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/magic.h>
18#include <linux/pipe_fs_i.h>
19#include <linux/uio.h>
20#include <linux/highmem.h>
21#include <linux/pagemap.h>
22#include <linux/audit.h>
23#include <linux/syscalls.h>
24#include <linux/fcntl.h>
25#include <linux/memcontrol.h>
26
27#include <linux/uaccess.h>
28#include <asm/ioctls.h>
29
30#include "internal.h"
31
32/*
33 * The max size that a non-root user is allowed to grow the pipe. Can
34 * be set by root in /proc/sys/fs/pipe-max-size
35 */
36unsigned int pipe_max_size = 1048576;
37
38/* Maximum allocatable pages per user. Hard limit is unset by default, soft
39 * matches default values.
40 */
41unsigned long pipe_user_pages_hard;
42unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
43
44/*
45 * We use a start+len construction, which provides full use of the
46 * allocated memory.
47 * -- Florian Coosmann (FGC)
48 *
49 * Reads with count = 0 should always return 0.
50 * -- Julian Bradfield 1999-06-07.
51 *
52 * FIFOs and Pipes now generate SIGIO for both readers and writers.
53 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
54 *
55 * pipe_read & write cleanup
56 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
57 */
58
59static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
60{
61 if (pipe->files)
62 mutex_lock_nested(&pipe->mutex, subclass);
63}
64
65void pipe_lock(struct pipe_inode_info *pipe)
66{
67 /*
68 * pipe_lock() nests non-pipe inode locks (for writing to a file)
69 */
70 pipe_lock_nested(pipe, I_MUTEX_PARENT);
71}
72EXPORT_SYMBOL(pipe_lock);
73
74void pipe_unlock(struct pipe_inode_info *pipe)
75{
76 if (pipe->files)
77 mutex_unlock(&pipe->mutex);
78}
79EXPORT_SYMBOL(pipe_unlock);
80
81static inline void __pipe_lock(struct pipe_inode_info *pipe)
82{
83 mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
84}
85
86static inline void __pipe_unlock(struct pipe_inode_info *pipe)
87{
88 mutex_unlock(&pipe->mutex);
89}
90
91void pipe_double_lock(struct pipe_inode_info *pipe1,
92 struct pipe_inode_info *pipe2)
93{
94 BUG_ON(pipe1 == pipe2);
95
96 if (pipe1 < pipe2) {
97 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
98 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
99 } else {
100 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
101 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
102 }
103}
104
105/* Drop the inode semaphore and wait for a pipe event, atomically */
106void pipe_wait(struct pipe_inode_info *pipe)
107{
108 DEFINE_WAIT(wait);
109
110 /*
111 * Pipes are system-local resources, so sleeping on them
112 * is considered a noninteractive wait:
113 */
114 prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
115 pipe_unlock(pipe);
116 schedule();
117 finish_wait(&pipe->wait, &wait);
118 pipe_lock(pipe);
119}
120
121static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
122 struct pipe_buffer *buf)
123{
124 struct page *page = buf->page;
125
126 /*
127 * If nobody else uses this page, and we don't already have a
128 * temporary page, let's keep track of it as a one-deep
129 * allocation cache. (Otherwise just release our reference to it)
130 */
131 if (page_count(page) == 1 && !pipe->tmp_page)
132 pipe->tmp_page = page;
133 else
134 put_page(page);
135}
136
137static int anon_pipe_buf_steal(struct pipe_inode_info *pipe,
138 struct pipe_buffer *buf)
139{
140 struct page *page = buf->page;
141
142 if (page_count(page) == 1) {
143 memcg_kmem_uncharge(page, 0);
144 __SetPageLocked(page);
145 return 0;
146 }
147 return 1;
148}
149
150/**
151 * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
152 * @pipe: the pipe that the buffer belongs to
153 * @buf: the buffer to attempt to steal
154 *
155 * Description:
156 * This function attempts to steal the &struct page attached to
157 * @buf. If successful, this function returns 0 and returns with
158 * the page locked. The caller may then reuse the page for whatever
159 * he wishes; the typical use is insertion into a different file
160 * page cache.
161 */
162int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
163 struct pipe_buffer *buf)
164{
165 struct page *page = buf->page;
166
167 /*
168 * A reference of one is golden, that means that the owner of this
169 * page is the only one holding a reference to it. lock the page
170 * and return OK.
