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1 | /* | |
2 | * linux/fs/pipe.c | |
3 | * | |
4 | * Copyright (C) 1991, 1992, 1999 Linus Torvalds | |
5 | */ | |
6 | ||
7 | #include <linux/mm.h> | |
8 | #include <linux/file.h> | |
9 | #include <linux/poll.h> | |
10 | #include <linux/slab.h> | |
11 | #include <linux/module.h> | |
12 | #include <linux/init.h> | |
13 | #include <linux/fs.h> | |
14 | #include <linux/log2.h> | |
15 | #include <linux/mount.h> | |
16 | #include <linux/magic.h> | |
17 | #include <linux/pipe_fs_i.h> | |
18 | #include <linux/uio.h> | |
19 | #include <linux/highmem.h> | |
20 | #include <linux/pagemap.h> | |
21 | #include <linux/audit.h> | |
22 | #include <linux/syscalls.h> | |
23 | #include <linux/fcntl.h> | |
24 | ||
25 | #include <asm/uaccess.h> | |
26 | #include <asm/ioctls.h> | |
27 | ||
28 | #include "internal.h" | |
29 | ||
30 | /* | |
31 | * The max size that a non-root user is allowed to grow the pipe. Can | |
32 | * be set by root in /proc/sys/fs/pipe-max-size | |
33 | */ | |
34 | unsigned int pipe_max_size = 1048576; | |
35 | ||
36 | /* | |
37 | * Minimum pipe size, as required by POSIX | |
38 | */ | |
39 | unsigned int pipe_min_size = PAGE_SIZE; | |
40 | ||
41 | /* | |
42 | * We use a start+len construction, which provides full use of the | |
43 | * allocated memory. | |
44 | * -- Florian Coosmann (FGC) | |
45 | * | |
46 | * Reads with count = 0 should always return 0. | |
47 | * -- Julian Bradfield 1999-06-07. | |
48 | * | |
49 | * FIFOs and Pipes now generate SIGIO for both readers and writers. | |
50 | * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16 | |
51 | * | |
52 | * pipe_read & write cleanup | |
53 | * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09 | |
54 | */ | |
55 | ||
56 | static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass) | |
57 | { | |
58 | if (pipe->files) | |
59 | mutex_lock_nested(&pipe->mutex, subclass); | |
60 | } | |
61 | ||
62 | void pipe_lock(struct pipe_inode_info *pipe) | |
63 | { | |
64 | /* | |
65 | * pipe_lock() nests non-pipe inode locks (for writing to a file) | |
66 | */ | |
67 | pipe_lock_nested(pipe, I_MUTEX_PARENT); | |
68 | } | |
69 | EXPORT_SYMBOL(pipe_lock); | |
70 | ||
71 | void pipe_unlock(struct pipe_inode_info *pipe) | |
72 | { | |
73 | if (pipe->files) | |
74 | mutex_unlock(&pipe->mutex); | |
75 | } | |
76 | EXPORT_SYMBOL(pipe_unlock); | |
77 | ||
78 | static inline void __pipe_lock(struct pipe_inode_info *pipe) | |
79 | { | |
80 | mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT); | |
81 | } | |
82 | ||
83 | static inline void __pipe_unlock(struct pipe_inode_info *pipe) | |
84 | { | |
85 | mutex_unlock(&pipe->mutex); | |
86 | } | |
87 | ||
88 | void pipe_double_lock(struct pipe_inode_info *pipe1, | |
89 | struct pipe_inode_info *pipe2) | |
90 | { | |
91 | BUG_ON(pipe1 == pipe2); | |
92 | ||
93 | if (pipe1 < pipe2) { | |
94 | pipe_lock_nested(pipe1, I_MUTEX_PARENT); | |
95 | pipe_lock_nested(pipe2, I_MUTEX_CHILD); | |
96 | } else { | |
97 | pipe_lock_nested(pipe2, I_MUTEX_PARENT); | |
98 | pipe_lock_nested(pipe1, I_MUTEX_CHILD); | |
99 | } | |
100 | } | |
101 | ||
102 | /* Drop the inode semaphore and wait for a pipe event, atomically */ | |
103 | void pipe_wait(struct pipe_inode_info *pipe) | |
104 | { | |
105 | DEFINE_WAIT(wait); | |
106 | ||
107 | /* | |
108 | * Pipes are system-local resources, so sleeping on them | |
109 | * is considered a noninteractive wait: | |
110 | */ | |
111 | prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE); | |
112 | pipe_unlock(pipe); | |
113 | schedule(); | |
114 | finish_wait(&pipe->wait, &wait); | |
115 | pipe_lock(pipe); | |
116 | } | |
117 | ||
118 | static void anon_pipe_buf_release(struct pipe_inode_info *pipe, | |
119 | struct pipe_buffer *buf) | |
120 | { | |
121 | struct page *page = buf->page; | |
122 | ||
123 | /* | |
124 | * If nobody else uses this page, and we don't already have a | |
125 | * temporary page, let's keep track of it as a one-deep | |
126 | * allocation cache. (Otherwise just release our reference to it) | |
127 | */ | |
128 | if (page_count(page) == 1 && !pipe->tmp_page) | |
129 | pipe->tmp_page = page; | |
130 | else | |
131 | page_cache_release(page); | |
132 | } | |
133 | ||
134 | /** | |
135 | * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer | |
136 | * @pipe: the pipe that the buffer belongs to | |
