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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 | int sysctl_nr_open_max = 1024 * 1024; /* raised later */ | |
29 | ||
30 | static void *alloc_fdmem(size_t size) | |
31 | { | |
32 | /* | |
33 | * Very large allocations can stress page reclaim, so fall back to | |
34 | * vmalloc() if the allocation size will be considered "large" by the VM. | |
35 | */ | |
36 | if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) { | |
37 | void *data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN); | |
38 | if (data != NULL) | |
39 | return data; | |
40 | } | |
41 | return vmalloc(size); | |
42 | } | |
43 | ||
44 | static void free_fdmem(void *ptr) | |
45 | { | |
46 | is_vmalloc_addr(ptr) ? vfree(ptr) : kfree(ptr); | |
47 | } | |
48 | ||
49 | static void __free_fdtable(struct fdtable *fdt) | |
50 | { | |
51 | free_fdmem(fdt->fd); | |
52 | free_fdmem(fdt->open_fds); | |
53 | kfree(fdt); | |
54 | } | |
55 | ||
56 | static void free_fdtable_rcu(struct rcu_head *rcu) | |
57 | { | |
58 | __free_fdtable(container_of(rcu, struct fdtable, rcu)); | |
59 | } | |
60 | ||
61 | /* | |
62 | * Expand the fdset in the files_struct. Called with the files spinlock | |
63 | * held for write. | |
64 | */ | |
65 | static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt) | |
66 | { | |
67 | unsigned int cpy, set; | |
68 | ||
69 | BUG_ON(nfdt->max_fds < ofdt->max_fds); | |
70 | ||
71 | cpy = ofdt->max_fds * sizeof(struct file *); | |
72 | set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *); | |
73 | memcpy(nfdt->fd, ofdt->fd, cpy); | |
74 | memset((char *)(nfdt->fd) + cpy, 0, set); | |
75 | ||
76 | cpy = ofdt->max_fds / BITS_PER_BYTE; | |
77 | set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE; | |
78 | memcpy(nfdt->open_fds, ofdt->open_fds, cpy); | |
79 | memset((char *)(nfdt->open_fds) + cpy, 0, set); | |
80 | memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy); | |
81 | memset((char *)(nfdt->close_on_exec) + cpy, 0, set); | |
82 | } | |
83 | ||
84 | static struct fdtable * alloc_fdtable(unsigned int nr) | |
85 | { | |
86 | struct fdtable *fdt; | |
87 | void *data; | |
88 | ||
89 | /* | |
90 | * Figure out how many fds we actually want to support in this fdtable. | |
91 | * Allocation steps are keyed to the size of the fdarray, since it | |
92 | * grows far faster than any of the other dynamic data. We try to fit | |
93 | * the fdarray into comfortable page-tuned chunks: starting at 1024B | |
94 | * and growing in powers of two from there on. | |
95 | */ | |
96 | nr /= (1024 / sizeof(struct file *)); | |
97 | nr = roundup_pow_of_two(nr + 1); | |
98 | nr *= (1024 / sizeof(struct file *)); | |
99 | /* | |
100 | * Note that this can drive nr *below* what we had passed if sysctl_nr_open | |
101 | * had been set lower between the check in expand_files() and here. Deal | |
102 | * with that in caller, it's cheaper that way. | |
103 | * | |
104 | * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise | |
105 | * bitmaps handling below becomes unpleasant, to put it mildly... | |
106 | */ | |
107 | if (unlikely(nr > sysctl_nr_open)) | |
108 | nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1; | |
109 | ||
110 | fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL); | |
111 | if (!fdt) | |
112 | goto out; | |
113 | fdt->max_fds = nr; | |
114 | data = alloc_fdmem(nr * sizeof(struct file *)); | |
115 | if (!data) | |
116 | goto out_fdt; | |
117 | fdt->fd = data; | |
118 | ||
119 | data = alloc_fdmem(max_t(size_t, | |
120 | 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES)); | |