171 */
172 if (page_count(page) == 1) {
173 lock_page(page);
174 return 0;
175 }
176
177 return 1;
178}
179EXPORT_SYMBOL(generic_pipe_buf_steal);
180
181/**
182 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
183 * @pipe: the pipe that the buffer belongs to
184 * @buf: the buffer to get a reference to
185 *
186 * Description:
187 * This function grabs an extra reference to @buf. It's used in
188 * in the tee() system call, when we duplicate the buffers in one
189 * pipe into another.
190 */
191void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
192{
193 get_page(buf->page);
194}
195EXPORT_SYMBOL(generic_pipe_buf_get);
196
197/**
198 * generic_pipe_buf_confirm - verify contents of the pipe buffer
199 * @info: the pipe that the buffer belongs to
200 * @buf: the buffer to confirm
201 *
202 * Description:
203 * This function does nothing, because the generic pipe code uses
204 * pages that are always good when inserted into the pipe.
205 */
206int generic_pipe_buf_confirm(struct pipe_inode_info *info,
207 struct pipe_buffer *buf)
208{
209 return 0;
210}
211EXPORT_SYMBOL(generic_pipe_buf_confirm);
212
213/**
214 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
215 * @pipe: the pipe that the buffer belongs to
216 * @buf: the buffer to put a reference to
217 *
218 * Description:
219 * This function releases a reference to @buf.
220 */
221void generic_pipe_buf_release(struct pipe_inode_info *pipe,
222 struct pipe_buffer *buf)
223{
224 put_page(buf->page);
225}
226EXPORT_SYMBOL(generic_pipe_buf_release);
227
228/* New data written to a pipe may be appended to a buffer with this type. */
229static const struct pipe_buf_operations anon_pipe_buf_ops = {
230 .confirm = generic_pipe_buf_confirm,
231 .release = anon_pipe_buf_release,
232 .steal = anon_pipe_buf_steal,
233 .get = generic_pipe_buf_get,
234};
235
236static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = {
237 .confirm = generic_pipe_buf_confirm,
238 .release = anon_pipe_buf_release,
239 .steal = anon_pipe_buf_steal,
240 .get = generic_pipe_buf_get,
241};
242
243static const struct pipe_buf_operations packet_pipe_buf_ops = {
244 .confirm = generic_pipe_buf_confirm,
245 .release = anon_pipe_buf_release,
246 .steal = anon_pipe_buf_steal,
247 .get = generic_pipe_buf_get,
248};
249
250/**
251 * pipe_buf_mark_unmergeable - mark a &struct pipe_buffer as unmergeable
252 * @buf: the buffer to mark
253 *
254 * Description:
255 * This function ensures that no future writes will be merged into the
256 * given &struct pipe_buffer. This is necessary when multiple pipe buffers
257 * share the same backing page.
258 */
259void pipe_buf_mark_unmergeable(struct pipe_buffer *buf)
260{
261 if (buf->ops == &anon_pipe_buf_ops)
262 buf->ops = &anon_pipe_buf_nomerge_ops;
263}
264
265static bool pipe_buf_can_merge(struct pipe_buffer *buf)
266{
267 return buf->ops == &anon_pipe_buf_ops;
268}
269
270static ssize_t
271pipe_read(struct kiocb *iocb, struct iov_iter *to)
272{
273 size_t total_len = iov_iter_count(to);
274 struct file *filp = iocb->ki_filp;
275 struct pipe_inode_info *pipe = filp->private_data;
276 int do_wakeup;
277 ssize_t ret;
278
279 /* Null read succeeds. */
280 if (unlikely(total_len == 0))
281 return 0;
282
283 do_wakeup = 0;
284 ret = 0;
285 __pipe_lock(pipe);
286 for (;;) {
287 int bufs = pipe->nrbufs;
288 if (bufs) {
289 int curbuf = pipe->curbuf;
290 struct pipe_buffer *buf = pipe->bufs + curbuf;
291 size_t chars = buf->len;
292 size_t written;
293 int error;
294
295 if (chars > total_len)
296 chars = total_len;
297
298 error = pipe_buf_confirm(pipe, buf);
299 if (error) {
300 if (!ret)
301 ret = error;
302 break;
303 }
304
305 written = copy_page_to_iter(buf->page, buf->offset, chars, to);
306 if (unlikely(written < chars)) {
307 if (!ret)
308 ret = -EFAULT;
309 break;
310 }
311 ret += chars;
312 buf->offset += chars;
313 buf->len -= chars;
314
315 /* Was it a packet buffer? Clean up and exit */
316 if (buf->flags & PIPE_BUF_FLAG_PACKET) {
317 total_len = chars;
318 buf->len = 0;
319 }
320
321 if (!buf->len) {
322 pipe_buf_release(pipe, buf);
323 curbuf = (curbuf + 1) & (pipe->buffers - 1);
324 pipe->curbuf = curbuf;
325 pipe->nrbufs = --bufs;
326 do_wakeup = 1;
327 }
328 total_len -= chars;
329 if (!total_len)
330 break; /* common path: read succeeded */
331 }
332 if (bufs) /* More to do? */
333 continue;
334 if (!pipe->writers)
335 break;
336 if (!pipe->waiting_writers) {
337 /* syscall merging: Usually we must not sleep
338 * if O_NONBLOCK is set, or if we got some data.