137 | * @buf: the buffer to attempt to steal | |
138 | * | |
139 | * Description: | |
140 | * This function attempts to steal the &struct page attached to | |
141 | * @buf. If successful, this function returns 0 and returns with | |
142 | * the page locked. The caller may then reuse the page for whatever | |
143 | * he wishes; the typical use is insertion into a different file | |
144 | * page cache. | |
145 | */ | |
146 | int generic_pipe_buf_steal(struct pipe_inode_info *pipe, | |
147 | struct pipe_buffer *buf) | |
148 | { | |
149 | struct page *page = buf->page; | |
150 | ||
151 | /* | |
152 | * A reference of one is golden, that means that the owner of this | |
153 | * page is the only one holding a reference to it. lock the page | |
154 | * and return OK. | |
155 | */ | |
156 | if (page_count(page) == 1) { | |
157 | lock_page(page); | |
158 | return 0; | |
159 | } | |
160 | ||
161 | return 1; | |
162 | } | |
163 | EXPORT_SYMBOL(generic_pipe_buf_steal); | |
164 | ||
165 | /** | |
166 | * generic_pipe_buf_get - get a reference to a &struct pipe_buffer | |
167 | * @pipe: the pipe that the buffer belongs to | |
168 | * @buf: the buffer to get a reference to | |
169 | * | |
170 | * Description: | |
171 | * This function grabs an extra reference to @buf. It's used in | |
172 | * in the tee() system call, when we duplicate the buffers in one | |
173 | * pipe into another. | |
174 | */ | |
175 | void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf) | |
176 | { | |
177 | page_cache_get(buf->page); | |
178 | } | |
179 | EXPORT_SYMBOL(generic_pipe_buf_get); | |
180 | ||
181 | /** | |
182 | * generic_pipe_buf_confirm - verify contents of the pipe buffer | |
183 | * @info: the pipe that the buffer belongs to | |
184 | * @buf: the buffer to confirm | |
185 | * | |
186 | * Description: | |
187 | * This function does nothing, because the generic pipe code uses | |
188 | * pages that are always good when inserted into the pipe. | |
189 | */ | |
190 | int generic_pipe_buf_confirm(struct pipe_inode_info *info, | |
191 | struct pipe_buffer *buf) | |
192 | { | |
193 | return 0; | |
194 | } | |
195 | EXPORT_SYMBOL(generic_pipe_buf_confirm); | |
196 | ||
197 | /** | |
198 | * generic_pipe_buf_release - put a reference to a &struct pipe_buffer | |
199 | * @pipe: the pipe that the buffer belongs to | |
200 | * @buf: the buffer to put a reference to | |
201 | * | |
202 | * Description: | |
203 | * This function releases a reference to @buf. | |
204 | */ | |
205 | void generic_pipe_buf_release(struct pipe_inode_info *pipe, | |
206 | struct pipe_buffer *buf) | |
207 | { | |
208 | page_cache_release(buf->page); | |
209 | } | |
210 | EXPORT_SYMBOL(generic_pipe_buf_release); | |
211 | ||
212 | static const struct pipe_buf_operations anon_pipe_buf_ops = { | |
213 | .can_merge = 1, | |
214 | .confirm = generic_pipe_buf_confirm, | |
215 | .release = anon_pipe_buf_release, | |
216 | .steal = generic_pipe_buf_steal, | |
217 | .get = generic_pipe_buf_get, | |
218 | }; | |
219 | ||
220 | static const struct pipe_buf_operations packet_pipe_buf_ops = { | |
221 | .can_merge = 0, | |
222 | .confirm = generic_pipe_buf_confirm, | |
223 | .release = anon_pipe_buf_release, | |
224 | .steal = generic_pipe_buf_steal, | |
225 | .get = generic_pipe_buf_get, | |
226 | }; | |
227 | ||
228 | static ssize_t | |
229 | pipe_read(struct kiocb *iocb, struct iov_iter *to) | |
230 | { | |
231 | size_t total_len = iov_iter_count(to); | |
232 | struct file *filp = iocb->ki_filp; | |
233 | struct pipe_inode_info *pipe = filp->private_data; | |
234 | int do_wakeup; | |
235 | ssize_t ret; | |
236 | ||
237 | /* Null read succeeds. */ | |
238 | if (unlikely(total_len == 0)) | |
239 | return 0; | |
240 | ||
241 | do_wakeup = 0; | |
242 | ret = 0; | |
243 | __pipe_lock(pipe); | |
244 | for (;;) { | |
245 | int bufs = pipe->nrbufs; | |
246 | if (bufs) { | |
247 | int curbuf = pipe->curbuf; | |
248 | struct pipe_buffer *buf = pipe->bufs + curbuf; | |
249 | const struct pipe_buf_operations *ops = buf->ops; | |
250 | size_t chars = buf->len; | |
251 | size_t written; | |
252 | int error; | |
253 | ||
254 | if (chars > total_len) | |
255 | chars = total_len; | |
256 | ||
257 | error = ops->confirm(pipe, buf); | |
258 | if (error) { | |
259 | if (!ret) | |
260 | ret = error; | |
261 | break; | |
262 | } | |
263 | ||
