GNU Linux-libre 4.9.308-gnu1
[releases.git] / fs / pipe.c
1 /*
2  *  linux/fs/pipe.c
3  *
4  *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
5  */
6
7 #include <linux/mm.h>
8 #include <linux/file.h>
9 #include <linux/poll.h>
10 #include <linux/slab.h>
11 #include <linux/module.h>
12 #include <linux/init.h>
13 #include <linux/fs.h>
14 #include <linux/log2.h>
15 #include <linux/mount.h>
16 #include <linux/magic.h>
17 #include <linux/pipe_fs_i.h>
18 #include <linux/uio.h>
19 #include <linux/highmem.h>
20 #include <linux/pagemap.h>
21 #include <linux/audit.h>
22 #include <linux/syscalls.h>
23 #include <linux/fcntl.h>
24 #include <linux/memcontrol.h>
25
26 #include <asm/uaccess.h>
27 #include <asm/ioctls.h>
28
29 #include "internal.h"
30
31 /*
32  * New pipe buffers will be restricted to this size while the user is exceeding
33  * their pipe buffer quota. The general pipe use case needs at least two
34  * buffers: one for data yet to be read, and one for new data. If this is less
35  * than two, then a write to a non-empty pipe may block even if the pipe is not
36  * full. This can occur with GNU make jobserver or similar uses of pipes as
37  * semaphores: multiple processes may be waiting to write tokens back to the
38  * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.
39  *
40  * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their
41  * own risk, namely: pipe writes to non-full pipes may block until the pipe is
42  * emptied.
43  */
44 #define PIPE_MIN_DEF_BUFFERS 2
45
46 /*
47  * The max size that a non-root user is allowed to grow the pipe. Can
48  * be set by root in /proc/sys/fs/pipe-max-size
49  */
50 unsigned int pipe_max_size = 1048576;
51
52 /*
53  * Minimum pipe size, as required by POSIX
54  */
55 unsigned int pipe_min_size = PAGE_SIZE;
56
57 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
58  * matches default values.
59  */
60 unsigned long pipe_user_pages_hard;
61 unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
62
63 /*
64  * We use a start+len construction, which provides full use of the 
65  * allocated memory.
66  * -- Florian Coosmann (FGC)
67  * 
68  * Reads with count = 0 should always return 0.
69  * -- Julian Bradfield 1999-06-07.
70  *
71  * FIFOs and Pipes now generate SIGIO for both readers and writers.
72  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
73  *
74  * pipe_read & write cleanup
75  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
76  */
77
78 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
79 {
80         if (pipe->files)
81                 mutex_lock_nested(&pipe->mutex, subclass);
82 }
83
84 void pipe_lock(struct pipe_inode_info *pipe)
85 {
86         /*
87          * pipe_lock() nests non-pipe inode locks (for writing to a file)
88          */
89         pipe_lock_nested(pipe, I_MUTEX_PARENT);
90 }
91 EXPORT_SYMBOL(pipe_lock);
92
93 void pipe_unlock(struct pipe_inode_info *pipe)
94 {
95         if (pipe->files)
96                 mutex_unlock(&pipe->mutex);
97 }
98 EXPORT_SYMBOL(pipe_unlock);
99
100 static inline void __pipe_lock(struct pipe_inode_info *pipe)
101 {
102         mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
103 }
104
105 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
106 {
107         mutex_unlock(&pipe->mutex);
108 }
109
110 void pipe_double_lock(struct pipe_inode_info *pipe1,
111                       struct pipe_inode_info *pipe2)
112 {
113         BUG_ON(pipe1 == pipe2);
114
115         if (pipe1 < pipe2) {
116                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
117                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
118         } else {
119                 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
120                 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
121         }
122 }
123
124 /* Drop the inode semaphore and wait for a pipe event, atomically */
125 void pipe_wait(struct pipe_inode_info *pipe)
126 {
127         DEFINE_WAIT(wait);
128
129         /*
130          * Pipes are system-local resources, so sleeping on them
131          * is considered a noninteractive wait:
132          */
133         prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
134         pipe_unlock(pipe);
135         schedule();
136         finish_wait(&pipe->wait, &wait);
137         pipe_lock(pipe);
138 }
139
140 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
141                                   struct pipe_buffer *buf)
142 {
143         struct page *page = buf->page;
144
145         /*
146          * If nobody else uses this page, and we don't already have a
147          * temporary page, let's keep track of it as a one-deep
148          * allocation cache. (Otherwise just release our reference to it)
149          */
150         if (page_count(page) == 1 && !pipe->tmp_page)
151                 pipe->tmp_page = page;
152         else
153                 put_page(page);
154 }
155
156 static int anon_pipe_buf_steal(struct pipe_inode_info *pipe,
157                                struct pipe_buffer *buf)
158 {
159         struct page *page = buf->page;
160
161         if (page_count(page) == 1) {
162                 if (memcg_kmem_enabled())
163                         memcg_kmem_uncharge(page, 0);
164                 __SetPageLocked(page);
165                 return 0;
166         }
167         return 1;
168 }
169
170 /**
171  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
172  * @pipe:       the pipe that the buffer belongs to
173  * @buf:        the buffer to attempt to steal
174  *
175  * Description:
176  *      This function attempts to steal the &struct page attached to
177  *      @buf. If successful, this function returns 0 and returns with
178  *      the page locked. The caller may then reuse the page for whatever
179  *      he wishes; the typical use is insertion into a different file
180  *      page cache.
