840 | spin_lock(&files->file_lock); | |
841 | err = expand_files(files, fd); | |
842 | if (unlikely(err < 0)) | |
843 | goto out_unlock; | |
844 | return do_dup2(files, file, fd, flags); | |
845 | ||
846 | out_unlock: | |
847 | spin_unlock(&files->file_lock); | |
848 | return err; | |
849 | } | |
850 | ||
851 | SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags) | |
852 | { | |
853 | int err = -EBADF; | |
854 | struct file *file; | |
855 | struct files_struct *files = current->files; | |
856 | ||
857 | if ((flags & ~O_CLOEXEC) != 0) | |
858 | return -EINVAL; | |
859 | ||
860 | if (unlikely(oldfd == newfd)) | |
861 | return -EINVAL; | |
862 | ||
863 | if (newfd >= rlimit(RLIMIT_NOFILE)) | |
864 | return -EBADF; | |
865 | ||
866 | spin_lock(&files->file_lock); | |
867 | err = expand_files(files, newfd); | |
868 | file = fcheck(oldfd); | |
869 | if (unlikely(!file)) | |
870 | goto Ebadf; | |
871 | if (unlikely(err < 0)) { | |
872 | if (err == -EMFILE) | |
873 | goto Ebadf; | |
874 | goto out_unlock; | |
875 | } | |
876 | return do_dup2(files, file, newfd, flags); | |
877 | ||
878 | Ebadf: | |
879 | err = -EBADF; | |
880 | out_unlock: | |
881 | spin_unlock(&files->file_lock); | |
882 | return err; | |
883 | } | |
884 | ||
885 | SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd) | |
886 | { | |
887 | if (unlikely(newfd == oldfd)) { /* corner case */ | |
888 | struct files_struct *files = current->files; | |
889 | int retval = oldfd; | |
890 | ||
891 | rcu_read_lock(); | |
892 | if (!fcheck_files(files, oldfd)) | |
893 | retval = -EBADF; | |
894 | rcu_read_unlock(); | |
895 | return retval; | |
896 | } | |
897 | return sys_dup3(oldfd, newfd, 0); | |
898 | } | |
899 | ||
900 | SYSCALL_DEFINE1(dup, unsigned int, fildes) | |
901 | { | |
902 | int ret = -EBADF; | |
903 | struct file *file = fget_raw(fildes); | |
904 | ||
905 | if (file) { | |
906 | ret = get_unused_fd_flags(0); | |
907 | if (ret >= 0) | |
908 | fd_install(ret, file); | |
909 | else | |
910 | fput(file); | |
911 | } | |
912 | return ret; | |
913 | } | |
914 | ||
915 | int f_dupfd(unsigned int from, struct file *file, unsigned flags) | |
916 | { | |
917 | int err; | |
918 | if (from >= rlimit(RLIMIT_NOFILE)) | |
919 | return -EINVAL; | |
920 | err = alloc_fd(from, flags); | |
921 | if (err >= 0) { | |
922 | get_file(file); | |
923 | fd_install(err, file); | |
924 | } | |
925 | return err; | |
926 | } | |
927 | ||
928 | int iterate_fd(struct files_struct *files, unsigned n, | |
929 | int (*f)(const void *, struct file *, unsigned), | |
930 | const void *p) | |
931 | { | |
932 | struct fdtable *fdt; | |
933 | int res = 0; | |
934 | if (!files) | |
935 | return 0; | |
936 | spin_lock(&files->file_lock); | |
937 | for (fdt = files_fdtable(files); n < fdt->max_fds; n++) { | |
938 | struct file *file; | |
939 | file = rcu_dereference_check_fdtable(files, fdt->fd[n]); | |
940 | if (!file) | |
941 | continue; | |
942 | res = f(p, file, n); | |
943 | if (res) | |
944 | break; | |
945 | } | |
946 | spin_unlock(&files->file_lock); | |
947 | return res; | |
948 | } | |
949 | EXPORT_SYMBOL(iterate_fd); |