264 | written = copy_page_to_iter(buf->page, buf->offset, chars, to); | |
265 | if (unlikely(written < chars)) { | |
266 | if (!ret) | |
267 | ret = -EFAULT; | |
268 | break; | |
269 | } | |
270 | ret += chars; | |
271 | buf->offset += chars; | |
272 | buf->len -= chars; | |
273 | ||
274 | /* Was it a packet buffer? Clean up and exit */ | |
275 | if (buf->flags & PIPE_BUF_FLAG_PACKET) { | |
276 | total_len = chars; | |
277 | buf->len = 0; | |
278 | } | |
279 | ||
280 | if (!buf->len) { | |
281 | buf->ops = NULL; | |
282 | ops->release(pipe, buf); | |
283 | curbuf = (curbuf + 1) & (pipe->buffers - 1); | |
284 | pipe->curbuf = curbuf; | |
285 | pipe->nrbufs = --bufs; | |
286 | do_wakeup = 1; | |
287 | } | |
288 | total_len -= chars; | |
289 | if (!total_len) | |
290 | break; /* common path: read succeeded */ | |
291 | } | |
292 | if (bufs) /* More to do? */ | |
293 | continue; | |
294 | if (!pipe->writers) | |
295 | break; | |
296 | if (!pipe->waiting_writers) { | |
297 | /* syscall merging: Usually we must not sleep | |
298 | * if O_NONBLOCK is set, or if we got some data. | |
299 | * But if a writer sleeps in kernel space, then | |
300 | * we can wait for that data without violating POSIX. | |
301 | */ | |
302 | if (ret) | |
303 | break; | |
304 | if (filp->f_flags & O_NONBLOCK) { | |
305 | ret = -EAGAIN; | |
306 | break; | |
307 | } | |
308 | } | |
309 | if (signal_pending(current)) { | |
310 | if (!ret) | |
311 | ret = -ERESTARTSYS; | |
312 | break; | |
313 | } | |
314 | if (do_wakeup) { | |
315 | wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM); | |
316 | kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); | |
317 | } | |
318 | pipe_wait(pipe); | |
319 | } | |
320 | __pipe_unlock(pipe); | |
321 | ||
322 | /* Signal writers asynchronously that there is more room. */ | |
323 | if (do_wakeup) { | |
324 | wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM); | |
325 | kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); | |
326 | } | |
327 | if (ret > 0) | |
328 | file_accessed(filp); | |
329 | return ret; | |
330 | } | |
331 | ||
332 | static inline int is_packetized(struct file *file) | |
333 | { | |
334 | return (file->f_flags & O_DIRECT) != 0; | |
335 | } | |
336 | ||
337 | static ssize_t | |
338 | pipe_write(struct kiocb *iocb, struct iov_iter *from) | |
339 | { | |
340 | struct file *filp = iocb->ki_filp; | |
341 | struct pipe_inode_info *pipe = filp->private_data; | |
342 | ssize_t ret = 0; | |
343 | int do_wakeup = 0; | |
344 | size_t total_len = iov_iter_count(from); | |
345 | ssize_t chars; | |
346 | ||
347 | /* Null write succeeds. */ | |
348 | if (unlikely(total_len == 0)) | |
349 | return 0; | |
350 | ||
351 | __pipe_lock(pipe); | |
352 | ||
353 | if (!pipe->readers) { | |
354 | send_sig(SIGPIPE, current, 0); | |
355 | ret = -EPIPE; | |
356 | goto out; | |
357 | } | |
358 | ||
359 | /* We try to merge small writes */ | |
360 | chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */ | |
361 | if (pipe->nrbufs && chars != 0) { | |
362 | int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) & | |
363 | (pipe->buffers - 1); | |
364 | struct pipe_buffer *buf = pipe->bufs + lastbuf; | |
365 | const struct pipe_buf_operations *ops = buf->ops; | |
366 | int offset = buf->offset + buf->len; | |
367 | ||
368 | if (ops->can_merge && offset + chars <= PAGE_SIZE) { | |
369 | ret = ops->confirm(pipe, buf); | |
370 | if (ret) | |
371 | goto out; | |
372 | ||
373 | ret = copy_page_from_iter(buf->page, offset, chars, from); | |
374 | if (unlikely(ret < chars)) { | |
375 | ret = -EFAULT; | |
376 | goto out; | |
377 | } | |
378 | do_wakeup = 1; | |
379 | buf->len += ret; | |
380 | if (!iov_iter_count(from)) | |
381 | goto out; | |
382 | } | |
383 | } | |
384 | ||
385 | for (;;) { | |
386 | int bufs; | |
387 | ||
388 | if (!pipe->readers) { | |
389 | send_sig(SIGPIPE, current, 0); | |
390 | if (!ret) | |
391 | ret = -EPIPE; | |
392 | break; | |
393 | } | |
394 | bufs = pipe->nrbufs; | |
395 | if (bufs < pipe->buffers) { | |
396 | int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1); | |
397 | struct pipe_buffer *buf = pipe->bufs + newbuf; | |
398 | struct page *page = pipe->tmp_page; | |
399 | int copied; | |
400 | ||
401 | if (!page) { | |
402 | page = alloc_page(GFP_HIGHUSER); | |
403 | if (unlikely(!page)) { | |
404 | ret = ret ? : -ENOMEM; | |
405 | break; | |
406 | } | |
