Merge tag 'mtd/for-5.2' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/mtd...
[sfrench/cifs-2.6.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/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  */
36 unsigned int pipe_max_size = 1048576;
37
38 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
39  * matches default values.
40  */
41 unsigned long pipe_user_pages_hard;
42 unsigned 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
59 static 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
65 void 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 }
72 EXPORT_SYMBOL(pipe_lock);
73
74 void pipe_unlock(struct pipe_inode_info *pipe)
75 {
76         if (pipe->files)
77                 mutex_unlock(&pipe->mutex);
78 }
79 EXPORT_SYMBOL(pipe_unlock);
80
81 static inline void __pipe_lock(struct pipe_inode_info *pipe)
82 {
83         mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
84 }
85
86 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
87 {
88         mutex_unlock(&pipe->mutex);
89 }
90
91 void 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 */
106 void 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
121 static 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
137 static 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                 memcg_kmem_uncharge(page, 0);
144                 __SetPageLocked(page);
145                 return 0;
146         }
147         return 1;
148 }
149
150 /**
151  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
152  * @pipe:       the pipe that the buffer belongs to
153  * @buf:        the buffer to attempt to steal
154  *
155  * Description:
156  *      This function attempts to steal the &struct page attached to
157  *      @buf. If successful, this function returns 0 and returns with
158  *      the page locked. The caller may then reuse the page for whatever
159  *      he wishes; the typical use is insertion into a different file
160  *      page cache.
161  */
162 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
163                            struct pipe_buffer *buf)
164 {
165         struct page *page = buf->page;
166
167         /*
168          * A reference of one is golden, that means that the owner of this
169          * page is the only one holding a reference to it. lock the page
170          * and return OK.
171          */
172         if (page_count(page) == 1) {
173                 lock_page(page);
174                 return 0;
175         }
176
177         return 1;
178 }
179 EXPORT_SYMBOL(generic_pipe_buf_steal);
180
181 /**
182  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
183  * @pipe:       the pipe that the buffer belongs to
184  * @buf:        the buffer to get a reference to
185  *
186  * Description:
187  *      This function grabs an extra reference to @buf. It's used in
188  *      in the tee() system call, when we duplicate the buffers in one
189  *      pipe into another.
190  */
191 bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
192 {
193         return try_get_page(buf->page);
194 }
195 EXPORT_SYMBOL(generic_pipe_buf_get);
196
197 /**
198  * generic_pipe_buf_confirm - verify contents of the pipe buffer
199  * @info:       the pipe that the buffer belongs to
200  * @buf:        the buffer to confirm
201  *
202  * Description:
203  *      This function does nothing, because the generic pipe code uses
204  *      pages that are always good when inserted into the pipe.
205  */
206 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
207                              struct pipe_buffer *buf)
208 {
209         return 0;
210 }
211 EXPORT_SYMBOL(generic_pipe_buf_confirm);
212
213 /**
214  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
215  * @pipe:       the pipe that the buffer belongs to
216  * @buf:        the buffer to put a reference to
217  *
218  * Description:
219  *      This function releases a reference to @buf.
220  */
221 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
222                               struct pipe_buffer *buf)
223 {
224         put_page(buf->page);
225 }
226 EXPORT_SYMBOL(generic_pipe_buf_release);
227
228 /* New data written to a pipe may be appended to a buffer with this type. */
229 static const struct pipe_buf_operations anon_pipe_buf_ops = {
230         .confirm = generic_pipe_buf_confirm,
231         .release = anon_pipe_buf_release,
232         .steal = anon_pipe_buf_steal,
233         .get = generic_pipe_buf_get,
234 };
235
236 static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = {
237         .confirm = generic_pipe_buf_confirm,
238         .release = anon_pipe_buf_release,
239         .steal = anon_pipe_buf_steal,
240         .get = generic_pipe_buf_get,
241 };
242
243 static const struct pipe_buf_operations packet_pipe_buf_ops = {
244         .confirm = generic_pipe_buf_confirm,
245         .release = anon_pipe_buf_release,
246         .steal = anon_pipe_buf_steal,
247         .get = generic_pipe_buf_get,
248 };
249
250 /**
251  * pipe_buf_mark_unmergeable - mark a &struct pipe_buffer as unmergeable
252  * @buf:        the buffer to mark
253  *
254  * Description:
255  *      This function ensures that no future writes will be merged into the
256  *      given &struct pipe_buffer. This is necessary when multiple pipe buffers
257  *      share the same backing page.