121 | if (!data) | |
122 | goto out_arr; | |
123 | fdt->open_fds = data; | |
124 | data += nr / BITS_PER_BYTE; | |
125 | fdt->close_on_exec = data; | |
126 | ||
127 | return fdt; | |
128 | ||
129 | out_arr: | |
130 | free_fdmem(fdt->fd); | |
131 | out_fdt: | |
132 | kfree(fdt); | |
133 | out: | |
134 | return NULL; | |
135 | } | |
136 | ||
137 | /* | |
138 | * Expand the file descriptor table. | |
139 | * This function will allocate a new fdtable and both fd array and fdset, of | |
140 | * the given size. | |
141 | * Return <0 error code on error; 1 on successful completion. | |
142 | * The files->file_lock should be held on entry, and will be held on exit. | |
143 | */ | |
144 | static int expand_fdtable(struct files_struct *files, int nr) | |
145 | __releases(files->file_lock) | |
146 | __acquires(files->file_lock) | |
147 | { | |
148 | struct fdtable *new_fdt, *cur_fdt; | |
149 | ||
150 | spin_unlock(&files->file_lock); | |
151 | new_fdt = alloc_fdtable(nr); | |
152 | spin_lock(&files->file_lock); | |
153 | if (!new_fdt) | |
154 | return -ENOMEM; | |
155 | /* | |
156 | * extremely unlikely race - sysctl_nr_open decreased between the check in | |
157 | * caller and alloc_fdtable(). Cheaper to catch it here... | |
158 | */ | |
159 | if (unlikely(new_fdt->max_fds <= nr)) { | |
160 | __free_fdtable(new_fdt); | |
161 | return -EMFILE; | |
162 | } | |
163 | /* | |
164 | * Check again since another task may have expanded the fd table while | |
165 | * we dropped the lock | |
166 | */ | |
167 | cur_fdt = files_fdtable(files); | |
168 | if (nr >= cur_fdt->max_fds) { | |
169 | /* Continue as planned */ | |
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 | } else { | |
175 | /* Somebody else expanded, so undo our attempt */ | |
176 | __free_fdtable(new_fdt); | |
177 | } | |
178 | return 1; | |
179 | } | |
180 | ||
181 | /* | |
182 | * Expand files. | |
183 | * This function will expand the file structures, if the requested size exceeds | |
184 | * the current capacity and there is room for expansion. | |
185 | * Return <0 error code on error; 0 when nothing done; 1 when files were | |
186 | * expanded and execution may have blocked. | |
187 | * The files->file_lock should be held on entry, and will be held on exit. | |
188 | */ | |
189 | static int expand_files(struct files_struct *files, int nr) | |
190 | { | |
191 | struct fdtable *fdt; | |
192 | ||
193 | fdt = files_fdtable(files); | |
194 | ||
195 | /* Do we need to expand? */ | |
196 | if (nr < fdt->max_fds) | |
197 | return 0; | |
198 | ||
199 | /* Can we expand? */ | |
200 | if (nr >= sysctl_nr_open) | |
201 | return -EMFILE; | |
202 | ||
203 | /* All good, so we try */ | |
204 | return expand_fdtable(files, nr); | |
205 | } | |
206 | ||
207 | static inline void __set_close_on_exec(int fd, struct fdtable *fdt) | |
208 | { | |
209 | __set_bit(fd, fdt->close_on_exec); | |
210 | } | |
211 | ||
212 | static inline void __clear_close_on_exec(int fd, struct fdtable *fdt) | |
213 | { | |
214 | __clear_bit(fd, fdt->close_on_exec); | |
215 | } | |
216 | ||
217 | static inline void __set_open_fd(int fd, struct fdtable *fdt) | |
218 | { | |
219 | __set_bit(fd, fdt->open_fds); | |
220 | } | |
221 | ||
222 | static inline void __clear_open_fd(int fd, struct fdtable *fdt) | |
223 | { | |
224 | __clear_bit(fd, fdt->open_fds); | |
225 | } | |
226 | ||
227 | static int count_open_files(struct fdtable *fdt) | |
228 | { | |
229 | int size = fdt->max_fds; | |
230 | int i; | |
231 | ||
232 | /* Find the last open fd */ | |
233 | for (i = size / BITS_PER_LONG; i > 0; ) { | |