407 | pipe->tmp_page = page; | |
408 | } | |
409 | /* Always wake up, even if the copy fails. Otherwise | |
410 | * we lock up (O_NONBLOCK-)readers that sleep due to | |
411 | * syscall merging. | |
412 | * FIXME! Is this really true? | |
413 | */ | |
414 | do_wakeup = 1; | |
415 | copied = copy_page_from_iter(page, 0, PAGE_SIZE, from); | |
416 | if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) { | |
417 | if (!ret) | |
418 | ret = -EFAULT; | |
419 | break; | |
420 | } | |
421 | ret += copied; | |
422 | ||
423 | /* Insert it into the buffer array */ | |
424 | buf->page = page; | |
425 | buf->ops = &anon_pipe_buf_ops; | |
426 | buf->offset = 0; | |
427 | buf->len = copied; | |
428 | buf->flags = 0; | |
429 | if (is_packetized(filp)) { | |
430 | buf->ops = &packet_pipe_buf_ops; | |
431 | buf->flags = PIPE_BUF_FLAG_PACKET; | |
432 | } | |
433 | pipe->nrbufs = ++bufs; | |
434 | pipe->tmp_page = NULL; | |
435 | ||
436 | if (!iov_iter_count(from)) | |
437 | break; | |
438 | } | |
439 | if (bufs < pipe->buffers) | |
440 | continue; | |
441 | if (filp->f_flags & O_NONBLOCK) { | |
442 | if (!ret) | |
443 | ret = -EAGAIN; | |
444 | break; | |
445 | } | |
446 | if (signal_pending(current)) { | |
447 | if (!ret) | |
448 | ret = -ERESTARTSYS; | |
449 | break; | |
450 | } | |
451 | if (do_wakeup) { | |
452 | wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM); | |
453 | kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); | |
454 | do_wakeup = 0; | |
455 | } | |
456 | pipe->waiting_writers++; | |
457 | pipe_wait(pipe); | |
458 | pipe->waiting_writers--; | |
459 | } | |
460 | out: | |
461 | __pipe_unlock(pipe); | |
462 | if (do_wakeup) { | |
463 | wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM); | |
464 | kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); | |
465 | } | |
466 | if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) { | |
467 | int err = file_update_time(filp); | |
468 | if (err) | |
469 | ret = err; | |
470 | sb_end_write(file_inode(filp)->i_sb); | |
471 | } | |
472 | return ret; | |
473 | } | |
474 | ||
475 | static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) | |
476 | { | |
477 | struct pipe_inode_info *pipe = filp->private_data; | |
478 | int count, buf, nrbufs; | |
479 | ||
480 | switch (cmd) { | |
481 | case FIONREAD: | |
482 | __pipe_lock(pipe); | |
483 | count = 0; | |
484 | buf = pipe->curbuf; | |
485 | nrbufs = pipe->nrbufs; | |
486 | while (--nrbufs >= 0) { | |
487 | count += pipe->bufs[buf].len; | |
488 | buf = (buf+1) & (pipe->buffers - 1); | |
489 | } | |
490 | __pipe_unlock(pipe); | |
491 | ||
492 | return put_user(count, (int __user *)arg); | |
493 | default: | |
494 | return -ENOIOCTLCMD; | |
495 | } | |
496 | } | |
497 | ||
498 | /* No kernel lock held - fine */ | |
499 | static unsigned int | |
500 | pipe_poll(struct file *filp, poll_table *wait) | |
501 | { | |
502 | unsigned int mask; | |
503 | struct pipe_inode_info *pipe = filp->private_data; | |
504 | int nrbufs; | |
505 | ||
506 | poll_wait(filp, &pipe->wait, wait); | |
507 | ||
508 | /* Reading only -- no need for acquiring the semaphore. */ | |
509 | nrbufs = pipe->nrbufs; | |
510 | mask = 0; | |
511 | if (filp->f_mode & FMODE_READ) { | |
512 | mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0; | |
513 | if (!pipe->writers && filp->f_version != pipe->w_counter) | |
514 | mask |= POLLHUP; | |
515 | } | |
516 | ||
517 | if (filp->f_mode & FMODE_WRITE) { | |
518 | mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0; | |
519 | /* | |
520 | * Most Unices do not set POLLERR for FIFOs but on Linux they | |
521 | * behave exactly like pipes for poll(). | |
522 | */ | |
523 | if (!pipe->readers) | |
524 | mask |= POLLERR; | |
525 | } | |
526 | ||
527 | return mask; | |
528 | } | |
529 | ||
530 | static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe) | |
531 | { | |
532 | int kill = 0; | |
533 | ||
534 | spin_lock(&inode->i_lock); | |
535 | if (!--pipe->files) { | |
536 | inode->i_pipe = NULL; | |
537 | kill = 1; | |
538 | } | |
539 | spin_unlock(&inode->i_lock); | |
540 | ||
541 | if (kill) | |
542 | free_pipe_info(pipe); | |
543 | } | |
544 | ||
545 | static int | |
546 | pipe_release(struct inode *inode, struct file *file) | |
547 | { | |
548 | struct pipe_inode_info *pipe = file->private_data; | |
549 | ||
550 | __pipe_lock(pipe); | |
