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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 */
34unsigned int pipe_max_size = 1048576;
35
36/*
37 * Minimum pipe size, as required by POSIX
38 */
39unsigned 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 */
44unsigned long pipe_user_pages_hard;
45unsigned 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
62static 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
68void 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}
75EXPORT_SYMBOL(pipe_lock);
76
77void pipe_unlock(struct pipe_inode_info *pipe)
78{
79 if (pipe->files)
80 mutex_unlock(&pipe->mutex);
81}
82EXPORT_SYMBOL(pipe_unlock);
83
84static inline void __pipe_lock(struct pipe_inode_info *pipe)
85{
86 mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
87}
88
89static inline void __pipe_unlock(struct pipe_inode_info *pipe)
90{
91 mutex_unlock(&pipe->mutex);
92}
93
94void 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 */
109void 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
124static 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 put_page(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 */
152int 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}
169EXPORT_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 */
181void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
182{
183 get_page(buf->page);
184}
185EXPORT_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 */
196int generic_pipe_buf_confirm(struct pipe_inode_info *info,
197 struct pipe_buffer *buf)
198{
199 return 0;
200}
201EXPORT_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 */
211void generic_pipe_buf_release(struct pipe_inode_info *pipe,
212 struct pipe_buffer *buf)
213{
214 put_page(buf->page);
215}
216EXPORT_SYMBOL(generic_pipe_buf_release);
217
218static 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
226static 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
234static ssize_t
235pipe_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
338static inline int is_packetized(struct file *file)
339{
340 return (file->f_flags & O_DIRECT) != 0;
341}
342
343static ssize_t
344pipe_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 }
466out:
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
481static 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 */
505static unsigned int
506pipe_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
536static 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
551static int
552pipe_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
573static int
574pipe_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
592static 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
598static 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
604static 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
610struct 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
641void 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
658static struct vfsmount *pipe_mnt __read_mostly;
659
660/*
661 * pipefs_dname() is called from d_path().
662 */
663static 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
669static const struct dentry_operations pipefs_dentry_operations = {
670 .d_dname = pipefs_dname,
671};
672
673static 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
706fail_iput:
707 iput(inode);
708
709fail_inode:
710 return NULL;
711}
712
713int 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
753err_file:
754 put_filp(f);
755err_dentry:
756 free_pipe_info(inode->i_pipe);
757 path_put(&path);
758 return err;
759
760err_inode:
761 free_pipe_info(inode->i_pipe);
762 iput(inode);
763 return err;
764}
765
766static 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
801int 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 */
816SYSCALL_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
838SYSCALL_DEFINE1(pipe, int __user *, fildes)
839{
840 return sys_pipe2(fildes, 0);
841}
842
843static 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
855static void wake_up_partner(struct pipe_inode_info *pipe)
856{
857 wake_up_interruptible(&pipe->wait);
858}
859
860static 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
966err_rd:
967 if (!--pipe->readers)
968 wake_up_interruptible(&pipe->wait);
969 ret = -ERESTARTSYS;
970 goto err;
971
972err_wr:
973 if (!--pipe->writers)
974 wake_up_interruptible(&pipe->wait);
975 ret = -ERESTARTSYS;
976 goto err;
977
978err:
979 __pipe_unlock(pipe);
980
981 put_pipe_info(inode, pipe);
982 return ret;
983}
984
985const 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 */
1000static 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 */
1050static 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 */
1062int 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 */
1080struct pipe_inode_info *get_pipe_info(struct file *file)
1081{
1082 return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1083}
1084
1085long 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
1127out:
1128 __pipe_unlock(pipe);
1129 return ret;
1130}
1131
1132static 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 */
1143static 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
1150static struct file_system_type pipe_fs_type = {
1151 .name = "pipefs",
1152 .mount = pipefs_mount,
1153 .kill_sb = kill_anon_super,
1154};
1155
1156static 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
1170fs_initcall(init_pipe_fs);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/fs/pipe.c
4 *
5 * Copyright (C) 1991, 1992, 1999 Linus Torvalds
6 */
7
8#include <linux/mm.h>
9#include <linux/file.h>
10#include <linux/poll.h>
11#include <linux/slab.h>
12#include <linux/module.h>
13#include <linux/init.h>
14#include <linux/fs.h>
15#include <linux/log2.h>
16#include <linux/mount.h>
17#include <linux/pseudo_fs.h>
18#include <linux/magic.h>
19#include <linux/pipe_fs_i.h>
20#include <linux/uio.h>
21#include <linux/highmem.h>
22#include <linux/pagemap.h>
23#include <linux/audit.h>
24#include <linux/syscalls.h>
25#include <linux/fcntl.h>
26#include <linux/memcontrol.h>
27#include <linux/watch_queue.h>
28#include <linux/sysctl.h>
29
30#include <linux/uaccess.h>
31#include <asm/ioctls.h>
32
33#include "internal.h"
34
35/*
36 * New pipe buffers will be restricted to this size while the user is exceeding
37 * their pipe buffer quota. The general pipe use case needs at least two
38 * buffers: one for data yet to be read, and one for new data. If this is less
39 * than two, then a write to a non-empty pipe may block even if the pipe is not
40 * full. This can occur with GNU make jobserver or similar uses of pipes as
41 * semaphores: multiple processes may be waiting to write tokens back to the
42 * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.
43 *
44 * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their
45 * own risk, namely: pipe writes to non-full pipes may block until the pipe is
46 * emptied.
47 */
48#define PIPE_MIN_DEF_BUFFERS 2
49
50/*
51 * The max size that a non-root user is allowed to grow the pipe. Can
52 * be set by root in /proc/sys/fs/pipe-max-size
53 */
54static unsigned int pipe_max_size = 1048576;
55
56/* Maximum allocatable pages per user. Hard limit is unset by default, soft
57 * matches default values.
58 */
59static unsigned long pipe_user_pages_hard;
60static unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
61
62/*
63 * We use head and tail indices that aren't masked off, except at the point of
64 * dereference, but rather they're allowed to wrap naturally. This means there
65 * isn't a dead spot in the buffer, but the ring has to be a power of two and
66 * <= 2^31.
