Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
[platform/kernel/linux-starfive.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
28 #include <linux/uaccess.h>
29 #include <asm/ioctls.h>
30
31 #include "internal.h"
32
33 /*
34  * The max size that a non-root user is allowed to grow the pipe. Can
35  * be set by root in /proc/sys/fs/pipe-max-size
36  */
37 unsigned int pipe_max_size = 1048576;
38
39 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
40  * matches default values.
41  */
42 unsigned long pipe_user_pages_hard;
43 unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
44
45 /*
46  * We use a start+len construction, which provides full use of the 
47  * allocated memory.
48  * -- Florian Coosmann (FGC)
49  * 
50  * Reads with count = 0 should always return 0.
51  * -- Julian Bradfield 1999-06-07.
52  *
53  * FIFOs and Pipes now generate SIGIO for both readers and writers.
54  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
55  *
56  * pipe_read & write cleanup
57  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
58  */
59
60 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
61 {
62         if (pipe->files)
63                 mutex_lock_nested(&pipe->mutex, subclass);
64 }
65
66 void pipe_lock(struct pipe_inode_info *pipe)
67 {
68         /*
69          * pipe_lock() nests non-pipe inode locks (for writing to a file)
70          */
71         pipe_lock_nested(pipe, I_MUTEX_PARENT);
72 }
73 EXPORT_SYMBOL(pipe_lock);
74
75 void pipe_unlock(struct pipe_inode_info *pipe)
76 {
77         if (pipe->files)
78                 mutex_unlock(&pipe->mutex);
79 }
80 EXPORT_SYMBOL(pipe_unlock);
81
82 static inline void __pipe_lock(struct pipe_inode_info *pipe)
83 {
84         mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
85 }
86
87 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
88 {
89         mutex_unlock(&pipe->mutex);
90 }
91
92 void pipe_double_lock(struct pipe_inode_info *pipe1,
93                       struct pipe_inode_info *pipe2)
94 {
95         BUG_ON(pipe1 == pipe2);
96
97         if (pipe1 < pipe2) {
98                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
99                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
100         } else {
101                 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
102                 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
103         }
104 }
105
106 /* Drop the inode semaphore and wait for a pipe event, atomically */
107 void pipe_wait(struct pipe_inode_info *pipe)
108 {
109         DEFINE_WAIT(wait);
110
111         /*
112          * Pipes are system-local resources, so sleeping on them
113          * is considered a noninteractive wait:
114          */
115         prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
116         pipe_unlock(pipe);
117         schedule();
118         finish_wait(&pipe->wait, &wait);
119         pipe_lock(pipe);
120 }
121
122 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
123                                   struct pipe_buffer *buf)
124 {
125         struct page *page = buf->page;
126
127         /*
128          * If nobody else uses this page, and we don't already have a
129          * temporary page, let's keep track of it as a one-deep
130          * allocation cache. (Otherwise just release our reference to it)
131          */
132         if (page_count(page) == 1 && !pipe->tmp_page)
133                 pipe->tmp_page = page;
134         else
135                 put_page(page);
136 }
137
138 static int anon_pipe_buf_steal(struct pipe_inode_info *pipe,
139                                struct pipe_buffer *buf)
140 {
141         struct page *page = buf->page;
142
143         if (page_count(page) == 1) {
144                 memcg_kmem_uncharge(page, 0);
145                 __SetPageLocked(page);
146                 return 0;
147         }
148         return 1;
149 }
150
151 /**
152  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
153  * @pipe:       the pipe that the buffer belongs to
154  * @buf:        the buffer to attempt to steal
155  *
156  * Description:
157  *      This function attempts to steal the &struct page attached to
158  *      @buf. If successful, this function returns 0 and returns with
159  *      the page locked. The caller may then reuse the page for whatever
160  *      he wishes; the typical use is insertion into a different file
161  *      page cache.
162  */
163 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
164                            struct pipe_buffer *buf)
165 {
166         struct page *page = buf->page;
167
168         /*
169          * A reference of one is golden, that means that the owner of this
170          * page is the only one holding a reference to it. lock the page
171          * and return OK.
