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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 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
42 * matches default values.
43 */
44 unsigned long pipe_user_pages_hard;
45 unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
46
47 /*
48 * We use a start+len construction, which provides full use of the
49 * allocated memory.
50 * -- Florian Coosmann (FGC)
51 *
52 * Reads with count = 0 should always return 0.
53 * -- Julian Bradfield 1999-06-07.
54 *
55 * FIFOs and Pipes now generate SIGIO for both readers and writers.
56 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
57 *
58 * pipe_read & write cleanup
59 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
60 */
61
62 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
63 {
64 if (pipe->files)
65 mutex_lock_nested(&pipe->mutex, subclass);
66 }
67
68 void pipe_lock(struct pipe_inode_info *pipe)
69 {
70 /*
71 * pipe_lock() nests non-pipe inode locks (for writing to a file)
72 */
73 pipe_lock_nested(pipe, I_MUTEX_PARENT);
74 }
75 EXPORT_SYMBOL(pipe_lock);
76
77 void pipe_unlock(struct pipe_inode_info *pipe)
78 {
79 if (pipe->files)
80 mutex_unlock(&pipe->mutex);
81 }
82 EXPORT_SYMBOL(pipe_unlock);
83
84 static inline void __pipe_lock(struct pipe_inode_info *pipe)
85 {
86 mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
87 }
88
89 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
90 {
91 mutex_unlock(&pipe->mutex);
92 }
93
94 void pipe_double_lock(struct pipe_inode_info *pipe1,
95 struct pipe_inode_info *pipe2)
96 {
97 BUG_ON(pipe1 == pipe2);
98
99 if (pipe1 < pipe2) {
100 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
101 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
102 } else {
103 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
104 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
105 }
106 }
107
108 /* Drop the inode semaphore and wait for a pipe event, atomically */
109 void pipe_wait(struct pipe_inode_info *pipe)
110 {
111 DEFINE_WAIT(wait);
112
113 /*
114 * Pipes are system-local resources, so sleeping on them
115 * is considered a noninteractive wait:
116 */
117 prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
118 pipe_unlock(pipe);
119 schedule();
120 finish_wait(&pipe->wait, &wait);
121 pipe_lock(pipe);
122 }
123
124 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
125 struct pipe_buffer *buf)
126 {
127 struct page *page = buf->page;
128
129 /*
130 * If nobody else uses this page, and we don't already have a
131 * temporary page, let's keep track of it as a one-deep
132 * allocation cache. (Otherwise just release our reference to it)
133 */
134 if (page_count(page) == 1 && !pipe->tmp_page)
135 pipe->tmp_page = page;
136 else
137 page_cache_release(page);
138 }
139
140 /**
141 * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
142 * @pipe: the pipe that the buffer belongs to
143 * @buf: the buffer to attempt to steal
144 *
145 * Description:
146 * This function attempts to steal the &struct page attached to
147 * @buf. If successful, this function returns 0 and returns with
148 * the page locked. The caller may then reuse the page for whatever
149 * he wishes; the typical use is insertion into a different file
150 * page cache.
151 */
152 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
153 struct pipe_buffer *buf)
154 {
155 struct page *page = buf->page;
156
157 /*
158 * A reference of one is golden, that means that the owner of this
159 * page is the only one holding a reference to it. lock the page
160 * and return OK.
161 */
162 if (page_count(page) == 1) {
163 lock_page(page);
164 return 0;
165 }
166
167 return 1;
168 }
169 EXPORT_SYMBOL(generic_pipe_buf_steal);
170
171 /**
172 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
173 * @pipe: the pipe that the buffer belongs to
174 * @buf: the buffer to get a reference to
175 *
176 * Description:
177 * This function grabs an extra reference to @buf. It's used in
178 * in the tee() system call, when we duplicate the buffers in one
179 * pipe into another.