67 * -- David Howells 2019-09-23.
68 *
69 * Reads with count = 0 should always return 0.
70 * -- Julian Bradfield 1999-06-07.
71 *
72 * FIFOs and Pipes now generate SIGIO for both readers and writers.
73 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
74 *
75 * pipe_read & write cleanup
76 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
77 */
78
79static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
80{
81 if (pipe->files)
82 mutex_lock_nested(&pipe->mutex, subclass);
83}
84
85void pipe_lock(struct pipe_inode_info *pipe)
86{
87 /*
88 * pipe_lock() nests non-pipe inode locks (for writing to a file)
89 */
90 pipe_lock_nested(pipe, I_MUTEX_PARENT);
91}
92EXPORT_SYMBOL(pipe_lock);
93
94void pipe_unlock(struct pipe_inode_info *pipe)
95{
96 if (pipe->files)
97 mutex_unlock(&pipe->mutex);
98}
99EXPORT_SYMBOL(pipe_unlock);
100
101static inline void __pipe_lock(struct pipe_inode_info *pipe)
102{
103 mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
104}
105
106static inline void __pipe_unlock(struct pipe_inode_info *pipe)
107{
108 mutex_unlock(&pipe->mutex);
109}
110
111void pipe_double_lock(struct pipe_inode_info *pipe1,
112 struct pipe_inode_info *pipe2)
113{
114 BUG_ON(pipe1 == pipe2);
115
116 if (pipe1 < pipe2) {
117 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
118 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
119 } else {
120 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
121 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
122 }
123}
124
125static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
126 struct pipe_buffer *buf)
127{
128 struct page *page = buf->page;
129
130 /*
131 * If nobody else uses this page, and we don't already have a
132 * temporary page, let's keep track of it as a one-deep
133 * allocation cache. (Otherwise just release our reference to it)
134 */
135 if (page_count(page) == 1 && !pipe->tmp_page)
136 pipe->tmp_page = page;
137 else
138 put_page(page);
139}
140
141static bool anon_pipe_buf_try_steal(struct pipe_inode_info *pipe,
142 struct pipe_buffer *buf)
143{
144 struct page *page = buf->page;
145
146 if (page_count(page) != 1)
147 return false;
148 memcg_kmem_uncharge_page(page, 0);
149 __SetPageLocked(page);
150 return true;
151}
152
153/**
154 * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
155 * @pipe: the pipe that the buffer belongs to
156 * @buf: the buffer to attempt to steal
157 *
158 * Description:
159 * This function attempts to steal the &struct page attached to
160 * @buf. If successful, this function returns 0 and returns with
161 * the page locked. The caller may then reuse the page for whatever
162 * he wishes; the typical use is insertion into a different file
163 * page cache.
164 */
165bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe,
166 struct pipe_buffer *buf)
167{
168 struct page *page = buf->page;
169
170 /*
171 * A reference of one is golden, that means that the owner of this
172 * page is the only one holding a reference to it. lock the page
173 * and return OK.
174 */
175 if (page_count(page) == 1) {
176 lock_page(page);
177 return true;
178 }
179 return false;
180}
181EXPORT_SYMBOL(generic_pipe_buf_try_steal);
182
183/**
184 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
185 * @pipe: the pipe that the buffer belongs to
186 * @buf: the buffer to get a reference to
187 *
188 * Description:
189 * This function grabs an extra reference to @buf. It's used in
190 * the tee() system call, when we duplicate the buffers in one
191 * pipe into another.
192 */
193bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
194{
195 return try_get_page(buf->page);
196}
197EXPORT_SYMBOL(generic_pipe_buf_get);
198
199/**
200 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
201 * @pipe: the pipe that the buffer belongs to
202 * @buf: the buffer to put a reference to
203 *
204 * Description:
205 * This function releases a reference to @buf.
206 */
207void generic_pipe_buf_release(struct pipe_inode_info *pipe,
208 struct pipe_buffer *buf)
209{
210 put_page(buf->page);
211}
212EXPORT_SYMBOL(generic_pipe_buf_release);
213
214static const struct pipe_buf_operations anon_pipe_buf_ops = {
215 .release = anon_pipe_buf_release,
216 .try_steal = anon_pipe_buf_try_steal,
217 .get = generic_pipe_buf_get,
218};
219
220/* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
221static inline bool pipe_readable(const struct pipe_inode_info *pipe)
222{
223 unsigned int head = READ_ONCE(pipe->head);
224 unsigned int tail = READ_ONCE(pipe->tail);
225 unsigned int writers = READ_ONCE(pipe->writers);
226
227 return !pipe_empty(head, tail) || !writers;
228}
229
230static ssize_t
231pipe_read(struct kiocb *iocb, struct iov_iter *to)
232{
233 size_t total_len = iov_iter_count(to);
234 struct file *filp = iocb->ki_filp;
235 struct pipe_inode_info *pipe = filp->private_data;
236 bool was_full, wake_next_reader = false;
237 ssize_t ret;
238
239 /* Null read succeeds. */
240 if (unlikely(total_len == 0))
241 return 0;
242
243 ret = 0;
244 __pipe_lock(pipe);
245
246 /*
247 * We only wake up writers if the pipe was full when we started
248 * reading in order to avoid unnecessary wakeups.
249 *
250 * But when we do wake up writers, we do so using a sync wakeup
251 * (WF_SYNC), because we want them to get going and generate more
252 * data for us.