181  */
182 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
183                            struct pipe_buffer *buf)
184 {
185         struct page *page = buf->page;
186
187         /*
188          * A reference of one is golden, that means that the owner of this
189          * page is the only one holding a reference to it. lock the page
190          * and return OK.
191          */
192         if (page_count(page) == 1) {
193                 lock_page(page);
194                 return 0;
195         }
196
197         return 1;
198 }
199 EXPORT_SYMBOL(generic_pipe_buf_steal);
200
201 /**
202  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
203  * @pipe:       the pipe that the buffer belongs to
204  * @buf:        the buffer to get a reference to
205  *
206  * Description:
207  *      This function grabs an extra reference to @buf. It's used in
208  *      in the tee() system call, when we duplicate the buffers in one
209  *      pipe into another.
210  */
211 bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
212 {
213         return try_get_page(buf->page);
214 }
215 EXPORT_SYMBOL(generic_pipe_buf_get);
216
217 /**
218  * generic_pipe_buf_confirm - verify contents of the pipe buffer
219  * @info:       the pipe that the buffer belongs to
220  * @buf:        the buffer to confirm
221  *
222  * Description:
223  *      This function does nothing, because the generic pipe code uses
224  *      pages that are always good when inserted into the pipe.
225  */
226 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
227                              struct pipe_buffer *buf)
228 {
229         return 0;
230 }
231 EXPORT_SYMBOL(generic_pipe_buf_confirm);
232
233 /**
234  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
235  * @pipe:       the pipe that the buffer belongs to
236  * @buf:        the buffer to put a reference to
237  *
238  * Description:
239  *      This function releases a reference to @buf.
240  */
241 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
242                               struct pipe_buffer *buf)
243 {
244         put_page(buf->page);
245 }
246 EXPORT_SYMBOL(generic_pipe_buf_release);
247
248 static const struct pipe_buf_operations anon_pipe_buf_ops = {
249         .can_merge = 1,
250         .confirm = generic_pipe_buf_confirm,
251         .release = anon_pipe_buf_release,
252         .steal = anon_pipe_buf_steal,
253         .get = generic_pipe_buf_get,
254 };
255
256 static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = {
257         .can_merge = 0,
258         .confirm = generic_pipe_buf_confirm,
259         .release = anon_pipe_buf_release,
260         .steal = anon_pipe_buf_steal,
261         .get = generic_pipe_buf_get,
262 };
263
264 static const struct pipe_buf_operations packet_pipe_buf_ops = {
265         .can_merge = 0,
266         .confirm = generic_pipe_buf_confirm,
267         .release = anon_pipe_buf_release,
268         .steal = anon_pipe_buf_steal,
269         .get = generic_pipe_buf_get,
270 };
271
272 void pipe_buf_mark_unmergeable(struct pipe_buffer *buf)
273 {
274         if (buf->ops == &anon_pipe_buf_ops)
275                 buf->ops = &anon_pipe_buf_nomerge_ops;
276 }
277
278 static ssize_t
279 pipe_read(struct kiocb *iocb, struct iov_iter *to)
280 {
281         size_t total_len = iov_iter_count(to);
282         struct file *filp = iocb->ki_filp;
283         struct pipe_inode_info *pipe = filp->private_data;
284         int do_wakeup;
285         ssize_t ret;
286
287         /* Null read succeeds. */
288         if (unlikely(total_len == 0))
289                 return 0;
290
291         do_wakeup = 0;
292         ret = 0;
293         __pipe_lock(pipe);
294         for (;;) {
295                 int bufs = pipe->nrbufs;
296                 if (bufs) {
297                         int curbuf = pipe->curbuf;
298                         struct pipe_buffer *buf = pipe->bufs + curbuf;
299                         size_t chars = buf->len;
300                         size_t written;
301                         int error;
302
303                         if (chars > total_len)
304                                 chars = total_len;
305
306                         error = pipe_buf_confirm(pipe, buf);
307                         if (error) {
308                                 if (!ret)
309                                         ret = error;
310                                 break;
311                         }
312
313                         written = copy_page_to_iter(buf->page, buf->offset, chars, to);
314                         if (unlikely(written < chars)) {
315                                 if (!ret)
316                                         ret = -EFAULT;
317                                 break;
318                         }
319                         ret += chars;
320                         buf->offset += chars;
321                         buf->len -= chars;
322
323                         /* Was it a packet buffer? Clean up and exit */
324                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
325                                 total_len = chars;
326                                 buf->len = 0;
327                         }
328
329                         if (!buf->len) {
330                                 pipe_buf_release(pipe, buf);
331                                 curbuf = (curbuf + 1) & (pipe->buffers - 1);
332                                 pipe->curbuf = curbuf;
333                                 pipe->nrbufs = --bufs;
334                                 do_wakeup = 1;
335                         }
336                         total_len -= chars;
337                         if (!total_len)
338                                 break;  /* common path: read succeeded */
339                 }
340                 if (bufs)       /* More to do? */
341                         continue;
342                 if (!pipe->writers)
343                         break;
344                 if (!pipe->waiting_writers) {
345                         /* syscall merging: Usually we must not sleep
346                          * if O_NONBLOCK is set, or if we got some data.