258  */
259 void pipe_buf_mark_unmergeable(struct pipe_buffer *buf)
260 {
261         if (buf->ops == &anon_pipe_buf_ops)
262                 buf->ops = &anon_pipe_buf_nomerge_ops;
263 }
264
265 static bool pipe_buf_can_merge(struct pipe_buffer *buf)
266 {
267         return buf->ops == &anon_pipe_buf_ops;
268 }
269
270 static ssize_t
271 pipe_read(struct kiocb *iocb, struct iov_iter *to)
272 {
273         size_t total_len = iov_iter_count(to);
274         struct file *filp = iocb->ki_filp;
275         struct pipe_inode_info *pipe = filp->private_data;
276         int do_wakeup;
277         ssize_t ret;
278
279         /* Null read succeeds. */
280         if (unlikely(total_len == 0))
281                 return 0;
282
283         do_wakeup = 0;
284         ret = 0;
285         __pipe_lock(pipe);
286         for (;;) {
287                 int bufs = pipe->nrbufs;
288                 if (bufs) {
289                         int curbuf = pipe->curbuf;
290                         struct pipe_buffer *buf = pipe->bufs + curbuf;
291                         size_t chars = buf->len;
292                         size_t written;
293                         int error;
294
295                         if (chars > total_len)
296                                 chars = total_len;
297
298                         error = pipe_buf_confirm(pipe, buf);
299                         if (error) {
300                                 if (!ret)
301                                         ret = error;
302                                 break;
303                         }
304
305                         written = copy_page_to_iter(buf->page, buf->offset, chars, to);
306                         if (unlikely(written < chars)) {
307                                 if (!ret)
308                                         ret = -EFAULT;
309                                 break;
310                         }
311                         ret += chars;
312                         buf->offset += chars;
313                         buf->len -= chars;
314
315                         /* Was it a packet buffer? Clean up and exit */
316                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
317                                 total_len = chars;
318                                 buf->len = 0;
319                         }
320
321                         if (!buf->len) {
322                                 pipe_buf_release(pipe, buf);
323                                 curbuf = (curbuf + 1) & (pipe->buffers - 1);
324                                 pipe->curbuf = curbuf;
325                                 pipe->nrbufs = --bufs;
326                                 do_wakeup = 1;
327                         }
328                         total_len -= chars;
329                         if (!total_len)
330                                 break;  /* common path: read succeeded */
331                 }
332                 if (bufs)       /* More to do? */
333                         continue;
334                 if (!pipe->writers)
335                         break;
336                 if (!pipe->waiting_writers) {
337                         /* syscall merging: Usually we must not sleep
338                          * if O_NONBLOCK is set, or if we got some data.
339                          * But if a writer sleeps in kernel space, then
340                          * we can wait for that data without violating POSIX.