234 | if (fdt->open_fds[--i]) | |
235 | break; | |
236 | } | |
237 | i = (i + 1) * BITS_PER_LONG; | |
238 | return i; | |
239 | } | |
240 | ||
241 | /* | |
242 | * Allocate a new files structure and copy contents from the | |
243 | * passed in files structure. | |
244 | * errorp will be valid only when the returned files_struct is NULL. | |
245 | */ | |
246 | struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) | |
247 | { | |
248 | struct files_struct *newf; | |
249 | struct file **old_fds, **new_fds; | |
250 | int open_files, size, i; | |
251 | struct fdtable *old_fdt, *new_fdt; | |
252 | ||
253 | *errorp = -ENOMEM; | |
254 | newf = kmem_cache_alloc(files_cachep, GFP_KERNEL); | |
255 | if (!newf) | |
256 | goto out; | |
257 | ||
258 | atomic_set(&newf->count, 1); | |
259 | ||
260 | spin_lock_init(&newf->file_lock); | |
261 | newf->next_fd = 0; | |
262 | new_fdt = &newf->fdtab; | |
263 | new_fdt->max_fds = NR_OPEN_DEFAULT; | |
264 | new_fdt->close_on_exec = newf->close_on_exec_init; | |
265 | new_fdt->open_fds = newf->open_fds_init; | |
266 | new_fdt->fd = &newf->fd_array[0]; | |
267 | ||
268 | spin_lock(&oldf->file_lock); | |
269 | old_fdt = files_fdtable(oldf); | |
270 | open_files = count_open_files(old_fdt); | |
271 | ||
272 | /* | |
273 | * Check whether we need to allocate a larger fd array and fd set. | |
274 | */ | |
275 | while (unlikely(open_files > new_fdt->max_fds)) { | |
276 | spin_unlock(&oldf->file_lock); | |
277 | ||
278 | if (new_fdt != &newf->fdtab) | |
279 | __free_fdtable(new_fdt); | |
280 | ||
281 | new_fdt = alloc_fdtable(open_files - 1); | |
282 | if (!new_fdt) { | |
283 | *errorp = -ENOMEM; | |
284 | goto out_release; | |
285 | } | |
286 | ||
287 | /* beyond sysctl_nr_open; nothing to do */ | |
288 | if (unlikely(new_fdt->max_fds < open_files)) { | |
289 | __free_fdtable(new_fdt); | |
290 | *errorp = -EMFILE; | |
291 | goto out_release; | |
292 | } | |
293 | ||
294 | /* | |
295 | * Reacquire the oldf lock and a pointer to its fd table | |
296 | * who knows it may have a new bigger fd table. We need | |
297 | * the latest pointer. | |
298 | */ | |
299 | spin_lock(&oldf->file_lock); | |
300 | old_fdt = files_fdtable(oldf); | |
301 | open_files = count_open_files(old_fdt); | |
302 | } | |
303 | ||
304 | old_fds = old_fdt->fd; | |
305 | new_fds = new_fdt->fd; | |
306 | ||
307 | memcpy(new_fdt->open_fds, old_fdt->open_fds, open_files / 8); | |
308 | memcpy(new_fdt->close_on_exec, old_fdt->close_on_exec, open_files / 8); | |
309 | ||
310 | for (i = open_files; i != 0; i--) { | |
311 | struct file *f = *old_fds++; | |
312 | if (f) { | |
313 | get_file(f); | |
314 | } else { | |
315 | /* | |
316 | * The fd may be claimed in the fd bitmap but not yet | |
317 | * instantiated in the files array if a sibling thread | |
318 | * is partway through open(). So make sure that this | |
319 | * fd is available to the new process. | |
320 | */ | |
321 | __clear_open_fd(open_files - i, new_fdt); | |
322 | } | |
323 | rcu_assign_pointer(*new_fds++, f); | |
324 | } | |
325 | spin_unlock(&oldf->file_lock); | |
326 | ||
327 | /* compute the remainder to be cleared */ | |
328 | size = (new_fdt->max_fds - open_files) * sizeof(struct file *); | |
329 | ||
330 | /* This is long word aligned thus could use a optimized version */ | |
331 | memset(new_fds, 0, size); | |
332 | ||
333 | if (new_fdt->max_fds > open_files) { | |
334 | int left = (new_fdt->max_fds - open_files) / 8; | |
335 | int start = open_files / BITS_PER_LONG; | |
336 | ||
337 | memset(&new_fdt->open_fds[start], 0, left); | |
