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