180 */
181 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
182 {
183 page_cache_get(buf->page);
184 }
185 EXPORT_SYMBOL(generic_pipe_buf_get);
186
187 /**
188 * generic_pipe_buf_confirm - verify contents of the pipe buffer
189 * @info: the pipe that the buffer belongs to
190 * @buf: the buffer to confirm
191 *
192 * Description:
193 * This function does nothing, because the generic pipe code uses
194 * pages that are always good when inserted into the pipe.
195 */
196 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
197 struct pipe_buffer *buf)
198 {
199 return 0;
200 }
201 EXPORT_SYMBOL(generic_pipe_buf_confirm);
202
203 /**
204 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
205 * @pipe: the pipe that the buffer belongs to
206 * @buf: the buffer to put a reference to
207 *
208 * Description:
209 * This function releases a reference to @buf.
210 */
211 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
212 struct pipe_buffer *buf)
213 {
214 page_cache_release(buf->page);
215 }
216 EXPORT_SYMBOL(generic_pipe_buf_release);
217
218 static const struct pipe_buf_operations anon_pipe_buf_ops = {
219 .can_merge = 1,
220 .confirm = generic_pipe_buf_confirm,
221 .release = anon_pipe_buf_release,
222 .steal = generic_pipe_buf_steal,
223 .get = generic_pipe_buf_get,
224 };
225
226 static const struct pipe_buf_operations packet_pipe_buf_ops = {
227 .can_merge = 0,
228 .confirm = generic_pipe_buf_confirm,
229 .release = anon_pipe_buf_release,
230 .steal = generic_pipe_buf_steal,
231 .get = generic_pipe_buf_get,
232 };
233
234 static ssize_t
235 pipe_read(struct kiocb *iocb, struct iov_iter *to)
236 {
237 size_t total_len = iov_iter_count(to);
238 struct file *filp = iocb->ki_filp;
239 struct pipe_inode_info *pipe = filp->private_data;
240 int do_wakeup;
241 ssize_t ret;
242
243 /* Null read succeeds. */
244 if (unlikely(total_len == 0))
245 return 0;
246
247 do_wakeup = 0;
248 ret = 0;
249 __pipe_lock(pipe);
250 for (;;) {
251 int bufs = pipe->nrbufs;
252 if (bufs) {
253 int curbuf = pipe->curbuf;
254 struct pipe_buffer *buf = pipe->bufs + curbuf;
255 const struct pipe_buf_operations *ops = buf->ops;
256 size_t chars = buf->len;
257 size_t written;
258 int error;
259
260 if (chars > total_len)
261 chars = total_len;
262
263 error = ops->confirm(pipe, buf);
264 if (error) {
265 if (!ret)
266 ret = error;
267 break;
268 }
269
270 written = copy_page_to_iter(buf->page, buf->offset, chars, to);
271 if (unlikely(written < chars)) {
272 if (!ret)
273 ret = -EFAULT;
274 break;
275 }
276 ret += chars;
277 buf->offset += chars;
278 buf->len -= chars;
279
280 /* Was it a packet buffer? Clean up and exit */
281 if (buf->flags & PIPE_BUF_FLAG_PACKET) {
282 total_len = chars;
283 buf->len = 0;
284 }
285
286 if (!buf->len) {
287 buf->ops = NULL;
288 ops->release(pipe, buf);
289 curbuf = (curbuf + 1) & (pipe->buffers - 1);
290 pipe->curbuf = curbuf;
291 pipe->nrbufs = --bufs;
292 do_wakeup = 1;
293 }
294 total_len -= chars;
295 if (!total_len)
296 break; /* common path: read succeeded */
297 }
298 if (bufs) /* More to do? */
299 continue;
300 if (!pipe->writers)
301 break;
302 if (!pipe->waiting_writers) {
303 /* syscall merging: Usually we must not sleep
304 * if O_NONBLOCK is set, or if we got some data.
305 * But if a writer sleeps in kernel space, then
306 * we can wait for that data without violating POSIX.