339 * But if a writer sleeps in kernel space, then
340 * we can wait for that data without violating POSIX.
341 */
342 if (ret)
343 break;
344 if (filp->f_flags & O_NONBLOCK) {
345 ret = -EAGAIN;
346 break;
347 }
348 }
349 if (signal_pending(current)) {
350 if (!ret)
351 ret = -ERESTARTSYS;
352 break;
353 }
354 if (do_wakeup) {
355 wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
356 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
357 }
358 pipe_wait(pipe);
359 }
360 __pipe_unlock(pipe);
361
362 /* Signal writers asynchronously that there is more room. */
363 if (do_wakeup) {
364 wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
365 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
366 }
367 if (ret > 0)
368 file_accessed(filp);
369 return ret;
370}
371
372static inline int is_packetized(struct file *file)
373{
374 return (file->f_flags & O_DIRECT) != 0;
375}
376
377static ssize_t
378pipe_write(struct kiocb *iocb, struct iov_iter *from)
379{
380 struct file *filp = iocb->ki_filp;
381 struct pipe_inode_info *pipe = filp->private_data;
382 ssize_t ret = 0;
383 int do_wakeup = 0;
384 size_t total_len = iov_iter_count(from);
385 ssize_t chars;
386
387 /* Null write succeeds. */
388 if (unlikely(total_len == 0))
389 return 0;
390
391 __pipe_lock(pipe);
392
393 if (!pipe->readers) {
394 send_sig(SIGPIPE, current, 0);
395 ret = -EPIPE;
396 goto out;
397 }
398
399 /* We try to merge small writes */
400 chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
401 if (pipe->nrbufs && chars != 0) {
402 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
403 (pipe->buffers - 1);
404 struct pipe_buffer *buf = pipe->bufs + lastbuf;
405 int offset = buf->offset + buf->len;
406
407 if (pipe_buf_can_merge(buf) && offset + chars <= PAGE_SIZE) {
408 ret = pipe_buf_confirm(pipe, buf);
409 if (ret)
410 goto out;
411
412 ret = copy_page_from_iter(buf->page, offset, chars, from);
413 if (unlikely(ret < chars)) {
414 ret = -EFAULT;
415 goto out;
416 }
417 do_wakeup = 1;
418 buf->len += ret;
419 if (!iov_iter_count(from))
420 goto out;
421 }
422 }
423
424 for (;;) {
425 int bufs;
426
427 if (!pipe->readers) {
428 send_sig(SIGPIPE, current, 0);
429 if (!ret)
430 ret = -EPIPE;
431 break;
432 }
433 bufs = pipe->nrbufs;
434 if (bufs < pipe->buffers) {
435 int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
436 struct pipe_buffer *buf = pipe->bufs + newbuf;
437 struct page *page = pipe->tmp_page;
438 int copied;
439
440 if (!page) {
441 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
442 if (unlikely(!page)) {
443 ret = ret ? : -ENOMEM;
444 break;
445 }
446 pipe->tmp_page = page;
447 }
448 /* Always wake up, even if the copy fails. Otherwise
449 * we lock up (O_NONBLOCK-)readers that sleep due to
450 * syscall merging.
451 * FIXME! Is this really true?