347                          * But if a writer sleeps in kernel space, then
348                          * we can wait for that data without violating POSIX.
349                          */
350                         if (ret)
351                                 break;
352                         if (filp->f_flags & O_NONBLOCK) {
353                                 ret = -EAGAIN;
354                                 break;
355                         }
356                 }
357                 if (signal_pending(current)) {
358                         if (!ret)
359                                 ret = -ERESTARTSYS;
360                         break;
361                 }
362                 if (do_wakeup) {
363                         wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
364                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
365                 }
366                 pipe_wait(pipe);
367         }
368         __pipe_unlock(pipe);
369
370         /* Signal writers asynchronously that there is more room. */
371         if (do_wakeup) {
372                 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
373                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
374         }
375         if (ret > 0)
376                 file_accessed(filp);
377         return ret;
378 }
379
380 static inline int is_packetized(struct file *file)
381 {
382         return (file->f_flags & O_DIRECT) != 0;
383 }
384
385 static ssize_t
386 pipe_write(struct kiocb *iocb, struct iov_iter *from)
387 {
388         struct file *filp = iocb->ki_filp;
389         struct pipe_inode_info *pipe = filp->private_data;
390         ssize_t ret = 0;
391         int do_wakeup = 0;
392         size_t total_len = iov_iter_count(from);
393         ssize_t chars;
394
395         /* Null write succeeds. */
396         if (unlikely(total_len == 0))
397                 return 0;
398
399         __pipe_lock(pipe);
400
401         if (!pipe->readers) {
402                 send_sig(SIGPIPE, current, 0);
403                 ret = -EPIPE;
404                 goto out;
405         }
406
407         /* We try to merge small writes */
408         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
409         if (pipe->nrbufs && chars != 0) {
410                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
411                                                         (pipe->buffers - 1);
412                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
413                 int offset = buf->offset + buf->len;
414
415                 if (buf->ops->can_merge && offset + chars <= PAGE_SIZE) {
416                         ret = pipe_buf_confirm(pipe, buf);
417                         if (ret)
418                                 goto out;
419
420                         ret = copy_page_from_iter(buf->page, offset, chars, from);
421                         if (unlikely(ret < chars)) {
422                                 ret = -EFAULT;
423                                 goto out;
424                         }
425                         do_wakeup = 1;
426                         buf->len += ret;
427                         if (!iov_iter_count(from))
428                                 goto out;
429                 }
430         }
431
432         for (;;) {
433                 int bufs;
434
435                 if (!pipe->readers) {
436                         send_sig(SIGPIPE, current, 0);
437                         if (!ret)
438                                 ret = -EPIPE;
439                         break;
440                 }
441                 bufs = pipe->nrbufs;
442                 if (bufs < pipe->buffers) {
443                         int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
444                         struct pipe_buffer *buf = pipe->bufs + newbuf;
445                         struct page *page = pipe->tmp_page;
446                         int copied;
447
448                         if (!page) {
449                                 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
450                                 if (unlikely(!page)) {
451                                         ret = ret ? : -ENOMEM;
452                                         break;
453                                 }
454                                 pipe->tmp_page = page;
455                         }
456                         /* Always wake up, even if the copy fails. Otherwise
457                          * we lock up (O_NONBLOCK-)readers that sleep due to
458                          * syscall merging.