307 */
308 if (ret)
309 break;
310 if (filp->f_flags & O_NONBLOCK) {
311 ret = -EAGAIN;
312 break;
313 }
314 }
315 if (signal_pending(current)) {
316 if (!ret)
317 ret = -ERESTARTSYS;
318 break;
319 }
320 if (do_wakeup) {
321 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
322 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
323 }
324 pipe_wait(pipe);
325 }
326 __pipe_unlock(pipe);
327
328 /* Signal writers asynchronously that there is more room. */
329 if (do_wakeup) {
330 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
331 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
332 }
333 if (ret > 0)
334 file_accessed(filp);
335 return ret;
336 }
337
338 static inline int is_packetized(struct file *file)
339 {
340 return (file->f_flags & O_DIRECT) != 0;
341 }
342
343 static ssize_t
344 pipe_write(struct kiocb *iocb, struct iov_iter *from)
345 {
346 struct file *filp = iocb->ki_filp;
347 struct pipe_inode_info *pipe = filp->private_data;
348 ssize_t ret = 0;
349 int do_wakeup = 0;
350 size_t total_len = iov_iter_count(from);
351 ssize_t chars;
352
353 /* Null write succeeds. */
354 if (unlikely(total_len == 0))
355 return 0;
356
357 __pipe_lock(pipe);
358
359 if (!pipe->readers) {
360 send_sig(SIGPIPE, current, 0);
361 ret = -EPIPE;
362 goto out;
363 }
364
365 /* We try to merge small writes */
366 chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
367 if (pipe->nrbufs && chars != 0) {
368 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
369 (pipe->buffers - 1);
370 struct pipe_buffer *buf = pipe->bufs + lastbuf;
371 const struct pipe_buf_operations *ops = buf->ops;
372 int offset = buf->offset + buf->len;
373
374 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
375 ret = ops->confirm(pipe, buf);
376 if (ret)
377 goto out;
378
379 ret = copy_page_from_iter(buf->page, offset, chars, from);
380 if (unlikely(ret < chars)) {
381 ret = -EFAULT;
382 goto out;
383 }
384 do_wakeup = 1;
385 buf->len += ret;
386 if (!iov_iter_count(from))
387 goto out;
388 }
389 }
390
391 for (;;) {
392 int bufs;
393
394 if (!pipe->readers) {
395 send_sig(SIGPIPE, current, 0);
396 if (!ret)
397 ret = -EPIPE;
398 break;
399 }
400 bufs = pipe->nrbufs;
401 if (bufs < pipe->buffers) {
402 int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
403 struct pipe_buffer *buf = pipe->bufs + newbuf;
404 struct page *page = pipe->tmp_page;
405 int copied;
406
407 if (!page) {
408 page = alloc_page(GFP_HIGHUSER);
409 if (unlikely(!page)) {
410 ret = ret ? : -ENOMEM;
411 break;
412 }
413 pipe->tmp_page = page;
414 }
415 /* Always wake up, even if the copy fails. Otherwise
416 * we lock up (O_NONBLOCK-)readers that sleep due to
417 * syscall merging.
418 * FIXME! Is this really true?