551 | if (file->f_mode & FMODE_READ) | |
552 | pipe->readers--; | |
553 | if (file->f_mode & FMODE_WRITE) | |
554 | pipe->writers--; | |
555 | ||
556 | if (pipe->readers || pipe->writers) { | |
557 | wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP); | |
558 | kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); | |
559 | kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); | |
560 | } | |
561 | __pipe_unlock(pipe); | |
562 | ||
563 | put_pipe_info(inode, pipe); | |
564 | return 0; | |
565 | } | |
566 | ||
567 | static int | |
568 | pipe_fasync(int fd, struct file *filp, int on) | |
569 | { | |
570 | struct pipe_inode_info *pipe = filp->private_data; | |
571 | int retval = 0; | |
572 | ||
573 | __pipe_lock(pipe); | |
574 | if (filp->f_mode & FMODE_READ) | |
575 | retval = fasync_helper(fd, filp, on, &pipe->fasync_readers); | |
576 | if ((filp->f_mode & FMODE_WRITE) && retval >= 0) { | |
577 | retval = fasync_helper(fd, filp, on, &pipe->fasync_writers); | |
578 | if (retval < 0 && (filp->f_mode & FMODE_READ)) | |
579 | /* this can happen only if on == T */ | |
580 | fasync_helper(-1, filp, 0, &pipe->fasync_readers); | |
581 | } | |
582 | __pipe_unlock(pipe); | |
583 | return retval; | |
584 | } | |
585 | ||
586 | struct pipe_inode_info *alloc_pipe_info(void) | |
587 | { | |
588 | struct pipe_inode_info *pipe; | |
589 | ||
590 | pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL); | |
591 | if (pipe) { | |
592 | pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL); | |
593 | if (pipe->bufs) { | |
594 | init_waitqueue_head(&pipe->wait); | |
595 | pipe->r_counter = pipe->w_counter = 1; | |
596 | pipe->buffers = PIPE_DEF_BUFFERS; | |
597 | mutex_init(&pipe->mutex); | |
598 | return pipe; | |
599 | } | |
600 | kfree(pipe); | |
601 | } | |
602 | ||
603 | return NULL; | |
604 | } | |
605 | ||
606 | void free_pipe_info(struct pipe_inode_info *pipe) | |
607 | { | |
608 | int i; | |
609 | ||
610 | for (i = 0; i < pipe->buffers; i++) { | |
611 | struct pipe_buffer *buf = pipe->bufs + i; | |
612 | if (buf->ops) | |
613 | buf->ops->release(pipe, buf); | |
614 | } | |
615 | if (pipe->tmp_page) | |
616 | __free_page(pipe->tmp_page); | |
617 | kfree(pipe->bufs); | |
618 | kfree(pipe); | |
619 | } | |
620 | ||
621 | static struct vfsmount *pipe_mnt __read_mostly; | |
622 | ||
623 | /* | |
624 | * pipefs_dname() is called from d_path(). | |
625 | */ | |
626 | static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen) | |
627 | { | |
628 | return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]", | |
629 | d_inode(dentry)->i_ino); | |
630 | } | |
631 | ||
632 | static const struct dentry_operations pipefs_dentry_operations = { | |
633 | .d_dname = pipefs_dname, | |
634 | }; | |
635 | ||
636 | static struct inode * get_pipe_inode(void) | |
637 | { | |
638 | struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb); | |
639 | struct pipe_inode_info *pipe; | |
640 | ||
641 | if (!inode) | |
642 | goto fail_inode; | |
643 | ||
644 | inode->i_ino = get_next_ino(); | |
645 | ||
646 | pipe = alloc_pipe_info(); | |
647 | if (!pipe) | |
648 | goto fail_iput; | |
649 | ||
650 | inode->i_pipe = pipe; | |
651 | pipe->files = 2; | |
652 | pipe->readers = pipe->writers = 1; | |
653 | inode->i_fop = &pipefifo_fops; | |
654 | ||
655 | /* | |
656 | * Mark the inode dirty from the very beginning, | |
657 | * that way it will never be moved to the dirty | |
658 | * list because "mark_inode_dirty()" will think | |
659 | * that it already _is_ on the dirty list. | |
660 | */ | |
661 | inode->i_state = I_DIRTY; | |
662 | inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR; | |
663 | inode->i_uid = current_fsuid(); | |
664 | inode->i_gid = current_fsgid(); | |
665 | inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; | |
666 | ||
667 | return inode; | |
668 | ||
669 | fail_iput: | |
670 | iput(inode); | |
671 | ||
672 | fail_inode: | |
673 | return NULL; | |
674 | } | |
675 | ||
676 | int create_pipe_files(struct file **res, int flags) | |
677 | { | |
678 | int err; | |
679 | struct inode *inode = get_pipe_inode(); | |
680 | struct file *f; | |
681 | struct path path; | |
682 | static struct qstr name = { .name = "" }; | |
683 | ||
684 | if (!inode) | |
685 | return -ENFILE; | |
686 | ||
687 | err = -ENOMEM; | |
688 | path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name); | |
689 | if (!path.dentry) | |