253 */
254 was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
255 for (;;) {
256 /* Read ->head with a barrier vs post_one_notification() */
257 unsigned int head = smp_load_acquire(&pipe->head);
258 unsigned int tail = pipe->tail;
259 unsigned int mask = pipe->ring_size - 1;
260
261#ifdef CONFIG_WATCH_QUEUE
262 if (pipe->note_loss) {
263 struct watch_notification n;
264
265 if (total_len < 8) {
266 if (ret == 0)
267 ret = -ENOBUFS;
268 break;
269 }
270
271 n.type = WATCH_TYPE_META;
272 n.subtype = WATCH_META_LOSS_NOTIFICATION;
273 n.info = watch_sizeof(n);
274 if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
275 if (ret == 0)
276 ret = -EFAULT;
277 break;
278 }
279 ret += sizeof(n);
280 total_len -= sizeof(n);
281 pipe->note_loss = false;
282 }
283#endif
284
285 if (!pipe_empty(head, tail)) {
286 struct pipe_buffer *buf = &pipe->bufs[tail & mask];
287 size_t chars = buf->len;
288 size_t written;
289 int error;
290
291 if (chars > total_len) {
292 if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
293 if (ret == 0)
294 ret = -ENOBUFS;
295 break;
296 }
297 chars = total_len;
298 }
299
300 error = pipe_buf_confirm(pipe, buf);
301 if (error) {
302 if (!ret)
303 ret = error;
304 break;
305 }
306
307 written = copy_page_to_iter(buf->page, buf->offset, chars, to);
308 if (unlikely(written < chars)) {
309 if (!ret)
310 ret = -EFAULT;
311 break;
312 }
313 ret += chars;
314 buf->offset += chars;
315 buf->len -= chars;
316
317 /* Was it a packet buffer? Clean up and exit */
318 if (buf->flags & PIPE_BUF_FLAG_PACKET) {
319 total_len = chars;
320 buf->len = 0;
321 }
322
323 if (!buf->len) {
324 pipe_buf_release(pipe, buf);
325 spin_lock_irq(&pipe->rd_wait.lock);
326#ifdef CONFIG_WATCH_QUEUE
327 if (buf->flags & PIPE_BUF_FLAG_LOSS)
328 pipe->note_loss = true;
329#endif
330 tail++;
331 pipe->tail = tail;
332 spin_unlock_irq(&pipe->rd_wait.lock);
333 }
334 total_len -= chars;
335 if (!total_len)
336 break; /* common path: read succeeded */
337 if (!pipe_empty(head, tail)) /* More to do? */
338 continue;
339 }
340
341 if (!pipe->writers)
342 break;
343 if (ret)
344 break;
345 if (filp->f_flags & O_NONBLOCK) {
346 ret = -EAGAIN;
347 break;
348 }
349 __pipe_unlock(pipe);
350
351 /*
352 * We only get here if we didn't actually read anything.
353 *
354 * However, we could have seen (and removed) a zero-sized
355 * pipe buffer, and might have made space in the buffers
356 * that way.
357 *
358 * You can't make zero-sized pipe buffers by doing an empty
359 * write (not even in packet mode), but they can happen if
360 * the writer gets an EFAULT when trying to fill a buffer
361 * that already got allocated and inserted in the buffer
362 * array.
363 *
364 * So we still need to wake up any pending writers in the
365 * _very_ unlikely case that the pipe was full, but we got
366 * no data.
367 */
368 if (unlikely(was_full))
369 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
370 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
371
372 /*
373 * But because we didn't read anything, at this point we can
374 * just return directly with -ERESTARTSYS if we're interrupted,
375 * since we've done any required wakeups and there's no need
376 * to mark anything accessed. And we've dropped the lock.
377 */
378 if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0)
379 return -ERESTARTSYS;
380
381 __pipe_lock(pipe);
382 was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
383 wake_next_reader = true;
384 }
385 if (pipe_empty(pipe->head, pipe->tail))
386 wake_next_reader = false;
387 __pipe_unlock(pipe);
388
389 if (was_full)
390 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
391 if (wake_next_reader)
392 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
393 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
394 if (ret > 0)
395 file_accessed(filp);
396 return ret;
397}
398
399static inline int is_packetized(struct file *file)
400{
401 return (file->f_flags & O_DIRECT) != 0;
402}
403
404/* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
405static inline bool pipe_writable(const struct pipe_inode_info *pipe)
406{
407 unsigned int head = READ_ONCE(pipe->head);
408 unsigned int tail = READ_ONCE(pipe->tail);
409 unsigned int max_usage = READ_ONCE(pipe->max_usage);
410
411 return !pipe_full(head, tail, max_usage) ||
412 !READ_ONCE(pipe->readers);
413}
414
415static ssize_t
416pipe_write(struct kiocb *iocb, struct iov_iter *from)
417{
418 struct file *filp = iocb->ki_filp;
419 struct pipe_inode_info *pipe = filp->private_data;
420 unsigned int head;
421 ssize_t ret = 0;
422 size_t total_len = iov_iter_count(from);
423 ssize_t chars;
424 bool was_empty = false;
425 bool wake_next_writer = false;
426
427 /* Null write succeeds. */
428 if (unlikely(total_len == 0))
429 return 0;
430
431 __pipe_lock(pipe);
432
433 if (!pipe->readers) {
434 send_sig(SIGPIPE, current, 0);
435 ret = -EPIPE;
436 goto out;
437 }
438
439#ifdef CONFIG_WATCH_QUEUE
440 if (pipe->watch_queue) {
441 ret = -EXDEV;
442 goto out;
443 }
444#endif
445
446 /*
447 * If it wasn't empty we try to merge new data into
448 * the last buffer.
449 *
450 * That naturally merges small writes, but it also
451 * page-aligns the rest of the writes for large writes
452 * spanning multiple pages.
453 */
454 head = pipe->head;
455 was_empty = pipe_empty(head, pipe->tail);
456 chars = total_len & (PAGE_SIZE-1);
457 if (chars && !was_empty) {
458 unsigned int mask = pipe->ring_size - 1;
459 struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
460 int offset = buf->offset + buf->len;
461
462 if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
463 offset + chars <= PAGE_SIZE) {
464 ret = pipe_buf_confirm(pipe, buf);
465 if (ret)
466 goto out;
467
468 ret = copy_page_from_iter(buf->page, offset, chars, from);
469 if (unlikely(ret < chars)) {
470 ret = -EFAULT;
471 goto out;
472 }
473
474 buf->len += ret;
475 if (!iov_iter_count(from))
476 goto out;
477 }
478 }
479
480 for (;;) {
481 if (!pipe->readers) {
482 send_sig(SIGPIPE, current, 0);
483 if (!ret)
484 ret = -EPIPE;
485 break;
486 }
487
488 head = pipe->head;
489 if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
490 unsigned int mask = pipe->ring_size - 1;
491 struct pipe_buffer *buf = &pipe->bufs[head & mask];
492 struct page *page = pipe->tmp_page;
493 int copied;
494
495 if (!page) {
496 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
497 if (unlikely(!page)) {
498 ret = ret ? : -ENOMEM;
499 break;
500 }
501 pipe->tmp_page = page;
502 }
503
504 /* Allocate a slot in the ring in advance and attach an
505 * empty buffer. If we fault or otherwise fail to use
506 * it, either the reader will consume it or it'll still
507 * be there for the next write.