459                          * FIXME! Is this really true?
460                          */
461                         do_wakeup = 1;
462                         copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
463                         if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
464                                 if (!ret)
465                                         ret = -EFAULT;
466                                 break;
467                         }
468                         ret += copied;
469
470                         /* Insert it into the buffer array */
471                         buf->page = page;
472                         buf->ops = &anon_pipe_buf_ops;
473                         buf->offset = 0;
474                         buf->len = copied;
475                         buf->flags = 0;
476                         if (is_packetized(filp)) {
477                                 buf->ops = &packet_pipe_buf_ops;
478                                 buf->flags = PIPE_BUF_FLAG_PACKET;
479                         }
480                         pipe->nrbufs = ++bufs;
481                         pipe->tmp_page = NULL;
482
483                         if (!iov_iter_count(from))
484                                 break;
485                 }
486                 if (bufs < pipe->buffers)
487                         continue;
488                 if (filp->f_flags & O_NONBLOCK) {
489                         if (!ret)
490                                 ret = -EAGAIN;
491                         break;
492                 }
493                 if (signal_pending(current)) {
494                         if (!ret)
495                                 ret = -ERESTARTSYS;
496                         break;
497                 }
498                 if (do_wakeup) {
499                         wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
500                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
501                         do_wakeup = 0;
502                 }
503                 pipe->waiting_writers++;
504                 pipe_wait(pipe);
505                 pipe->waiting_writers--;
506         }
507 out:
508         __pipe_unlock(pipe);
509         if (do_wakeup) {
510                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
511                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
512         }
513         if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
514                 int err = file_update_time(filp);
515                 if (err)
516                         ret = err;
517                 sb_end_write(file_inode(filp)->i_sb);
518         }
519         return ret;
520 }
521
522 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
523 {
524         struct pipe_inode_info *pipe = filp->private_data;
525         int count, buf, nrbufs;
526
527         switch (cmd) {
528                 case FIONREAD:
529                         __pipe_lock(pipe);
530                         count = 0;
531                         buf = pipe->curbuf;
532                         nrbufs = pipe->nrbufs;
533                         while (--nrbufs >= 0) {
534                                 count += pipe->bufs[buf].len;
535                                 buf = (buf+1) & (pipe->buffers - 1);
536                         }
537                         __pipe_unlock(pipe);
538
539                         return put_user(count, (int __user *)arg);
540                 default:
541                         return -ENOIOCTLCMD;
542         }
543 }
544
545 /* No kernel lock held - fine */
546 static unsigned int
547 pipe_poll(struct file *filp, poll_table *wait)
548 {
549         unsigned int mask;
550         struct pipe_inode_info *pipe = filp->private_data;
551         int nrbufs;
552
553         poll_wait(filp, &pipe->wait, wait);
554
555         /* Reading only -- no need for acquiring the semaphore.  */
556         nrbufs = pipe->nrbufs;
557         mask = 0;
558         if (filp->f_mode & FMODE_READ) {
559                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
560                 if (!pipe->writers && filp->f_version != pipe->w_counter)
561                         mask |= POLLHUP;
562         }
563
564         if (filp->f_mode & FMODE_WRITE) {
565                 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
566                 /*
567                  * Most Unices do not set POLLERR for FIFOs but on Linux they
568                  * behave exactly like pipes for poll().