338 | memset(&new_fdt->close_on_exec[start], 0, left); | |
339 | } | |
340 | ||
341 | rcu_assign_pointer(newf->fdt, new_fdt); | |
342 | ||
343 | return newf; | |
344 | ||
345 | out_release: | |
346 | kmem_cache_free(files_cachep, newf); | |
347 | out: | |
348 | return NULL; | |
349 | } | |
350 | ||
351 | static struct fdtable *close_files(struct files_struct * files) | |
352 | { | |
353 | /* | |
354 | * It is safe to dereference the fd table without RCU or | |
355 | * ->file_lock because this is the last reference to the | |
356 | * files structure. | |
357 | */ | |
358 | struct fdtable *fdt = rcu_dereference_raw(files->fdt); | |
359 | int i, j = 0; | |
360 | ||
361 | for (;;) { | |
362 | unsigned long set; | |
363 | i = j * BITS_PER_LONG; | |
364 | if (i >= fdt->max_fds) | |
365 | break; | |
366 | set = fdt->open_fds[j++]; | |
367 | while (set) { | |
368 | if (set & 1) { | |
369 | struct file * file = xchg(&fdt->fd[i], NULL); | |
370 | if (file) { | |
371 | filp_close(file, files); | |
372 | cond_resched(); | |
373 | } | |
374 | } | |
375 | i++; | |
376 | set >>= 1; | |
377 | } | |
378 | } | |
379 | ||
380 | return fdt; | |
381 | } | |
382 | ||
383 | struct files_struct *get_files_struct(struct task_struct *task) | |
384 | { | |
385 | struct files_struct *files; | |
386 | ||
387 | task_lock(task); | |
388 | files = task->files; | |
389 | if (files) | |
390 | atomic_inc(&files->count); | |
391 | task_unlock(task); | |
392 | ||
393 | return files; | |
394 | } | |
395 | ||
396 | void put_files_struct(struct files_struct *files) | |
397 | { | |
398 | if (atomic_dec_and_test(&files->count)) { | |
399 | struct fdtable *fdt = close_files(files); | |
400 | ||
401 | /* free the arrays if they are not embedded */ | |
402 | if (fdt != &files->fdtab) | |
403 | __free_fdtable(fdt); | |
404 | kmem_cache_free(files_cachep, files); | |
405 | } | |
406 | } | |
407 | ||
408 | void reset_files_struct(struct files_struct *files) | |
409 | { | |
410 | struct task_struct *tsk = current; | |
411 | struct files_struct *old; | |
412 | ||
413 | old = tsk->files; | |
414 | task_lock(tsk); | |
415 | tsk->files = files; | |
416 | task_unlock(tsk); | |
417 | put_files_struct(old); | |
418 | } | |
419 | ||
420 | void exit_files(struct task_struct *tsk) | |
421 | { | |
422 | struct files_struct * files = tsk->files; | |
423 | ||
424 | if (files) { | |
425 | task_lock(tsk); | |
426 | tsk->files = NULL; | |
427 | task_unlock(tsk); | |
428 | put_files_struct(files); | |
429 | } | |
430 | } | |
431 | ||
432 | void __init files_defer_init(void) | |
433 | { | |
434 | sysctl_nr_open_max = min((size_t)INT_MAX, ~(size_t)0/sizeof(void *)) & | |
435 | -BITS_PER_LONG; | |
436 | } | |
437 | ||
438 | struct files_struct init_files = { | |
439 | .count = ATOMIC_INIT(1), | |
440 | .fdt = &init_files.fdtab, | |
441 | .fdtab = { | |
442 | .max_fds = NR_OPEN_DEFAULT, | |
443 | .fd = &init_files.fd_array[0], | |
444 | .close_on_exec = init_files.close_on_exec_init, | |
445 | .open_fds = init_files.open_fds_init, | |
446 | }, | |
447 | .file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock), | |
448 | }; | |
449 | ||
450 | /* | |
451 | * allocate a file descriptor, mark it busy. | |
452 | */ | |
453 | int __alloc_fd(struct files_struct *files, | |
454 | unsigned start, unsigned end, unsigned flags) | |
455 | { | |
456 | unsigned int fd; | |
457 | int error; | |
458 | struct fdtable *fdt; | |
459 | ||
460 | spin_lock(&files->file_lock); | |
461 | repeat: | |
462 | fdt = files_fdtable(files); | |
463 | fd = start; | |
464 | if (fd < files->next_fd) | |
465 | fd = files->next_fd; | |
466 | ||