508 */
509 spin_lock_irq(&pipe->rd_wait.lock);
510
511 head = pipe->head;
512 if (pipe_full(head, pipe->tail, pipe->max_usage)) {
513 spin_unlock_irq(&pipe->rd_wait.lock);
514 continue;
515 }
516
517 pipe->head = head + 1;
518 spin_unlock_irq(&pipe->rd_wait.lock);
519
520 /* Insert it into the buffer array */
521 buf = &pipe->bufs[head & mask];
522 buf->page = page;
523 buf->ops = &anon_pipe_buf_ops;
524 buf->offset = 0;
525 buf->len = 0;
526 if (is_packetized(filp))
527 buf->flags = PIPE_BUF_FLAG_PACKET;
528 else
529 buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
530 pipe->tmp_page = NULL;
531
532 copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
533 if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
534 if (!ret)
535 ret = -EFAULT;
536 break;
537 }
538 ret += copied;
539 buf->offset = 0;
540 buf->len = copied;
541
542 if (!iov_iter_count(from))
543 break;
544 }
545
546 if (!pipe_full(head, pipe->tail, pipe->max_usage))
547 continue;
548
549 /* Wait for buffer space to become available. */
550 if (filp->f_flags & O_NONBLOCK) {
551 if (!ret)
552 ret = -EAGAIN;
553 break;
554 }
555 if (signal_pending(current)) {
556 if (!ret)
557 ret = -ERESTARTSYS;
558 break;
559 }
560
561 /*
562 * We're going to release the pipe lock and wait for more
563 * space. We wake up any readers if necessary, and then
564 * after waiting we need to re-check whether the pipe
565 * become empty while we dropped the lock.
566 */
567 __pipe_unlock(pipe);
568 if (was_empty)
569 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
570 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
571 wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
572 __pipe_lock(pipe);
573 was_empty = pipe_empty(pipe->head, pipe->tail);
574 wake_next_writer = true;
575 }
576out:
577 if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
578 wake_next_writer = false;
579 __pipe_unlock(pipe);
580
581 /*
582 * If we do do a wakeup event, we do a 'sync' wakeup, because we
583 * want the reader to start processing things asap, rather than
584 * leave the data pending.
585 *
586 * This is particularly important for small writes, because of
587 * how (for example) the GNU make jobserver uses small writes to
588 * wake up pending jobs
589 *
590 * Epoll nonsensically wants a wakeup whether the pipe
591 * was already empty or not.
592 */
593 if (was_empty || pipe->poll_usage)
594 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
595 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
596 if (wake_next_writer)
597 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
598 if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
599 int err = file_update_time(filp);
600 if (err)
601 ret = err;
602 sb_end_write(file_inode(filp)->i_sb);
603 }
604 return ret;
605}
606
607static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
608{
609 struct pipe_inode_info *pipe = filp->private_data;
610 unsigned int count, head, tail, mask;
611
612 switch (cmd) {
613 case FIONREAD:
614 __pipe_lock(pipe);
615 count = 0;
616 head = pipe->head;
617 tail = pipe->tail;
618 mask = pipe->ring_size - 1;
619
620 while (tail != head) {
621 count += pipe->bufs[tail & mask].len;
622 tail++;
623 }
624 __pipe_unlock(pipe);
625
626 return put_user(count, (int __user *)arg);
627
628#ifdef CONFIG_WATCH_QUEUE
629 case IOC_WATCH_QUEUE_SET_SIZE: {
630 int ret;
631 __pipe_lock(pipe);
632 ret = watch_queue_set_size(pipe, arg);
633 __pipe_unlock(pipe);
634 return ret;
635 }
636
637 case IOC_WATCH_QUEUE_SET_FILTER:
638 return watch_queue_set_filter(
639 pipe, (struct watch_notification_filter __user *)arg);
640#endif
641
642 default:
643 return -ENOIOCTLCMD;
644 }
645}
646
647/* No kernel lock held - fine */
648static __poll_t
649pipe_poll(struct file *filp, poll_table *wait)
650{
651 __poll_t mask;
652 struct pipe_inode_info *pipe = filp->private_data;
653 unsigned int head, tail;
654
655 /* Epoll has some historical nasty semantics, this enables them */
656 WRITE_ONCE(pipe->poll_usage, true);
657
658 /*
659 * Reading pipe state only -- no need for acquiring the semaphore.
660 *
661 * But because this is racy, the code has to add the
662 * entry to the poll table _first_ ..
663 */
664 if (filp->f_mode & FMODE_READ)
665 poll_wait(filp, &pipe->rd_wait, wait);
666 if (filp->f_mode & FMODE_WRITE)
667 poll_wait(filp, &pipe->wr_wait, wait);
668
669 /*
670 * .. and only then can you do the racy tests. That way,
671 * if something changes and you got it wrong, the poll
672 * table entry will wake you up and fix it.
673 */
674 head = READ_ONCE(pipe->head);
675 tail = READ_ONCE(pipe->tail);
676
677 mask = 0;
678 if (filp->f_mode & FMODE_READ) {
679 if (!pipe_empty(head, tail))
680 mask |= EPOLLIN | EPOLLRDNORM;
681 if (!pipe->writers && filp->f_version != pipe->w_counter)
682 mask |= EPOLLHUP;
683 }
684
685 if (filp->f_mode & FMODE_WRITE) {
686 if (!pipe_full(head, tail, pipe->max_usage))
687 mask |= EPOLLOUT | EPOLLWRNORM;
688 /*
689 * Most Unices do not set EPOLLERR for FIFOs but on Linux they
690 * behave exactly like pipes for poll().