419 */
420 do_wakeup = 1;
421 copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
422 if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
423 if (!ret)
424 ret = -EFAULT;
425 break;
426 }
427 ret += copied;
428
429 /* Insert it into the buffer array */
430 buf->page = page;
431 buf->ops = &anon_pipe_buf_ops;
432 buf->offset = 0;
433 buf->len = copied;
434 buf->flags = 0;
435 if (is_packetized(filp)) {
436 buf->ops = &packet_pipe_buf_ops;
437 buf->flags = PIPE_BUF_FLAG_PACKET;
438 }
439 pipe->nrbufs = ++bufs;
440 pipe->tmp_page = NULL;
441
442 if (!iov_iter_count(from))
443 break;
444 }
445 if (bufs < pipe->buffers)
446 continue;
447 if (filp->f_flags & O_NONBLOCK) {
448 if (!ret)
449 ret = -EAGAIN;
450 break;
451 }
452 if (signal_pending(current)) {
453 if (!ret)
454 ret = -ERESTARTSYS;
455 break;
456 }
457 if (do_wakeup) {
458 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
459 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
460 do_wakeup = 0;
461 }
462 pipe->waiting_writers++;
463 pipe_wait(pipe);
464 pipe->waiting_writers--;
465 }
466 out:
467 __pipe_unlock(pipe);
468 if (do_wakeup) {
469 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
470 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
471 }
472 if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
473 int err = file_update_time(filp);
474 if (err)
475 ret = err;
476 sb_end_write(file_inode(filp)->i_sb);
477 }
478 return ret;
479 }
480
481 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
482 {
483 struct pipe_inode_info *pipe = filp->private_data;
484 int count, buf, nrbufs;
485
486 switch (cmd) {
487 case FIONREAD:
488 __pipe_lock(pipe);
489 count = 0;
490 buf = pipe->curbuf;
491 nrbufs = pipe->nrbufs;
492 while (--nrbufs >= 0) {
493 count += pipe->bufs[buf].len;
494 buf = (buf+1) & (pipe->buffers - 1);
495 }
496 __pipe_unlock(pipe);
497
498 return put_user(count, (int __user *)arg);
499 default:
500 return -ENOIOCTLCMD;
501 }
502 }
503
504 /* No kernel lock held - fine */
505 static unsigned int
506 pipe_poll(struct file *filp, poll_table *wait)
507 {
508 unsigned int mask;
509 struct pipe_inode_info *pipe = filp->private_data;
510 int nrbufs;
511
512 poll_wait(filp, &pipe->wait, wait);
513
514 /* Reading only -- no need for acquiring the semaphore. */
515 nrbufs = pipe->nrbufs;
516 mask = 0;
517 if (filp->f_mode & FMODE_READ) {
518 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
519 if (!pipe->writers && filp->f_version != pipe->w_counter)
520 mask |= POLLHUP;
521 }
522
523 if (filp->f_mode & FMODE_WRITE) {
524 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
525 /*
526 * Most Unices do not set POLLERR for FIFOs but on Linux they
527 * behave exactly like pipes for poll().
528 */
529 if (!pipe->readers)
530 mask |= POLLERR;
531 }
532
533 return mask;
534 }
535
536 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
537 {
538 int kill = 0;
539
540 spin_lock(&inode->i_lock);
541 if (!--pipe->files) {
542 inode->i_pipe = NULL;
543 kill = 1;
544 }
545 spin_unlock(&inode->i_lock);
546
547 if (kill)
548 free_pipe_info(pipe);
549 }
550
551 static int
552 pipe_release(struct inode *inode, struct file *file)
553 {
554 struct pipe_inode_info *pipe = file->private_data;
555
556 __pipe_lock(pipe);
557 if (file->f_mode & FMODE_READ)
558 pipe->readers--;
559 if (file->f_mode & FMODE_WRITE)
560 pipe->writers--;
561
562 if (pipe->readers || pipe->writers) {
563 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
564 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