341                          */
342                         if (ret)
343                                 break;
344                         if (filp->f_flags & O_NONBLOCK) {
345                                 ret = -EAGAIN;
346                                 break;
347                         }
348                 }
349                 if (signal_pending(current)) {
350                         if (!ret)
351                                 ret = -ERESTARTSYS;
352                         break;
353                 }
354                 if (do_wakeup) {
355                         wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
356                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
357                 }
358                 pipe_wait(pipe);
359         }
360         __pipe_unlock(pipe);
361
362         /* Signal writers asynchronously that there is more room. */
363         if (do_wakeup) {
364                 wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
365                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
366         }
367         if (ret > 0)
368                 file_accessed(filp);
369         return ret;
370 }
371
372 static inline int is_packetized(struct file *file)
373 {
374         return (file->f_flags & O_DIRECT) != 0;
375 }
376
377 static ssize_t
378 pipe_write(struct kiocb *iocb, struct iov_iter *from)
379 {
380         struct file *filp = iocb->ki_filp;
381         struct pipe_inode_info *pipe = filp->private_data;
382         ssize_t ret = 0;
383         int do_wakeup = 0;
384         size_t total_len = iov_iter_count(from);
385         ssize_t chars;
386
387         /* Null write succeeds. */
388         if (unlikely(total_len == 0))
389                 return 0;
390
391         __pipe_lock(pipe);
392
393         if (!pipe->readers) {
394                 send_sig(SIGPIPE, current, 0);
395                 ret = -EPIPE;
396                 goto out;
397         }
398
399         /* We try to merge small writes */
400         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
401         if (pipe->nrbufs && chars != 0) {
402                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
403                                                         (pipe->buffers - 1);
404                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
405                 int offset = buf->offset + buf->len;
406
407                 if (pipe_buf_can_merge(buf) && offset + chars <= PAGE_SIZE) {
408                         ret = pipe_buf_confirm(pipe, buf);
409                         if (ret)
410                                 goto out;
411
412                         ret = copy_page_from_iter(buf->page, offset, chars, from);
413                         if (unlikely(ret < chars)) {
414                                 ret = -EFAULT;
415                                 goto out;
416                         }
417                         do_wakeup = 1;
418                         buf->len += ret;
419                         if (!iov_iter_count(from))
420                                 goto out;
421                 }
422         }
423
424         for (;;) {
425                 int bufs;
426
427                 if (!pipe->readers) {
428                         send_sig(SIGPIPE, current, 0);
429                         if (!ret)
430                                 ret = -EPIPE;
431                         break;
432                 }
433                 bufs = pipe->nrbufs;
434                 if (bufs < pipe->buffers) {
435                         int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
436                         struct pipe_buffer *buf = pipe->bufs + newbuf;
437                         struct page *page = pipe->tmp_page;
438                         int copied;
439
440                         if (!page) {
441                                 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
442                                 if (unlikely(!page)) {
443                                         ret = ret ? : -ENOMEM;
444                                         break;
445                                 }
446                                 pipe->tmp_page = page;
447                         }
448                         /* Always wake up, even if the copy fails. Otherwise
449                          * we lock up (O_NONBLOCK-)readers that sleep due to
450                          * syscall merging.
451                          * FIXME! Is this really true?
452                          */
453                         do_wakeup = 1;
454                         copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
455                         if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
456                                 if (!ret)
457                                         ret = -EFAULT;
458                                 break;
459                         }
460                         ret += copied;
461
462                         /* Insert it into the buffer array */
463                         buf->page = page;