172          */
173         if (page_count(page) == 1) {
174                 lock_page(page);
175                 return 0;
176         }
177
178         return 1;
179 }
180 EXPORT_SYMBOL(generic_pipe_buf_steal);
181
182 /**
183  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
184  * @pipe:       the pipe that the buffer belongs to
185  * @buf:        the buffer to get a reference to
186  *
187  * Description:
188  *      This function grabs an extra reference to @buf. It's used in
189  *      in the tee() system call, when we duplicate the buffers in one
190  *      pipe into another.
191  */
192 bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
193 {
194         return try_get_page(buf->page);
195 }
196 EXPORT_SYMBOL(generic_pipe_buf_get);
197
198 /**
199  * generic_pipe_buf_confirm - verify contents of the pipe buffer
200  * @info:       the pipe that the buffer belongs to
201  * @buf:        the buffer to confirm
202  *
203  * Description:
204  *      This function does nothing, because the generic pipe code uses
205  *      pages that are always good when inserted into the pipe.
206  */
207 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
208                              struct pipe_buffer *buf)
209 {
210         return 0;
211 }
212 EXPORT_SYMBOL(generic_pipe_buf_confirm);
213
214 /**
215  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
216  * @pipe:       the pipe that the buffer belongs to
217  * @buf:        the buffer to put a reference to
218  *
219  * Description:
220  *      This function releases a reference to @buf.
221  */
222 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
223                               struct pipe_buffer *buf)
224 {
225         put_page(buf->page);
226 }
227 EXPORT_SYMBOL(generic_pipe_buf_release);
228
229 /* New data written to a pipe may be appended to a buffer with this type. */
230 static const struct pipe_buf_operations anon_pipe_buf_ops = {
231         .confirm = generic_pipe_buf_confirm,
232         .release = anon_pipe_buf_release,
233         .steal = anon_pipe_buf_steal,
234         .get = generic_pipe_buf_get,
235 };
236
237 static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = {
238         .confirm = generic_pipe_buf_confirm,
239         .release = anon_pipe_buf_release,
240         .steal = anon_pipe_buf_steal,
241         .get = generic_pipe_buf_get,
242 };
243
244 static const struct pipe_buf_operations packet_pipe_buf_ops = {
245         .confirm = generic_pipe_buf_confirm,
246         .release = anon_pipe_buf_release,
247         .steal = anon_pipe_buf_steal,
248         .get = generic_pipe_buf_get,
249 };
250
251 /**
252  * pipe_buf_mark_unmergeable - mark a &struct pipe_buffer as unmergeable
253  * @buf:        the buffer to mark
254  *
255  * Description:
256  *      This function ensures that no future writes will be merged into the
257  *      given &struct pipe_buffer. This is necessary when multiple pipe buffers
258  *      share the same backing page.
259  */
260 void pipe_buf_mark_unmergeable(struct pipe_buffer *buf)
261 {
262         if (buf->ops == &anon_pipe_buf_ops)
263                 buf->ops = &anon_pipe_buf_nomerge_ops;
264 }
265
266 static bool pipe_buf_can_merge(struct pipe_buffer *buf)
267 {
268         return buf->ops == &anon_pipe_buf_ops;
269 }
270
271 static ssize_t
272 pipe_read(struct kiocb *iocb, struct iov_iter *to)
273 {
274         size_t total_len = iov_iter_count(to);
275         struct file *filp = iocb->ki_filp;
276         struct pipe_inode_info *pipe = filp->private_data;
277         int do_wakeup;
278         ssize_t ret;
279
280         /* Null read succeeds. */
281         if (unlikely(total_len == 0))
282                 return 0;
283
284         do_wakeup = 0;
285         ret = 0;
286         __pipe_lock(pipe);
287         for (;;) {
288                 int bufs = pipe->nrbufs;
289                 if (bufs) {
290                         int curbuf = pipe->curbuf;
291                         struct pipe_buffer *buf = pipe->bufs + curbuf;
292                         size_t chars = buf->len;
293                         size_t written;
294                         int error;
295
296                         if (chars > total_len)
297                                 chars = total_len;
298
299                         error = pipe_buf_confirm(pipe, buf);
300                         if (error) {
301                                 if (!ret)
302                                         ret = error;
303                                 break;
304                         }
305
306                         written = copy_page_to_iter(buf->page, buf->offset, chars, to);
307                         if (unlikely(written < chars)) {
308                                 if (!ret)
309                                         ret = -EFAULT;
310                                 break;
311                         }
312                         ret += chars;
313                         buf->offset += chars;
314                         buf->len -= chars;
315
316                         /* Was it a packet buffer? Clean up and exit */
317                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
318                                 total_len = chars;
319                                 buf->len = 0;
320                         }
321
322                         if (!buf->len) {
323                                 pipe_buf_release(pipe, buf);
324                                 curbuf = (curbuf + 1) & (pipe->buffers - 1);
325                                 pipe->curbuf = curbuf;
326                                 pipe->nrbufs = --bufs;
327                                 do_wakeup = 1;
328                         }
329                         total_len -= chars;
330                         if (!total_len)
331                                 break;  /* common path: read succeeded */
332                 }
333                 if (bufs)       /* More to do? */
334                         continue;
335                 if (!pipe->writers)
336                         break;
337                 if (!pipe->waiting_writers) {
338                         /* syscall merging: Usually we must not sleep
339                          * if O_NONBLOCK is set, or if we got some data.