569                  */
570                 if (!pipe->readers)
571                         mask |= POLLERR;
572         }
573
574         return mask;
575 }
576
577 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
578 {
579         int kill = 0;
580
581         spin_lock(&inode->i_lock);
582         if (!--pipe->files) {
583                 inode->i_pipe = NULL;
584                 kill = 1;
585         }
586         spin_unlock(&inode->i_lock);
587
588         if (kill)
589                 free_pipe_info(pipe);
590 }
591
592 static int
593 pipe_release(struct inode *inode, struct file *file)
594 {
595         struct pipe_inode_info *pipe = file->private_data;
596
597         __pipe_lock(pipe);
598         if (file->f_mode & FMODE_READ)
599                 pipe->readers--;
600         if (file->f_mode & FMODE_WRITE)
601                 pipe->writers--;
602
603         if (pipe->readers || pipe->writers) {
604                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
605                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
606                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
607         }
608         __pipe_unlock(pipe);
609
610         put_pipe_info(inode, pipe);
611         return 0;
612 }
613
614 static int
615 pipe_fasync(int fd, struct file *filp, int on)
616 {
617         struct pipe_inode_info *pipe = filp->private_data;
618         int retval = 0;
619
620         __pipe_lock(pipe);
621         if (filp->f_mode & FMODE_READ)
622                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
623         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
624                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
625                 if (retval < 0 && (filp->f_mode & FMODE_READ))
626                         /* this can happen only if on == T */
627                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
628         }
629         __pipe_unlock(pipe);
630         return retval;
631 }
632
633 static unsigned long account_pipe_buffers(struct user_struct *user,
634                                  unsigned long old, unsigned long new)
635 {
636         return atomic_long_add_return(new - old, &user->pipe_bufs);
637 }
638
639 static bool too_many_pipe_buffers_soft(unsigned long user_bufs)
640 {
641         return pipe_user_pages_soft && user_bufs > pipe_user_pages_soft;
642 }
643
644 static bool too_many_pipe_buffers_hard(unsigned long user_bufs)
645 {
646         return pipe_user_pages_hard && user_bufs > pipe_user_pages_hard;
647 }
648
649 static bool is_unprivileged_user(void)
650 {
651         return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
652 }
653
654 struct pipe_inode_info *alloc_pipe_info(void)
655 {
656         struct pipe_inode_info *pipe;
657         unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
658         struct user_struct *user = get_current_user();
659         unsigned long user_bufs;
660
661         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
662         if (pipe == NULL)
663                 goto out_free_uid;
664
665         if (pipe_bufs * PAGE_SIZE > pipe_max_size && !capable(CAP_SYS_RESOURCE))
666                 pipe_bufs = pipe_max_size >> PAGE_SHIFT;
667
668         user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
669
670         if (too_many_pipe_buffers_soft(user_bufs) && is_unprivileged_user()) {
671                 user_bufs = account_pipe_buffers(user, pipe_bufs, PIPE_MIN_DEF_BUFFERS);
672                 pipe_bufs = PIPE_MIN_DEF_BUFFERS;
673         }
674
675         if (too_many_pipe_buffers_hard(user_bufs) && is_unprivileged_user())
676                 goto out_revert_acct;
677
678         pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
679                              GFP_KERNEL_ACCOUNT);
680
681         if (pipe->bufs) {
682                 init_waitqueue_head(&pipe->wait);
683                 pipe->r_counter = pipe->w_counter = 1;
684                 pipe->buffers = pipe_bufs;
685                 pipe->user = user;
686                 mutex_init(&pipe->mutex);
687                 return pipe;
688         }
689
690 out_revert_acct:
691         (void) account_pipe_buffers(user, pipe_bufs, 0);
692         kfree(pipe);
693 out_free_uid:
694         free_uid(user);
695         return NULL;
696 }
697
698 void free_pipe_info(struct pipe_inode_info *pipe)
699 {
700         int i;
701
702         (void) account_pipe_buffers(pipe->user, pipe->buffers, 0);
703         free_uid(pipe->user);
704         for (i = 0; i < pipe->buffers; i++) {
705                 struct pipe_buffer *buf = pipe->bufs + i;
706                 if (buf->ops)
707                         pipe_buf_release(pipe, buf);
708         }
709         if (pipe->tmp_page)
710                 __free_page(pipe->tmp_page);
711         kfree(pipe->bufs);
712         kfree(pipe);
713 }
714
715 static struct vfsmount *pipe_mnt __read_mostly;
716
717 /*
718  * pipefs_dname() is called from d_path().
719  */
720 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
721 {
722         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
723                                 d_inode(dentry)->i_ino);
724 }
725
726 static const struct dentry_operations pipefs_dentry_operations = {
727         .d_dname        = pipefs_dname,
728 };
729
730 static struct inode * get_pipe_inode(void)
731 {
732         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
733         struct pipe_inode_info *pipe;
734
735         if (!inode)
736                 goto fail_inode;
737
738         inode->i_ino = get_next_ino();
739
740         pipe = alloc_pipe_info();
741         if (!pipe)
742                 goto fail_iput;
743
744         inode->i_pipe = pipe;
745         pipe->files = 2;
746         pipe->readers = pipe->writers = 1;
747         inode->i_fop = &pipefifo_fops;
748
749         /*
750          * Mark the inode dirty from the very beginning,
751          * that way it will never be moved to the dirty
752          * list because "mark_inode_dirty()" will think
753          * that it already _is_ on the dirty list.
