Merge tag 'perf-tools-fixes-for-v6.6-2-2023-10-20' of git://git.kernel.org/pub/scm...
[platform/kernel/linux-rpi.git] / fs / pipe.c
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/pseudo_fs.h>
18 #include <linux/magic.h>
19 #include <linux/pipe_fs_i.h>
20 #include <linux/uio.h>
21 #include <linux/highmem.h>
22 #include <linux/pagemap.h>
23 #include <linux/audit.h>
24 #include <linux/syscalls.h>
25 #include <linux/fcntl.h>
26 #include <linux/memcontrol.h>
27 #include <linux/watch_queue.h>
28 #include <linux/sysctl.h>
29
30 #include <linux/uaccess.h>
31 #include <asm/ioctls.h>
32
33 #include "internal.h"
34
35 /*
36  * New pipe buffers will be restricted to this size while the user is exceeding
37  * their pipe buffer quota. The general pipe use case needs at least two
38  * buffers: one for data yet to be read, and one for new data. If this is less
39  * than two, then a write to a non-empty pipe may block even if the pipe is not
40  * full. This can occur with GNU make jobserver or similar uses of pipes as
41  * semaphores: multiple processes may be waiting to write tokens back to the
42  * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.
43  *
44  * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their
45  * own risk, namely: pipe writes to non-full pipes may block until the pipe is
46  * emptied.
47  */
48 #define PIPE_MIN_DEF_BUFFERS 2
49
50 /*
51  * The max size that a non-root user is allowed to grow the pipe. Can
52  * be set by root in /proc/sys/fs/pipe-max-size
53  */
54 static unsigned int pipe_max_size = 1048576;
55
56 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
57  * matches default values.
58  */
59 static unsigned long pipe_user_pages_hard;
60 static unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
61
62 /*
63  * We use head and tail indices that aren't masked off, except at the point of
64  * dereference, but rather they're allowed to wrap naturally.  This means there
65  * isn't a dead spot in the buffer, but the ring has to be a power of two and
66  * <= 2^31.
67  * -- David Howells 2019-09-23.
68  *
69  * Reads with count = 0 should always return 0.
70  * -- Julian Bradfield 1999-06-07.
71  *
72  * FIFOs and Pipes now generate SIGIO for both readers and writers.
73  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
74  *
75  * pipe_read & write cleanup
76  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
77  */
78
79 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
80 {
81         if (pipe->files)
82                 mutex_lock_nested(&pipe->mutex, subclass);
83 }
84
85 void pipe_lock(struct pipe_inode_info *pipe)
86 {
87         /*
88          * pipe_lock() nests non-pipe inode locks (for writing to a file)
89          */
90         pipe_lock_nested(pipe, I_MUTEX_PARENT);
91 }
92 EXPORT_SYMBOL(pipe_lock);
93
94 void pipe_unlock(struct pipe_inode_info *pipe)
95 {
96         if (pipe->files)
97                 mutex_unlock(&pipe->mutex);
98 }
99 EXPORT_SYMBOL(pipe_unlock);
100
101 static inline void __pipe_lock(struct pipe_inode_info *pipe)
102 {
103         mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
104 }
105
106 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
107 {
108         mutex_unlock(&pipe->mutex);
109 }
110
111 void pipe_double_lock(struct pipe_inode_info *pipe1,
112                       struct pipe_inode_info *pipe2)
113 {
114         BUG_ON(pipe1 == pipe2);
115
116         if (pipe1 < pipe2) {
117                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
118                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
119         } else {
120                 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
121                 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
122         }
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 bool anon_pipe_buf_try_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                 return false;
148         memcg_kmem_uncharge_page(page, 0);
149         __SetPageLocked(page);
150         return true;
151 }
152
153 /**
154  * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
155  * @pipe:       the pipe that the buffer belongs to
156  * @buf:        the buffer to attempt to steal
157  *
158  * Description:
159  *      This function attempts to steal the &struct page attached to
160  *      @buf. If successful, this function returns 0 and returns with
161  *      the page locked. The caller may then reuse the page for whatever
162  *      he wishes; the typical use is insertion into a different file
163  *      page cache.
164  */
165 bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe,
166                 struct pipe_buffer *buf)
167 {
168         struct page *page = buf->page;
169
170         /*
171          * A reference of one is golden, that means that the owner of this
172          * page is the only one holding a reference to it. lock the page
173          * and return OK.
174          */
175         if (page_count(page) == 1) {
176                 lock_page(page);
177                 return true;
178         }
179         return false;
180 }
181 EXPORT_SYMBOL(generic_pipe_buf_try_steal);
182
183 /**
184  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
185  * @pipe:       the pipe that the buffer belongs to
186  * @buf:        the buffer to get a reference to
187  *
188  * Description:
189  *      This function grabs an extra reference to @buf. It's used in
190  *      the tee() system call, when we duplicate the buffers in one
191  *      pipe into another.
192  */
193 bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
194 {
195         return try_get_page(buf->page);
196 }
197 EXPORT_SYMBOL(generic_pipe_buf_get);
198
199 /**
200  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
201  * @pipe:       the pipe that the buffer belongs to
202  * @buf:        the buffer to put a reference to
203  *
204  * Description:
205  *      This function releases a reference to @buf.
