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1/*
2 * linux/fs/pipe.c
3 *
4 * Copyright (C) 1991, 1992, 1999 Linus Torvalds
5 */
6
7#include <linux/mm.h>
8#include <linux/file.h>
9#include <linux/poll.h>
10#include <linux/slab.h>
11#include <linux/module.h>
12#include <linux/init.h>
13#include <linux/fs.h>
14#include <linux/log2.h>
15#include <linux/mount.h>
16#include <linux/magic.h>
17#include <linux/pipe_fs_i.h>
18#include <linux/uio.h>
19#include <linux/highmem.h>
20#include <linux/pagemap.h>
21#include <linux/audit.h>
22#include <linux/syscalls.h>
23#include <linux/fcntl.h>
24
25#include <asm/uaccess.h>
26#include <asm/ioctls.h>
27
28/*
29 * The max size that a non-root user is allowed to grow the pipe. Can
30 * be set by root in /proc/sys/fs/pipe-max-size
31 */
32unsigned int pipe_max_size = 1048576;
33
34/*
35 * Minimum pipe size, as required by POSIX
36 */
37unsigned int pipe_min_size = PAGE_SIZE;
38
39/*
40 * We use a start+len construction, which provides full use of the
41 * allocated memory.
42 * -- Florian Coosmann (FGC)
43 *
44 * Reads with count = 0 should always return 0.
45 * -- Julian Bradfield 1999-06-07.
46 *
47 * FIFOs and Pipes now generate SIGIO for both readers and writers.
48 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
49 *
50 * pipe_read & write cleanup
51 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
52 */
53
54static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
55{
56 if (pipe->inode)
57 mutex_lock_nested(&pipe->inode->i_mutex, subclass);
58}
59
60void pipe_lock(struct pipe_inode_info *pipe)
61{
62 /*
63 * pipe_lock() nests non-pipe inode locks (for writing to a file)
64 */
65 pipe_lock_nested(pipe, I_MUTEX_PARENT);
66}
67EXPORT_SYMBOL(pipe_lock);
68
69void pipe_unlock(struct pipe_inode_info *pipe)
70{
71 if (pipe->inode)
72 mutex_unlock(&pipe->inode->i_mutex);
73}
74EXPORT_SYMBOL(pipe_unlock);
75
76void pipe_double_lock(struct pipe_inode_info *pipe1,
77 struct pipe_inode_info *pipe2)
78{
79 BUG_ON(pipe1 == pipe2);
80
81 if (pipe1 < pipe2) {
82 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
83 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
84 } else {
85 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
86 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
87 }
88}
89
90/* Drop the inode semaphore and wait for a pipe event, atomically */
91void pipe_wait(struct pipe_inode_info *pipe)
92{
93 DEFINE_WAIT(wait);
94
95 /*
96 * Pipes are system-local resources, so sleeping on them
97 * is considered a noninteractive wait:
98 */
99 prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
100 pipe_unlock(pipe);
101 schedule();
102 finish_wait(&pipe->wait, &wait);
103 pipe_lock(pipe);
104}
105
106static int
107pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
108 int atomic)
109{
110 unsigned long copy;
111
112 while (len > 0) {
113 while (!iov->iov_len)
114 iov++;
115 copy = min_t(unsigned long, len, iov->iov_len);
116
117 if (atomic) {
118 if (__copy_from_user_inatomic(to, iov->iov_base, copy))
119 return -EFAULT;
120 } else {
121 if (copy_from_user(to, iov->iov_base, copy))
122 return -EFAULT;
123 }
124 to += copy;
125 len -= copy;
126 iov->iov_base += copy;
127 iov->iov_len -= copy;
128 }
129 return 0;
130}
131
132static int
133pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
134 int atomic)
135{
136 unsigned long copy;
137
138 while (len > 0) {
139 while (!iov->iov_len)
140 iov++;
141 copy = min_t(unsigned long, len, iov->iov_len);
142
143 if (atomic) {
144 if (__copy_to_user_inatomic(iov->iov_base, from, copy))
145 return -EFAULT;
146 } else {
147 if (copy_to_user(iov->iov_base, from, copy))
148 return -EFAULT;
149 }
150 from += copy;
151 len -= copy;
152 iov->iov_base += copy;
153 iov->iov_len -= copy;
154 }
155 return 0;
156}
157
158/*
159 * Attempt to pre-fault in the user memory, so we can use atomic copies.
160 * Returns the number of bytes not faulted in.