464                         buf->ops = &anon_pipe_buf_ops;
465                         buf->offset = 0;
466                         buf->len = copied;
467                         buf->flags = 0;
468                         if (is_packetized(filp)) {
469                                 buf->ops = &packet_pipe_buf_ops;
470                                 buf->flags = PIPE_BUF_FLAG_PACKET;
471                         }
472                         pipe->nrbufs = ++bufs;
473                         pipe->tmp_page = NULL;
474
475                         if (!iov_iter_count(from))
476                                 break;
477                 }
478                 if (bufs < pipe->buffers)
479                         continue;
480                 if (filp->f_flags & O_NONBLOCK) {
481                         if (!ret)
482                                 ret = -EAGAIN;
483                         break;
484                 }
485                 if (signal_pending(current)) {
486                         if (!ret)
487                                 ret = -ERESTARTSYS;
488                         break;
489                 }
490                 if (do_wakeup) {
491                         wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLRDNORM);
492                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
493                         do_wakeup = 0;
494                 }
495                 pipe->waiting_writers++;
496                 pipe_wait(pipe);
497                 pipe->waiting_writers--;
498         }
499 out:
500         __pipe_unlock(pipe);
501         if (do_wakeup) {
502                 wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLRDNORM);
503                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
504         }
505         if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
506                 int err = file_update_time(filp);
507                 if (err)
508                         ret = err;
509                 sb_end_write(file_inode(filp)->i_sb);
510         }
511         return ret;
512 }
513
514 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
515 {
516         struct pipe_inode_info *pipe = filp->private_data;
517         int count, buf, nrbufs;
518
519         switch (cmd) {
520                 case FIONREAD:
521                         __pipe_lock(pipe);
522                         count = 0;
523                         buf = pipe->curbuf;
524                         nrbufs = pipe->nrbufs;
525                         while (--nrbufs >= 0) {
526                                 count += pipe->bufs[buf].len;
527                                 buf = (buf+1) & (pipe->buffers - 1);
528                         }
529                         __pipe_unlock(pipe);
530
531                         return put_user(count, (int __user *)arg);
532                 default:
533                         return -ENOIOCTLCMD;
534         }
535 }
536
537 /* No kernel lock held - fine */
538 static __poll_t
539 pipe_poll(struct file *filp, poll_table *wait)
540 {
541         __poll_t mask;
542         struct pipe_inode_info *pipe = filp->private_data;
543         int nrbufs;
544
545         poll_wait(filp, &pipe->wait, wait);
546
547         /* Reading only -- no need for acquiring the semaphore.  */
548         nrbufs = pipe->nrbufs;
549         mask = 0;
550         if (filp->f_mode & FMODE_READ) {
551                 mask = (nrbufs > 0) ? EPOLLIN | EPOLLRDNORM : 0;
552                 if (!pipe->writers && filp->f_version != pipe->w_counter)
553                         mask |= EPOLLHUP;
554         }
555
556         if (filp->f_mode & FMODE_WRITE) {
557                 mask |= (nrbufs < pipe->buffers) ? EPOLLOUT | EPOLLWRNORM : 0;
558                 /*
559                  * Most Unices do not set EPOLLERR for FIFOs but on Linux they
560                  * behave exactly like pipes for poll().
561                  */
562                 if (!pipe->readers)
563                         mask |= EPOLLERR;
564         }
565
566         return mask;
567 }
568
569 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
570 {
571         int kill = 0;
572
573         spin_lock(&inode->i_lock);
574         if (!--pipe->files) {
575                 inode->i_pipe = NULL;
576                 kill = 1;
577         }
578         spin_unlock(&inode->i_lock);
579
580         if (kill)
581                 free_pipe_info(pipe);
582 }
583
584 static int
585 pipe_release(struct inode *inode, struct file *file)
586 {
587         struct pipe_inode_info *pipe = file->private_data;
588
589         __pipe_lock(pipe);
590         if (file->f_mode & FMODE_READ)
591                 pipe->readers--;
592         if (file->f_mode & FMODE_WRITE)
593                 pipe->writers--;
594
595         if (pipe->readers || pipe->writers) {
596                 wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLOUT | EPOLLRDNORM | EPOLLWRNORM | EPOLLERR | EPOLLHUP);
597                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
598                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