690 | goto err_inode; | |
691 | path.mnt = mntget(pipe_mnt); | |
692 | ||
693 | d_instantiate(path.dentry, inode); | |
694 | ||
695 | f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops); | |
696 | if (IS_ERR(f)) { | |
697 | err = PTR_ERR(f); | |
698 | goto err_dentry; | |
699 | } | |
700 | ||
701 | f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)); | |
702 | f->private_data = inode->i_pipe; | |
703 | ||
704 | res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops); | |
705 | if (IS_ERR(res[0])) { | |
706 | err = PTR_ERR(res[0]); | |
707 | goto err_file; | |
708 | } | |
709 | ||
710 | path_get(&path); | |
711 | res[0]->private_data = inode->i_pipe; | |
712 | res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK); | |
713 | res[1] = f; | |
714 | return 0; | |
715 | ||
716 | err_file: | |
717 | put_filp(f); | |
718 | err_dentry: | |
719 | free_pipe_info(inode->i_pipe); | |
720 | path_put(&path); | |
721 | return err; | |
722 | ||
723 | err_inode: | |
724 | free_pipe_info(inode->i_pipe); | |
725 | iput(inode); | |
726 | return err; | |
727 | } | |
728 | ||
729 | static int __do_pipe_flags(int *fd, struct file **files, int flags) | |
730 | { | |
731 | int error; | |
732 | int fdw, fdr; | |
733 | ||
734 | if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT)) | |
735 | return -EINVAL; | |
736 | ||
737 | error = create_pipe_files(files, flags); | |
738 | if (error) | |
739 | return error; | |
740 | ||
741 | error = get_unused_fd_flags(flags); | |
742 | if (error < 0) | |
743 | goto err_read_pipe; | |
744 | fdr = error; | |
745 | ||
746 | error = get_unused_fd_flags(flags); | |
747 | if (error < 0) | |
748 | goto err_fdr; | |
749 | fdw = error; | |
750 | ||
751 | audit_fd_pair(fdr, fdw); | |
752 | fd[0] = fdr; | |
753 | fd[1] = fdw; | |
754 | return 0; | |
755 | ||
756 | err_fdr: | |
757 | put_unused_fd(fdr); | |
758 | err_read_pipe: | |
759 | fput(files[0]); | |
760 | fput(files[1]); | |
761 | return error; | |
762 | } | |
763 | ||
764 | int do_pipe_flags(int *fd, int flags) | |
765 | { | |
766 | struct file *files[2]; | |
767 | int error = __do_pipe_flags(fd, files, flags); | |
768 | if (!error) { | |
769 | fd_install(fd[0], files[0]); | |
770 | fd_install(fd[1], files[1]); | |
771 | } | |
772 | return error; | |
773 | } | |
774 | ||
775 | /* | |
776 | * sys_pipe() is the normal C calling standard for creating | |
777 | * a pipe. It's not the way Unix traditionally does this, though. | |
778 | */ | |
779 | SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags) | |
780 | { | |
781 | struct file *files[2]; | |
782 | int fd[2]; | |
783 | int error; | |
784 | ||
785 | error = __do_pipe_flags(fd, files, flags); | |
786 | if (!error) { | |
787 | if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) { | |
788 | fput(files[0]); | |
789 | fput(files[1]); | |
790 | put_unused_fd(fd[0]); | |
791 | put_unused_fd(fd[1]); | |
792 | error = -EFAULT; | |
793 | } else { | |
794 | fd_install(fd[0], files[0]); | |
795 | fd_install(fd[1], files[1]); | |
796 | } | |
797 | } | |
798 | return error; | |
799 | } | |
800 | ||
801 | SYSCALL_DEFINE1(pipe, int __user *, fildes) | |
802 | { | |
803 | return sys_pipe2(fildes, 0); | |
804 | } | |
805 | ||
806 | static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt) | |
807 | { | |
808 | int cur = *cnt; | |
809 | ||
810 | while (cur == *cnt) { | |
811 | pipe_wait(pipe); | |
812 | if (signal_pending(current)) | |
813 | break; | |
814 | } | |
815 | return cur == *cnt ? -ERESTARTSYS : 0; | |
816 | } | |
817 | ||
818 | static void wake_up_partner(struct pipe_inode_info *pipe) | |
819 | { | |
820 | wake_up_interruptible(&pipe->wait); | |
821 | } | |
822 | ||
823 | static int fifo_open(struct inode *inode, struct file *filp) | |
824 | { | |
825 | struct pipe_inode_info *pipe; | |
826 | bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC; | |
827 | int ret; | |
828 | ||
829 | filp->f_version = 0; | |
830 | ||
831 | spin_lock(&inode->i_lock); | |
832 | if (inode->i_pipe) { | |
833 | pipe = inode->i_pipe; | |
834 | pipe->files++; | |
835 | spin_unlock(&inode->i_lock); | |
836 | } else { | |
837 | spin_unlock(&inode->i_lock); | |
838 | pipe = alloc_pipe_info(); | |
839 | if (!pipe) | |
840 | return -ENOMEM; | |
841 | pipe->files = 1; | |
842 | spin_lock(&inode->i_lock); | |
843 | if (unlikely(inode->i_pipe)) { | |