452 */
453 do_wakeup = 1;
454 copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
455 if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
456 if (!ret)
457 ret = -EFAULT;
458 break;
459 }
460 ret += copied;
461
462 /* Insert it into the buffer array */
463 buf->page = page;
464 buf->ops = &anon_pipe_buf_ops;
465 buf->offset = 0;
466 buf->len = copied;
467 buf->flags = 0;
468 if (is_packetized(filp)) {
469 buf->ops = &packet_pipe_buf_ops;
470 buf->flags = PIPE_BUF_FLAG_PACKET;
471 }
472 pipe->nrbufs = ++bufs;
473 pipe->tmp_page = NULL;
474
475 if (!iov_iter_count(from))
476 break;
477 }
478 if (bufs < pipe->buffers)
479 continue;
480 if (filp->f_flags & O_NONBLOCK) {
481 if (!ret)
482 ret = -EAGAIN;
483 break;
484 }
485 if (signal_pending(current)) {
486 if (!ret)
487 ret = -ERESTARTSYS;
488 break;
489 }
490 if (do_wakeup) {
491 wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLRDNORM);
492 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
493 do_wakeup = 0;
494 }
495 pipe->waiting_writers++;
496 pipe_wait(pipe);
497 pipe->waiting_writers--;
498 }
499out:
500 __pipe_unlock(pipe);
501 if (do_wakeup) {
502 wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLRDNORM);
503 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
504 }
505 if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
506 int err = file_update_time(filp);
507 if (err)
508 ret = err;
509 sb_end_write(file_inode(filp)->i_sb);
510 }
511 return ret;
512}
513
514static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
515{
516 struct pipe_inode_info *pipe = filp->private_data;
517 int count, buf, nrbufs;
518
519 switch (cmd) {
520 case FIONREAD:
521 __pipe_lock(pipe);
522 count = 0;
523 buf = pipe->curbuf;
524 nrbufs = pipe->nrbufs;
525 while (--nrbufs >= 0) {
526 count += pipe->bufs[buf].len;
527 buf = (buf+1) & (pipe->buffers - 1);
528 }
529 __pipe_unlock(pipe);
530
531 return put_user(count, (int __user *)arg);
532 default:
533 return -ENOIOCTLCMD;
534 }
535}
536
537/* No kernel lock held - fine */
538static __poll_t
539pipe_poll(struct file *filp, poll_table *wait)
540{
541 __poll_t mask;
542 struct pipe_inode_info *pipe = filp->private_data;
543 int nrbufs;
544
545 poll_wait(filp, &pipe->wait, wait);
546
547 /* Reading only -- no need for acquiring the semaphore. */
548 nrbufs = pipe->nrbufs;
549 mask = 0;
550 if (filp->f_mode & FMODE_READ) {
551 mask = (nrbufs > 0) ? EPOLLIN | EPOLLRDNORM : 0;
552 if (!pipe->writers && filp->f_version != pipe->w_counter)
553 mask |= EPOLLHUP;
554 }
555
556 if (filp->f_mode & FMODE_WRITE) {
557 mask |= (nrbufs < pipe->buffers) ? EPOLLOUT | EPOLLWRNORM : 0;
558 /*
559 * Most Unices do not set EPOLLERR for FIFOs but on Linux they
560 * behave exactly like pipes for poll().
