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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 #include <linux/memcontrol.h>
25
26 #include <asm/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 */
35 unsigned int pipe_max_size = 1048576;
36
37 /*
38 * Minimum pipe size, as required by POSIX
39 */
40 unsigned 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 */
45 unsigned long pipe_user_pages_hard;
46 unsigned 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
63 static 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
69 void 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 }
76 EXPORT_SYMBOL(pipe_lock);
77
78 void pipe_unlock(struct pipe_inode_info *pipe)
79 {
80 if (pipe->files)
81 mutex_unlock(&pipe->mutex);
82 }
83 EXPORT_SYMBOL(pipe_unlock);
84
85 static inline void __pipe_lock(struct pipe_inode_info *pipe)
86 {
87 mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
88 }
89
90 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
91 {
92 mutex_unlock(&pipe->mutex);
93 }
94
95 void 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 */
110 void 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
125 static 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
141 static 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 */
167 int 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 }
184 EXPORT_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 */
196 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
197 {
198 get_page(buf->page);
199 }
200 EXPORT_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 */
211 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
212 struct pipe_buffer *buf)
213 {
214 return 0;
215 }
216 EXPORT_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 */
226 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
227 struct pipe_buffer *buf)
228 {
229 put_page(buf->page);
230 }
231 EXPORT_SYMBOL(generic_pipe_buf_release);
232
233 static 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
241 static 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
249 static ssize_t
250 pipe_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
351 static inline int is_packetized(struct file *file)
352 {
353 return (file->f_flags & O_DIRECT) != 0;
354 }
355
356 static ssize_t
357 pipe_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 }
478 out:
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
493 static 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 */
517 static unsigned int
518 pipe_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
548 static 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
563 static int
564 pipe_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
585 static int
586 pipe_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
604 static void account_pipe_buffers(struct pipe_inode_info *pipe,
605 unsigned long old, unsigned long new)
606 {
607 atomic_long_add(new - old, &pipe->user->pipe_bufs);
608 }
609
610 static bool too_many_pipe_buffers_soft(struct user_struct *user)
611 {
612 return pipe_user_pages_soft &&
613 atomic_long_read(&user->pipe_bufs) >= pipe_user_pages_soft;
614 }
615
616 static bool too_many_pipe_buffers_hard(struct user_struct *user)
617 {
618 return pipe_user_pages_hard &&
619 atomic_long_read(&user->pipe_bufs) >= pipe_user_pages_hard;
620 }
621
622 struct pipe_inode_info *alloc_pipe_info(void)
623 {
624 struct pipe_inode_info *pipe;
625
626 pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
627 if (pipe) {
628 unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
629 struct user_struct *user = get_current_user();
630
631 if (!too_many_pipe_buffers_hard(user)) {
632 if (too_many_pipe_buffers_soft(user))
633 pipe_bufs = 1;
634 pipe->bufs = kcalloc(pipe_bufs,
635 sizeof(struct pipe_buffer),
636 GFP_KERNEL_ACCOUNT);
637 }
638
639 if (pipe->bufs) {
640 init_waitqueue_head(&pipe->wait);
641 pipe->r_counter = pipe->w_counter = 1;
642 pipe->buffers = pipe_bufs;
643 pipe->user = user;
644 account_pipe_buffers(pipe, 0, pipe_bufs);
645 mutex_init(&pipe->mutex);
646 return pipe;
647 }
648 free_uid(user);
649 kfree(pipe);
650 }
651
652 return NULL;
653 }
654
655 void free_pipe_info(struct pipe_inode_info *pipe)
656 {
657 int i;
658
659 account_pipe_buffers(pipe, pipe->buffers, 0);
660 free_uid(pipe->user);
661 for (i = 0; i < pipe->buffers; i++) {
662 struct pipe_buffer *buf = pipe->bufs + i;
663 if (buf->ops)
664 pipe_buf_release(pipe, buf);
665 }
666 if (pipe->tmp_page)
667 __free_page(pipe->tmp_page);
668 kfree(pipe->bufs);
669 kfree(pipe);
670 }
671
672 static struct vfsmount *pipe_mnt __read_mostly;
673
674 /*
675 * pipefs_dname() is called from d_path().