844 | inode->i_pipe->files++; | |
845 | spin_unlock(&inode->i_lock); | |
846 | free_pipe_info(pipe); | |
847 | pipe = inode->i_pipe; | |
848 | } else { | |
849 | inode->i_pipe = pipe; | |
850 | spin_unlock(&inode->i_lock); | |
851 | } | |
852 | } | |
853 | filp->private_data = pipe; | |
854 | /* OK, we have a pipe and it's pinned down */ | |
855 | ||
856 | __pipe_lock(pipe); | |
857 | ||
858 | /* We can only do regular read/write on fifos */ | |
859 | filp->f_mode &= (FMODE_READ | FMODE_WRITE); | |
860 | ||
861 | switch (filp->f_mode) { | |
862 | case FMODE_READ: | |
863 | /* | |
864 | * O_RDONLY | |
865 | * POSIX.1 says that O_NONBLOCK means return with the FIFO | |
866 | * opened, even when there is no process writing the FIFO. | |
867 | */ | |
868 | pipe->r_counter++; | |
869 | if (pipe->readers++ == 0) | |
870 | wake_up_partner(pipe); | |
871 | ||
872 | if (!is_pipe && !pipe->writers) { | |
873 | if ((filp->f_flags & O_NONBLOCK)) { | |
874 | /* suppress POLLHUP until we have | |
875 | * seen a writer */ | |
876 | filp->f_version = pipe->w_counter; | |
877 | } else { | |
878 | if (wait_for_partner(pipe, &pipe->w_counter)) | |
879 | goto err_rd; | |
880 | } | |
881 | } | |
882 | break; | |
883 | ||
884 | case FMODE_WRITE: | |
885 | /* | |
886 | * O_WRONLY | |
887 | * POSIX.1 says that O_NONBLOCK means return -1 with | |
888 | * errno=ENXIO when there is no process reading the FIFO. | |
889 | */ | |
890 | ret = -ENXIO; | |
891 | if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers) | |
892 | goto err; | |
893 | ||
894 | pipe->w_counter++; | |
895 | if (!pipe->writers++) | |
896 | wake_up_partner(pipe); | |
897 | ||
898 | if (!is_pipe && !pipe->readers) { | |
899 | if (wait_for_partner(pipe, &pipe->r_counter)) | |
900 | goto err_wr; | |
901 | } | |
902 | break; | |
903 | ||
904 | case FMODE_READ | FMODE_WRITE: | |
905 | /* | |
906 | * O_RDWR | |
907 | * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set. | |
908 | * This implementation will NEVER block on a O_RDWR open, since | |
909 | * the process can at least talk to itself. | |
910 | */ | |
911 | ||
912 | pipe->readers++; | |
913 | pipe->writers++; | |
914 | pipe->r_counter++; | |
915 | pipe->w_counter++; | |
916 | if (pipe->readers == 1 || pipe->writers == 1) | |
917 | wake_up_partner(pipe); | |
918 | break; | |
919 | ||
920 | default: | |
921 | ret = -EINVAL; | |
922 | goto err; | |
923 | } | |
924 | ||
925 | /* Ok! */ | |
926 | __pipe_unlock(pipe); | |
927 | return 0; | |
928 | ||
929 | err_rd: | |
930 | if (!--pipe->readers) | |
931 | wake_up_interruptible(&pipe->wait); | |
932 | ret = -ERESTARTSYS; | |
933 | goto err; | |
934 | ||
935 | err_wr: | |
936 | if (!--pipe->writers) | |
937 | wake_up_interruptible(&pipe->wait); | |
938 | ret = -ERESTARTSYS; | |
939 | goto err; | |
940 | ||
941 | err: | |
942 | __pipe_unlock(pipe); | |
943 | ||
944 | put_pipe_info(inode, pipe); | |
945 | return ret; | |
946 | } | |
947 | ||
948 | const struct file_operations pipefifo_fops = { | |
949 | .open = fifo_open, | |
950 | .llseek = no_llseek, | |
951 | .read_iter = pipe_read, | |
952 | .write_iter = pipe_write, | |
953 | .poll = pipe_poll, | |
954 | .unlocked_ioctl = pipe_ioctl, | |
955 | .release = pipe_release, | |
956 | .fasync = pipe_fasync, | |
957 | }; | |
958 | ||
959 | /* | |
960 | * Allocate a new array of pipe buffers and copy the info over. Returns the | |
961 | * pipe size if successful, or return -ERROR on error. | |
962 | */ | |
963 | static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages) | |
964 | { | |
965 | struct pipe_buffer *bufs; | |
966 | ||
967 | /* | |
968 | * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't | |
969 | * expect a lot of shrink+grow operations, just free and allocate | |
970 | * again like we would do for growing. If the pipe currently | |
971 | * contains more buffers than arg, then return busy. | |
972 | */ | |
973 | if (nr_pages < pipe->nrbufs) | |
974 | return -EBUSY; | |
975 | ||
976 | bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN); | |
977 | if (unlikely(!bufs)) | |
978 | return -ENOMEM; | |
979 | ||
980 | /* | |
981 | * The pipe array wraps around, so just start the new one at zero | |
982 | * and adjust the indexes. | |
983 | */ | |
984 | if (pipe->nrbufs) { | |
985 | unsigned int tail; | |
986 | unsigned int head; | |
987 | ||
988 | tail = pipe->curbuf + pipe->nrbufs; | |