340                          * But if a writer sleeps in kernel space, then
341                          * we can wait for that data without violating POSIX.
342                          */
343                         if (ret)
344                                 break;
345                         if (filp->f_flags & O_NONBLOCK) {
346                                 ret = -EAGAIN;
347                                 break;
348                         }
349                 }
350                 if (signal_pending(current)) {
351                         if (!ret)
352                                 ret = -ERESTARTSYS;
353                         break;
354                 }
355                 if (do_wakeup) {
356                         wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
357                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
358                 }
359                 pipe_wait(pipe);
360         }
361         __pipe_unlock(pipe);
362
363         /* Signal writers asynchronously that there is more room. */
364         if (do_wakeup) {
365                 wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
366                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
367         }
368         if (ret > 0)
369                 file_accessed(filp);
370         return ret;
371 }
372
373 static inline int is_packetized(struct file *file)
374 {
375         return (file->f_flags & O_DIRECT) != 0;
376 }
377
378 static ssize_t
379 pipe_write(struct kiocb *iocb, struct iov_iter *from)
380 {
381         struct file *filp = iocb->ki_filp;
382         struct pipe_inode_info *pipe = filp->private_data;
383         ssize_t ret = 0;
384         int do_wakeup = 0;
385         size_t total_len = iov_iter_count(from);
386         ssize_t chars;
387
388         /* Null write succeeds. */
389         if (unlikely(total_len == 0))
390                 return 0;
391
392         __pipe_lock(pipe);
393
394         if (!pipe->readers) {
395                 send_sig(SIGPIPE, current, 0);
396                 ret = -EPIPE;
397                 goto out;
398         }
399
400         /* We try to merge small writes */
401         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
402         if (pipe->nrbufs && chars != 0) {
403                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
404                                                         (pipe->buffers - 1);
405                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
406                 int offset = buf->offset + buf->len;
407
408                 if (pipe_buf_can_merge(buf) && offset + chars <= PAGE_SIZE) {
409                         ret = pipe_buf_confirm(pipe, buf);
410                         if (ret)
411                                 goto out;
412
413                         ret = copy_page_from_iter(buf->page, offset, chars, from);
414                         if (unlikely(ret < chars)) {
415                                 ret = -EFAULT;
416                                 goto out;
417                         }
418                         do_wakeup = 1;
419                         buf->len += ret;
420                         if (!iov_iter_count(from))
421                                 goto out;
422                 }
423         }
424
425         for (;;) {
426                 int bufs;
427
428                 if (!pipe->readers) {
429                         send_sig(SIGPIPE, current, 0);
430                         if (!ret)
431                                 ret = -EPIPE;
432                         break;
433                 }
434                 bufs = pipe->nrbufs;
435                 if (bufs < pipe->buffers) {
436                         int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
437                         struct pipe_buffer *buf = pipe->bufs + newbuf;
438                         struct page *page = pipe->tmp_page;
439                         int copied;
440
441                         if (!page) {
442                                 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
443                                 if (unlikely(!page)) {
444                                         ret = ret ? : -ENOMEM;
445                                         break;
446                                 }
447                                 pipe->tmp_page = page;
448                         }
449                         /* Always wake up, even if the copy fails. Otherwise
450                          * we lock up (O_NONBLOCK-)readers that sleep due to
451                          * syscall merging.