206  */
207 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
208                               struct pipe_buffer *buf)
209 {
210         put_page(buf->page);
211 }
212 EXPORT_SYMBOL(generic_pipe_buf_release);
213
214 static const struct pipe_buf_operations anon_pipe_buf_ops = {
215         .release        = anon_pipe_buf_release,
216         .try_steal      = anon_pipe_buf_try_steal,
217         .get            = generic_pipe_buf_get,
218 };
219
220 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
221 static inline bool pipe_readable(const struct pipe_inode_info *pipe)
222 {
223         unsigned int head = READ_ONCE(pipe->head);
224         unsigned int tail = READ_ONCE(pipe->tail);
225         unsigned int writers = READ_ONCE(pipe->writers);
226
227         return !pipe_empty(head, tail) || !writers;
228 }
229
230 static ssize_t
231 pipe_read(struct kiocb *iocb, struct iov_iter *to)
232 {
233         size_t total_len = iov_iter_count(to);
234         struct file *filp = iocb->ki_filp;
235         struct pipe_inode_info *pipe = filp->private_data;
236         bool was_full, wake_next_reader = false;
237         ssize_t ret;
238
239         /* Null read succeeds. */
240         if (unlikely(total_len == 0))
241                 return 0;
242
243         ret = 0;
244         __pipe_lock(pipe);
245
246         /*
247          * We only wake up writers if the pipe was full when we started
248          * reading in order to avoid unnecessary wakeups.
249          *
250          * But when we do wake up writers, we do so using a sync wakeup
251          * (WF_SYNC), because we want them to get going and generate more
252          * data for us.
253          */
254         was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
255         for (;;) {
256                 /* Read ->head with a barrier vs post_one_notification() */
257                 unsigned int head = smp_load_acquire(&pipe->head);
258                 unsigned int tail = pipe->tail;
259                 unsigned int mask = pipe->ring_size - 1;
260
261 #ifdef CONFIG_WATCH_QUEUE
262                 if (pipe->note_loss) {
263                         struct watch_notification n;
264
265                         if (total_len < 8) {
266                                 if (ret == 0)
267                                         ret = -ENOBUFS;
268                                 break;
269                         }
270
271                         n.type = WATCH_TYPE_META;
272                         n.subtype = WATCH_META_LOSS_NOTIFICATION;
273                         n.info = watch_sizeof(n);
274                         if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
275                                 if (ret == 0)
276                                         ret = -EFAULT;
277                                 break;
278                         }
279                         ret += sizeof(n);
280                         total_len -= sizeof(n);
281                         pipe->note_loss = false;
282                 }
283 #endif
284
285                 if (!pipe_empty(head, tail)) {
286                         struct pipe_buffer *buf = &pipe->bufs[tail & mask];
287                         size_t chars = buf->len;
288                         size_t written;
289                         int error;
290
291                         if (chars > total_len) {
292                                 if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
293                                         if (ret == 0)
294                                                 ret = -ENOBUFS;
295                                         break;
296                                 }
297                                 chars = total_len;
298                         }
299
300                         error = pipe_buf_confirm(pipe, buf);
301                         if (error) {
302                                 if (!ret)
303                                         ret = error;
304                                 break;
305                         }
306
307                         written = copy_page_to_iter(buf->page, buf->offset, chars, to);
308                         if (unlikely(written < chars)) {
309                                 if (!ret)
310                                         ret = -EFAULT;
311                                 break;
312                         }
313                         ret += chars;
314                         buf->offset += chars;
315                         buf->len -= chars;
316
317                         /* Was it a packet buffer? Clean up and exit */
318                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
319                                 total_len = chars;
320                                 buf->len = 0;
321                         }
322
323                         if (!buf->len) {
324                                 pipe_buf_release(pipe, buf);
325                                 spin_lock_irq(&pipe->rd_wait.lock);
326 #ifdef CONFIG_WATCH_QUEUE
327                                 if (buf->flags & PIPE_BUF_FLAG_LOSS)
328                                         pipe->note_loss = true;
329 #endif
330                                 tail++;
331                                 pipe->tail = tail;
332                                 spin_unlock_irq(&pipe->rd_wait.lock);
333                         }
334                         total_len -= chars;
335                         if (!total_len)
336                                 break;  /* common path: read succeeded */
337                         if (!pipe_empty(head, tail))    /* More to do? */
338                                 continue;
339                 }
340
341                 if (!pipe->writers)
342                         break;
343                 if (ret)
344                         break;
345                 if ((filp->f_flags & O_NONBLOCK) ||
346                     (iocb->ki_flags & IOCB_NOWAIT)) {
347                         ret = -EAGAIN;
348                         break;
349                 }
350                 __pipe_unlock(pipe);
351
352                 /*
353                  * We only get here if we didn't actually read anything.
354                  *
355                  * However, we could have seen (and removed) a zero-sized
356                  * pipe buffer, and might have made space in the buffers
357                  * that way.
358                  *
359                  * You can't make zero-sized pipe buffers by doing an empty
360                  * write (not even in packet mode), but they can happen if
361                  * the writer gets an EFAULT when trying to fill a buffer
362                  * that already got allocated and inserted in the buffer
363                  * array.
364                  *
365                  * So we still need to wake up any pending writers in the
366                  * _very_ unlikely case that the pipe was full, but we got
367                  * no data.
368                  */
369                 if (unlikely(was_full))
370                         wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
371                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
372
373                 /*
374                  * But because we didn't read anything, at this point we can
375                  * just return directly with -ERESTARTSYS if we're interrupted,
376                  * since we've done any required wakeups and there's no need
377                  * to mark anything accessed. And we've dropped the lock.