599         }
600         __pipe_unlock(pipe);
601
602         put_pipe_info(inode, pipe);
603         return 0;
604 }
605
606 static int
607 pipe_fasync(int fd, struct file *filp, int on)
608 {
609         struct pipe_inode_info *pipe = filp->private_data;
610         int retval = 0;
611
612         __pipe_lock(pipe);
613         if (filp->f_mode & FMODE_READ)
614                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
615         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
616                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
617                 if (retval < 0 && (filp->f_mode & FMODE_READ))
618                         /* this can happen only if on == T */
619                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
620         }
621         __pipe_unlock(pipe);
622         return retval;
623 }
624
625 static unsigned long account_pipe_buffers(struct user_struct *user,
626                                  unsigned long old, unsigned long new)
627 {
628         return atomic_long_add_return(new - old, &user->pipe_bufs);
629 }
630
631 static bool too_many_pipe_buffers_soft(unsigned long user_bufs)
632 {
633         unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
634
635         return soft_limit && user_bufs > soft_limit;
636 }
637
638 static bool too_many_pipe_buffers_hard(unsigned long user_bufs)
639 {
640         unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
641
642         return hard_limit && user_bufs > hard_limit;
643 }
644
645 static bool is_unprivileged_user(void)
646 {
647         return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
648 }
649
650 struct pipe_inode_info *alloc_pipe_info(void)
651 {
652         struct pipe_inode_info *pipe;
653         unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
654         struct user_struct *user = get_current_user();
655         unsigned long user_bufs;
656         unsigned int max_size = READ_ONCE(pipe_max_size);
657
658         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
659         if (pipe == NULL)
660                 goto out_free_uid;
661
662         if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
663                 pipe_bufs = max_size >> PAGE_SHIFT;
664
665         user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
666
667         if (too_many_pipe_buffers_soft(user_bufs) && is_unprivileged_user()) {
668                 user_bufs = account_pipe_buffers(user, pipe_bufs, 1);
669                 pipe_bufs = 1;
670         }
671
672         if (too_many_pipe_buffers_hard(user_bufs) && is_unprivileged_user())
673                 goto out_revert_acct;
674
675         pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
676                              GFP_KERNEL_ACCOUNT);
677
678         if (pipe->bufs) {
679                 init_waitqueue_head(&pipe->wait);
680                 pipe->r_counter = pipe->w_counter = 1;
681                 pipe->buffers = pipe_bufs;
682                 pipe->user = user;
683                 mutex_init(&pipe->mutex);
684                 return pipe;
685         }
686
687 out_revert_acct:
688         (void) account_pipe_buffers(user, pipe_bufs, 0);
689         kfree(pipe);
690 out_free_uid:
691         free_uid(user);
692         return NULL;
693 }
694
695 void free_pipe_info(struct pipe_inode_info *pipe)
696 {
697         int i;
698
699         (void) account_pipe_buffers(pipe->user, pipe->buffers, 0);
700         free_uid(pipe->user);
701         for (i = 0; i < pipe->buffers; i++) {
702                 struct pipe_buffer *buf = pipe->bufs + i;
703                 if (buf->ops)
704                         pipe_buf_release(pipe, buf);
705         }
706         if (pipe->tmp_page)
707                 __free_page(pipe->tmp_page);
708         kfree(pipe->bufs);
709         kfree(pipe);
710 }
711
712 static struct vfsmount *pipe_mnt __read_mostly;
713
714 /*
715  * pipefs_dname() is called from d_path().
716  */
717 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
718 {
719         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
720                                 d_inode(dentry)->i_ino);
721 }
722
723 static const struct dentry_operations pipefs_dentry_operations = {
724         .d_dname        = pipefs_dname,
725 };
726
727 static struct inode * get_pipe_inode(void)
728 {
729         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
730         struct pipe_inode_info *pipe;
731
732         if (!inode)
733                 goto fail_inode;
734
735         inode->i_ino = get_next_ino();
736
737         pipe = alloc_pipe_info();
738         if (!pipe)
739                 goto fail_iput;
740
741         inode->i_pipe = pipe;
742         pipe->files = 2;
743         pipe->readers = pipe->writers = 1;
744         inode->i_fop = &pipefifo_fops;
745
746         /*
747          * Mark the inode dirty from the very beginning,
748          * that way it will never be moved to the dirty
749          * list because "mark_inode_dirty()" will think
750          * that it already _is_ on the dirty list.