161 */
162static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
163{
164 while (!iov->iov_len)
165 iov++;
166
167 while (len > 0) {
168 unsigned long this_len;
169
170 this_len = min_t(unsigned long, len, iov->iov_len);
171 if (fault_in_pages_writeable(iov->iov_base, this_len))
172 break;
173
174 len -= this_len;
175 iov++;
176 }
177
178 return len;
179}
180
181/*
182 * Pre-fault in the user memory, so we can use atomic copies.
183 */
184static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
185{
186 while (!iov->iov_len)
187 iov++;
188
189 while (len > 0) {
190 unsigned long this_len;
191
192 this_len = min_t(unsigned long, len, iov->iov_len);
193 fault_in_pages_readable(iov->iov_base, this_len);
194 len -= this_len;
195 iov++;
196 }
197}
198
199static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
200 struct pipe_buffer *buf)
201{
202 struct page *page = buf->page;
203
204 /*
205 * If nobody else uses this page, and we don't already have a
206 * temporary page, let's keep track of it as a one-deep
207 * allocation cache. (Otherwise just release our reference to it)
208 */
209 if (page_count(page) == 1 && !pipe->tmp_page)
210 pipe->tmp_page = page;
211 else
212 page_cache_release(page);
213}
214
215/**
216 * generic_pipe_buf_map - virtually map a pipe buffer
217 * @pipe: the pipe that the buffer belongs to
218 * @buf: the buffer that should be mapped
219 * @atomic: whether to use an atomic map
220 *
221 * Description:
222 * This function returns a kernel virtual address mapping for the
223 * pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided
224 * and the caller has to be careful not to fault before calling
225 * the unmap function.
226 *
227 * Note that this function occupies KM_USER0 if @atomic != 0.
228 */
229void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
230 struct pipe_buffer *buf, int atomic)
231{
232 if (atomic) {
233 buf->flags |= PIPE_BUF_FLAG_ATOMIC;
234 return kmap_atomic(buf->page);
235 }
236
237 return kmap(buf->page);
238}
239EXPORT_SYMBOL(generic_pipe_buf_map);
240
241/**
242 * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
243 * @pipe: the pipe that the buffer belongs to
244 * @buf: the buffer that should be unmapped
245 * @map_data: the data that the mapping function returned
246 *
247 * Description:
248 * This function undoes the mapping that ->map() provided.
249 */
250void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
251 struct pipe_buffer *buf, void *map_data)
252{
253 if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
254 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
255 kunmap_atomic(map_data);
256 } else
257 kunmap(buf->page);
258}
259EXPORT_SYMBOL(generic_pipe_buf_unmap);
260
261/**
262 * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
263 * @pipe: the pipe that the buffer belongs to
264 * @buf: the buffer to attempt to steal
265 *
266 * Description:
267 * This function attempts to steal the &struct page attached to
268 * @buf. If successful, this function returns 0 and returns with
269 * the page locked. The caller may then reuse the page for whatever
270 * he wishes; the typical use is insertion into a different file
271 * page cache.
272 */
273int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
274 struct pipe_buffer *buf)
275{
276 struct page *page = buf->page;
277
278 /*
279 * A reference of one is golden, that means that the owner of this
280 * page is the only one holding a reference to it. lock the page
281 * and return OK.
282 */
283 if (page_count(page) == 1) {
284 lock_page(page);
285 return 0;
286 }
287
288 return 1;
289}
290EXPORT_SYMBOL(generic_pipe_buf_steal);
291
292/**
293 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
294 * @pipe: the pipe that the buffer belongs to
295 * @buf: the buffer to get a reference to
296 *
297 * Description:
298 * This function grabs an extra reference to @buf. It's used in
299 * in the tee() system call, when we duplicate the buffers in one
300 * pipe into another.
301 */
302void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
303{
304 page_cache_get(buf->page);
305}
306EXPORT_SYMBOL(generic_pipe_buf_get);
307
308/**
309 * generic_pipe_buf_confirm - verify contents of the pipe buffer
310 * @info: the pipe that the buffer belongs to
311 * @buf: the buffer to confirm
312 *
313 * Description:
314 * This function does nothing, because the generic pipe code uses
315 * pages that are always good when inserted into the pipe.
316 */
317int generic_pipe_buf_confirm(struct pipe_inode_info *info,
318 struct pipe_buffer *buf)
319{
320 return 0;
321}
322EXPORT_SYMBOL(generic_pipe_buf_confirm);
323
324/**
325 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
326 * @pipe: the pipe that the buffer belongs to
327 * @buf: the buffer to put a reference to
328 *
329 * Description:
330 * This function releases a reference to @buf.