378                  */
379                 if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0)
380                         return -ERESTARTSYS;
381
382                 __pipe_lock(pipe);
383                 was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
384                 wake_next_reader = true;
385         }
386         if (pipe_empty(pipe->head, pipe->tail))
387                 wake_next_reader = false;
388         __pipe_unlock(pipe);
389
390         if (was_full)
391                 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
392         if (wake_next_reader)
393                 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
394         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
395         if (ret > 0)
396                 file_accessed(filp);
397         return ret;
398 }
399
400 static inline int is_packetized(struct file *file)
401 {
402         return (file->f_flags & O_DIRECT) != 0;
403 }
404
405 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
406 static inline bool pipe_writable(const struct pipe_inode_info *pipe)
407 {
408         unsigned int head = READ_ONCE(pipe->head);
409         unsigned int tail = READ_ONCE(pipe->tail);
410         unsigned int max_usage = READ_ONCE(pipe->max_usage);
411
412         return !pipe_full(head, tail, max_usage) ||
413                 !READ_ONCE(pipe->readers);
414 }
415
416 static ssize_t
417 pipe_write(struct kiocb *iocb, struct iov_iter *from)
418 {
419         struct file *filp = iocb->ki_filp;
420         struct pipe_inode_info *pipe = filp->private_data;
421         unsigned int head;
422         ssize_t ret = 0;
423         size_t total_len = iov_iter_count(from);
424         ssize_t chars;
425         bool was_empty = false;
426         bool wake_next_writer = false;
427
428         /* Null write succeeds. */
429         if (unlikely(total_len == 0))
430                 return 0;
431
432         __pipe_lock(pipe);
433
434         if (!pipe->readers) {
435                 send_sig(SIGPIPE, current, 0);
436                 ret = -EPIPE;
437                 goto out;
438         }
439
440 #ifdef CONFIG_WATCH_QUEUE
441         if (pipe->watch_queue) {
442                 ret = -EXDEV;
443                 goto out;
444         }
445 #endif
446
447         /*
448          * If it wasn't empty we try to merge new data into
449          * the last buffer.
450          *
451          * That naturally merges small writes, but it also
452          * page-aligns the rest of the writes for large writes
453          * spanning multiple pages.
454          */
455         head = pipe->head;
456         was_empty = pipe_empty(head, pipe->tail);
457         chars = total_len & (PAGE_SIZE-1);
458         if (chars && !was_empty) {
459                 unsigned int mask = pipe->ring_size - 1;
460                 struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
461                 int offset = buf->offset + buf->len;
462
463                 if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
464                     offset + chars <= PAGE_SIZE) {
465                         ret = pipe_buf_confirm(pipe, buf);
466                         if (ret)
467                                 goto out;
468
469                         ret = copy_page_from_iter(buf->page, offset, chars, from);
470                         if (unlikely(ret < chars)) {
471                                 ret = -EFAULT;
472                                 goto out;
473                         }
474
475                         buf->len += ret;
476                         if (!iov_iter_count(from))
477                                 goto out;
478                 }
479         }
480
481         for (;;) {
482                 if (!pipe->readers) {
483                         send_sig(SIGPIPE, current, 0);
484                         if (!ret)
485                                 ret = -EPIPE;
486                         break;
487                 }
488
489                 head = pipe->head;
490                 if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
491                         unsigned int mask = pipe->ring_size - 1;
492                         struct pipe_buffer *buf;
493                         struct page *page = pipe->tmp_page;
494                         int copied;
495
496                         if (!page) {
497                                 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
498                                 if (unlikely(!page)) {
499                                         ret = ret ? : -ENOMEM;
500                                         break;
501                                 }
502                                 pipe->tmp_page = page;
503                         }
504
505                         /* Allocate a slot in the ring in advance and attach an
506                          * empty buffer.  If we fault or otherwise fail to use
507                          * it, either the reader will consume it or it'll still
508                          * be there for the next write.
509                          */
510                         spin_lock_irq(&pipe->rd_wait.lock);
511
512                         head = pipe->head;
513                         if (pipe_full(head, pipe->tail, pipe->max_usage)) {
514                                 spin_unlock_irq(&pipe->rd_wait.lock);
515                                 continue;
516                         }
517
518                         pipe->head = head + 1;
519                         spin_unlock_irq(&pipe->rd_wait.lock);
520
521                         /* Insert it into the buffer array */
522                         buf = &pipe->bufs[head & mask];
523                         buf->page = page;
524                         buf->ops = &anon_pipe_buf_ops;
525                         buf->offset = 0;
526                         buf->len = 0;
527                         if (is_packetized(filp))
528                                 buf->flags = PIPE_BUF_FLAG_PACKET;
529                         else
530                                 buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
531                         pipe->tmp_page = NULL;
532
533                         copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
534                         if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
535                                 if (!ret)
536                                         ret = -EFAULT;
537                                 break;
538                         }
539                         ret += copied;
540                         buf->len = copied;
541
542                         if (!iov_iter_count(from))
543                                 break;
544                 }
545
546                 if (!pipe_full(head, pipe->tail, pipe->max_usage))
547                         continue;
548
549                 /* Wait for buffer space to become available. */
550                 if ((filp->f_flags & O_NONBLOCK) ||
551                     (iocb->ki_flags & IOCB_NOWAIT)) {
552                         if (!ret)
553                                 ret = -EAGAIN;
554                         break;
555                 }
556                 if (signal_pending(current)) {
557                         if (!ret)
558                                 ret = -ERESTARTSYS;
559                         break;
560                 }
561
562                 /*
563                  * We're going to release the pipe lock and wait for more
564                  * space. We wake up any readers if necessary, and then
565                  * after waiting we need to re-check whether the pipe
566                  * become empty while we dropped the lock.
567                  */
568                 __pipe_unlock(pipe);
569                 if (was_empty)
570                         wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
571                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
572                 wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
573                 __pipe_lock(pipe);
574                 was_empty = pipe_empty(pipe->head, pipe->tail);
575                 wake_next_writer = true;
576         }
577 out:
578         if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
579                 wake_next_writer = false;
580         __pipe_unlock(pipe);
581
582         /*
583          * If we do do a wakeup event, we do a 'sync' wakeup, because we
584          * want the reader to start processing things asap, rather than
585          * leave the data pending.
586          *
587          * This is particularly important for small writes, because of
588          * how (for example) the GNU make jobserver uses small writes to
589          * wake up pending jobs
590          *
591          * Epoll nonsensically wants a wakeup whether the pipe
592          * was already empty or not.