467 | if (fd < fdt->max_fds) | |
468 | fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd); | |
469 | ||
470 | /* | |
471 | * N.B. For clone tasks sharing a files structure, this test | |
472 | * will limit the total number of files that can be opened. | |
473 | */ | |
474 | error = -EMFILE; | |
475 | if (fd >= end) | |
476 | goto out; | |
477 | ||
478 | error = expand_files(files, fd); | |
479 | if (error < 0) | |
480 | goto out; | |
481 | ||
482 | /* | |
483 | * If we needed to expand the fs array we | |
484 | * might have blocked - try again. | |
485 | */ | |
486 | if (error) | |
487 | goto repeat; | |
488 | ||
489 | if (start <= files->next_fd) | |
490 | files->next_fd = fd + 1; | |
491 | ||
492 | __set_open_fd(fd, fdt); | |
493 | if (flags & O_CLOEXEC) | |
494 | __set_close_on_exec(fd, fdt); | |
495 | else | |
496 | __clear_close_on_exec(fd, fdt); | |
497 | error = fd; | |
498 | #if 1 | |
499 | /* Sanity check */ | |
500 | if (rcu_dereference_raw(fdt->fd[fd]) != NULL) { | |
501 | printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd); | |
502 | rcu_assign_pointer(fdt->fd[fd], NULL); | |
503 | } | |
504 | #endif | |
505 | ||
506 | out: | |
507 | spin_unlock(&files->file_lock); | |
508 | return error; | |
509 | } | |
510 | ||
511 | static int alloc_fd(unsigned start, unsigned flags) | |
512 | { | |
513 | return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags); | |
514 | } | |
515 | ||
516 | int get_unused_fd_flags(unsigned flags) | |
517 | { | |
518 | return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags); | |
519 | } | |
520 | EXPORT_SYMBOL(get_unused_fd_flags); | |
521 | ||
522 | static void __put_unused_fd(struct files_struct *files, unsigned int fd) | |
523 | { | |
524 | struct fdtable *fdt = files_fdtable(files); | |
525 | __clear_open_fd(fd, fdt); | |
526 | if (fd < files->next_fd) | |
527 | files->next_fd = fd; | |
528 | } | |
529 | ||
530 | void put_unused_fd(unsigned int fd) | |
531 | { | |
532 | struct files_struct *files = current->files; | |
533 | spin_lock(&files->file_lock); | |
534 | __put_unused_fd(files, fd); | |
535 | spin_unlock(&files->file_lock); | |
536 | } | |
537 | ||
538 | EXPORT_SYMBOL(put_unused_fd); | |
539 | ||
540 | /* | |
541 | * Install a file pointer in the fd array. | |
542 | * | |
543 | * The VFS is full of places where we drop the files lock between | |
544 | * setting the open_fds bitmap and installing the file in the file | |
545 | * array. At any such point, we are vulnerable to a dup2() race | |
546 | * installing a file in the array before us. We need to detect this and | |
547 | * fput() the struct file we are about to overwrite in this case. | |
548 | * | |
549 | * It should never happen - if we allow dup2() do it, _really_ bad things | |
550 | * will follow. | |
551 | * | |
552 | * NOTE: __fd_install() variant is really, really low-level; don't | |
553 | * use it unless you are forced to by truly lousy API shoved down | |
554 | * your throat. 'files' *MUST* be either current->files or obtained | |
555 | * by get_files_struct(current) done by whoever had given it to you, | |
556 | * or really bad things will happen. Normally you want to use | |
557 | * fd_install() instead. | |
558 | */ | |
559 | ||
560 | void __fd_install(struct files_struct *files, unsigned int fd, | |
561 | struct file *file) | |
562 | { | |
563 | struct fdtable *fdt; | |
564 | spin_lock(&files->file_lock); | |
565 | fdt = files_fdtable(files); | |
566 | BUG_ON(fdt->fd[fd] != NULL); | |
567 | rcu_assign_pointer(fdt->fd[fd], file); | |
568 | spin_unlock(&files->file_lock); | |
569 | } | |