565 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
566 }
567 __pipe_unlock(pipe);
568
569 put_pipe_info(inode, pipe);
570 return 0;
571 }
572
573 static int
574 pipe_fasync(int fd, struct file *filp, int on)
575 {
576 struct pipe_inode_info *pipe = filp->private_data;
577 int retval = 0;
578
579 __pipe_lock(pipe);
580 if (filp->f_mode & FMODE_READ)
581 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
582 if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
583 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
584 if (retval < 0 && (filp->f_mode & FMODE_READ))
585 /* this can happen only if on == T */
586 fasync_helper(-1, filp, 0, &pipe->fasync_readers);
587 }
588 __pipe_unlock(pipe);
589 return retval;
590 }
591
592 static void account_pipe_buffers(struct pipe_inode_info *pipe,
593 unsigned long old, unsigned long new)
594 {
595 atomic_long_add(new - old, &pipe->user->pipe_bufs);
596 }
597
598 static bool too_many_pipe_buffers_soft(struct user_struct *user)
599 {
600 return pipe_user_pages_soft &&
601 atomic_long_read(&user->pipe_bufs) >= pipe_user_pages_soft;
602 }
603
604 static bool too_many_pipe_buffers_hard(struct user_struct *user)
605 {
606 return pipe_user_pages_hard &&
607 atomic_long_read(&user->pipe_bufs) >= pipe_user_pages_hard;
608 }
609
610 struct pipe_inode_info *alloc_pipe_info(void)
611 {
612 struct pipe_inode_info *pipe;
613
614 pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
615 if (pipe) {
616 unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
617 struct user_struct *user = get_current_user();
618
619 if (!too_many_pipe_buffers_hard(user)) {
620 if (too_many_pipe_buffers_soft(user))
621 pipe_bufs = 1;
622 pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * pipe_bufs, GFP_KERNEL);
623 }
624
625 if (pipe->bufs) {
626 init_waitqueue_head(&pipe->wait);
627 pipe->r_counter = pipe->w_counter = 1;
628 pipe->buffers = pipe_bufs;
629 pipe->user = user;
630 account_pipe_buffers(pipe, 0, pipe_bufs);
631 mutex_init(&pipe->mutex);
632 return pipe;
633 }
634 free_uid(user);
635 kfree(pipe);
636 }
637
638 return NULL;
639 }
640
641 void free_pipe_info(struct pipe_inode_info *pipe)
642 {
643 int i;
644
645 account_pipe_buffers(pipe, pipe->buffers, 0);
646 free_uid(pipe->user);
647 for (i = 0; i < pipe->buffers; i++) {
648 struct pipe_buffer *buf = pipe->bufs + i;
649 if (buf->ops)
650 buf->ops->release(pipe, buf);
651 }
652 if (pipe->tmp_page)
653 __free_page(pipe->tmp_page);
654 kfree(pipe->bufs);
655 kfree(pipe);
656 }
657
658 static struct vfsmount *pipe_mnt __read_mostly;
659
660 /*
661 * pipefs_dname() is called from d_path().
662 */
663 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
664 {
665 return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
666 d_inode(dentry)->i_ino);
667 }
668
669 static const struct dentry_operations pipefs_dentry_operations = {
670 .d_dname = pipefs_dname,
671 };
672
673 static struct inode * get_pipe_inode(void)
674 {
675 struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
676 struct pipe_inode_info *pipe;
677
678 if (!inode)
679 goto fail_inode;
680
681 inode->i_ino = get_next_ino();
682
683 pipe = alloc_pipe_info();
684 if (!pipe)
685 goto fail_iput;
686
687 inode->i_pipe = pipe;
688 pipe->files = 2;
689 pipe->readers = pipe->writers = 1;
690 inode->i_fop = &pipefifo_fops;
691
692 /*
693 * Mark the inode dirty from the very beginning,
694 * that way it will never be moved to the dirty
695 * list because "mark_inode_dirty()" will think
696 * that it already _is_ on the dirty list.