593          */
594         if (was_empty || pipe->poll_usage)
595                 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
596         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
597         if (wake_next_writer)
598                 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
599         if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
600                 int err = file_update_time(filp);
601                 if (err)
602                         ret = err;
603                 sb_end_write(file_inode(filp)->i_sb);
604         }
605         return ret;
606 }
607
608 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
609 {
610         struct pipe_inode_info *pipe = filp->private_data;
611         unsigned int count, head, tail, mask;
612
613         switch (cmd) {
614         case FIONREAD:
615                 __pipe_lock(pipe);
616                 count = 0;
617                 head = pipe->head;
618                 tail = pipe->tail;
619                 mask = pipe->ring_size - 1;
620
621                 while (tail != head) {
622                         count += pipe->bufs[tail & mask].len;
623                         tail++;
624                 }
625                 __pipe_unlock(pipe);
626
627                 return put_user(count, (int __user *)arg);
628
629 #ifdef CONFIG_WATCH_QUEUE
630         case IOC_WATCH_QUEUE_SET_SIZE: {
631                 int ret;
632                 __pipe_lock(pipe);
633                 ret = watch_queue_set_size(pipe, arg);
634                 __pipe_unlock(pipe);
635                 return ret;
636         }
637
638         case IOC_WATCH_QUEUE_SET_FILTER:
639                 return watch_queue_set_filter(
640                         pipe, (struct watch_notification_filter __user *)arg);
641 #endif
642
643         default:
644                 return -ENOIOCTLCMD;
645         }
646 }
647
648 /* No kernel lock held - fine */
649 static __poll_t
650 pipe_poll(struct file *filp, poll_table *wait)
651 {
652         __poll_t mask;
653         struct pipe_inode_info *pipe = filp->private_data;
654         unsigned int head, tail;
655
656         /* Epoll has some historical nasty semantics, this enables them */
657         WRITE_ONCE(pipe->poll_usage, true);
658
659         /*
660          * Reading pipe state only -- no need for acquiring the semaphore.
661          *
662          * But because this is racy, the code has to add the
663          * entry to the poll table _first_ ..
664          */
665         if (filp->f_mode & FMODE_READ)
666                 poll_wait(filp, &pipe->rd_wait, wait);
667         if (filp->f_mode & FMODE_WRITE)
668                 poll_wait(filp, &pipe->wr_wait, wait);
669
670         /*
671          * .. and only then can you do the racy tests. That way,
672          * if something changes and you got it wrong, the poll
673          * table entry will wake you up and fix it.
674          */
675         head = READ_ONCE(pipe->head);
676         tail = READ_ONCE(pipe->tail);
677
678         mask = 0;
679         if (filp->f_mode & FMODE_READ) {
680                 if (!pipe_empty(head, tail))
681                         mask |= EPOLLIN | EPOLLRDNORM;
682                 if (!pipe->writers && filp->f_version != pipe->w_counter)
683                         mask |= EPOLLHUP;
684         }
685
686         if (filp->f_mode & FMODE_WRITE) {
687                 if (!pipe_full(head, tail, pipe->max_usage))
688                         mask |= EPOLLOUT | EPOLLWRNORM;
689                 /*
690                  * Most Unices do not set EPOLLERR for FIFOs but on Linux they
691                  * behave exactly like pipes for poll().
692                  */
693                 if (!pipe->readers)
694                         mask |= EPOLLERR;
695         }
696
697         return mask;
698 }
699
700 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
701 {
702         int kill = 0;
703
704         spin_lock(&inode->i_lock);
705         if (!--pipe->files) {
706                 inode->i_pipe = NULL;
707                 kill = 1;
708         }
709         spin_unlock(&inode->i_lock);
710
711         if (kill)
712                 free_pipe_info(pipe);
713 }
714
715 static int
716 pipe_release(struct inode *inode, struct file *file)
717 {
718         struct pipe_inode_info *pipe = file->private_data;
719
720         __pipe_lock(pipe);
721         if (file->f_mode & FMODE_READ)
722                 pipe->readers--;
723         if (file->f_mode & FMODE_WRITE)
724                 pipe->writers--;
725
726         /* Was that the last reader or writer, but not the other side? */
727         if (!pipe->readers != !pipe->writers) {
728                 wake_up_interruptible_all(&pipe->rd_wait);
729                 wake_up_interruptible_all(&pipe->wr_wait);
730                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
731                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
732         }
733         __pipe_unlock(pipe);
734
735         put_pipe_info(inode, pipe);
736         return 0;
737 }
738
739 static int
740 pipe_fasync(int fd, struct file *filp, int on)
741 {
742         struct pipe_inode_info *pipe = filp->private_data;
743         int retval = 0;
744
745         __pipe_lock(pipe);
746         if (filp->f_mode & FMODE_READ)
747                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
748         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
749                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
750                 if (retval < 0 && (filp->f_mode & FMODE_READ))
751                         /* this can happen only if on == T */
752                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
753         }
754         __pipe_unlock(pipe);
755         return retval;
756 }
757
758 unsigned long account_pipe_buffers(struct user_struct *user,
759                                    unsigned long old, unsigned long new)
760 {
761         return atomic_long_add_return(new - old, &user->pipe_bufs);
762 }
763
764 bool too_many_pipe_buffers_soft(unsigned long user_bufs)
765 {
766         unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
767
768         return soft_limit && user_bufs > soft_limit;
769 }
770
771 bool too_many_pipe_buffers_hard(unsigned long user_bufs)
772 {
773         unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
774
775         return hard_limit && user_bufs > hard_limit;
776 }
777
778 bool pipe_is_unprivileged_user(void)
779 {
780         return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
781 }
782
783 struct pipe_inode_info *alloc_pipe_info(void)
784 {
785         struct pipe_inode_info *pipe;
786         unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
787         struct user_struct *user = get_current_user();
788         unsigned long user_bufs;
789         unsigned int max_size = READ_ONCE(pipe_max_size);
790