751          */
752         inode->i_state = I_DIRTY;
753         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
754         inode->i_uid = current_fsuid();
755         inode->i_gid = current_fsgid();
756         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
757
758         return inode;
759
760 fail_iput:
761         iput(inode);
762
763 fail_inode:
764         return NULL;
765 }
766
767 int create_pipe_files(struct file **res, int flags)
768 {
769         struct inode *inode = get_pipe_inode();
770         struct file *f;
771
772         if (!inode)
773                 return -ENFILE;
774
775         f = alloc_file_pseudo(inode, pipe_mnt, "",
776                                 O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
777                                 &pipefifo_fops);
778         if (IS_ERR(f)) {
779                 free_pipe_info(inode->i_pipe);
780                 iput(inode);
781                 return PTR_ERR(f);
782         }
783
784         f->private_data = inode->i_pipe;
785
786         res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
787                                   &pipefifo_fops);
788         if (IS_ERR(res[0])) {
789                 put_pipe_info(inode, inode->i_pipe);
790                 fput(f);
791                 return PTR_ERR(res[0]);
792         }
793         res[0]->private_data = inode->i_pipe;
794         res[1] = f;
795         return 0;
796 }
797
798 static int __do_pipe_flags(int *fd, struct file **files, int flags)
799 {
800         int error;
801         int fdw, fdr;
802
803         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
804                 return -EINVAL;
805
806         error = create_pipe_files(files, flags);
807         if (error)
808                 return error;
809
810         error = get_unused_fd_flags(flags);
811         if (error < 0)
812                 goto err_read_pipe;
813         fdr = error;
814
815         error = get_unused_fd_flags(flags);
816         if (error < 0)
817                 goto err_fdr;
818         fdw = error;
819
820         audit_fd_pair(fdr, fdw);
821         fd[0] = fdr;
822         fd[1] = fdw;
823         return 0;
824
825  err_fdr:
826         put_unused_fd(fdr);
827  err_read_pipe:
828         fput(files[0]);
829         fput(files[1]);
830         return error;
831 }
832
833 int do_pipe_flags(int *fd, int flags)
834 {
835         struct file *files[2];
836         int error = __do_pipe_flags(fd, files, flags);
837         if (!error) {
838                 fd_install(fd[0], files[0]);
839                 fd_install(fd[1], files[1]);
840         }
841         return error;
842 }
843
844 /*
845  * sys_pipe() is the normal C calling standard for creating
846  * a pipe. It's not the way Unix traditionally does this, though.
847  */
848 static int do_pipe2(int __user *fildes, int flags)
849 {
850         struct file *files[2];
851         int fd[2];
852         int error;
853
854         error = __do_pipe_flags(fd, files, flags);
855         if (!error) {
856                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
857                         fput(files[0]);
858                         fput(files[1]);
859                         put_unused_fd(fd[0]);
860                         put_unused_fd(fd[1]);
861                         error = -EFAULT;
862                 } else {
863                         fd_install(fd[0], files[0]);
864                         fd_install(fd[1], files[1]);
865                 }
866         }
867         return error;
868 }
869
870 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
871 {
872         return do_pipe2(fildes, flags);
873 }
874
875 SYSCALL_DEFINE1(pipe, int __user *, fildes)
876 {
877         return do_pipe2(fildes, 0);
878 }
879
880 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
881 {
882         int cur = *cnt; 
883
884         while (cur == *cnt) {
885                 pipe_wait(pipe);
886                 if (signal_pending(current))
887                         break;
888         }
889         return cur == *cnt ? -ERESTARTSYS : 0;
890 }
891
892 static void wake_up_partner(struct pipe_inode_info *pipe)
893 {
894         wake_up_interruptible(&pipe->wait);
895 }
896
897 static int fifo_open(struct inode *inode, struct file *filp)
898 {
899         struct pipe_inode_info *pipe;
900         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
901         int ret;
902
903         filp->f_version = 0;
904
905         spin_lock(&inode->i_lock);
906         if (inode->i_pipe) {
907                 pipe = inode->i_pipe;
908                 pipe->files++;
909                 spin_unlock(&inode->i_lock);
910         } else {
911                 spin_unlock(&inode->i_lock);
912                 pipe = alloc_pipe_info();
913                 if (!pipe)
914                         return -ENOMEM;
915                 pipe->files = 1;
916                 spin_lock(&inode->i_lock);
917                 if (unlikely(inode->i_pipe)) {
918                         inode->i_pipe->files++;
919                         spin_unlock(&inode->i_lock);
920                         free_pipe_info(pipe);
921                         pipe = inode->i_pipe;
922                 } else {
923                         inode->i_pipe = pipe;
924                         spin_unlock(&inode->i_lock);
925                 }
926         }
927         filp->private_data = pipe;
928         /* OK, we have a pipe and it's pinned down */
929
930         __pipe_lock(pipe);
931
932         /* We can only do regular read/write on fifos */
933         filp->f_mode &= (FMODE_READ | FMODE_WRITE);
934
935         switch (filp->f_mode) {
936         case FMODE_READ:
937         /*
938          *  O_RDONLY
939          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
940          *  opened, even when there is no process writing the FIFO.