754          */
755         inode->i_state = I_DIRTY;
756         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
757         inode->i_uid = current_fsuid();
758         inode->i_gid = current_fsgid();
759         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
760
761         return inode;
762
763 fail_iput:
764         iput(inode);
765
766 fail_inode:
767         return NULL;
768 }
769
770 int create_pipe_files(struct file **res, int flags)
771 {
772         int err;
773         struct inode *inode = get_pipe_inode();
774         struct file *f;
775         struct path path;
776         static struct qstr name = { .name = "" };
777
778         if (!inode)
779                 return -ENFILE;
780
781         err = -ENOMEM;
782         path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
783         if (!path.dentry)
784                 goto err_inode;
785         path.mnt = mntget(pipe_mnt);
786
787         d_instantiate(path.dentry, inode);
788
789         f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops);
790         if (IS_ERR(f)) {
791                 err = PTR_ERR(f);
792                 goto err_dentry;
793         }
794
795         f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
796         f->private_data = inode->i_pipe;
797
798         res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
799         if (IS_ERR(res[0])) {
800                 err = PTR_ERR(res[0]);
801                 goto err_file;
802         }
803
804         path_get(&path);
805         res[0]->private_data = inode->i_pipe;
806         res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
807         res[1] = f;
808         return 0;
809
810 err_file:
811         put_filp(f);
812 err_dentry:
813         free_pipe_info(inode->i_pipe);
814         path_put(&path);
815         return err;
816
817 err_inode:
818         free_pipe_info(inode->i_pipe);
819         iput(inode);
820         return err;
821 }
822
823 static int __do_pipe_flags(int *fd, struct file **files, int flags)
824 {
825         int error;
826         int fdw, fdr;
827
828         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
829                 return -EINVAL;
830
831         error = create_pipe_files(files, flags);
832         if (error)
833                 return error;
834
835         error = get_unused_fd_flags(flags);
836         if (error < 0)
837                 goto err_read_pipe;
838         fdr = error;
839
840         error = get_unused_fd_flags(flags);
841         if (error < 0)
842                 goto err_fdr;
843         fdw = error;
844
845         audit_fd_pair(fdr, fdw);
846         fd[0] = fdr;
847         fd[1] = fdw;
848         return 0;
849
850  err_fdr:
851         put_unused_fd(fdr);
852  err_read_pipe:
853         fput(files[0]);
854         fput(files[1]);
855         return error;
856 }
857
858 int do_pipe_flags(int *fd, int flags)
859 {
860         struct file *files[2];
861         int error = __do_pipe_flags(fd, files, flags);
862         if (!error) {
863                 fd_install(fd[0], files[0]);
864                 fd_install(fd[1], files[1]);
865         }
866         return error;
867 }
868
869 /*
870  * sys_pipe() is the normal C calling standard for creating
871  * a pipe. It's not the way Unix traditionally does this, though.
872  */
873 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
874 {
875         struct file *files[2];
876         int fd[2];
877         int error;
878
879         error = __do_pipe_flags(fd, files, flags);
880         if (!error) {
881                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
882                         fput(files[0]);
883                         fput(files[1]);
884                         put_unused_fd(fd[0]);
885                         put_unused_fd(fd[1]);
886                         error = -EFAULT;
887                 } else {
888                         fd_install(fd[0], files[0]);
889                         fd_install(fd[1], files[1]);
890                 }
891         }
892         return error;
893 }
894
895 SYSCALL_DEFINE1(pipe, int __user *, fildes)
896 {
897         return sys_pipe2(fildes, 0);
898 }
899
900 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
901 {
902         int cur = *cnt; 
903
904         while (cur == *cnt) {
905                 pipe_wait(pipe);
906                 if (signal_pending(current))
907                         break;
908         }
909         return cur == *cnt ? -ERESTARTSYS : 0;
910 }
911
912 static void wake_up_partner(struct pipe_inode_info *pipe)
913 {
914         wake_up_interruptible(&pipe->wait);
915 }
916
917 static int fifo_open(struct inode *inode, struct file *filp)
918 {
919         struct pipe_inode_info *pipe;
920         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
921         int ret;
922
923         filp->f_version = 0;
924
925         spin_lock(&inode->i_lock);
926         if (inode->i_pipe) {
927                 pipe = inode->i_pipe;
928                 pipe->files++;
929                 spin_unlock(&inode->i_lock);
930         } else {
931                 spin_unlock(&inode->i_lock);
932                 pipe = alloc_pipe_info();
933                 if (!pipe)
934                         return -ENOMEM;
935                 pipe->files = 1;
936                 spin_lock(&inode->i_lock);
937                 if (unlikely(inode->i_pipe)) {
938                         inode->i_pipe->files++;
939                         spin_unlock(&inode->i_lock);
940                         free_pipe_info(pipe);
941                         pipe = inode->i_pipe;
942                 } else {
943                         inode->i_pipe = pipe;
944                         spin_unlock(&inode->i_lock);
945                 }
946         }
947         filp->private_data = pipe;
948         /* OK, we have a pipe and it's pinned down */
949
950         __pipe_lock(pipe);
951
952         /* We can only do regular read/write on fifos */
953         filp->f_mode &= (FMODE_READ | FMODE_WRITE);
954
955         switch (filp->f_mode) {
956         case FMODE_READ:
957         /*
958          *  O_RDONLY
959          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
960          *  opened, even when there is no process writing the FIFO.