691 */
692 if (!pipe->readers)
693 mask |= EPOLLERR;
694 }
695
696 return mask;
697}
698
699static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
700{
701 int kill = 0;
702
703 spin_lock(&inode->i_lock);
704 if (!--pipe->files) {
705 inode->i_pipe = NULL;
706 kill = 1;
707 }
708 spin_unlock(&inode->i_lock);
709
710 if (kill)
711 free_pipe_info(pipe);
712}
713
714static int
715pipe_release(struct inode *inode, struct file *file)
716{
717 struct pipe_inode_info *pipe = file->private_data;
718
719 __pipe_lock(pipe);
720 if (file->f_mode & FMODE_READ)
721 pipe->readers--;
722 if (file->f_mode & FMODE_WRITE)
723 pipe->writers--;
724
725 /* Was that the last reader or writer, but not the other side? */
726 if (!pipe->readers != !pipe->writers) {
727 wake_up_interruptible_all(&pipe->rd_wait);
728 wake_up_interruptible_all(&pipe->wr_wait);
729 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
730 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
731 }
732 __pipe_unlock(pipe);
733
734 put_pipe_info(inode, pipe);
735 return 0;
736}
737
738static int
739pipe_fasync(int fd, struct file *filp, int on)
740{
741 struct pipe_inode_info *pipe = filp->private_data;
742 int retval = 0;
743
744 __pipe_lock(pipe);
745 if (filp->f_mode & FMODE_READ)
746 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
747 if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
748 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
749 if (retval < 0 && (filp->f_mode & FMODE_READ))
750 /* this can happen only if on == T */
751 fasync_helper(-1, filp, 0, &pipe->fasync_readers);
752 }
753 __pipe_unlock(pipe);
754 return retval;
755}
756
757unsigned long account_pipe_buffers(struct user_struct *user,
758 unsigned long old, unsigned long new)
759{
760 return atomic_long_add_return(new - old, &user->pipe_bufs);
761}
762
763bool too_many_pipe_buffers_soft(unsigned long user_bufs)
764{
765 unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
766
767 return soft_limit && user_bufs > soft_limit;
768}
769
770bool too_many_pipe_buffers_hard(unsigned long user_bufs)
771{
772 unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
773
774 return hard_limit && user_bufs > hard_limit;
775}
776
777bool pipe_is_unprivileged_user(void)
778{
779 return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
780}
781
782struct pipe_inode_info *alloc_pipe_info(void)
783{
784 struct pipe_inode_info *pipe;
785 unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
786 struct user_struct *user = get_current_user();
787 unsigned long user_bufs;
788 unsigned int max_size = READ_ONCE(pipe_max_size);
789
790 pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
791 if (pipe == NULL)
792 goto out_free_uid;
793
794 if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
795 pipe_bufs = max_size >> PAGE_SHIFT;
796
797 user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
798
799 if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
800 user_bufs = account_pipe_buffers(user, pipe_bufs, PIPE_MIN_DEF_BUFFERS);
801 pipe_bufs = PIPE_MIN_DEF_BUFFERS;
802 }
803
804 if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
805 goto out_revert_acct;
806
807 pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
808 GFP_KERNEL_ACCOUNT);
809
810 if (pipe->bufs) {
811 init_waitqueue_head(&pipe->rd_wait);
812 init_waitqueue_head(&pipe->wr_wait);
813 pipe->r_counter = pipe->w_counter = 1;
814 pipe->max_usage = pipe_bufs;
815 pipe->ring_size = pipe_bufs;
816 pipe->nr_accounted = pipe_bufs;
817 pipe->user = user;
818 mutex_init(&pipe->mutex);
819 return pipe;
820 }
821
822out_revert_acct:
823 (void) account_pipe_buffers(user, pipe_bufs, 0);
824 kfree(pipe);
825out_free_uid:
826 free_uid(user);
827 return NULL;
828}
829
830void free_pipe_info(struct pipe_inode_info *pipe)
831{
832 unsigned int i;
833
834#ifdef CONFIG_WATCH_QUEUE
835 if (pipe->watch_queue)
836 watch_queue_clear(pipe->watch_queue);
837#endif
838
839 (void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
840 free_uid(pipe->user);
841 for (i = 0; i < pipe->ring_size; i++) {
842 struct pipe_buffer *buf = pipe->bufs + i;
843 if (buf->ops)
844 pipe_buf_release(pipe, buf);
845 }
846#ifdef CONFIG_WATCH_QUEUE
847 if (pipe->watch_queue)
848 put_watch_queue(pipe->watch_queue);
849#endif
850 if (pipe->tmp_page)
851 __free_page(pipe->tmp_page);
852 kfree(pipe->bufs);
853 kfree(pipe);
854}
855
856static struct vfsmount *pipe_mnt __read_mostly;
857
858/*
859 * pipefs_dname() is called from d_path().
860 */
861static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
862{
863 return dynamic_dname(buffer, buflen, "pipe:[%lu]",
864 d_inode(dentry)->i_ino);
865}
866
867static const struct dentry_operations pipefs_dentry_operations = {
868 .d_dname = pipefs_dname,
869};
870
871static struct inode * get_pipe_inode(void)
872{
873 struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
874 struct pipe_inode_info *pipe;
875
876 if (!inode)
877 goto fail_inode;
878
879 inode->i_ino = get_next_ino();
880
881 pipe = alloc_pipe_info();
882 if (!pipe)
883 goto fail_iput;
884
885 inode->i_pipe = pipe;
886 pipe->files = 2;
887 pipe->readers = pipe->writers = 1;
888 inode->i_fop = &pipefifo_fops;
889
890 /*
891 * Mark the inode dirty from the very beginning,
892 * that way it will never be moved to the dirty
893 * list because "mark_inode_dirty()" will think
894 * that it already _is_ on the dirty list.