331 */
332void generic_pipe_buf_release(struct pipe_inode_info *pipe,
333 struct pipe_buffer *buf)
334{
335 page_cache_release(buf->page);
336}
337EXPORT_SYMBOL(generic_pipe_buf_release);
338
339static const struct pipe_buf_operations anon_pipe_buf_ops = {
340 .can_merge = 1,
341 .map = generic_pipe_buf_map,
342 .unmap = generic_pipe_buf_unmap,
343 .confirm = generic_pipe_buf_confirm,
344 .release = anon_pipe_buf_release,
345 .steal = generic_pipe_buf_steal,
346 .get = generic_pipe_buf_get,
347};
348
349static const struct pipe_buf_operations packet_pipe_buf_ops = {
350 .can_merge = 0,
351 .map = generic_pipe_buf_map,
352 .unmap = generic_pipe_buf_unmap,
353 .confirm = generic_pipe_buf_confirm,
354 .release = anon_pipe_buf_release,
355 .steal = generic_pipe_buf_steal,
356 .get = generic_pipe_buf_get,
357};
358
359static ssize_t
360pipe_read(struct kiocb *iocb, const struct iovec *_iov,
361 unsigned long nr_segs, loff_t pos)
362{
363 struct file *filp = iocb->ki_filp;
364 struct inode *inode = filp->f_path.dentry->d_inode;
365 struct pipe_inode_info *pipe;
366 int do_wakeup;
367 ssize_t ret;
368 struct iovec *iov = (struct iovec *)_iov;
369 size_t total_len;
370
371 total_len = iov_length(iov, nr_segs);
372 /* Null read succeeds. */
373 if (unlikely(total_len == 0))
374 return 0;
375
376 do_wakeup = 0;
377 ret = 0;
378 mutex_lock(&inode->i_mutex);
379 pipe = inode->i_pipe;
380 for (;;) {
381 int bufs = pipe->nrbufs;
382 if (bufs) {
383 int curbuf = pipe->curbuf;
384 struct pipe_buffer *buf = pipe->bufs + curbuf;
385 const struct pipe_buf_operations *ops = buf->ops;
386 void *addr;
387 size_t chars = buf->len;
388 int error, atomic;
389
390 if (chars > total_len)
391 chars = total_len;
392
393 error = ops->confirm(pipe, buf);
394 if (error) {
395 if (!ret)
396 ret = error;
397 break;
398 }
399
400 atomic = !iov_fault_in_pages_write(iov, chars);
401redo:
402 addr = ops->map(pipe, buf, atomic);
403 error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
404 ops->unmap(pipe, buf, addr);
405 if (unlikely(error)) {
406 /*
407 * Just retry with the slow path if we failed.
408 */
409 if (atomic) {
410 atomic = 0;
411 goto redo;
412 }
413 if (!ret)
414 ret = error;
415 break;
416 }
417 ret += chars;
418 buf->offset += chars;
419 buf->len -= chars;
420
421 /* Was it a packet buffer? Clean up and exit */
422 if (buf->flags & PIPE_BUF_FLAG_PACKET) {
423 total_len = chars;
424 buf->len = 0;
425 }
426
427 if (!buf->len) {
428 buf->ops = NULL;
429 ops->release(pipe, buf);
430 curbuf = (curbuf + 1) & (pipe->buffers - 1);
431 pipe->curbuf = curbuf;
432 pipe->nrbufs = --bufs;
433 do_wakeup = 1;
434 }
435 total_len -= chars;
436 if (!total_len)
437 break; /* common path: read succeeded */
438 }
439 if (bufs) /* More to do? */
440 continue;
441 if (!pipe->writers)
442 break;
443 if (!pipe->waiting_writers) {
444 /* syscall merging: Usually we must not sleep
445 * if O_NONBLOCK is set, or if we got some data.
446 * But if a writer sleeps in kernel space, then
447 * we can wait for that data without violating POSIX.