961          */
962                 pipe->r_counter++;
963                 if (pipe->readers++ == 0)
964                         wake_up_partner(pipe);
965
966                 if (!is_pipe && !pipe->writers) {
967                         if ((filp->f_flags & O_NONBLOCK)) {
968                                 /* suppress POLLHUP until we have
969                                  * seen a writer */
970                                 filp->f_version = pipe->w_counter;
971                         } else {
972                                 if (wait_for_partner(pipe, &pipe->w_counter))
973                                         goto err_rd;
974                         }
975                 }
976                 break;
977         
978         case FMODE_WRITE:
979         /*
980          *  O_WRONLY
981          *  POSIX.1 says that O_NONBLOCK means return -1 with
982          *  errno=ENXIO when there is no process reading the FIFO.
983          */
984                 ret = -ENXIO;
985                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
986                         goto err;
987
988                 pipe->w_counter++;
989                 if (!pipe->writers++)
990                         wake_up_partner(pipe);
991
992                 if (!is_pipe && !pipe->readers) {
993                         if (wait_for_partner(pipe, &pipe->r_counter))
994                                 goto err_wr;
995                 }
996                 break;
997         
998         case FMODE_READ | FMODE_WRITE:
999         /*
1000          *  O_RDWR
1001          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1002          *  This implementation will NEVER block on a O_RDWR open, since
1003          *  the process can at least talk to itself.
1004          */
1005
1006                 pipe->readers++;
1007                 pipe->writers++;
1008                 pipe->r_counter++;
1009                 pipe->w_counter++;
1010                 if (pipe->readers == 1 || pipe->writers == 1)
1011                         wake_up_partner(pipe);
1012                 break;
1013
1014         default:
1015                 ret = -EINVAL;
1016                 goto err;
1017         }
1018
1019         /* Ok! */
1020         __pipe_unlock(pipe);
1021         return 0;
1022
1023 err_rd:
1024         if (!--pipe->readers)
1025                 wake_up_interruptible(&pipe->wait);
1026         ret = -ERESTARTSYS;
1027         goto err;
1028
1029 err_wr:
1030         if (!--pipe->writers)
1031                 wake_up_interruptible(&pipe->wait);
1032         ret = -ERESTARTSYS;
1033         goto err;
1034
1035 err:
1036         __pipe_unlock(pipe);
1037
1038         put_pipe_info(inode, pipe);
1039         return ret;
1040 }
1041
1042 const struct file_operations pipefifo_fops = {
1043         .open           = fifo_open,
1044         .llseek         = no_llseek,
1045         .read_iter      = pipe_read,
1046         .write_iter     = pipe_write,
1047         .poll           = pipe_poll,
1048         .unlocked_ioctl = pipe_ioctl,
1049         .release        = pipe_release,
1050         .fasync         = pipe_fasync,
1051 };
1052
1053 /*
1054  * Currently we rely on the pipe array holding a power-of-2 number
1055  * of pages. Returns 0 on error.
1056  */
1057 static inline unsigned int round_pipe_size(unsigned int size)
1058 {
1059         unsigned long nr_pages;
1060
1061         if (size < pipe_min_size)
1062                 size = pipe_min_size;
1063
1064         nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1065         if (nr_pages == 0)
1066                 return 0;
1067
1068         return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1069 }
1070
1071 /*
1072  * Allocate a new array of pipe buffers and copy the info over. Returns the
1073  * pipe size if successful, or return -ERROR on error.
1074  */
1075 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1076 {
1077         struct pipe_buffer *bufs;
1078         unsigned int size, nr_pages;
1079         unsigned long user_bufs;
1080         long ret = 0;
1081
1082         size = round_pipe_size(arg);
1083         if (size == 0)
1084                 return -EINVAL;
1085         nr_pages = size >> PAGE_SHIFT;
1086
1087         if (!nr_pages)
1088                 return -EINVAL;
1089
1090         /*
1091          * If trying to increase the pipe capacity, check that an
1092          * unprivileged user is not trying to exceed various limits
1093          * (soft limit check here, hard limit check just below).
1094          * Decreasing the pipe capacity is always permitted, even
1095          * if the user is currently over a limit.