989 | if (tail < pipe->buffers) | |
990 | tail = 0; | |
991 | else | |
992 | tail &= (pipe->buffers - 1); | |
993 | ||
994 | head = pipe->nrbufs - tail; | |
995 | if (head) | |
996 | memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer)); | |
997 | if (tail) | |
998 | memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer)); | |
999 | } | |
1000 | ||
1001 | pipe->curbuf = 0; | |
1002 | kfree(pipe->bufs); | |
1003 | pipe->bufs = bufs; | |
1004 | pipe->buffers = nr_pages; | |
1005 | return nr_pages * PAGE_SIZE; | |
1006 | } | |
1007 | ||
1008 | /* | |
1009 | * Currently we rely on the pipe array holding a power-of-2 number | |
1010 | * of pages. | |
1011 | */ | |
1012 | static inline unsigned int round_pipe_size(unsigned int size) | |
1013 | { | |
1014 | unsigned long nr_pages; | |
1015 | ||
1016 | nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; | |
1017 | return roundup_pow_of_two(nr_pages) << PAGE_SHIFT; | |
1018 | } | |
1019 | ||
1020 | /* | |
1021 | * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax | |
1022 | * will return an error. | |
1023 | */ | |
1024 | int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf, | |
1025 | size_t *lenp, loff_t *ppos) | |
1026 | { | |
1027 | int ret; | |
1028 | ||
1029 | ret = proc_dointvec_minmax(table, write, buf, lenp, ppos); | |
1030 | if (ret < 0 || !write) | |
1031 | return ret; | |
1032 | ||
1033 | pipe_max_size = round_pipe_size(pipe_max_size); | |
1034 | return ret; | |
1035 | } | |
1036 | ||
1037 | /* | |
1038 | * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same | |
1039 | * location, so checking ->i_pipe is not enough to verify that this is a | |
1040 | * pipe. | |
1041 | */ | |
1042 | struct pipe_inode_info *get_pipe_info(struct file *file) | |
1043 | { | |
1044 | return file->f_op == &pipefifo_fops ? file->private_data : NULL; | |
1045 | } | |
1046 | ||
1047 | long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg) | |
1048 | { | |
1049 | struct pipe_inode_info *pipe; | |
1050 | long ret; | |
1051 | ||
1052 | pipe = get_pipe_info(file); | |
1053 | if (!pipe) | |
1054 | return -EBADF; | |
1055 | ||
1056 | __pipe_lock(pipe); | |
1057 | ||
1058 | switch (cmd) { | |
1059 | case F_SETPIPE_SZ: { | |
1060 | unsigned int size, nr_pages; | |
1061 | ||
1062 | size = round_pipe_size(arg); | |
1063 | nr_pages = size >> PAGE_SHIFT; | |
1064 | ||
1065 | ret = -EINVAL; | |
1066 | if (!nr_pages) | |
1067 | goto out; | |
1068 | ||
1069 | if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) { | |
1070 | ret = -EPERM; | |
1071 | goto out; | |
1072 | } | |
1073 | ret = pipe_set_size(pipe, nr_pages); | |
1074 | break; | |
1075 | } | |
1076 | case F_GETPIPE_SZ: | |
1077 | ret = pipe->buffers * PAGE_SIZE; | |
1078 | break; | |
1079 | default: | |
1080 | ret = -EINVAL; | |
1081 | break; | |
1082 | } | |
1083 | ||
1084 | out: | |
1085 | __pipe_unlock(pipe); | |
1086 | return ret; | |
1087 | } | |
1088 | ||
1089 | static const struct super_operations pipefs_ops = { | |
1090 | .destroy_inode = free_inode_nonrcu, | |
1091 | .statfs = simple_statfs, | |
1092 | }; | |
1093 | ||
1094 | /* | |
1095 | * pipefs should _never_ be mounted by userland - too much of security hassle, | |
1096 | * no real gain from having the whole whorehouse mounted. So we don't need | |
1097 | * any operations on the root directory. However, we need a non-trivial | |
1098 | * d_name - pipe: will go nicely and kill the special-casing in procfs. | |
1099 | */ | |
1100 | static struct dentry *pipefs_mount(struct file_system_type *fs_type, | |
1101 | int flags, const char *dev_name, void *data) | |
1102 | { | |
1103 | return mount_pseudo(fs_type, "pipe:", &pipefs_ops, | |
1104 | &pipefs_dentry_operations, PIPEFS_MAGIC); | |
1105 | } | |
1106 | ||
1107 | static struct file_system_type pipe_fs_type = { | |
1108 | .name = "pipefs", | |
1109 | .mount = pipefs_mount, | |
1110 | .kill_sb = kill_anon_super, | |
1111 | }; | |
1112 | ||
1113 | static int __init init_pipe_fs(void) | |
1114 | { | |
1115 | int err = register_filesystem(&pipe_fs_type); | |
1116 | ||
1117 | if (!err) { | |
1118 | pipe_mnt = kern_mount(&pipe_fs_type); | |
1119 | if (IS_ERR(pipe_mnt)) { | |
1120 | err = PTR_ERR(pipe_mnt); | |
1121 | unregister_filesystem(&pipe_fs_type); | |
1122 | } | |
1123 | } | |
1124 | return err; | |
1125 | } | |
1126 | ||
1127 | fs_initcall(init_pipe_fs); |