561 */
562 if (!pipe->readers)
563 mask |= EPOLLERR;
564 }
565
566 return mask;
567}
568
569static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
570{
571 int kill = 0;
572
573 spin_lock(&inode->i_lock);
574 if (!--pipe->files) {
575 inode->i_pipe = NULL;
576 kill = 1;
577 }
578 spin_unlock(&inode->i_lock);
579
580 if (kill)
581 free_pipe_info(pipe);
582}
583
584static int
585pipe_release(struct inode *inode, struct file *file)
586{
587 struct pipe_inode_info *pipe = file->private_data;
588
589 __pipe_lock(pipe);
590 if (file->f_mode & FMODE_READ)
591 pipe->readers--;
592 if (file->f_mode & FMODE_WRITE)
593 pipe->writers--;
594
595 if (pipe->readers || pipe->writers) {
596 wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLOUT | EPOLLRDNORM | EPOLLWRNORM | EPOLLERR | EPOLLHUP);
597 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
598 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
599 }
600 __pipe_unlock(pipe);
601
602 put_pipe_info(inode, pipe);
603 return 0;
604}
605
606static int
607pipe_fasync(int fd, struct file *filp, int on)
608{
609 struct pipe_inode_info *pipe = filp->private_data;
610 int retval = 0;
611
612 __pipe_lock(pipe);
613 if (filp->f_mode & FMODE_READ)
614 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
615 if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
616 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
617 if (retval < 0 && (filp->f_mode & FMODE_READ))
618 /* this can happen only if on == T */
619 fasync_helper(-1, filp, 0, &pipe->fasync_readers);
620 }
621 __pipe_unlock(pipe);
622 return retval;
623}
624
625static unsigned long account_pipe_buffers(struct user_struct *user,
626 unsigned long old, unsigned long new)
627{
628 return atomic_long_add_return(new - old, &user->pipe_bufs);
629}
630
631static bool too_many_pipe_buffers_soft(unsigned long user_bufs)
632{
633 unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
634
635 return soft_limit && user_bufs > soft_limit;
636}
637
638static bool too_many_pipe_buffers_hard(unsigned long user_bufs)
639{
640 unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
641
642 return hard_limit && user_bufs > hard_limit;
643}
644
645static bool is_unprivileged_user(void)
646{
647 return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
648}
649
650struct pipe_inode_info *alloc_pipe_info(void)
651{
652 struct pipe_inode_info *pipe;
653 unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
654 struct user_struct *user = get_current_user();
655 unsigned long user_bufs;
656 unsigned int max_size = READ_ONCE(pipe_max_size);
657
658 pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
659 if (pipe == NULL)
660 goto out_free_uid;
661
662 if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
663 pipe_bufs = max_size >> PAGE_SHIFT;
664
665 user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
666
667 if (too_many_pipe_buffers_soft(user_bufs) && is_unprivileged_user()) {
668 user_bufs = account_pipe_buffers(user, pipe_bufs, 1);
669 pipe_bufs = 1;
670 }
671
672 if (too_many_pipe_buffers_hard(user_bufs) && is_unprivileged_user())
673 goto out_revert_acct;
674
675 pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
676 GFP_KERNEL_ACCOUNT);
677
678 if (pipe->bufs) {
679 init_waitqueue_head(&pipe->wait);
680 pipe->r_counter = pipe->w_counter = 1;
681 pipe->buffers = pipe_bufs;
682 pipe->user = user;
683 mutex_init(&pipe->mutex);
684 return pipe;
685 }
686
687out_revert_acct:
688 (void) account_pipe_buffers(user, pipe_bufs, 0);
689 kfree(pipe);
690out_free_uid:
691 free_uid(user);
692 return NULL;
693}
694
695void free_pipe_info(struct pipe_inode_info *pipe)
696{
697 int i;
698
699 (void) account_pipe_buffers(pipe->user, pipe->buffers, 0);
700 free_uid(pipe->user);
701 for (i = 0; i < pipe->buffers; i++) {
702 struct pipe_buffer *buf = pipe->bufs + i;
703 if (buf->ops)
704 pipe_buf_release(pipe, buf);
705 }
706 if (pipe->tmp_page)
707 __free_page(pipe->tmp_page);
708 kfree(pipe->bufs);
709 kfree(pipe);
710}
711
712static struct vfsmount *pipe_mnt __read_mostly;
713
714/*
715 * pipefs_dname() is called from d_path().
716 */
717static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
718{
719 return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
720 d_inode(dentry)->i_ino);
721}
722
723static const struct dentry_operations pipefs_dentry_operations = {
724 .d_dname = pipefs_dname,
725};
726
727static struct inode * get_pipe_inode(void)
728{
729 struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
730 struct pipe_inode_info *pipe;
731
732 if (!inode)
733 goto fail_inode;
734
735 inode->i_ino = get_next_ino();
736
737 pipe = alloc_pipe_info();
738 if (!pipe)
739 goto fail_iput;
740
741 inode->i_pipe = pipe;
742 pipe->files = 2;
743 pipe->readers = pipe->writers = 1;
744 inode->i_fop = &pipefifo_fops;
745
746 /*
747 * Mark the inode dirty from the very beginning,
748 * that way it will never be moved to the dirty
749 * list because "mark_inode_dirty()" will think
750 * that it already _is_ on the dirty list.