791         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
792         if (pipe == NULL)
793                 goto out_free_uid;
794
795         if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
796                 pipe_bufs = max_size >> PAGE_SHIFT;
797
798         user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
799
800         if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
801                 user_bufs = account_pipe_buffers(user, pipe_bufs, PIPE_MIN_DEF_BUFFERS);
802                 pipe_bufs = PIPE_MIN_DEF_BUFFERS;
803         }
804
805         if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
806                 goto out_revert_acct;
807
808         pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
809                              GFP_KERNEL_ACCOUNT);
810
811         if (pipe->bufs) {
812                 init_waitqueue_head(&pipe->rd_wait);
813                 init_waitqueue_head(&pipe->wr_wait);
814                 pipe->r_counter = pipe->w_counter = 1;
815                 pipe->max_usage = pipe_bufs;
816                 pipe->ring_size = pipe_bufs;
817                 pipe->nr_accounted = pipe_bufs;
818                 pipe->user = user;
819                 mutex_init(&pipe->mutex);
820                 return pipe;
821         }
822
823 out_revert_acct:
824         (void) account_pipe_buffers(user, pipe_bufs, 0);
825         kfree(pipe);
826 out_free_uid:
827         free_uid(user);
828         return NULL;
829 }
830
831 void free_pipe_info(struct pipe_inode_info *pipe)
832 {
833         unsigned int i;
834
835 #ifdef CONFIG_WATCH_QUEUE
836         if (pipe->watch_queue)
837                 watch_queue_clear(pipe->watch_queue);
838 #endif
839
840         (void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
841         free_uid(pipe->user);
842         for (i = 0; i < pipe->ring_size; i++) {
843                 struct pipe_buffer *buf = pipe->bufs + i;
844                 if (buf->ops)
845                         pipe_buf_release(pipe, buf);
846         }
847 #ifdef CONFIG_WATCH_QUEUE
848         if (pipe->watch_queue)
849                 put_watch_queue(pipe->watch_queue);
850 #endif
851         if (pipe->tmp_page)
852                 __free_page(pipe->tmp_page);
853         kfree(pipe->bufs);
854         kfree(pipe);
855 }
856
857 static struct vfsmount *pipe_mnt __read_mostly;
858
859 /*
860  * pipefs_dname() is called from d_path().
861  */
862 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
863 {
864         return dynamic_dname(buffer, buflen, "pipe:[%lu]",
865                                 d_inode(dentry)->i_ino);
866 }
867
868 static const struct dentry_operations pipefs_dentry_operations = {
869         .d_dname        = pipefs_dname,
870 };
871
872 static struct inode * get_pipe_inode(void)
873 {
874         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
875         struct pipe_inode_info *pipe;
876
877         if (!inode)
878                 goto fail_inode;
879
880         inode->i_ino = get_next_ino();
881
882         pipe = alloc_pipe_info();
883         if (!pipe)
884                 goto fail_iput;
885
886         inode->i_pipe = pipe;
887         pipe->files = 2;
888         pipe->readers = pipe->writers = 1;
889         inode->i_fop = &pipefifo_fops;
890
891         /*
892          * Mark the inode dirty from the very beginning,
893          * that way it will never be moved to the dirty
894          * list because "mark_inode_dirty()" will think
895          * that it already _is_ on the dirty list.
896          */
897         inode->i_state = I_DIRTY;
898         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
899         inode->i_uid = current_fsuid();
900         inode->i_gid = current_fsgid();
901         inode->i_atime = inode->i_mtime = inode_set_ctime_current(inode);
902
903         return inode;
904
905 fail_iput:
906         iput(inode);
907
908 fail_inode:
909         return NULL;
910 }
911
912 int create_pipe_files(struct file **res, int flags)
913 {
914         struct inode *inode = get_pipe_inode();
915         struct file *f;
916         int error;
917
918         if (!inode)
919                 return -ENFILE;
920
921         if (flags & O_NOTIFICATION_PIPE) {
922                 error = watch_queue_init(inode->i_pipe);
923                 if (error) {
924                         free_pipe_info(inode->i_pipe);
925                         iput(inode);
926                         return error;
927                 }
928         }
929
930         f = alloc_file_pseudo(inode, pipe_mnt, "",
931                                 O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
932                                 &pipefifo_fops);
933         if (IS_ERR(f)) {
934                 free_pipe_info(inode->i_pipe);
935                 iput(inode);
936                 return PTR_ERR(f);
937         }
938
939         f->private_data = inode->i_pipe;
940
941         res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
942                                   &pipefifo_fops);
943         if (IS_ERR(res[0])) {
944                 put_pipe_info(inode, inode->i_pipe);
945                 fput(f);
946                 return PTR_ERR(res[0]);
947         }
948         res[0]->private_data = inode->i_pipe;
949         res[1] = f;
950         stream_open(inode, res[0]);
951         stream_open(inode, res[1]);
952         return 0;
953 }
954
955 static int __do_pipe_flags(int *fd, struct file **files, int flags)
956 {
957         int error;
958         int fdw, fdr;
959
960         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
961                 return -EINVAL;
962
963         error = create_pipe_files(files, flags);
964         if (error)
965                 return error;
966
967         error = get_unused_fd_flags(flags);
968         if (error < 0)
969                 goto err_read_pipe;
970         fdr = error;
971
972         error = get_unused_fd_flags(flags);
973         if (error < 0)
974                 goto err_fdr;
975         fdw = error;
976
977         audit_fd_pair(fdr, fdw);
978         fd[0] = fdr;
979         fd[1] = fdw;
980         /* pipe groks IOCB_NOWAIT */
981         files[0]->f_mode |= FMODE_NOWAIT;
982         files[1]->f_mode |= FMODE_NOWAIT;
983         return 0;
984
985  err_fdr:
986         put_unused_fd(fdr);
987  err_read_pipe:
988         fput(files[0]);
989         fput(files[1]);
990         return error;
991 }
992
993 int do_pipe_flags(int *fd, int flags)
994 {
995         struct file *files[2];
996         int error = __do_pipe_flags(fd, files, flags);
997         if (!error) {
998                 fd_install(fd[0], files[0]);
999                 fd_install(fd[1], files[1]);
1000         }
1001         return error;
1002 }
1003
1004 /*
1005  * sys_pipe() is the normal C calling standard for creating
1006  * a pipe. It's not the way Unix traditionally does this, though.