448 */
449 if (ret)
450 break;
451 if (filp->f_flags & O_NONBLOCK) {
452 ret = -EAGAIN;
453 break;
454 }
455 }
456 if (signal_pending(current)) {
457 if (!ret)
458 ret = -ERESTARTSYS;
459 break;
460 }
461 if (do_wakeup) {
462 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
463 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
464 }
465 pipe_wait(pipe);
466 }
467 mutex_unlock(&inode->i_mutex);
468
469 /* Signal writers asynchronously that there is more room. */
470 if (do_wakeup) {
471 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
472 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
473 }
474 if (ret > 0)
475 file_accessed(filp);
476 return ret;
477}
478
479static inline int is_packetized(struct file *file)
480{
481 return (file->f_flags & O_DIRECT) != 0;
482}
483
484static ssize_t
485pipe_write(struct kiocb *iocb, const struct iovec *_iov,
486 unsigned long nr_segs, loff_t ppos)
487{
488 struct file *filp = iocb->ki_filp;
489 struct inode *inode = filp->f_path.dentry->d_inode;
490 struct pipe_inode_info *pipe;
491 ssize_t ret;
492 int do_wakeup;
493 struct iovec *iov = (struct iovec *)_iov;
494 size_t total_len;
495 ssize_t chars;
496
497 total_len = iov_length(iov, nr_segs);
498 /* Null write succeeds. */
499 if (unlikely(total_len == 0))
500 return 0;
501
502 do_wakeup = 0;
503 ret = 0;
504 mutex_lock(&inode->i_mutex);
505 pipe = inode->i_pipe;
506
507 if (!pipe->readers) {
508 send_sig(SIGPIPE, current, 0);
509 ret = -EPIPE;
510 goto out;
511 }
512
513 /* We try to merge small writes */
514 chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
515 if (pipe->nrbufs && chars != 0) {
516 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
517 (pipe->buffers - 1);
518 struct pipe_buffer *buf = pipe->bufs + lastbuf;
519 const struct pipe_buf_operations *ops = buf->ops;
520 int offset = buf->offset + buf->len;
521
522 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
523 int error, atomic = 1;
524 void *addr;
525
526 error = ops->confirm(pipe, buf);
527 if (error)
528 goto out;
529
530 iov_fault_in_pages_read(iov, chars);
531redo1:
532 addr = ops->map(pipe, buf, atomic);
533 error = pipe_iov_copy_from_user(offset + addr, iov,
534 chars, atomic);
535 ops->unmap(pipe, buf, addr);
536 ret = error;
537 do_wakeup = 1;
538 if (error) {
539 if (atomic) {
540 atomic = 0;
541 goto redo1;
542 }
543 goto out;
544 }
545 buf->len += chars;
546 total_len -= chars;
547 ret = chars;
548 if (!total_len)
549 goto out;
550 }
551 }
552
553 for (;;) {
554 int bufs;
555
556 if (!pipe->readers) {
557 send_sig(SIGPIPE, current, 0);
558 if (!ret)
559 ret = -EPIPE;
560 break;
561 }
562 bufs = pipe->nrbufs;
563 if (bufs < pipe->buffers) {
564 int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
565 struct pipe_buffer *buf = pipe->bufs + newbuf;
566 struct page *page = pipe->tmp_page;
567 char *src;
568 int error, atomic = 1;
569
570 if (!page) {
571 page = alloc_page(GFP_HIGHUSER);
572 if (unlikely(!page)) {
573 ret = ret ? : -ENOMEM;
574 break;
575 }
576 pipe->tmp_page = page;
577 }
578 /* Always wake up, even if the copy fails. Otherwise
579 * we lock up (O_NONBLOCK-)readers that sleep due to
580 * syscall merging.
581 * FIXME! Is this really true?
582 */
583 do_wakeup = 1;
584 chars = PAGE_SIZE;
585 if (chars > total_len)
586 chars = total_len;
587
588 iov_fault_in_pages_read(iov, chars);
589redo2:
590 if (atomic)
591 src = kmap_atomic(page);
592 else
593 src = kmap(page);
594
595 error = pipe_iov_copy_from_user(src, iov, chars,
596 atomic);
597 if (atomic)
598 kunmap_atomic(src);
599 else
600 kunmap(page);
601
602 if (unlikely(error)) {
603 if (atomic) {
604 atomic = 0;
605 goto redo2;
606 }
607 if (!ret)
608 ret = error;
609 break;
610 }
611 ret += chars;
612
613 /* Insert it into the buffer array */
614 buf->page = page;
615 buf->ops = &anon_pipe_buf_ops;
616 buf->offset = 0;
617 buf->len = chars;
618 buf->flags = 0;
619 if (is_packetized(filp)) {
620 buf->ops = &packet_pipe_buf_ops;
621 buf->flags = PIPE_BUF_FLAG_PACKET;
622 }
623 pipe->nrbufs = ++bufs;
624 pipe->tmp_page = NULL;
625
626 total_len -= chars;
627 if (!total_len)
628 break;
629 }
630 if (bufs < pipe->buffers)
631 continue;
632 if (filp->f_flags & O_NONBLOCK) {
633 if (!ret)
634 ret = -EAGAIN;
635 break;
636 }
637 if (signal_pending(current)) {
638 if (!ret)
639 ret = -ERESTARTSYS;
640 break;
641 }
642 if (do_wakeup) {
643 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
644 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
645 do_wakeup = 0;
646 }
647 pipe->waiting_writers++;
648 pipe_wait(pipe);
649 pipe->waiting_writers--;
650 }
651out:
652 mutex_unlock(&inode->i_mutex);
653 if (do_wakeup) {
654 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
655 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
656 }
657 if (ret > 0) {
658 int err = file_update_time(filp);
659 if (err)
660 ret = err;
661 }
662 return ret;
663}
664
665static ssize_t
666bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
667{