697 */
698 inode->i_state = I_DIRTY;
699 inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
700 inode->i_uid = current_fsuid();
701 inode->i_gid = current_fsgid();
702 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
703
704 return inode;
705
706 fail_iput:
707 iput(inode);
708
709 fail_inode:
710 return NULL;
711 }
712
713 int create_pipe_files(struct file **res, int flags)
714 {
715 int err;
716 struct inode *inode = get_pipe_inode();
717 struct file *f;
718 struct path path;
719 static struct qstr name = { .name = "" };
720
721 if (!inode)
722 return -ENFILE;
723
724 err = -ENOMEM;
725 path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
726 if (!path.dentry)
727 goto err_inode;
728 path.mnt = mntget(pipe_mnt);
729
730 d_instantiate(path.dentry, inode);
731
732 f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops);
733 if (IS_ERR(f)) {
734 err = PTR_ERR(f);
735 goto err_dentry;
736 }
737
738 f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
739 f->private_data = inode->i_pipe;
740
741 res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
742 if (IS_ERR(res[0])) {
743 err = PTR_ERR(res[0]);
744 goto err_file;
745 }
746
747 path_get(&path);
748 res[0]->private_data = inode->i_pipe;
749 res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
750 res[1] = f;
751 return 0;
752
753 err_file:
754 put_filp(f);
755 err_dentry:
756 free_pipe_info(inode->i_pipe);
757 path_put(&path);
758 return err;
759
760 err_inode:
761 free_pipe_info(inode->i_pipe);
762 iput(inode);
763 return err;
764 }
765
766 static int __do_pipe_flags(int *fd, struct file **files, int flags)
767 {
768 int error;
769 int fdw, fdr;
770
771 if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
772 return -EINVAL;
773
774 error = create_pipe_files(files, flags);
775 if (error)
776 return error;
777
778 error = get_unused_fd_flags(flags);
779 if (error < 0)
780 goto err_read_pipe;
781 fdr = error;
782
783 error = get_unused_fd_flags(flags);
784 if (error < 0)
785 goto err_fdr;
786 fdw = error;
787
788 audit_fd_pair(fdr, fdw);
789 fd[0] = fdr;
790 fd[1] = fdw;
791 return 0;
792
793 err_fdr:
794 put_unused_fd(fdr);
795 err_read_pipe:
796 fput(files[0]);
797 fput(files[1]);
798 return error;
799 }
800
801 int do_pipe_flags(int *fd, int flags)
802 {
803 struct file *files[2];
804 int error = __do_pipe_flags(fd, files, flags);
805 if (!error) {
806 fd_install(fd[0], files[0]);
807 fd_install(fd[1], files[1]);
808 }
809 return error;
810 }
811
812 /*
813 * sys_pipe() is the normal C calling standard for creating
814 * a pipe. It's not the way Unix traditionally does this, though.
815 */
816 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
817 {
818 struct file *files[2];
819 int fd[2];
820 int error;
821
822 error = __do_pipe_flags(fd, files, flags);
823 if (!error) {
824 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
825 fput(files[0]);
826 fput(files[1]);
827 put_unused_fd(fd[0]);
828 put_unused_fd(fd[1]);
829 error = -EFAULT;
830 } else {
831 fd_install(fd[0], files[0]);
832 fd_install(fd[1], files[1]);
833 }
834 }
835 return error;
836 }
837
838 SYSCALL_DEFINE1(pipe, int __user *, fildes)
839 {
840 return sys_pipe2(fildes, 0);
841 }
842
843 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
844 {
845 int cur = *cnt;
846
847 while (cur == *cnt) {
848 pipe_wait(pipe);
849 if (signal_pending(current))
850 break;
851 }
852 return cur == *cnt ? -ERESTARTSYS : 0;
853 }
854
855 static void wake_up_partner(struct pipe_inode_info *pipe)
856 {
857 wake_up_interruptible(&pipe->wait);
858 }
859
860 static int fifo_open(struct inode *inode, struct file *filp)
861 {
862 struct pipe_inode_info *pipe;
863 bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
864 int ret;
865
866 filp->f_version = 0;
867
868 spin_lock(&inode->i_lock);
869 if (inode->i_pipe) {
870 pipe = inode->i_pipe;
871 pipe->files++;
872 spin_unlock(&inode->i_lock);
873 } else {
874 spin_unlock(&inode->i_lock);
875 pipe = alloc_pipe_info();
876 if (!pipe)
877 return -ENOMEM;
878 pipe->files = 1;
879 spin_lock(&inode->i_lock);
880 if (unlikely(inode->i_pipe)) {
881 inode->i_pipe->files++;
882 spin_unlock(&inode->i_lock);
883 free_pipe_info(pipe);
884 pipe = inode->i_pipe;
885 } else {
886 inode->i_pipe = pipe;
887 spin_unlock(&inode->i_lock);
888 }
889 }
890 filp->private_data = pipe;
891 /* OK, we have a pipe and it's pinned down */
892
893 __pipe_lock(pipe);
894
895 /* We can only do regular read/write on fifos */
896 filp->f_mode &= (FMODE_READ | FMODE_WRITE);
897
898 switch (filp->f_mode) {
899 case FMODE_READ:
900 /*
901 * O_RDONLY
902 * POSIX.1 says that O_NONBLOCK means return with the FIFO
903 * opened, even when there is no process writing the FIFO.