676 */
677 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
678 {
679 return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
680 d_inode(dentry)->i_ino);
681 }
682
683 static const struct dentry_operations pipefs_dentry_operations = {
684 .d_dname = pipefs_dname,
685 };
686
687 static struct inode * get_pipe_inode(void)
688 {
689 struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
690 struct pipe_inode_info *pipe;
691
692 if (!inode)
693 goto fail_inode;
694
695 inode->i_ino = get_next_ino();
696
697 pipe = alloc_pipe_info();
698 if (!pipe)
699 goto fail_iput;
700
701 inode->i_pipe = pipe;
702 pipe->files = 2;
703 pipe->readers = pipe->writers = 1;
704 inode->i_fop = &pipefifo_fops;
705
706 /*
707 * Mark the inode dirty from the very beginning,
708 * that way it will never be moved to the dirty
709 * list because "mark_inode_dirty()" will think
710 * that it already _is_ on the dirty list.
711 */
712 inode->i_state = I_DIRTY;
713 inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
714 inode->i_uid = current_fsuid();
715 inode->i_gid = current_fsgid();
716 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
717
718 return inode;
719
720 fail_iput:
721 iput(inode);
722
723 fail_inode:
724 return NULL;
725 }
726
727 int create_pipe_files(struct file **res, int flags)
728 {
729 int err;
730 struct inode *inode = get_pipe_inode();
731 struct file *f;
732 struct path path;
733 static struct qstr name = { .name = "" };
734
735 if (!inode)
736 return -ENFILE;
737
738 err = -ENOMEM;
739 path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
740 if (!path.dentry)
741 goto err_inode;
742 path.mnt = mntget(pipe_mnt);
743
744 d_instantiate(path.dentry, inode);
745
746 f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops);
747 if (IS_ERR(f)) {
748 err = PTR_ERR(f);
749 goto err_dentry;
750 }
751
752 f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
753 f->private_data = inode->i_pipe;
754
755 res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
756 if (IS_ERR(res[0])) {
757 err = PTR_ERR(res[0]);
758 goto err_file;
759 }
760
761 path_get(&path);
762 res[0]->private_data = inode->i_pipe;
763 res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
764 res[1] = f;
765 return 0;
766
767 err_file:
768 put_filp(f);
769 err_dentry:
770 free_pipe_info(inode->i_pipe);
771 path_put(&path);
772 return err;
773
774 err_inode:
775 free_pipe_info(inode->i_pipe);
776 iput(inode);
777 return err;
778 }
779
780 static int __do_pipe_flags(int *fd, struct file **files, int flags)
781 {
782 int error;
783 int fdw, fdr;
784
785 if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
786 return -EINVAL;
787
788 error = create_pipe_files(files, flags);
789 if (error)
790 return error;
791
792 error = get_unused_fd_flags(flags);
793 if (error < 0)
794 goto err_read_pipe;
795 fdr = error;
796
797 error = get_unused_fd_flags(flags);
798 if (error < 0)
799 goto err_fdr;
800 fdw = error;
801
802 audit_fd_pair(fdr, fdw);
803 fd[0] = fdr;
804 fd[1] = fdw;
805 return 0;
806
807 err_fdr:
808 put_unused_fd(fdr);
809 err_read_pipe:
810 fput(files[0]);
811 fput(files[1]);
812 return error;
813 }
814
815 int do_pipe_flags(int *fd, int flags)
816 {
817 struct file *files[2];
818 int error = __do_pipe_flags(fd, files, flags);
819 if (!error) {
820 fd_install(fd[0], files[0]);
821 fd_install(fd[1], files[1]);
822 }
823 return error;
824 }
825
826 /*
827 * sys_pipe() is the normal C calling standard for creating
828 * a pipe. It's not the way Unix traditionally does this, though.