668 return -EBADF;
669}
670
671static ssize_t
672bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
673 loff_t *ppos)
674{
675 return -EBADF;
676}
677
678static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
679{
680 struct inode *inode = filp->f_path.dentry->d_inode;
681 struct pipe_inode_info *pipe;
682 int count, buf, nrbufs;
683
684 switch (cmd) {
685 case FIONREAD:
686 mutex_lock(&inode->i_mutex);
687 pipe = inode->i_pipe;
688 count = 0;
689 buf = pipe->curbuf;
690 nrbufs = pipe->nrbufs;
691 while (--nrbufs >= 0) {
692 count += pipe->bufs[buf].len;
693 buf = (buf+1) & (pipe->buffers - 1);
694 }
695 mutex_unlock(&inode->i_mutex);
696
697 return put_user(count, (int __user *)arg);
698 default:
699 return -ENOIOCTLCMD;
700 }
701}
702
703/* No kernel lock held - fine */
704static unsigned int
705pipe_poll(struct file *filp, poll_table *wait)
706{
707 unsigned int mask;
708 struct inode *inode = filp->f_path.dentry->d_inode;
709 struct pipe_inode_info *pipe = inode->i_pipe;
710 int nrbufs;
711
712 poll_wait(filp, &pipe->wait, wait);
713
714 /* Reading only -- no need for acquiring the semaphore. */
715 nrbufs = pipe->nrbufs;
716 mask = 0;
717 if (filp->f_mode & FMODE_READ) {
718 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
719 if (!pipe->writers && filp->f_version != pipe->w_counter)
720 mask |= POLLHUP;
721 }
722
723 if (filp->f_mode & FMODE_WRITE) {
724 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
725 /*
726 * Most Unices do not set POLLERR for FIFOs but on Linux they
727 * behave exactly like pipes for poll().
728 */
729 if (!pipe->readers)
730 mask |= POLLERR;
731 }
732
733 return mask;
734}
735
736static int
737pipe_release(struct inode *inode, int decr, int decw)
738{
739 struct pipe_inode_info *pipe;
740
741 mutex_lock(&inode->i_mutex);
742 pipe = inode->i_pipe;
743 pipe->readers -= decr;
744 pipe->writers -= decw;
745
746 if (!pipe->readers && !pipe->writers) {
747 free_pipe_info(inode);
748 } else {
749 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
750 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
751 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
752 }
753 mutex_unlock(&inode->i_mutex);
754
755 return 0;
756}
757
758static int
759pipe_read_fasync(int fd, struct file *filp, int on)
760{
761 struct inode *inode = filp->f_path.dentry->d_inode;
762 int retval;
763
764 mutex_lock(&inode->i_mutex);
765 retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
766 mutex_unlock(&inode->i_mutex);
767
768 return retval;
769}
770
771
772static int
773pipe_write_fasync(int fd, struct file *filp, int on)
774{
775 struct inode *inode = filp->f_path.dentry->d_inode;
776 int retval;
777
778 mutex_lock(&inode->i_mutex);
779 retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
780 mutex_unlock(&inode->i_mutex);
781
782 return retval;
783}
784
785
786static int
787pipe_rdwr_fasync(int fd, struct file *filp, int on)
788{
789 struct inode *inode = filp->f_path.dentry->d_inode;
790 struct pipe_inode_info *pipe = inode->i_pipe;
791 int retval;
792
793 mutex_lock(&inode->i_mutex);
794 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
795 if (retval >= 0) {
796 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
797 if (retval < 0) /* this can happen only if on == T */
798 fasync_helper(-1, filp, 0, &pipe->fasync_readers);
799 }
800 mutex_unlock(&inode->i_mutex);
801 return retval;
802}
803
804
805static int
806pipe_read_release(struct inode *inode, struct file *filp)
807{
808 return pipe_release(inode, 1, 0);
809}
810
811static int
812pipe_write_release(struct inode *inode, struct file *filp)
813{
814 return pipe_release(inode, 0, 1);
815}
816
817static int
818pipe_rdwr_release(struct inode *inode, struct file *filp)
819{
820 int decr, decw;
821
822 decr = (filp->f_mode & FMODE_READ) != 0;
823 decw = (filp->f_mode & FMODE_WRITE) != 0;
824 return pipe_release(inode, decr, decw);
825}
826
827static int
828pipe_read_open(struct inode *inode, struct file *filp)
829{
830 int ret = -ENOENT;
831
832 mutex_lock(&inode->i_mutex);
833
834 if (inode->i_pipe) {
835 ret = 0;
836 inode->i_pipe->readers++;
837 }
838
839 mutex_unlock(&inode->i_mutex);
840
841 return ret;
842}
843
844static int
845pipe_write_open(struct inode *inode, struct file *filp)
846{
847 int ret = -ENOENT;
848
849 mutex_lock(&inode->i_mutex);
850
851 if (inode->i_pipe) {
852 ret = 0;
853 inode->i_pipe->writers++;
854 }
855
856 mutex_unlock(&inode->i_mutex);
857
858 return ret;
859}
860
861static int
862pipe_rdwr_open(struct inode *inode, struct file *filp)
863{
864 int ret = -ENOENT;
865
866 mutex_lock(&inode->i_mutex);
867
868 if (inode->i_pipe) {
869 ret = 0;
870 if (filp->f_mode & FMODE_READ)
871 inode->i_pipe->readers++;
872 if (filp->f_mode & FMODE_WRITE)
873 inode->i_pipe->writers++;
874 }
875
876 mutex_unlock(&inode->i_mutex);
877
878 return ret;
879}
880
881/*
882 * The file_operations structs are not static because they
883 * are also used in linux/fs/fifo.c to do operations on FIFOs.