904 */
905 pipe->r_counter++;
906 if (pipe->readers++ == 0)
907 wake_up_partner(pipe);
908
909 if (!is_pipe && !pipe->writers) {
910 if ((filp->f_flags & O_NONBLOCK)) {
911 /* suppress POLLHUP until we have
912 * seen a writer */
913 filp->f_version = pipe->w_counter;
914 } else {
915 if (wait_for_partner(pipe, &pipe->w_counter))
916 goto err_rd;
917 }
918 }
919 break;
920
921 case FMODE_WRITE:
922 /*
923 * O_WRONLY
924 * POSIX.1 says that O_NONBLOCK means return -1 with
925 * errno=ENXIO when there is no process reading the FIFO.
926 */
927 ret = -ENXIO;
928 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
929 goto err;
930
931 pipe->w_counter++;
932 if (!pipe->writers++)
933 wake_up_partner(pipe);
934
935 if (!is_pipe && !pipe->readers) {
936 if (wait_for_partner(pipe, &pipe->r_counter))
937 goto err_wr;
938 }
939 break;
940
941 case FMODE_READ | FMODE_WRITE:
942 /*
943 * O_RDWR
944 * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
945 * This implementation will NEVER block on a O_RDWR open, since
946 * the process can at least talk to itself.
947 */
948
949 pipe->readers++;
950 pipe->writers++;
951 pipe->r_counter++;
952 pipe->w_counter++;
953 if (pipe->readers == 1 || pipe->writers == 1)
954 wake_up_partner(pipe);
955 break;
956
957 default:
958 ret = -EINVAL;
959 goto err;
960 }
961
962 /* Ok! */
963 __pipe_unlock(pipe);
964 return 0;
965
966 err_rd:
967 if (!--pipe->readers)
968 wake_up_interruptible(&pipe->wait);
969 ret = -ERESTARTSYS;
970 goto err;
971
972 err_wr:
973 if (!--pipe->writers)
974 wake_up_interruptible(&pipe->wait);
975 ret = -ERESTARTSYS;
976 goto err;
977
978 err:
979 __pipe_unlock(pipe);
980
981 put_pipe_info(inode, pipe);
982 return ret;
983 }
984
985 const struct file_operations pipefifo_fops = {
986 .open = fifo_open,
987 .llseek = no_llseek,
988 .read_iter = pipe_read,
989 .write_iter = pipe_write,
990 .poll = pipe_poll,
991 .unlocked_ioctl = pipe_ioctl,
992 .release = pipe_release,
993 .fasync = pipe_fasync,
994 };
995
996 /*
997 * Allocate a new array of pipe buffers and copy the info over. Returns the
998 * pipe size if successful, or return -ERROR on error.
999 */
1000 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
1001 {
1002 struct pipe_buffer *bufs;
1003
1004 /*
1005 * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1006 * expect a lot of shrink+grow operations, just free and allocate
1007 * again like we would do for growing. If the pipe currently
1008 * contains more buffers than arg, then return busy.
1009 */
1010 if (nr_pages < pipe->nrbufs)
1011 return -EBUSY;
1012
1013 bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN);
1014 if (unlikely(!bufs))
1015 return -ENOMEM;
1016
1017 /*
1018 * The pipe array wraps around, so just start the new one at zero
1019 * and adjust the indexes.