829 */
830 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
831 {
832 struct file *files[2];
833 int fd[2];
834 int error;
835
836 error = __do_pipe_flags(fd, files, flags);
837 if (!error) {
838 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
839 fput(files[0]);
840 fput(files[1]);
841 put_unused_fd(fd[0]);
842 put_unused_fd(fd[1]);
843 error = -EFAULT;
844 } else {
845 fd_install(fd[0], files[0]);
846 fd_install(fd[1], files[1]);
847 }
848 }
849 return error;
850 }
851
852 SYSCALL_DEFINE1(pipe, int __user *, fildes)
853 {
854 return sys_pipe2(fildes, 0);
855 }
856
857 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
858 {
859 int cur = *cnt;
860
861 while (cur == *cnt) {
862 pipe_wait(pipe);
863 if (signal_pending(current))
864 break;
865 }
866 return cur == *cnt ? -ERESTARTSYS : 0;
867 }
868
869 static void wake_up_partner(struct pipe_inode_info *pipe)
870 {
871 wake_up_interruptible(&pipe->wait);
872 }
873
874 static int fifo_open(struct inode *inode, struct file *filp)
875 {
876 struct pipe_inode_info *pipe;
877 bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
878 int ret;
879
880 filp->f_version = 0;
881
882 spin_lock(&inode->i_lock);
883 if (inode->i_pipe) {
884 pipe = inode->i_pipe;
885 pipe->files++;
886 spin_unlock(&inode->i_lock);
887 } else {
888 spin_unlock(&inode->i_lock);
889 pipe = alloc_pipe_info();
890 if (!pipe)
891 return -ENOMEM;
892 pipe->files = 1;
893 spin_lock(&inode->i_lock);
894 if (unlikely(inode->i_pipe)) {
895 inode->i_pipe->files++;
896 spin_unlock(&inode->i_lock);
897 free_pipe_info(pipe);
898 pipe = inode->i_pipe;
899 } else {
900 inode->i_pipe = pipe;
901 spin_unlock(&inode->i_lock);
902 }
903 }
904 filp->private_data = pipe;
905 /* OK, we have a pipe and it's pinned down */
906
907 __pipe_lock(pipe);
908
909 /* We can only do regular read/write on fifos */
910 filp->f_mode &= (FMODE_READ | FMODE_WRITE);
911
912 switch (filp->f_mode) {
913 case FMODE_READ:
914 /*
915 * O_RDONLY
916 * POSIX.1 says that O_NONBLOCK means return with the FIFO
917 * opened, even when there is no process writing the FIFO.
918 */
919 pipe->r_counter++;
920 if (pipe->readers++ == 0)
921 wake_up_partner(pipe);
922
923 if (!is_pipe && !pipe->writers) {
924 if ((filp->f_flags & O_NONBLOCK)) {
925 /* suppress POLLHUP until we have
926 * seen a writer */
927 filp->f_version = pipe->w_counter;
928 } else {
929 if (wait_for_partner(pipe, &pipe->w_counter))
930 goto err_rd;
931 }
932 }
933 break;
934
935 case FMODE_WRITE:
936 /*
937 * O_WRONLY
938 * POSIX.1 says that O_NONBLOCK means return -1 with
939 * errno=ENXIO when there is no process reading the FIFO.
940 */
941 ret = -ENXIO;
942 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
943 goto err;
944
945 pipe->w_counter++;
946 if (!pipe->writers++)
947 wake_up_partner(pipe);
948
949 if (!is_pipe && !pipe->readers) {
950 if (wait_for_partner(pipe, &pipe->r_counter))
951 goto err_wr;
952 }
953 break;
954
955 case FMODE_READ | FMODE_WRITE:
956 /*
957 * O_RDWR
958 * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
959 * This implementation will NEVER block on a O_RDWR open, since
960 * the process can at least talk to itself.
961 */
962
963 pipe->readers++;
964 pipe->writers++;
965 pipe->r_counter++;
966 pipe->w_counter++;
967 if (pipe->readers == 1 || pipe->writers == 1)
968 wake_up_partner(pipe);
969 break;
970
971 default:
972 ret = -EINVAL;
973 goto err;
974 }
975
976 /* Ok! */
977 __pipe_unlock(pipe);
978 return 0;
979
980 err_rd:
981 if (!--pipe->readers)
982 wake_up_interruptible(&pipe->wait);
983 ret = -ERESTARTSYS;
984 goto err;
985
986 err_wr:
987 if (!--pipe->writers)
988 wake_up_interruptible(&pipe->wait);
989 ret = -ERESTARTSYS;
990 goto err;
991
992 err:
993 __pipe_unlock(pipe);
994
995 put_pipe_info(inode, pipe);
996 return ret;
997 }
998
999 const struct file_operations pipefifo_fops = {
1000 .open = fifo_open,
1001 .llseek = no_llseek,
1002 .read_iter = pipe_read,
1003 .write_iter = pipe_write,
1004 .poll = pipe_poll,
1005 .unlocked_ioctl = pipe_ioctl,
1006 .release = pipe_release,
1007 .fasync = pipe_fasync,
1008 };
1009
1010 /*
1011 * Allocate a new array of pipe buffers and copy the info over. Returns the
1012 * pipe size if successful, or return -ERROR on error.
1013 */
1014 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
1015 {
1016 struct pipe_buffer *bufs;
1017
1018 /*
1019 * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1020 * expect a lot of shrink+grow operations, just free and allocate
1021 * again like we would do for growing. If the pipe currently
1022 * contains more buffers than arg, then return busy.