941          */
942                 pipe->r_counter++;
943                 if (pipe->readers++ == 0)
944                         wake_up_partner(pipe);
945
946                 if (!is_pipe && !pipe->writers) {
947                         if ((filp->f_flags & O_NONBLOCK)) {
948                                 /* suppress EPOLLHUP until we have
949                                  * seen a writer */
950                                 filp->f_version = pipe->w_counter;
951                         } else {
952                                 if (wait_for_partner(pipe, &pipe->w_counter))
953                                         goto err_rd;
954                         }
955                 }
956                 break;
957         
958         case FMODE_WRITE:
959         /*
960          *  O_WRONLY
961          *  POSIX.1 says that O_NONBLOCK means return -1 with
962          *  errno=ENXIO when there is no process reading the FIFO.
963          */
964                 ret = -ENXIO;
965                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
966                         goto err;
967
968                 pipe->w_counter++;
969                 if (!pipe->writers++)
970                         wake_up_partner(pipe);
971
972                 if (!is_pipe && !pipe->readers) {
973                         if (wait_for_partner(pipe, &pipe->r_counter))
974                                 goto err_wr;
975                 }
976                 break;
977         
978         case FMODE_READ | FMODE_WRITE:
979         /*
980          *  O_RDWR
981          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
982          *  This implementation will NEVER block on a O_RDWR open, since
983          *  the process can at least talk to itself.
984          */
985
986                 pipe->readers++;
987                 pipe->writers++;
988                 pipe->r_counter++;
989                 pipe->w_counter++;
990                 if (pipe->readers == 1 || pipe->writers == 1)
991                         wake_up_partner(pipe);
992                 break;
993
994         default:
995                 ret = -EINVAL;
996                 goto err;
997         }
998
999         /* Ok! */
1000         __pipe_unlock(pipe);
1001         return 0;
1002
1003 err_rd:
1004         if (!--pipe->readers)
1005                 wake_up_interruptible(&pipe->wait);
1006         ret = -ERESTARTSYS;
1007         goto err;
1008
1009 err_wr:
1010         if (!--pipe->writers)
1011                 wake_up_interruptible(&pipe->wait);
1012         ret = -ERESTARTSYS;
1013         goto err;
1014
1015 err:
1016         __pipe_unlock(pipe);
1017
1018         put_pipe_info(inode, pipe);
1019         return ret;
1020 }
1021
1022 const struct file_operations pipefifo_fops = {
1023         .open           = fifo_open,
1024         .llseek         = no_llseek,
1025         .read_iter      = pipe_read,
1026         .write_iter     = pipe_write,
1027         .poll           = pipe_poll,
1028         .unlocked_ioctl = pipe_ioctl,
1029         .release        = pipe_release,
1030         .fasync         = pipe_fasync,
1031 };
1032
1033 /*
1034  * Currently we rely on the pipe array holding a power-of-2 number
1035  * of pages. Returns 0 on error.
1036  */
1037 unsigned int round_pipe_size(unsigned long size)
1038 {
1039         if (size > (1U << 31))
1040                 return 0;
1041
1042         /* Minimum pipe size, as required by POSIX */
1043         if (size < PAGE_SIZE)
1044                 return PAGE_SIZE;
1045
1046         return roundup_pow_of_two(size);
1047 }
1048
1049 /*
1050  * Allocate a new array of pipe buffers and copy the info over. Returns the
1051  * pipe size if successful, or return -ERROR on error.
1052  */
1053 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1054 {
1055         struct pipe_buffer *bufs;
1056         unsigned int size, nr_pages;
1057         unsigned long user_bufs;
1058         long ret = 0;
1059
1060         size = round_pipe_size(arg);
1061         nr_pages = size >> PAGE_SHIFT;
1062
1063         if (!nr_pages)
1064                 return -EINVAL;
1065
1066         /*
1067          * If trying to increase the pipe capacity, check that an
1068          * unprivileged user is not trying to exceed various limits
1069          * (soft limit check here, hard limit check just below).
1070          * Decreasing the pipe capacity is always permitted, even
1071          * if the user is currently over a limit.