1020 */
1021 if (pipe->nrbufs) {
1022 unsigned int tail;
1023 unsigned int head;
1024
1025 tail = pipe->curbuf + pipe->nrbufs;
1026 if (tail < pipe->buffers)
1027 tail = 0;
1028 else
1029 tail &= (pipe->buffers - 1);
1030
1031 head = pipe->nrbufs - tail;
1032 if (head)
1033 memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1034 if (tail)
1035 memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1036 }
1037
1038 account_pipe_buffers(pipe, pipe->buffers, nr_pages);
1039 pipe->curbuf = 0;
1040 kfree(pipe->bufs);
1041 pipe->bufs = bufs;
1042 pipe->buffers = nr_pages;
1043 return nr_pages * PAGE_SIZE;
1044 }
1045
1046 /*
1047 * Currently we rely on the pipe array holding a power-of-2 number
1048 * of pages.
1049 */
1050 static inline unsigned int round_pipe_size(unsigned int size)
1051 {
1052 unsigned long nr_pages;
1053
1054 nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1055 return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1056 }
1057
1058 /*
1059 * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1060 * will return an error.
1061 */
1062 int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1063 size_t *lenp, loff_t *ppos)
1064 {
1065 int ret;
1066
1067 ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1068 if (ret < 0 || !write)
1069 return ret;
1070
1071 pipe_max_size = round_pipe_size(pipe_max_size);
1072 return ret;
1073 }
1074
1075 /*
1076 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1077 * location, so checking ->i_pipe is not enough to verify that this is a
1078 * pipe.
1079 */
1080 struct pipe_inode_info *get_pipe_info(struct file *file)
1081 {
1082 return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1083 }
1084
1085 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1086 {
1087 struct pipe_inode_info *pipe;
1088 long ret;
1089
1090 pipe = get_pipe_info(file);
1091 if (!pipe)
1092 return -EBADF;
1093
1094 __pipe_lock(pipe);
1095
1096 switch (cmd) {
1097 case F_SETPIPE_SZ: {
1098 unsigned int size, nr_pages;
1099
1100 size = round_pipe_size(arg);
1101 nr_pages = size >> PAGE_SHIFT;
1102
1103 ret = -EINVAL;
1104 if (!nr_pages)
1105 goto out;
1106
1107 if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1108 ret = -EPERM;
1109 goto out;
1110 } else if ((too_many_pipe_buffers_hard(pipe->user) ||
1111 too_many_pipe_buffers_soft(pipe->user)) &&
1112 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) {
1113 ret = -EPERM;
1114 goto out;
1115 }
1116 ret = pipe_set_size(pipe, nr_pages);
1117 break;
1118 }
1119 case F_GETPIPE_SZ:
1120 ret = pipe->buffers * PAGE_SIZE;
1121 break;
1122 default:
1123 ret = -EINVAL;
1124 break;
1125 }
1126
1127 out:
1128 __pipe_unlock(pipe);
1129 return ret;
1130 }
1131
1132 static const struct super_operations pipefs_ops = {
1133 .destroy_inode = free_inode_nonrcu,
1134 .statfs = simple_statfs,
1135 };
1136
1137 /*
1138 * pipefs should _never_ be mounted by userland - too much of security hassle,
1139 * no real gain from having the whole whorehouse mounted. So we don't need
1140 * any operations on the root directory. However, we need a non-trivial
1141 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1142 */
1143 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1144 int flags, const char *dev_name, void *data)
1145 {
1146 return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1147 &pipefs_dentry_operations, PIPEFS_MAGIC);
1148 }
1149
1150 static struct file_system_type pipe_fs_type = {
1151 .name = "pipefs",
1152 .mount = pipefs_mount,
1153 .kill_sb = kill_anon_super,
1154 };
1155
1156 static int __init init_pipe_fs(void)
1157 {
1158 int err = register_filesystem(&pipe_fs_type);
1159
1160 if (!err) {
1161 pipe_mnt = kern_mount(&pipe_fs_type);
1162 if (IS_ERR(pipe_mnt)) {
1163 err = PTR_ERR(pipe_mnt);
1164 unregister_filesystem(&pipe_fs_type);
1165 }
1166 }
1167 return err;
1168 }
1169
1170 fs_initcall(init_pipe_fs);