895 */
896 inode->i_state = I_DIRTY;
897 inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
898 inode->i_uid = current_fsuid();
899 inode->i_gid = current_fsgid();
900 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
901
902 return inode;
903
904fail_iput:
905 iput(inode);
906
907fail_inode:
908 return NULL;
909}
910
911int create_pipe_files(struct file **res, int flags)
912{
913 struct inode *inode = get_pipe_inode();
914 struct file *f;
915 int error;
916
917 if (!inode)
918 return -ENFILE;
919
920 if (flags & O_NOTIFICATION_PIPE) {
921 error = watch_queue_init(inode->i_pipe);
922 if (error) {
923 free_pipe_info(inode->i_pipe);
924 iput(inode);
925 return error;
926 }
927 }
928
929 f = alloc_file_pseudo(inode, pipe_mnt, "",
930 O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
931 &pipefifo_fops);
932 if (IS_ERR(f)) {
933 free_pipe_info(inode->i_pipe);
934 iput(inode);
935 return PTR_ERR(f);
936 }
937
938 f->private_data = inode->i_pipe;
939
940 res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
941 &pipefifo_fops);
942 if (IS_ERR(res[0])) {
943 put_pipe_info(inode, inode->i_pipe);
944 fput(f);
945 return PTR_ERR(res[0]);
946 }
947 res[0]->private_data = inode->i_pipe;
948 res[1] = f;
949 stream_open(inode, res[0]);
950 stream_open(inode, res[1]);
951 return 0;
952}
953
954static int __do_pipe_flags(int *fd, struct file **files, int flags)
955{
956 int error;
957 int fdw, fdr;
958
959 if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
960 return -EINVAL;
961
962 error = create_pipe_files(files, flags);
963 if (error)
964 return error;
965
966 error = get_unused_fd_flags(flags);
967 if (error < 0)
968 goto err_read_pipe;
969 fdr = error;
970
971 error = get_unused_fd_flags(flags);
972 if (error < 0)
973 goto err_fdr;
974 fdw = error;
975
976 audit_fd_pair(fdr, fdw);
977 fd[0] = fdr;
978 fd[1] = fdw;
979 return 0;
980
981 err_fdr:
982 put_unused_fd(fdr);
983 err_read_pipe:
984 fput(files[0]);
985 fput(files[1]);
986 return error;
987}
988
989int do_pipe_flags(int *fd, int flags)
990{
991 struct file *files[2];
992 int error = __do_pipe_flags(fd, files, flags);
993 if (!error) {
994 fd_install(fd[0], files[0]);
995 fd_install(fd[1], files[1]);
996 }
997 return error;
998}
999
1000/*
1001 * sys_pipe() is the normal C calling standard for creating
1002 * a pipe. It's not the way Unix traditionally does this, though.
1003 */
1004static int do_pipe2(int __user *fildes, int flags)
1005{
1006 struct file *files[2];
1007 int fd[2];
1008 int error;
1009
1010 error = __do_pipe_flags(fd, files, flags);
1011 if (!error) {
1012 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
1013 fput(files[0]);
1014 fput(files[1]);
1015 put_unused_fd(fd[0]);
1016 put_unused_fd(fd[1]);
1017 error = -EFAULT;
1018 } else {
1019 fd_install(fd[0], files[0]);
1020 fd_install(fd[1], files[1]);
1021 }
1022 }
1023 return error;
1024}
1025
1026SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1027{
1028 return do_pipe2(fildes, flags);
1029}
1030
1031SYSCALL_DEFINE1(pipe, int __user *, fildes)
1032{
1033 return do_pipe2(fildes, 0);
1034}
1035
1036/*
1037 * This is the stupid "wait for pipe to be readable or writable"
1038 * model.
1039 *
1040 * See pipe_read/write() for the proper kind of exclusive wait,
1041 * but that requires that we wake up any other readers/writers
1042 * if we then do not end up reading everything (ie the whole
1043 * "wake_next_reader/writer" logic in pipe_read/write()).
1044 */
1045void pipe_wait_readable(struct pipe_inode_info *pipe)
1046{
1047 pipe_unlock(pipe);
1048 wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
1049 pipe_lock(pipe);
1050}
1051
1052void pipe_wait_writable(struct pipe_inode_info *pipe)
1053{
1054 pipe_unlock(pipe);
1055 wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
1056 pipe_lock(pipe);
1057}
1058
1059/*
1060 * This depends on both the wait (here) and the wakeup (wake_up_partner)
1061 * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
1062 * race with the count check and waitqueue prep.
1063 *
1064 * Normally in order to avoid races, you'd do the prepare_to_wait() first,
1065 * then check the condition you're waiting for, and only then sleep. But
1066 * because of the pipe lock, we can check the condition before being on
1067 * the wait queue.
1068 *
1069 * We use the 'rd_wait' waitqueue for pipe partner waiting.
1070 */
1071static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1072{
1073 DEFINE_WAIT(rdwait);
1074 int cur = *cnt;
1075
1076 while (cur == *cnt) {
1077 prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
1078 pipe_unlock(pipe);
1079 schedule();
1080 finish_wait(&pipe->rd_wait, &rdwait);
1081 pipe_lock(pipe);
1082 if (signal_pending(current))
1083 break;
1084 }
1085 return cur == *cnt ? -ERESTARTSYS : 0;
1086}
1087
1088static void wake_up_partner(struct pipe_inode_info *pipe)
1089{
1090 wake_up_interruptible_all(&pipe->rd_wait);
1091}
1092
1093static int fifo_open(struct inode *inode, struct file *filp)
1094{
1095 struct pipe_inode_info *pipe;
1096 bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1097 int ret;
1098
1099 filp->f_version = 0;
1100
1101 spin_lock(&inode->i_lock);
1102 if (inode->i_pipe) {
1103 pipe = inode->i_pipe;
1104 pipe->files++;
1105 spin_unlock(&inode->i_lock);
1106 } else {
1107 spin_unlock(&inode->i_lock);
1108 pipe = alloc_pipe_info();
1109 if (!pipe)
1110 return -ENOMEM;
1111 pipe->files = 1;
1112 spin_lock(&inode->i_lock);
1113 if (unlikely(inode->i_pipe)) {
1114 inode->i_pipe->files++;
1115 spin_unlock(&inode->i_lock);
1116 free_pipe_info(pipe);
1117 pipe = inode->i_pipe;
1118 } else {
1119 inode->i_pipe = pipe;
1120 spin_unlock(&inode->i_lock);
1121 }
1122 }
1123 filp->private_data = pipe;
1124 /* OK, we have a pipe and it's pinned down */
1125
1126 __pipe_lock(pipe);
1127
1128 /* We can only do regular read/write on fifos */
1129 stream_open(inode, filp);
1130
1131 switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
1132 case FMODE_READ:
1133 /*
1134 * O_RDONLY
1135 * POSIX.1 says that O_NONBLOCK means return with the FIFO
1136 * opened, even when there is no process writing the FIFO.