1007  */
1008 static int do_pipe2(int __user *fildes, int flags)
1009 {
1010         struct file *files[2];
1011         int fd[2];
1012         int error;
1013
1014         error = __do_pipe_flags(fd, files, flags);
1015         if (!error) {
1016                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
1017                         fput(files[0]);
1018                         fput(files[1]);
1019                         put_unused_fd(fd[0]);
1020                         put_unused_fd(fd[1]);
1021                         error = -EFAULT;
1022                 } else {
1023                         fd_install(fd[0], files[0]);
1024                         fd_install(fd[1], files[1]);
1025                 }
1026         }
1027         return error;
1028 }
1029
1030 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1031 {
1032         return do_pipe2(fildes, flags);
1033 }
1034
1035 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1036 {
1037         return do_pipe2(fildes, 0);
1038 }
1039
1040 /*
1041  * This is the stupid "wait for pipe to be readable or writable"
1042  * model.
1043  *
1044  * See pipe_read/write() for the proper kind of exclusive wait,
1045  * but that requires that we wake up any other readers/writers
1046  * if we then do not end up reading everything (ie the whole
1047  * "wake_next_reader/writer" logic in pipe_read/write()).
1048  */
1049 void pipe_wait_readable(struct pipe_inode_info *pipe)
1050 {
1051         pipe_unlock(pipe);
1052         wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
1053         pipe_lock(pipe);
1054 }
1055
1056 void pipe_wait_writable(struct pipe_inode_info *pipe)
1057 {
1058         pipe_unlock(pipe);
1059         wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
1060         pipe_lock(pipe);
1061 }
1062
1063 /*
1064  * This depends on both the wait (here) and the wakeup (wake_up_partner)
1065  * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
1066  * race with the count check and waitqueue prep.
1067  *
1068  * Normally in order to avoid races, you'd do the prepare_to_wait() first,
1069  * then check the condition you're waiting for, and only then sleep. But
1070  * because of the pipe lock, we can check the condition before being on
1071  * the wait queue.
1072  *
1073  * We use the 'rd_wait' waitqueue for pipe partner waiting.
1074  */
1075 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1076 {
1077         DEFINE_WAIT(rdwait);
1078         int cur = *cnt;
1079
1080         while (cur == *cnt) {
1081                 prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
1082                 pipe_unlock(pipe);
1083                 schedule();
1084                 finish_wait(&pipe->rd_wait, &rdwait);
1085                 pipe_lock(pipe);
1086                 if (signal_pending(current))
1087                         break;
1088         }
1089         return cur == *cnt ? -ERESTARTSYS : 0;
1090 }
1091
1092 static void wake_up_partner(struct pipe_inode_info *pipe)
1093 {
1094         wake_up_interruptible_all(&pipe->rd_wait);
1095 }
1096
1097 static int fifo_open(struct inode *inode, struct file *filp)
1098 {
1099         struct pipe_inode_info *pipe;
1100         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1101         int ret;
1102
1103         filp->f_version = 0;
1104
1105         spin_lock(&inode->i_lock);
1106         if (inode->i_pipe) {
1107                 pipe = inode->i_pipe;
1108                 pipe->files++;
1109                 spin_unlock(&inode->i_lock);
1110         } else {
1111                 spin_unlock(&inode->i_lock);
1112                 pipe = alloc_pipe_info();
1113                 if (!pipe)
1114                         return -ENOMEM;
1115                 pipe->files = 1;
1116                 spin_lock(&inode->i_lock);
1117                 if (unlikely(inode->i_pipe)) {
1118                         inode->i_pipe->files++;
1119                         spin_unlock(&inode->i_lock);
1120                         free_pipe_info(pipe);
1121                         pipe = inode->i_pipe;
1122                 } else {
1123                         inode->i_pipe = pipe;
1124                         spin_unlock(&inode->i_lock);
1125                 }
1126         }
1127         filp->private_data = pipe;
1128         /* OK, we have a pipe and it's pinned down */
1129
1130         __pipe_lock(pipe);
1131
1132         /* We can only do regular read/write on fifos */
1133         stream_open(inode, filp);
1134
1135         switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
1136         case FMODE_READ:
1137         /*
1138          *  O_RDONLY
1139          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
1140          *  opened, even when there is no process writing the FIFO.
1141          */
1142                 pipe->r_counter++;
1143                 if (pipe->readers++ == 0)
1144                         wake_up_partner(pipe);
1145
1146                 if (!is_pipe && !pipe->writers) {
1147                         if ((filp->f_flags & O_NONBLOCK)) {
1148                                 /* suppress EPOLLHUP until we have
1149                                  * seen a writer */
1150                                 filp->f_version = pipe->w_counter;
1151                         } else {
1152                                 if (wait_for_partner(pipe, &pipe->w_counter))
1153                                         goto err_rd;
1154                         }
1155                 }
1156                 break;
1157
1158         case FMODE_WRITE:
1159         /*
1160          *  O_WRONLY
1161          *  POSIX.1 says that O_NONBLOCK means return -1 with
1162          *  errno=ENXIO when there is no process reading the FIFO.