751 */
752 inode->i_state = I_DIRTY;
753 inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
754 inode->i_uid = current_fsuid();
755 inode->i_gid = current_fsgid();
756 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
757
758 return inode;
759
760fail_iput:
761 iput(inode);
762
763fail_inode:
764 return NULL;
765}
766
767int create_pipe_files(struct file **res, int flags)
768{
769 struct inode *inode = get_pipe_inode();
770 struct file *f;
771
772 if (!inode)
773 return -ENFILE;
774
775 f = alloc_file_pseudo(inode, pipe_mnt, "",
776 O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
777 &pipefifo_fops);
778 if (IS_ERR(f)) {
779 free_pipe_info(inode->i_pipe);
780 iput(inode);
781 return PTR_ERR(f);
782 }
783
784 f->private_data = inode->i_pipe;
785
786 res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
787 &pipefifo_fops);
788 if (IS_ERR(res[0])) {
789 put_pipe_info(inode, inode->i_pipe);
790 fput(f);
791 return PTR_ERR(res[0]);
792 }
793 res[0]->private_data = inode->i_pipe;
794 res[1] = f;
795 return 0;
796}
797
798static int __do_pipe_flags(int *fd, struct file **files, int flags)
799{
800 int error;
801 int fdw, fdr;
802
803 if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
804 return -EINVAL;
805
806 error = create_pipe_files(files, flags);
807 if (error)
808 return error;
809
810 error = get_unused_fd_flags(flags);
811 if (error < 0)
812 goto err_read_pipe;
813 fdr = error;
814
815 error = get_unused_fd_flags(flags);
816 if (error < 0)
817 goto err_fdr;
818 fdw = error;
819
820 audit_fd_pair(fdr, fdw);
821 fd[0] = fdr;
822 fd[1] = fdw;
823 return 0;
824
825 err_fdr:
826 put_unused_fd(fdr);
827 err_read_pipe:
828 fput(files[0]);
829 fput(files[1]);
830 return error;
831}
832
833int do_pipe_flags(int *fd, int flags)
834{
835 struct file *files[2];
836 int error = __do_pipe_flags(fd, files, flags);
837 if (!error) {
838 fd_install(fd[0], files[0]);
839 fd_install(fd[1], files[1]);
840 }
841 return error;
842}
843
844/*
845 * sys_pipe() is the normal C calling standard for creating
846 * a pipe. It's not the way Unix traditionally does this, though.
847 */
848static int do_pipe2(int __user *fildes, int flags)
849{
850 struct file *files[2];
851 int fd[2];
852 int error;
853
854 error = __do_pipe_flags(fd, files, flags);
855 if (!error) {
856 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
857 fput(files[0]);
858 fput(files[1]);
859 put_unused_fd(fd[0]);
860 put_unused_fd(fd[1]);
861 error = -EFAULT;
862 } else {
863 fd_install(fd[0], files[0]);
864 fd_install(fd[1], files[1]);
865 }
866 }
867 return error;
868}
869
870SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
871{
872 return do_pipe2(fildes, flags);
873}
874
875SYSCALL_DEFINE1(pipe, int __user *, fildes)
876{
877 return do_pipe2(fildes, 0);
878}
879
880static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
881{
882 int cur = *cnt;
883
884 while (cur == *cnt) {
885 pipe_wait(pipe);
886 if (signal_pending(current))
887 break;
888 }
889 return cur == *cnt ? -ERESTARTSYS : 0;
890}
891
892static void wake_up_partner(struct pipe_inode_info *pipe)
893{
894 wake_up_interruptible(&pipe->wait);
895}
896
897static int fifo_open(struct inode *inode, struct file *filp)
898{
899 struct pipe_inode_info *pipe;
900 bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
901 int ret;
902
903 filp->f_version = 0;
904
905 spin_lock(&inode->i_lock);
906 if (inode->i_pipe) {
907 pipe = inode->i_pipe;
908 pipe->files++;
909 spin_unlock(&inode->i_lock);
910 } else {
911 spin_unlock(&inode->i_lock);
912 pipe = alloc_pipe_info();
913 if (!pipe)
914 return -ENOMEM;
915 pipe->files = 1;
916 spin_lock(&inode->i_lock);
917 if (unlikely(inode->i_pipe)) {
918 inode->i_pipe->files++;
919 spin_unlock(&inode->i_lock);
920 free_pipe_info(pipe);
921 pipe = inode->i_pipe;
922 } else {
923 inode->i_pipe = pipe;
924 spin_unlock(&inode->i_lock);
925 }
926 }
927 filp->private_data = pipe;
928 /* OK, we have a pipe and it's pinned down */
929
930 __pipe_lock(pipe);
931
932 /* We can only do regular read/write on fifos */
933 filp->f_mode &= (FMODE_READ | FMODE_WRITE);
934
935 switch (filp->f_mode) {
936 case FMODE_READ:
937 /*
938 * O_RDONLY
939 * POSIX.1 says that O_NONBLOCK means return with the FIFO
940 * opened, even when there is no process writing the FIFO.