1137 */
1138 pipe->r_counter++;
1139 if (pipe->readers++ == 0)
1140 wake_up_partner(pipe);
1141
1142 if (!is_pipe && !pipe->writers) {
1143 if ((filp->f_flags & O_NONBLOCK)) {
1144 /* suppress EPOLLHUP until we have
1145 * seen a writer */
1146 filp->f_version = pipe->w_counter;
1147 } else {
1148 if (wait_for_partner(pipe, &pipe->w_counter))
1149 goto err_rd;
1150 }
1151 }
1152 break;
1153
1154 case FMODE_WRITE:
1155 /*
1156 * O_WRONLY
1157 * POSIX.1 says that O_NONBLOCK means return -1 with
1158 * errno=ENXIO when there is no process reading the FIFO.
1159 */
1160 ret = -ENXIO;
1161 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1162 goto err;
1163
1164 pipe->w_counter++;
1165 if (!pipe->writers++)
1166 wake_up_partner(pipe);
1167
1168 if (!is_pipe && !pipe->readers) {
1169 if (wait_for_partner(pipe, &pipe->r_counter))
1170 goto err_wr;
1171 }
1172 break;
1173
1174 case FMODE_READ | FMODE_WRITE:
1175 /*
1176 * O_RDWR
1177 * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1178 * This implementation will NEVER block on a O_RDWR open, since
1179 * the process can at least talk to itself.
1180 */
1181
1182 pipe->readers++;
1183 pipe->writers++;
1184 pipe->r_counter++;
1185 pipe->w_counter++;
1186 if (pipe->readers == 1 || pipe->writers == 1)
1187 wake_up_partner(pipe);
1188 break;
1189
1190 default:
1191 ret = -EINVAL;
1192 goto err;
1193 }
1194
1195 /* Ok! */
1196 __pipe_unlock(pipe);
1197 return 0;
1198
1199err_rd:
1200 if (!--pipe->readers)
1201 wake_up_interruptible(&pipe->wr_wait);
1202 ret = -ERESTARTSYS;
1203 goto err;
1204
1205err_wr:
1206 if (!--pipe->writers)
1207 wake_up_interruptible_all(&pipe->rd_wait);
1208 ret = -ERESTARTSYS;
1209 goto err;
1210
1211err:
1212 __pipe_unlock(pipe);
1213
1214 put_pipe_info(inode, pipe);
1215 return ret;
1216}
1217
1218const struct file_operations pipefifo_fops = {
1219 .open = fifo_open,
1220 .llseek = no_llseek,
1221 .read_iter = pipe_read,
1222 .write_iter = pipe_write,
1223 .poll = pipe_poll,
1224 .unlocked_ioctl = pipe_ioctl,
1225 .release = pipe_release,
1226 .fasync = pipe_fasync,
1227 .splice_write = iter_file_splice_write,
1228};
1229
1230/*
1231 * Currently we rely on the pipe array holding a power-of-2 number
1232 * of pages. Returns 0 on error.
1233 */
1234unsigned int round_pipe_size(unsigned long size)
1235{
1236 if (size > (1U << 31))
1237 return 0;
1238
1239 /* Minimum pipe size, as required by POSIX */
1240 if (size < PAGE_SIZE)
1241 return PAGE_SIZE;
1242
1243 return roundup_pow_of_two(size);
1244}
1245
1246/*
1247 * Resize the pipe ring to a number of slots.
1248 *
1249 * Note the pipe can be reduced in capacity, but only if the current
1250 * occupancy doesn't exceed nr_slots; if it does, EBUSY will be
1251 * returned instead.
1252 */
1253int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
1254{
1255 struct pipe_buffer *bufs;
1256 unsigned int head, tail, mask, n;
1257
1258 bufs = kcalloc(nr_slots, sizeof(*bufs),
1259 GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1260 if (unlikely(!bufs))
1261 return -ENOMEM;
1262
1263 spin_lock_irq(&pipe->rd_wait.lock);
1264 mask = pipe->ring_size - 1;
1265 head = pipe->head;
1266 tail = pipe->tail;
1267
1268 n = pipe_occupancy(head, tail);
1269 if (nr_slots < n) {
1270 spin_unlock_irq(&pipe->rd_wait.lock);
1271 kfree(bufs);
1272 return -EBUSY;
1273 }
1274
1275 /*
1276 * The pipe array wraps around, so just start the new one at zero
1277 * and adjust the indices.
1278 */
1279 if (n > 0) {
1280 unsigned int h = head & mask;
1281 unsigned int t = tail & mask;
1282 if (h > t) {
1283 memcpy(bufs, pipe->bufs + t,
1284 n * sizeof(struct pipe_buffer));
1285 } else {
1286 unsigned int tsize = pipe->ring_size - t;
1287 if (h > 0)
1288 memcpy(bufs + tsize, pipe->bufs,
1289 h * sizeof(struct pipe_buffer));
1290 memcpy(bufs, pipe->bufs + t,
1291 tsize * sizeof(struct pipe_buffer));
1292 }
1293 }
1294
1295 head = n;
1296 tail = 0;
1297
1298 kfree(pipe->bufs);
1299 pipe->bufs = bufs;
1300 pipe->ring_size = nr_slots;
1301 if (pipe->max_usage > nr_slots)
1302 pipe->max_usage = nr_slots;
1303 pipe->tail = tail;
1304 pipe->head = head;
1305
1306 spin_unlock_irq(&pipe->rd_wait.lock);
1307
1308 /* This might have made more room for writers */
1309 wake_up_interruptible(&pipe->wr_wait);
1310 return 0;
1311}
1312
1313/*
1314 * Allocate a new array of pipe buffers and copy the info over. Returns the
1315 * pipe size if successful, or return -ERROR on error.