1163          */
1164                 ret = -ENXIO;
1165                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1166                         goto err;
1167
1168                 pipe->w_counter++;
1169                 if (!pipe->writers++)
1170                         wake_up_partner(pipe);
1171
1172                 if (!is_pipe && !pipe->readers) {
1173                         if (wait_for_partner(pipe, &pipe->r_counter))
1174                                 goto err_wr;
1175                 }
1176                 break;
1177
1178         case FMODE_READ | FMODE_WRITE:
1179         /*
1180          *  O_RDWR
1181          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1182          *  This implementation will NEVER block on a O_RDWR open, since
1183          *  the process can at least talk to itself.
1184          */
1185
1186                 pipe->readers++;
1187                 pipe->writers++;
1188                 pipe->r_counter++;
1189                 pipe->w_counter++;
1190                 if (pipe->readers == 1 || pipe->writers == 1)
1191                         wake_up_partner(pipe);
1192                 break;
1193
1194         default:
1195                 ret = -EINVAL;
1196                 goto err;
1197         }
1198
1199         /* Ok! */
1200         __pipe_unlock(pipe);
1201         return 0;
1202
1203 err_rd:
1204         if (!--pipe->readers)
1205                 wake_up_interruptible(&pipe->wr_wait);
1206         ret = -ERESTARTSYS;
1207         goto err;
1208
1209 err_wr:
1210         if (!--pipe->writers)
1211                 wake_up_interruptible_all(&pipe->rd_wait);
1212         ret = -ERESTARTSYS;
1213         goto err;
1214
1215 err:
1216         __pipe_unlock(pipe);
1217
1218         put_pipe_info(inode, pipe);
1219         return ret;
1220 }
1221
1222 const struct file_operations pipefifo_fops = {
1223         .open           = fifo_open,
1224         .llseek         = no_llseek,
1225         .read_iter      = pipe_read,
1226         .write_iter     = pipe_write,
1227         .poll           = pipe_poll,
1228         .unlocked_ioctl = pipe_ioctl,
1229         .release        = pipe_release,
1230         .fasync         = pipe_fasync,
1231         .splice_write   = iter_file_splice_write,
1232 };
1233
1234 /*
1235  * Currently we rely on the pipe array holding a power-of-2 number
1236  * of pages. Returns 0 on error.
1237  */
1238 unsigned int round_pipe_size(unsigned int size)
1239 {
1240         if (size > (1U << 31))
1241                 return 0;
1242
1243         /* Minimum pipe size, as required by POSIX */
1244         if (size < PAGE_SIZE)
1245                 return PAGE_SIZE;
1246
1247         return roundup_pow_of_two(size);
1248 }
1249
1250 /*
1251  * Resize the pipe ring to a number of slots.
1252  *
1253  * Note the pipe can be reduced in capacity, but only if the current
1254  * occupancy doesn't exceed nr_slots; if it does, EBUSY will be
1255  * returned instead.
1256  */
1257 int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
1258 {
1259         struct pipe_buffer *bufs;
1260         unsigned int head, tail, mask, n;
1261
1262         bufs = kcalloc(nr_slots, sizeof(*bufs),
1263                        GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1264         if (unlikely(!bufs))
1265                 return -ENOMEM;
1266
1267         spin_lock_irq(&pipe->rd_wait.lock);
1268         mask = pipe->ring_size - 1;
1269         head = pipe->head;
1270         tail = pipe->tail;
1271
1272         n = pipe_occupancy(head, tail);
1273         if (nr_slots < n) {
1274                 spin_unlock_irq(&pipe->rd_wait.lock);
1275                 kfree(bufs);
1276                 return -EBUSY;
1277         }
1278
1279         /*
1280          * The pipe array wraps around, so just start the new one at zero
1281          * and adjust the indices.
1282          */
1283         if (n > 0) {
1284                 unsigned int h = head & mask;
1285                 unsigned int t = tail & mask;
1286                 if (h > t) {
1287                         memcpy(bufs, pipe->bufs + t,
1288                                n * sizeof(struct pipe_buffer));
1289                 } else {
1290                         unsigned int tsize = pipe->ring_size - t;
1291                         if (h > 0)
1292                                 memcpy(bufs + tsize, pipe->bufs,
1293                                        h * sizeof(struct pipe_buffer));
1294                         memcpy(bufs, pipe->bufs + t,
1295                                tsize * sizeof(struct pipe_buffer));
1296                 }
1297         }
1298
1299         head = n;
1300         tail = 0;
1301
1302         kfree(pipe->bufs);
1303         pipe->bufs = bufs;
1304         pipe->ring_size = nr_slots;
1305         if (pipe->max_usage > nr_slots)
1306                 pipe->max_usage = nr_slots;
1307         pipe->tail = tail;
1308         pipe->head = head;
1309
1310         spin_unlock_irq(&pipe->rd_wait.lock);
1311
1312         /* This might have made more room for writers */
1313         wake_up_interruptible(&pipe->wr_wait);
1314         return 0;
1315 }
1316
1317 /*
1318  * Allocate a new array of pipe buffers and copy the info over. Returns the
1319  * pipe size if successful, or return -ERROR on error.
1320  */
1321 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned int arg)
1322 {
1323         unsigned long user_bufs;
1324         unsigned int nr_slots, size;
1325         long ret = 0;
1326
1327 #ifdef CONFIG_WATCH_QUEUE
1328         if (pipe->watch_queue)
1329                 return -EBUSY;
1330 #endif
1331
1332         size = round_pipe_size(arg);
1333         nr_slots = size >> PAGE_SHIFT;
1334
1335         if (!nr_slots)
1336                 return -EINVAL;
1337
1338         /*
1339          * If trying to increase the pipe capacity, check that an
1340          * unprivileged user is not trying to exceed various limits
1341          * (soft limit check here, hard limit check just below).
