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