570 | ||
571 | void fd_install(unsigned int fd, struct file *file) | |
572 | { | |
573 | __fd_install(current->files, fd, file); | |
574 | } | |
575 | ||
576 | EXPORT_SYMBOL(fd_install); | |
577 | ||
578 | /* | |
579 | * The same warnings as for __alloc_fd()/__fd_install() apply here... | |
580 | */ | |
581 | int __close_fd(struct files_struct *files, unsigned fd) | |
582 | { | |
583 | struct file *file; | |
584 | struct fdtable *fdt; | |
585 | ||
586 | spin_lock(&files->file_lock); | |
587 | fdt = files_fdtable(files); | |
588 | if (fd >= fdt->max_fds) | |
589 | goto out_unlock; | |
590 | file = fdt->fd[fd]; | |
591 | if (!file) | |
592 | goto out_unlock; | |
593 | rcu_assign_pointer(fdt->fd[fd], NULL); | |
594 | __clear_close_on_exec(fd, fdt); | |
595 | __put_unused_fd(files, fd); | |
596 | spin_unlock(&files->file_lock); | |
597 | return filp_close(file, files); | |
598 | ||
599 | out_unlock: | |
600 | spin_unlock(&files->file_lock); | |
601 | return -EBADF; | |
602 | } | |
603 | ||
604 | void do_close_on_exec(struct files_struct *files) | |
605 | { | |
606 | unsigned i; | |
607 | struct fdtable *fdt; | |
608 | ||
609 | /* exec unshares first */ | |
610 | spin_lock(&files->file_lock); | |
611 | for (i = 0; ; i++) { | |
612 | unsigned long set; | |
613 | unsigned fd = i * BITS_PER_LONG; | |
614 | fdt = files_fdtable(files); | |
615 | if (fd >= fdt->max_fds) | |
616 | break; | |
617 | set = fdt->close_on_exec[i]; | |
618 | if (!set) | |
619 | continue; | |
620 | fdt->close_on_exec[i] = 0; | |
621 | for ( ; set ; fd++, set >>= 1) { | |
622 | struct file *file; | |
623 | if (!(set & 1)) | |
624 | continue; | |
625 | file = fdt->fd[fd]; | |
626 | if (!file) | |
627 | continue; | |
628 | rcu_assign_pointer(fdt->fd[fd], NULL); | |
629 | __put_unused_fd(files, fd); | |
630 | spin_unlock(&files->file_lock); | |
631 | filp_close(file, files); | |
632 | cond_resched(); | |
633 | spin_lock(&files->file_lock); | |
634 | } | |
635 | ||
636 | } | |
637 | spin_unlock(&files->file_lock); | |
638 | } | |
639 | ||
640 | static struct file *__fget(unsigned int fd, fmode_t mask) | |
641 | { | |
642 | struct files_struct *files = current->files; | |
643 | struct file *file; | |
644 | ||
645 | rcu_read_lock(); | |
646 | file = fcheck_files(files, fd); | |
647 | if (file) { | |
648 | /* File object ref couldn't be taken */ | |
649 | if ((file->f_mode & mask) || | |
650 | !atomic_long_inc_not_zero(&file->f_count)) | |
651 | file = NULL; | |
652 | } | |
653 | rcu_read_unlock(); | |
654 | ||
655 | return file; | |
656 | } | |
657 | ||
658 | struct file *fget(unsigned int fd) | |
659 | { | |
660 | return __fget(fd, FMODE_PATH); | |
661 | } | |
662 | EXPORT_SYMBOL(fget); | |
663 | ||
664 | struct file *fget_raw(unsigned int fd) | |
665 | { | |
666 | return __fget(fd, 0); | |
667 | } | |
668 | EXPORT_SYMBOL(fget_raw); | |
669 | ||
670 | /* | |
671 | * Lightweight file lookup - no refcnt increment if fd table isn't shared. | |
672 | * | |
673 | * You can use this instead of fget if you satisfy all of the following | |
674 | * conditions: | |
675 | * 1) You must call fput_light before exiting the syscall and returning control | |
676 | * to userspace (i.e. you cannot remember the returned struct file * after | |
677 | * returning to userspace). | |
678 | * 2) You must not call filp_close on the returned struct file * in between | |
679 | * calls to fget_light and fput_light. | |
680 | * 3) You must not clone the current task in between the calls to fget_light | |
681 | * and fput_light. | |
682 | * | |
683 | * The fput_needed flag returned by fget_light should be passed to the | |