884 *
885 * Pipes reuse fifos' file_operations structs.
886 */
887const struct file_operations read_pipefifo_fops = {
888 .llseek = no_llseek,
889 .read = do_sync_read,
890 .aio_read = pipe_read,
891 .write = bad_pipe_w,
892 .poll = pipe_poll,
893 .unlocked_ioctl = pipe_ioctl,
894 .open = pipe_read_open,
895 .release = pipe_read_release,
896 .fasync = pipe_read_fasync,
897};
898
899const struct file_operations write_pipefifo_fops = {
900 .llseek = no_llseek,
901 .read = bad_pipe_r,
902 .write = do_sync_write,
903 .aio_write = pipe_write,
904 .poll = pipe_poll,
905 .unlocked_ioctl = pipe_ioctl,
906 .open = pipe_write_open,
907 .release = pipe_write_release,
908 .fasync = pipe_write_fasync,
909};
910
911const struct file_operations rdwr_pipefifo_fops = {
912 .llseek = no_llseek,
913 .read = do_sync_read,
914 .aio_read = pipe_read,
915 .write = do_sync_write,
916 .aio_write = pipe_write,
917 .poll = pipe_poll,
918 .unlocked_ioctl = pipe_ioctl,
919 .open = pipe_rdwr_open,
920 .release = pipe_rdwr_release,
921 .fasync = pipe_rdwr_fasync,
922};
923
924struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
925{
926 struct pipe_inode_info *pipe;
927
928 pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
929 if (pipe) {
930 pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
931 if (pipe->bufs) {
932 init_waitqueue_head(&pipe->wait);
933 pipe->r_counter = pipe->w_counter = 1;
934 pipe->inode = inode;
935 pipe->buffers = PIPE_DEF_BUFFERS;
936 return pipe;
937 }
938 kfree(pipe);
939 }
940
941 return NULL;
942}
943
944void __free_pipe_info(struct pipe_inode_info *pipe)
945{
946 int i;
947
948 for (i = 0; i < pipe->buffers; i++) {
949 struct pipe_buffer *buf = pipe->bufs + i;
950 if (buf->ops)
951 buf->ops->release(pipe, buf);
952 }
953 if (pipe->tmp_page)
954 __free_page(pipe->tmp_page);
955 kfree(pipe->bufs);
956 kfree(pipe);
957}
958
959void free_pipe_info(struct inode *inode)
960{
961 __free_pipe_info(inode->i_pipe);
962 inode->i_pipe = NULL;
963}
964
965static struct vfsmount *pipe_mnt __read_mostly;
966
967/*
968 * pipefs_dname() is called from d_path().
969 */
970static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
971{
972 return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
973 dentry->d_inode->i_ino);
974}
975
976static const struct dentry_operations pipefs_dentry_operations = {
977 .d_dname = pipefs_dname,
978};
979
980static struct inode * get_pipe_inode(void)
981{
982 struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
983 struct pipe_inode_info *pipe;
984
985 if (!inode)
986 goto fail_inode;
987
988 inode->i_ino = get_next_ino();
989
990 pipe = alloc_pipe_info(inode);
991 if (!pipe)
992 goto fail_iput;
993 inode->i_pipe = pipe;
994
995 pipe->readers = pipe->writers = 1;
996 inode->i_fop = &rdwr_pipefifo_fops;
997
998 /*
999 * Mark the inode dirty from the very beginning,
1000 * that way it will never be moved to the dirty
1001 * list because "mark_inode_dirty()" will think
1002 * that it already _is_ on the dirty list.