941 */
942 pipe->r_counter++;
943 if (pipe->readers++ == 0)
944 wake_up_partner(pipe);
945
946 if (!is_pipe && !pipe->writers) {
947 if ((filp->f_flags & O_NONBLOCK)) {
948 /* suppress EPOLLHUP until we have
949 * seen a writer */
950 filp->f_version = pipe->w_counter;
951 } else {
952 if (wait_for_partner(pipe, &pipe->w_counter))
953 goto err_rd;
954 }
955 }
956 break;
957
958 case FMODE_WRITE:
959 /*
960 * O_WRONLY
961 * POSIX.1 says that O_NONBLOCK means return -1 with
962 * errno=ENXIO when there is no process reading the FIFO.
963 */
964 ret = -ENXIO;
965 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
966 goto err;
967
968 pipe->w_counter++;
969 if (!pipe->writers++)
970 wake_up_partner(pipe);
971
972 if (!is_pipe && !pipe->readers) {
973 if (wait_for_partner(pipe, &pipe->r_counter))
974 goto err_wr;
975 }
976 break;
977
978 case FMODE_READ | FMODE_WRITE:
979 /*
980 * O_RDWR
981 * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
982 * This implementation will NEVER block on a O_RDWR open, since
983 * the process can at least talk to itself.
984 */
985
986 pipe->readers++;
987 pipe->writers++;
988 pipe->r_counter++;
989 pipe->w_counter++;
990 if (pipe->readers == 1 || pipe->writers == 1)
991 wake_up_partner(pipe);
992 break;
993
994 default:
995 ret = -EINVAL;
996 goto err;
997 }
998
999 /* Ok! */
1000 __pipe_unlock(pipe);
1001 return 0;
1002
1003err_rd:
1004 if (!--pipe->readers)
1005 wake_up_interruptible(&pipe->wait);
1006 ret = -ERESTARTSYS;
1007 goto err;
1008
1009err_wr:
1010 if (!--pipe->writers)
1011 wake_up_interruptible(&pipe->wait);
1012 ret = -ERESTARTSYS;
1013 goto err;
1014
1015err:
1016 __pipe_unlock(pipe);
1017
1018 put_pipe_info(inode, pipe);
1019 return ret;
1020}
1021
1022const struct file_operations pipefifo_fops = {
1023 .open = fifo_open,
1024 .llseek = no_llseek,
1025 .read_iter = pipe_read,
1026 .write_iter = pipe_write,
1027 .poll = pipe_poll,
1028 .unlocked_ioctl = pipe_ioctl,
1029 .release = pipe_release,
1030 .fasync = pipe_fasync,
1031};
1032
1033/*
1034 * Currently we rely on the pipe array holding a power-of-2 number
1035 * of pages. Returns 0 on error.
1036 */
1037unsigned int round_pipe_size(unsigned long size)
1038{
1039 if (size > (1U << 31))
1040 return 0;
1041
1042 /* Minimum pipe size, as required by POSIX */
1043 if (size < PAGE_SIZE)
1044 return PAGE_SIZE;
1045
1046 return roundup_pow_of_two(size);
1047}
1048
1049/*
1050 * Allocate a new array of pipe buffers and copy the info over. Returns the
1051 * pipe size if successful, or return -ERROR on error.
1052 */
1053static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1054{
1055 struct pipe_buffer *bufs;
1056 unsigned int size, nr_pages;
1057 unsigned long user_bufs;
1058 long ret = 0;
1059
1060 size = round_pipe_size(arg);
1061 nr_pages = size >> PAGE_SHIFT;
1062
1063 if (!nr_pages)
1064 return -EINVAL;
1065
1066 /*
1067 * If trying to increase the pipe capacity, check that an
1068 * unprivileged user is not trying to exceed various limits
1069 * (soft limit check here, hard limit check just below).