1096          */
1097         if (nr_pages > pipe->buffers &&
1098                         size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1099                 return -EPERM;
1100
1101         user_bufs = account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
1102
1103         if (nr_pages > pipe->buffers &&
1104                         (too_many_pipe_buffers_hard(user_bufs) ||
1105                          too_many_pipe_buffers_soft(user_bufs)) &&
1106                         is_unprivileged_user()) {
1107                 ret = -EPERM;
1108                 goto out_revert_acct;
1109         }
1110
1111         /*
1112          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1113          * expect a lot of shrink+grow operations, just free and allocate
1114          * again like we would do for growing. If the pipe currently
1115          * contains more buffers than arg, then return busy.
1116          */
1117         if (nr_pages < pipe->nrbufs) {
1118                 ret = -EBUSY;
1119                 goto out_revert_acct;
1120         }
1121
1122         bufs = kcalloc(nr_pages, sizeof(*bufs),
1123                        GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1124         if (unlikely(!bufs)) {
1125                 ret = -ENOMEM;
1126                 goto out_revert_acct;
1127         }
1128
1129         /*
1130          * The pipe array wraps around, so just start the new one at zero
1131          * and adjust the indexes.
1132          */
1133         if (pipe->nrbufs) {
1134                 unsigned int tail;
1135                 unsigned int head;
1136
1137                 tail = pipe->curbuf + pipe->nrbufs;
1138                 if (tail < pipe->buffers)
1139                         tail = 0;
1140                 else
1141                         tail &= (pipe->buffers - 1);
1142
1143                 head = pipe->nrbufs - tail;
1144                 if (head)
1145                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1146                 if (tail)
1147                         memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1148         }
1149
1150         pipe->curbuf = 0;
1151         kfree(pipe->bufs);
1152         pipe->bufs = bufs;
1153         pipe->buffers = nr_pages;
1154         return nr_pages * PAGE_SIZE;
1155
1156 out_revert_acct:
1157         (void) account_pipe_buffers(pipe->user, nr_pages, pipe->buffers);
1158         return ret;
1159 }
1160
1161 /*
1162  * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1163  * will return an error.
1164  */
1165 int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1166                  size_t *lenp, loff_t *ppos)
1167 {
1168         unsigned int rounded_pipe_max_size;
1169         int ret;
1170
1171         ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1172         if (ret < 0 || !write)
1173                 return ret;
1174
1175         rounded_pipe_max_size = round_pipe_size(pipe_max_size);
1176         if (rounded_pipe_max_size == 0)
1177                 return -EINVAL;
1178
1179         pipe_max_size = rounded_pipe_max_size;
1180         return ret;
1181 }
1182
1183 /*
1184  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1185  * location, so checking ->i_pipe is not enough to verify that this is a
1186  * pipe.
1187  */
1188 struct pipe_inode_info *get_pipe_info(struct file *file)
1189 {
1190         return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1191 }
1192
1193 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1194 {
1195         struct pipe_inode_info *pipe;
1196         long ret;
1197
1198         pipe = get_pipe_info(file);
1199         if (!pipe)
1200                 return -EBADF;
1201
1202         __pipe_lock(pipe);
1203
1204         switch (cmd) {
1205         case F_SETPIPE_SZ:
1206                 ret = pipe_set_size(pipe, arg);
1207                 break;
1208         case F_GETPIPE_SZ:
1209                 ret = pipe->buffers * PAGE_SIZE;
1210                 break;
1211         default:
1212                 ret = -EINVAL;
1213                 break;
1214         }
1215
1216         __pipe_unlock(pipe);
1217         return ret;
1218 }
1219
1220 static const struct super_operations pipefs_ops = {
1221         .destroy_inode = free_inode_nonrcu,
1222         .statfs = simple_statfs,
1223 };
1224
1225 /*
1226  * pipefs should _never_ be mounted by userland - too much of security hassle,
1227  * no real gain from having the whole whorehouse mounted. So we don't need
1228  * any operations on the root directory. However, we need a non-trivial
1229  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1230  */
1231 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1232                          int flags, const char *dev_name, void *data)
1233 {
1234         return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1235                         &pipefs_dentry_operations, PIPEFS_MAGIC);
1236 }
1237
1238 static struct file_system_type pipe_fs_type = {
1239         .name           = "pipefs",
1240         .mount          = pipefs_mount,
1241         .kill_sb        = kill_anon_super,
1242 };
1243
1244 static int __init init_pipe_fs(void)
1245 {
1246         int err = register_filesystem(&pipe_fs_type);
1247
1248         if (!err) {
1249                 pipe_mnt = kern_mount(&pipe_fs_type);
1250                 if (IS_ERR(pipe_mnt)) {
1251                         err = PTR_ERR(pipe_mnt);
1252                         unregister_filesystem(&pipe_fs_type);
1253                 }
1254         }
1255         return err;
1256 }
1257
1258 fs_initcall(init_pipe_fs);