1003 */
1004 inode->i_state = I_DIRTY;
1005 inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
1006 inode->i_uid = current_fsuid();
1007 inode->i_gid = current_fsgid();
1008 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1009
1010 return inode;
1011
1012fail_iput:
1013 iput(inode);
1014
1015fail_inode:
1016 return NULL;
1017}
1018
1019struct file *create_write_pipe(int flags)
1020{
1021 int err;
1022 struct inode *inode;
1023 struct file *f;
1024 struct path path;
1025 struct qstr name = { .name = "" };
1026
1027 err = -ENFILE;
1028 inode = get_pipe_inode();
1029 if (!inode)
1030 goto err;
1031
1032 err = -ENOMEM;
1033 path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
1034 if (!path.dentry)
1035 goto err_inode;
1036 path.mnt = mntget(pipe_mnt);
1037
1038 d_instantiate(path.dentry, inode);
1039
1040 err = -ENFILE;
1041 f = alloc_file(&path, FMODE_WRITE, &write_pipefifo_fops);
1042 if (!f)
1043 goto err_dentry;
1044 f->f_mapping = inode->i_mapping;
1045
1046 f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
1047 f->f_version = 0;
1048
1049 return f;
1050
1051 err_dentry:
1052 free_pipe_info(inode);
1053 path_put(&path);
1054 return ERR_PTR(err);
1055
1056 err_inode:
1057 free_pipe_info(inode);
1058 iput(inode);
1059 err:
1060 return ERR_PTR(err);
1061}
1062
1063void free_write_pipe(struct file *f)
1064{
1065 free_pipe_info(f->f_dentry->d_inode);
1066 path_put(&f->f_path);
1067 put_filp(f);
1068}
1069
1070struct file *create_read_pipe(struct file *wrf, int flags)
1071{
1072 /* Grab pipe from the writer */
1073 struct file *f = alloc_file(&wrf->f_path, FMODE_READ,
1074 &read_pipefifo_fops);
1075 if (!f)
1076 return ERR_PTR(-ENFILE);
1077
1078 path_get(&wrf->f_path);
1079 f->f_flags = O_RDONLY | (flags & O_NONBLOCK);
1080
1081 return f;
1082}
1083
1084int do_pipe_flags(int *fd, int flags)
1085{
1086 struct file *fw, *fr;
1087 int error;
1088 int fdw, fdr;
1089
1090 if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
1091 return -EINVAL;
1092
1093 fw = create_write_pipe(flags);
1094 if (IS_ERR(fw))
1095 return PTR_ERR(fw);
1096 fr = create_read_pipe(fw, flags);
1097 error = PTR_ERR(fr);
1098 if (IS_ERR(fr))
1099 goto err_write_pipe;
1100
1101 error = get_unused_fd_flags(flags);
1102 if (error < 0)
1103 goto err_read_pipe;
1104 fdr = error;
1105
1106 error = get_unused_fd_flags(flags);
1107 if (error < 0)
1108 goto err_fdr;
1109 fdw = error;
1110
1111 audit_fd_pair(fdr, fdw);
1112 fd_install(fdr, fr);
1113 fd_install(fdw, fw);
1114 fd[0] = fdr;
1115 fd[1] = fdw;
1116
1117 return 0;
1118
1119 err_fdr:
1120 put_unused_fd(fdr);
1121 err_read_pipe:
1122 path_put(&fr->f_path);
1123 put_filp(fr);
1124 err_write_pipe:
1125 free_write_pipe(fw);
1126 return error;
1127}
1128
1129/*
1130 * sys_pipe() is the normal C calling standard for creating
1131 * a pipe. It's not the way Unix traditionally does this, though.
1132 */
1133SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1134{
1135 int fd[2];
1136 int error;
1137
1138 error = do_pipe_flags(fd, flags);
1139 if (!error) {
1140 if (copy_to_user(fildes, fd, sizeof(fd))) {
1141 sys_close(fd[0]);
1142 sys_close(fd[1]);
1143 error = -EFAULT;
1144 }
1145 }
1146 return error;
1147}
1148
1149SYSCALL_DEFINE1(pipe, int __user *, fildes)
1150{
1151 return sys_pipe2(fildes, 0);
1152}
1153
1154/*
1155 * Allocate a new array of pipe buffers and copy the info over. Returns the
1156 * pipe size if successful, or return -ERROR on error.