1342          * Decreasing the pipe capacity is always permitted, even
1343          * if the user is currently over a limit.
1344          */
1345         if (nr_slots > pipe->max_usage &&
1346                         size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1347                 return -EPERM;
1348
1349         user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
1350
1351         if (nr_slots > pipe->max_usage &&
1352                         (too_many_pipe_buffers_hard(user_bufs) ||
1353                          too_many_pipe_buffers_soft(user_bufs)) &&
1354                         pipe_is_unprivileged_user()) {
1355                 ret = -EPERM;
1356                 goto out_revert_acct;
1357         }
1358
1359         ret = pipe_resize_ring(pipe, nr_slots);
1360         if (ret < 0)
1361                 goto out_revert_acct;
1362
1363         pipe->max_usage = nr_slots;
1364         pipe->nr_accounted = nr_slots;
1365         return pipe->max_usage * PAGE_SIZE;
1366
1367 out_revert_acct:
1368         (void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
1369         return ret;
1370 }
1371
1372 /*
1373  * Note that i_pipe and i_cdev share the same location, so checking ->i_pipe is
1374  * not enough to verify that this is a pipe.
1375  */
1376 struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
1377 {
1378         struct pipe_inode_info *pipe = file->private_data;
1379
1380         if (file->f_op != &pipefifo_fops || !pipe)
1381                 return NULL;
1382 #ifdef CONFIG_WATCH_QUEUE
1383         if (for_splice && pipe->watch_queue)
1384                 return NULL;
1385 #endif
1386         return pipe;
1387 }
1388
1389 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
1390 {
1391         struct pipe_inode_info *pipe;
1392         long ret;
1393
1394         pipe = get_pipe_info(file, false);
1395         if (!pipe)
1396                 return -EBADF;
1397
1398         __pipe_lock(pipe);
1399
1400         switch (cmd) {
1401         case F_SETPIPE_SZ:
1402                 ret = pipe_set_size(pipe, arg);
1403                 break;
1404         case F_GETPIPE_SZ:
1405                 ret = pipe->max_usage * PAGE_SIZE;
1406                 break;
1407         default:
1408                 ret = -EINVAL;
1409                 break;
1410         }
1411
1412         __pipe_unlock(pipe);
1413         return ret;
1414 }
1415
1416 static const struct super_operations pipefs_ops = {
1417         .destroy_inode = free_inode_nonrcu,
1418         .statfs = simple_statfs,
1419 };
1420
1421 /*
1422  * pipefs should _never_ be mounted by userland - too much of security hassle,
1423  * no real gain from having the whole whorehouse mounted. So we don't need
1424  * any operations on the root directory. However, we need a non-trivial
1425  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1426  */
1427
1428 static int pipefs_init_fs_context(struct fs_context *fc)
1429 {
1430         struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
1431         if (!ctx)
1432                 return -ENOMEM;
1433         ctx->ops = &pipefs_ops;
1434         ctx->dops = &pipefs_dentry_operations;
1435         return 0;
1436 }
1437
1438 static struct file_system_type pipe_fs_type = {
1439         .name           = "pipefs",
1440         .init_fs_context = pipefs_init_fs_context,
1441         .kill_sb        = kill_anon_super,
1442 };
1443
1444 #ifdef CONFIG_SYSCTL
1445 static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
1446                                         unsigned int *valp,
1447                                         int write, void *data)
1448 {
1449         if (write) {
1450                 unsigned int val;
1451
1452                 val = round_pipe_size(*lvalp);
1453                 if (val == 0)
1454                         return -EINVAL;
1455
1456                 *valp = val;
1457         } else {
1458                 unsigned int val = *valp;
1459                 *lvalp = (unsigned long) val;
1460         }
1461
1462         return 0;
1463 }
1464
1465 static int proc_dopipe_max_size(struct ctl_table *table, int write,
1466                                 void *buffer, size_t *lenp, loff_t *ppos)
1467 {
1468         return do_proc_douintvec(table, write, buffer, lenp, ppos,
1469                                  do_proc_dopipe_max_size_conv, NULL);
1470 }
1471
1472 static struct ctl_table fs_pipe_sysctls[] = {
1473         {
1474                 .procname       = "pipe-max-size",
1475                 .data           = &pipe_max_size,
1476                 .maxlen         = sizeof(pipe_max_size),
1477                 .mode           = 0644,
1478                 .proc_handler   = proc_dopipe_max_size,
1479         },
1480         {
1481                 .procname       = "pipe-user-pages-hard",
1482                 .data           = &pipe_user_pages_hard,
1483                 .maxlen         = sizeof(pipe_user_pages_hard),
1484                 .mode           = 0644,
1485                 .proc_handler   = proc_doulongvec_minmax,
1486         },
1487         {
1488                 .procname       = "pipe-user-pages-soft",
1489                 .data           = &pipe_user_pages_soft,
1490                 .maxlen         = sizeof(pipe_user_pages_soft),
1491                 .mode           = 0644,
1492                 .proc_handler   = proc_doulongvec_minmax,
1493         },
1494         { }
1495 };
1496 #endif
1497
1498 static int __init init_pipe_fs(void)
1499 {
1500         int err = register_filesystem(&pipe_fs_type);
1501
1502         if (!err) {
1503                 pipe_mnt = kern_mount(&pipe_fs_type);
1504                 if (IS_ERR(pipe_mnt)) {
1505                         err = PTR_ERR(pipe_mnt);
1506                         unregister_filesystem(&pipe_fs_type);
1507                 }
1508         }
1509 #ifdef CONFIG_SYSCTL
1510         register_sysctl_init("fs", fs_pipe_sysctls);
1511 #endif
1512         return err;
1513 }
1514
1515 fs_initcall(init_pipe_fs);