684 | * corresponding fput_light. | |
685 | */ | |
686 | struct file *__fget_light(unsigned int fd, fmode_t mask, int *fput_needed) | |
687 | { | |
688 | struct files_struct *files = current->files; | |
689 | struct file *file; | |
690 | ||
691 | *fput_needed = 0; | |
692 | if (atomic_read(&files->count) == 1) { | |
693 | file = __fcheck_files(files, fd); | |
694 | if (file && (file->f_mode & mask)) | |
695 | file = NULL; | |
696 | } else { | |
697 | rcu_read_lock(); | |
698 | file = fcheck_files(files, fd); | |
699 | if (file) { | |
700 | if (!(file->f_mode & mask) && | |
701 | atomic_long_inc_not_zero(&file->f_count)) | |
702 | *fput_needed = 1; | |
703 | else | |
704 | /* Didn't get the reference, someone's freed */ | |
705 | file = NULL; | |
706 | } | |
707 | rcu_read_unlock(); | |
708 | } | |
709 | ||
710 | return file; | |
711 | } | |
712 | struct file *fget_light(unsigned int fd, int *fput_needed) | |
713 | { | |
714 | return __fget_light(fd, FMODE_PATH, fput_needed); | |
715 | } | |
716 | EXPORT_SYMBOL(fget_light); | |
717 | ||
718 | struct file *fget_raw_light(unsigned int fd, int *fput_needed) | |
719 | { | |
720 | return __fget_light(fd, 0, fput_needed); | |
721 | } | |
722 | ||
723 | void set_close_on_exec(unsigned int fd, int flag) | |
724 | { | |
725 | struct files_struct *files = current->files; | |
726 | struct fdtable *fdt; | |
727 | spin_lock(&files->file_lock); | |
728 | fdt = files_fdtable(files); | |
729 | if (flag) | |
730 | __set_close_on_exec(fd, fdt); | |
731 | else | |
732 | __clear_close_on_exec(fd, fdt); | |
733 | spin_unlock(&files->file_lock); | |
734 | } | |
735 | ||
736 | bool get_close_on_exec(unsigned int fd) | |
737 | { | |
738 | struct files_struct *files = current->files; | |
739 | struct fdtable *fdt; | |
740 | bool res; | |
741 | rcu_read_lock(); | |
742 | fdt = files_fdtable(files); | |
743 | res = close_on_exec(fd, fdt); | |
744 | rcu_read_unlock(); | |
745 | return res; | |
746 | } | |
747 | ||
748 | static int do_dup2(struct files_struct *files, | |
749 | struct file *file, unsigned fd, unsigned flags) | |
750 | { | |
751 | struct file *tofree; | |
752 | struct fdtable *fdt; | |
753 | ||
754 | /* | |
755 | * We need to detect attempts to do dup2() over allocated but still | |
756 | * not finished descriptor. NB: OpenBSD avoids that at the price of | |
757 | * extra work in their equivalent of fget() - they insert struct | |
758 | * file immediately after grabbing descriptor, mark it larval if | |
759 | * more work (e.g. actual opening) is needed and make sure that | |
760 | * fget() treats larval files as absent. Potentially interesting, | |
761 | * but while extra work in fget() is trivial, locking implications | |
762 | * and amount of surgery on open()-related paths in VFS are not. | |
763 | * FreeBSD fails with -EBADF in the same situation, NetBSD "solution" | |
764 | * deadlocks in rather amusing ways, AFAICS. All of that is out of | |
765 | * scope of POSIX or SUS, since neither considers shared descriptor | |
766 | * tables and this condition does not arise without those. | |
767 | */ | |
768 | fdt = files_fdtable(files); | |
769 | tofree = fdt->fd[fd]; | |
770 | if (!tofree && fd_is_open(fd, fdt)) | |
771 | goto Ebusy; | |
772 | get_file(file); | |
773 | rcu_assign_pointer(fdt->fd[fd], file); | |
774 | __set_open_fd(fd, fdt); | |
775 | if (flags & O_CLOEXEC) | |
776 | __set_close_on_exec(fd, fdt); | |
777 | else | |
778 | __clear_close_on_exec(fd, fdt); | |
779 | spin_unlock(&files->file_lock); | |
780 | ||
781 | if (tofree) | |