1023 */
1024 if (nr_pages < pipe->nrbufs)
1025 return -EBUSY;
1026
1027 bufs = kcalloc(nr_pages, sizeof(*bufs),
1028 GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1029 if (unlikely(!bufs))
1030 return -ENOMEM;
1031
1032 /*
1033 * The pipe array wraps around, so just start the new one at zero
1034 * and adjust the indexes.
1035 */
1036 if (pipe->nrbufs) {
1037 unsigned int tail;
1038 unsigned int head;
1039
1040 tail = pipe->curbuf + pipe->nrbufs;
1041 if (tail < pipe->buffers)
1042 tail = 0;
1043 else
1044 tail &= (pipe->buffers - 1);
1045
1046 head = pipe->nrbufs - tail;
1047 if (head)
1048 memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1049 if (tail)
1050 memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1051 }
1052
1053 account_pipe_buffers(pipe, pipe->buffers, nr_pages);
1054 pipe->curbuf = 0;
1055 kfree(pipe->bufs);
1056 pipe->bufs = bufs;
1057 pipe->buffers = nr_pages;
1058 return nr_pages * PAGE_SIZE;
1059 }
1060
1061 /*
1062 * Currently we rely on the pipe array holding a power-of-2 number
1063 * of pages.
1064 */
1065 static inline unsigned int round_pipe_size(unsigned int size)
1066 {
1067 unsigned long nr_pages;
1068
1069 nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1070 return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1071 }
1072
1073 /*
1074 * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1075 * will return an error.
1076 */
1077 int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1078 size_t *lenp, loff_t *ppos)
1079 {
1080 int ret;
1081
1082 ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1083 if (ret < 0 || !write)
1084 return ret;
1085
1086 pipe_max_size = round_pipe_size(pipe_max_size);
1087 return ret;
1088 }
1089
1090 /*
1091 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1092 * location, so checking ->i_pipe is not enough to verify that this is a
1093 * pipe.
1094 */
1095 struct pipe_inode_info *get_pipe_info(struct file *file)
1096 {
1097 return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1098 }
1099
1100 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1101 {
1102 struct pipe_inode_info *pipe;
1103 long ret;
1104
1105 pipe = get_pipe_info(file);
1106 if (!pipe)
1107 return -EBADF;
1108
1109 __pipe_lock(pipe);
1110
1111 switch (cmd) {
1112 case F_SETPIPE_SZ: {
1113 unsigned int size, nr_pages;
1114
1115 size = round_pipe_size(arg);
1116 nr_pages = size >> PAGE_SHIFT;
1117
1118 ret = -EINVAL;
1119 if (!nr_pages)
1120 goto out;
1121
1122 if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1123 ret = -EPERM;
1124 goto out;
1125 } else if ((too_many_pipe_buffers_hard(pipe->user) ||
1126 too_many_pipe_buffers_soft(pipe->user)) &&
1127 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) {
1128 ret = -EPERM;
1129 goto out;
1130 }
1131 ret = pipe_set_size(pipe, nr_pages);
1132 break;
1133 }
1134 case F_GETPIPE_SZ:
1135 ret = pipe->buffers * PAGE_SIZE;
1136 break;
1137 default:
1138 ret = -EINVAL;
1139 break;
1140 }
1141
1142 out:
1143 __pipe_unlock(pipe);
1144 return ret;
1145 }
1146
1147 static const struct super_operations pipefs_ops = {
1148 .destroy_inode = free_inode_nonrcu,
1149 .statfs = simple_statfs,
1150 };
1151
1152 /*
1153 * pipefs should _never_ be mounted by userland - too much of security hassle,
1154 * no real gain from having the whole whorehouse mounted. So we don't need
1155 * any operations on the root directory. However, we need a non-trivial
1156 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1157 */
1158 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1159 int flags, const char *dev_name, void *data)
1160 {
1161 return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1162 &pipefs_dentry_operations, PIPEFS_MAGIC);
1163 }
1164
1165 static struct file_system_type pipe_fs_type = {
1166 .name = "pipefs",
1167 .mount = pipefs_mount,
1168 .kill_sb = kill_anon_super,
1169 };
1170
1171 static int __init init_pipe_fs(void)
1172 {
1173 int err = register_filesystem(&pipe_fs_type);
1174
1175 if (!err) {
1176 pipe_mnt = kern_mount(&pipe_fs_type);
1177 if (IS_ERR(pipe_mnt)) {
1178 err = PTR_ERR(pipe_mnt);
1179 unregister_filesystem(&pipe_fs_type);
1180 }
1181 }
1182 return err;
1183 }
1184
1185 fs_initcall(init_pipe_fs);