1157 */
1158static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
1159{
1160 struct pipe_buffer *bufs;
1161
1162 /*
1163 * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1164 * expect a lot of shrink+grow operations, just free and allocate
1165 * again like we would do for growing. If the pipe currently
1166 * contains more buffers than arg, then return busy.
1167 */
1168 if (nr_pages < pipe->nrbufs)
1169 return -EBUSY;
1170
1171 bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN);
1172 if (unlikely(!bufs))
1173 return -ENOMEM;
1174
1175 /*
1176 * The pipe array wraps around, so just start the new one at zero
1177 * and adjust the indexes.
1178 */
1179 if (pipe->nrbufs) {
1180 unsigned int tail;
1181 unsigned int head;
1182
1183 tail = pipe->curbuf + pipe->nrbufs;
1184 if (tail < pipe->buffers)
1185 tail = 0;
1186 else
1187 tail &= (pipe->buffers - 1);
1188
1189 head = pipe->nrbufs - tail;
1190 if (head)
1191 memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1192 if (tail)
1193 memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1194 }
1195
1196 pipe->curbuf = 0;
1197 kfree(pipe->bufs);
1198 pipe->bufs = bufs;
1199 pipe->buffers = nr_pages;
1200 return nr_pages * PAGE_SIZE;
1201}
1202
1203/*
1204 * Currently we rely on the pipe array holding a power-of-2 number
1205 * of pages.
1206 */
1207static inline unsigned int round_pipe_size(unsigned int size)
1208{
1209 unsigned long nr_pages;
1210
1211 nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1212 return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1213}
1214
1215/*
1216 * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1217 * will return an error.
1218 */
1219int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1220 size_t *lenp, loff_t *ppos)
1221{
1222 int ret;
1223
1224 ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1225 if (ret < 0 || !write)
1226 return ret;
1227
1228 pipe_max_size = round_pipe_size(pipe_max_size);
1229 return ret;
1230}
1231
1232/*
1233 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1234 * location, so checking ->i_pipe is not enough to verify that this is a
1235 * pipe.
1236 */
1237struct pipe_inode_info *get_pipe_info(struct file *file)
1238{
1239 struct inode *i = file->f_path.dentry->d_inode;
1240
1241 return S_ISFIFO(i->i_mode) ? i->i_pipe : NULL;
1242}
1243
1244long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1245{
1246 struct pipe_inode_info *pipe;
1247 long ret;
1248
1249 pipe = get_pipe_info(file);
1250 if (!pipe)
1251 return -EBADF;
1252
1253 mutex_lock(&pipe->inode->i_mutex);
1254
1255 switch (cmd) {
1256 case F_SETPIPE_SZ: {
1257 unsigned int size, nr_pages;
1258
1259 size = round_pipe_size(arg);
1260 nr_pages = size >> PAGE_SHIFT;
1261
1262 ret = -EINVAL;
1263 if (!nr_pages)
1264 goto out;
1265
1266 if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1267 ret = -EPERM;
1268 goto out;
1269 }
1270 ret = pipe_set_size(pipe, nr_pages);
1271 break;
1272 }
1273 case F_GETPIPE_SZ:
1274 ret = pipe->buffers * PAGE_SIZE;
1275 break;
1276 default:
1277 ret = -EINVAL;
1278 break;
1279 }
1280
1281out:
1282 mutex_unlock(&pipe->inode->i_mutex);
1283 return ret;
1284}
1285
1286static const struct super_operations pipefs_ops = {
1287 .destroy_inode = free_inode_nonrcu,
1288 .statfs = simple_statfs,
1289};
1290
1291/*
1292 * pipefs should _never_ be mounted by userland - too much of security hassle,
1293 * no real gain from having the whole whorehouse mounted. So we don't need
1294 * any operations on the root directory. However, we need a non-trivial
1295 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1296 */
1297static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1298 int flags, const char *dev_name, void *data)
1299{
1300 return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1301 &pipefs_dentry_operations, PIPEFS_MAGIC);
1302}
1303
1304static struct file_system_type pipe_fs_type = {
1305 .name = "pipefs",
1306 .mount = pipefs_mount,
1307 .kill_sb = kill_anon_super,
1308};
1309
1310static int __init init_pipe_fs(void)
1311{
1312 int err = register_filesystem(&pipe_fs_type);
1313
1314 if (!err) {
1315 pipe_mnt = kern_mount(&pipe_fs_type);
1316 if (IS_ERR(pipe_mnt)) {
1317 err = PTR_ERR(pipe_mnt);
1318 unregister_filesystem(&pipe_fs_type);
1319 }
1320 }
1321 return err;
1322}
1323
1324fs_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/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);