782 | filp_close(tofree, files); | |
783 | ||
784 | return fd; | |
785 | ||
786 | Ebusy: | |
787 | spin_unlock(&files->file_lock); | |
788 | return -EBUSY; | |
789 | } | |
790 | ||
791 | int replace_fd(unsigned fd, struct file *file, unsigned flags) | |
792 | { | |
793 | int err; | |
794 | struct files_struct *files = current->files; | |
795 | ||
796 | if (!file) | |
797 | return __close_fd(files, fd); | |
798 | ||
799 | if (fd >= rlimit(RLIMIT_NOFILE)) | |
800 | return -EBADF; | |
801 | ||
802 | spin_lock(&files->file_lock); | |
803 | err = expand_files(files, fd); | |
804 | if (unlikely(err < 0)) | |
805 | goto out_unlock; | |
806 | return do_dup2(files, file, fd, flags); | |
807 | ||
808 | out_unlock: | |
809 | spin_unlock(&files->file_lock); | |
810 | return err; | |
811 | } | |
812 | ||
813 | SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags) | |
814 | { | |
815 | int err = -EBADF; | |
816 | struct file *file; | |
817 | struct files_struct *files = current->files; | |
818 | ||
819 | if ((flags & ~O_CLOEXEC) != 0) | |
820 | return -EINVAL; | |
821 | ||
822 | if (unlikely(oldfd == newfd)) | |
823 | return -EINVAL; | |
824 | ||
825 | if (newfd >= rlimit(RLIMIT_NOFILE)) | |
826 | return -EBADF; | |
827 | ||
828 | spin_lock(&files->file_lock); | |
829 | err = expand_files(files, newfd); | |
830 | file = fcheck(oldfd); | |
831 | if (unlikely(!file)) | |
832 | goto Ebadf; | |
833 | if (unlikely(err < 0)) { | |
834 | if (err == -EMFILE) | |
835 | goto Ebadf; | |
836 | goto out_unlock; | |
837 | } | |
838 | return do_dup2(files, file, newfd, flags); | |
839 | ||
840 | Ebadf: | |
841 | err = -EBADF; | |
842 | out_unlock: | |
843 | spin_unlock(&files->file_lock); | |
844 | return err; | |
845 | } | |
846 | ||
847 | SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd) | |
848 | { | |
849 | if (unlikely(newfd == oldfd)) { /* corner case */ | |
850 | struct files_struct *files = current->files; | |
851 | int retval = oldfd; | |
852 | ||
853 | rcu_read_lock(); | |
854 | if (!fcheck_files(files, oldfd)) | |
855 | retval = -EBADF; | |
856 | rcu_read_unlock(); | |
857 | return retval; | |
858 | } | |
859 | return sys_dup3(oldfd, newfd, 0); | |
860 | } | |
861 | ||
862 | SYSCALL_DEFINE1(dup, unsigned int, fildes) | |
863 | { | |
864 | int ret = -EBADF; | |
865 | struct file *file = fget_raw(fildes); | |
866 | ||
867 | if (file) { | |
868 | ret = get_unused_fd(); | |
869 | if (ret >= 0) | |
870 | fd_install(ret, file); | |
871 | else | |
872 | fput(file); | |
873 | } | |
874 | return ret; | |
875 | } | |
876 | ||
877 | int f_dupfd(unsigned int from, struct file *file, unsigned flags) | |
878 | { | |
879 | int err; | |
880 | if (from >= rlimit(RLIMIT_NOFILE)) | |
881 | return -EINVAL; | |
882 | err = alloc_fd(from, flags); | |
883 | if (err >= 0) { | |
884 | get_file(file); | |
885 | fd_install(err, file); | |
886 | } | |
887 | return err; | |
888 | } | |
889 | ||
890 | int iterate_fd(struct files_struct *files, unsigned n, | |
891 | int (*f)(const void *, struct file *, unsigned), | |
892 | const void *p) | |
893 | { | |
894 | struct fdtable *fdt; | |
895 | int res = 0; | |
896 | if (!files) | |
897 | return 0; | |
898 | spin_lock(&files->file_lock); | |
899 | for (fdt = files_fdtable(files); n < fdt->max_fds; n++) { | |
900 | struct file *file; | |
901 | file = rcu_dereference_check_fdtable(files, fdt->fd[n]); | |
902 | if (!file) | |
903 | continue; | |
904 | res = f(p, file, n); | |
905 | if (res) | |
906 | break; | |
907 | } | |
908 | spin_unlock(&files->file_lock); | |
909 | return res; | |
910 | } | |
911 | EXPORT_SYMBOL(iterate_fd); |