1316 */
1317static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1318{
1319 unsigned long user_bufs;
1320 unsigned int nr_slots, size;
1321 long ret = 0;
1322
1323#ifdef CONFIG_WATCH_QUEUE
1324 if (pipe->watch_queue)
1325 return -EBUSY;
1326#endif
1327
1328 size = round_pipe_size(arg);
1329 nr_slots = size >> PAGE_SHIFT;
1330
1331 if (!nr_slots)
1332 return -EINVAL;
1333
1334 /*
1335 * If trying to increase the pipe capacity, check that an
1336 * unprivileged user is not trying to exceed various limits
1337 * (soft limit check here, hard limit check just below).
1338 * Decreasing the pipe capacity is always permitted, even
1339 * if the user is currently over a limit.
1340 */
1341 if (nr_slots > pipe->max_usage &&
1342 size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1343 return -EPERM;
1344
1345 user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
1346
1347 if (nr_slots > pipe->max_usage &&
1348 (too_many_pipe_buffers_hard(user_bufs) ||
1349 too_many_pipe_buffers_soft(user_bufs)) &&
1350 pipe_is_unprivileged_user()) {
1351 ret = -EPERM;
1352 goto out_revert_acct;
1353 }
1354
1355 ret = pipe_resize_ring(pipe, nr_slots);
1356 if (ret < 0)
1357 goto out_revert_acct;
1358
1359 pipe->max_usage = nr_slots;
1360 pipe->nr_accounted = nr_slots;
1361 return pipe->max_usage * PAGE_SIZE;
1362
1363out_revert_acct:
1364 (void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
1365 return ret;
1366}
1367
1368/*
1369 * Note that i_pipe and i_cdev share the same location, so checking ->i_pipe is
1370 * not enough to verify that this is a pipe.
1371 */
1372struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
1373{
1374 struct pipe_inode_info *pipe = file->private_data;
1375
1376 if (file->f_op != &pipefifo_fops || !pipe)
1377 return NULL;
1378#ifdef CONFIG_WATCH_QUEUE
1379 if (for_splice && pipe->watch_queue)
1380 return NULL;
1381#endif
1382 return pipe;
1383}
1384
1385long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1386{
1387 struct pipe_inode_info *pipe;
1388 long ret;
1389
1390 pipe = get_pipe_info(file, false);
1391 if (!pipe)
1392 return -EBADF;
1393
1394 __pipe_lock(pipe);
1395
1396 switch (cmd) {
1397 case F_SETPIPE_SZ:
1398 ret = pipe_set_size(pipe, arg);
1399 break;
1400 case F_GETPIPE_SZ:
1401 ret = pipe->max_usage * PAGE_SIZE;
1402 break;
1403 default:
1404 ret = -EINVAL;
1405 break;
1406 }
1407
1408 __pipe_unlock(pipe);
1409 return ret;
1410}
1411
1412static const struct super_operations pipefs_ops = {
1413 .destroy_inode = free_inode_nonrcu,
1414 .statfs = simple_statfs,
1415};
1416
1417/*
1418 * pipefs should _never_ be mounted by userland - too much of security hassle,
1419 * no real gain from having the whole whorehouse mounted. So we don't need
1420 * any operations on the root directory. However, we need a non-trivial
1421 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1422 */
1423
1424static int pipefs_init_fs_context(struct fs_context *fc)
1425{
1426 struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
1427 if (!ctx)
1428 return -ENOMEM;
1429 ctx->ops = &pipefs_ops;
1430 ctx->dops = &pipefs_dentry_operations;
1431 return 0;
1432}
1433
1434static struct file_system_type pipe_fs_type = {
1435 .name = "pipefs",
1436 .init_fs_context = pipefs_init_fs_context,
1437 .kill_sb = kill_anon_super,
1438};
1439
1440#ifdef CONFIG_SYSCTL
1441static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
1442 unsigned int *valp,
1443 int write, void *data)
1444{
1445 if (write) {
1446 unsigned int val;
1447
1448 val = round_pipe_size(*lvalp);
1449 if (val == 0)
1450 return -EINVAL;
1451
1452 *valp = val;
1453 } else {
1454 unsigned int val = *valp;
1455 *lvalp = (unsigned long) val;
1456 }
1457
1458 return 0;
1459}
1460
1461static int proc_dopipe_max_size(struct ctl_table *table, int write,
1462 void *buffer, size_t *lenp, loff_t *ppos)
1463{
1464 return do_proc_douintvec(table, write, buffer, lenp, ppos,
1465 do_proc_dopipe_max_size_conv, NULL);
1466}
1467
1468static struct ctl_table fs_pipe_sysctls[] = {
1469 {
1470 .procname = "pipe-max-size",
1471 .data = &pipe_max_size,
1472 .maxlen = sizeof(pipe_max_size),
1473 .mode = 0644,
1474 .proc_handler = proc_dopipe_max_size,
1475 },
1476 {
1477 .procname = "pipe-user-pages-hard",
1478 .data = &pipe_user_pages_hard,
1479 .maxlen = sizeof(pipe_user_pages_hard),
1480 .mode = 0644,
1481 .proc_handler = proc_doulongvec_minmax,
1482 },
1483 {
1484 .procname = "pipe-user-pages-soft",
1485 .data = &pipe_user_pages_soft,
1486 .maxlen = sizeof(pipe_user_pages_soft),
1487 .mode = 0644,
1488 .proc_handler = proc_doulongvec_minmax,
1489 },
1490 { }
1491};
1492#endif
1493
1494static int __init init_pipe_fs(void)
1495{
1496 int err = register_filesystem(&pipe_fs_type);
1497
1498 if (!err) {
1499 pipe_mnt = kern_mount(&pipe_fs_type);
1500 if (IS_ERR(pipe_mnt)) {
1501 err = PTR_ERR(pipe_mnt);
1502 unregister_filesystem(&pipe_fs_type);
1503 }
1504 }
1505#ifdef CONFIG_SYSCTL
1506 register_sysctl_init("fs", fs_pipe_sysctls);
1507#endif
1508 return err;
1509}
1510
1511fs_initcall(init_pipe_fs);