1070 * Decreasing the pipe capacity is always permitted, even
1071 * if the user is currently over a limit.
1072 */
1073 if (nr_pages > pipe->buffers &&
1074 size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1075 return -EPERM;
1076
1077 user_bufs = account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
1078
1079 if (nr_pages > pipe->buffers &&
1080 (too_many_pipe_buffers_hard(user_bufs) ||
1081 too_many_pipe_buffers_soft(user_bufs)) &&
1082 is_unprivileged_user()) {
1083 ret = -EPERM;
1084 goto out_revert_acct;
1085 }
1086
1087 /*
1088 * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1089 * expect a lot of shrink+grow operations, just free and allocate
1090 * again like we would do for growing. If the pipe currently
1091 * contains more buffers than arg, then return busy.
1092 */
1093 if (nr_pages < pipe->nrbufs) {
1094 ret = -EBUSY;
1095 goto out_revert_acct;
1096 }
1097
1098 bufs = kcalloc(nr_pages, sizeof(*bufs),
1099 GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1100 if (unlikely(!bufs)) {
1101 ret = -ENOMEM;
1102 goto out_revert_acct;
1103 }
1104
1105 /*
1106 * The pipe array wraps around, so just start the new one at zero
1107 * and adjust the indexes.
1108 */
1109 if (pipe->nrbufs) {
1110 unsigned int tail;
1111 unsigned int head;
1112
1113 tail = pipe->curbuf + pipe->nrbufs;
1114 if (tail < pipe->buffers)
1115 tail = 0;
1116 else
1117 tail &= (pipe->buffers - 1);
1118
1119 head = pipe->nrbufs - tail;
1120 if (head)
1121 memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1122 if (tail)
1123 memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1124 }
1125
1126 pipe->curbuf = 0;
1127 kfree(pipe->bufs);
1128 pipe->bufs = bufs;
1129 pipe->buffers = nr_pages;
1130 return nr_pages * PAGE_SIZE;
1131
1132out_revert_acct:
1133 (void) account_pipe_buffers(pipe->user, nr_pages, pipe->buffers);
1134 return ret;
1135}
1136
1137/*
1138 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1139 * location, so checking ->i_pipe is not enough to verify that this is a
1140 * pipe.
1141 */
1142struct pipe_inode_info *get_pipe_info(struct file *file)
1143{
1144 return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1145}
1146
1147long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1148{
1149 struct pipe_inode_info *pipe;
1150 long ret;
1151
1152 pipe = get_pipe_info(file);
1153 if (!pipe)
1154 return -EBADF;
1155
1156 __pipe_lock(pipe);
1157
1158 switch (cmd) {
1159 case F_SETPIPE_SZ:
1160 ret = pipe_set_size(pipe, arg);
1161 break;
1162 case F_GETPIPE_SZ:
1163 ret = pipe->buffers * PAGE_SIZE;
1164 break;
1165 default:
1166 ret = -EINVAL;
1167 break;
1168 }
1169
1170 __pipe_unlock(pipe);
1171 return ret;
1172}
1173
1174static const struct super_operations pipefs_ops = {
1175 .destroy_inode = free_inode_nonrcu,
1176 .statfs = simple_statfs,
1177};
1178
1179/*
1180 * pipefs should _never_ be mounted by userland - too much of security hassle,
1181 * no real gain from having the whole whorehouse mounted. So we don't need
1182 * any operations on the root directory. However, we need a non-trivial
1183 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1184 */
1185static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1186 int flags, const char *dev_name, void *data)
1187{
1188 return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1189 &pipefs_dentry_operations, PIPEFS_MAGIC);
1190}
1191
1192static struct file_system_type pipe_fs_type = {
1193 .name = "pipefs",
1194 .mount = pipefs_mount,
1195 .kill_sb = kill_anon_super,
1196};
1197
1198static int __init init_pipe_fs(void)
1199{
1200 int err = register_filesystem(&pipe_fs_type);
1201
1202 if (!err) {
1203 pipe_mnt = kern_mount(&pipe_fs_type);
1204 if (IS_ERR(pipe_mnt)) {
1205 err = PTR_ERR(pipe_mnt);
1206 unregister_filesystem(&pipe_fs_type);
1207 }
1208 }
1209 return err;
1210}
1211
1212fs_initcall(init_pipe_fs);
1213