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