1072          */
1073         if (nr_pages > pipe->buffers &&
1074                         size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1075                 return -EPERM;
1076
1077         user_bufs = account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
1078
1079         if (nr_pages > pipe->buffers &&
1080                         (too_many_pipe_buffers_hard(user_bufs) ||
1081                          too_many_pipe_buffers_soft(user_bufs)) &&
1082                         is_unprivileged_user()) {
1083                 ret = -EPERM;
1084                 goto out_revert_acct;
1085         }
1086
1087         /*
1088          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1089          * expect a lot of shrink+grow operations, just free and allocate
1090          * again like we would do for growing. If the pipe currently
1091          * contains more buffers than arg, then return busy.
1092          */
1093         if (nr_pages < pipe->nrbufs) {
1094                 ret = -EBUSY;
1095                 goto out_revert_acct;
1096         }
1097
1098         bufs = kcalloc(nr_pages, sizeof(*bufs),
1099                        GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1100         if (unlikely(!bufs)) {
1101                 ret = -ENOMEM;
1102                 goto out_revert_acct;
1103         }
1104
1105         /*
1106          * The pipe array wraps around, so just start the new one at zero
1107          * and adjust the indexes.
1108          */
1109         if (pipe->nrbufs) {
1110                 unsigned int tail;
1111                 unsigned int head;
1112
1113                 tail = pipe->curbuf + pipe->nrbufs;
1114                 if (tail < pipe->buffers)
1115                         tail = 0;
1116                 else
1117                         tail &= (pipe->buffers - 1);
1118
1119                 head = pipe->nrbufs - tail;
1120                 if (head)
1121                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1122                 if (tail)
1123                         memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1124         }
1125
1126         pipe->curbuf = 0;
1127         kfree(pipe->bufs);
1128         pipe->bufs = bufs;
1129         pipe->buffers = nr_pages;
1130         return nr_pages * PAGE_SIZE;
1131
1132 out_revert_acct:
1133         (void) account_pipe_buffers(pipe->user, nr_pages, pipe->buffers);
1134         return ret;
1135 }
1136
1137 /*
1138  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1139  * location, so checking ->i_pipe is not enough to verify that this is a
1140  * pipe.
1141  */
1142 struct pipe_inode_info *get_pipe_info(struct file *file)
1143 {
1144         return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1145 }
1146
1147 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1148 {
1149         struct pipe_inode_info *pipe;
1150         long ret;
1151
1152         pipe = get_pipe_info(file);
1153         if (!pipe)
1154                 return -EBADF;
1155
1156         __pipe_lock(pipe);
1157
1158         switch (cmd) {
1159         case F_SETPIPE_SZ:
1160                 ret = pipe_set_size(pipe, arg);
1161                 break;
1162         case F_GETPIPE_SZ:
1163                 ret = pipe->buffers * PAGE_SIZE;
1164                 break;
1165         default:
1166                 ret = -EINVAL;
1167                 break;
1168         }
1169
1170         __pipe_unlock(pipe);
1171         return ret;
1172 }
1173
1174 static const struct super_operations pipefs_ops = {
1175         .destroy_inode = free_inode_nonrcu,
1176         .statfs = simple_statfs,
1177 };
1178
1179 /*
1180  * pipefs should _never_ be mounted by userland - too much of security hassle,
1181  * no real gain from having the whole whorehouse mounted. So we don't need
1182  * any operations on the root directory. However, we need a non-trivial
1183  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1184  */
1185 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1186                          int flags, const char *dev_name, void *data)
1187 {
1188         return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1189                         &pipefs_dentry_operations, PIPEFS_MAGIC);
1190 }
1191
1192 static struct file_system_type pipe_fs_type = {
1193         .name           = "pipefs",
1194         .mount          = pipefs_mount,
1195         .kill_sb        = kill_anon_super,
1196 };
1197
1198 static int __init init_pipe_fs(void)
1199 {
1200         int err = register_filesystem(&pipe_fs_type);
1201
1202         if (!err) {
1203                 pipe_mnt = kern_mount(&pipe_fs_type);
1204                 if (IS_ERR(pipe_mnt)) {
1205                         err = PTR_ERR(pipe_mnt);
1206                         unregister_filesystem(&pipe_fs_type);
1207                 }
1208         }
1209         return err;
1210 }
1211
1212 fs_initcall(init_pipe_fs);