452                          * FIXME! Is this really true?
453                          */
454                         do_wakeup = 1;
455                         copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
456                         if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
457                                 if (!ret)
458                                         ret = -EFAULT;
459                                 break;
460                         }
461                         ret += copied;
462
463                         /* Insert it into the buffer array */
464                         buf->page = page;
465                         buf->ops = &anon_pipe_buf_ops;
466                         buf->offset = 0;
467                         buf->len = copied;
468                         buf->flags = 0;
469                         if (is_packetized(filp)) {
470                                 buf->ops = &packet_pipe_buf_ops;
471                                 buf->flags = PIPE_BUF_FLAG_PACKET;
472                         }
473                         pipe->nrbufs = ++bufs;
474                         pipe->tmp_page = NULL;
475
476                         if (!iov_iter_count(from))
477                                 break;
478                 }
479                 if (bufs < pipe->buffers)
480                         continue;
481                 if (filp->f_flags & O_NONBLOCK) {
482                         if (!ret)
483                                 ret = -EAGAIN;
484                         break;
485                 }
486                 if (signal_pending(current)) {
487                         if (!ret)
488                                 ret = -ERESTARTSYS;
489                         break;
490                 }
491                 if (do_wakeup) {
492                         wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLRDNORM);
493                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
494                         do_wakeup = 0;
495                 }
496                 pipe->waiting_writers++;
497                 pipe_wait(pipe);
498                 pipe->waiting_writers--;
499         }
500 out:
501         __pipe_unlock(pipe);
502         if (do_wakeup) {
503                 wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLRDNORM);
504                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
505         }
506         if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
507                 int err = file_update_time(filp);
508                 if (err)
509                         ret = err;
510                 sb_end_write(file_inode(filp)->i_sb);
511         }
512         return ret;
513 }
514
515 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
516 {
517         struct pipe_inode_info *pipe = filp->private_data;
518         int count, buf, nrbufs;
519
520         switch (cmd) {
521                 case FIONREAD:
522                         __pipe_lock(pipe);
523                         count = 0;
524                         buf = pipe->curbuf;
525                         nrbufs = pipe->nrbufs;
526                         while (--nrbufs >= 0) {
527                                 count += pipe->bufs[buf].len;
528                                 buf = (buf+1) & (pipe->buffers - 1);
529                         }
530                         __pipe_unlock(pipe);
531
532                         return put_user(count, (int __user *)arg);
533                 default:
534                         return -ENOIOCTLCMD;
535         }
536 }
537
538 /* No kernel lock held - fine */
539 static __poll_t
540 pipe_poll(struct file *filp, poll_table *wait)
541 {
542         __poll_t mask;
543         struct pipe_inode_info *pipe = filp->private_data;
544         int nrbufs;
545
546         poll_wait(filp, &pipe->wait, wait);
547
548         /* Reading only -- no need for acquiring the semaphore.  */
549         nrbufs = pipe->nrbufs;
550         mask = 0;
551         if (filp->f_mode & FMODE_READ) {
552                 mask = (nrbufs > 0) ? EPOLLIN | EPOLLRDNORM : 0;
553                 if (!pipe->writers && filp->f_version != pipe->w_counter)
554                         mask |= EPOLLHUP;
555         }
556
557         if (filp->f_mode & FMODE_WRITE) {
558                 mask |= (nrbufs < pipe->buffers) ? EPOLLOUT | EPOLLWRNORM : 0;
559                 /*
560                  * Most Unices do not set EPOLLERR for FIFOs but on Linux they
561                  * behave exactly like pipes for poll().
562                  */
563                 if (!pipe->readers)
564                         mask |= EPOLLERR;
565         }
566
567         return mask;
568 }
569
570 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
571 {
572         int kill = 0;
573
574         spin_lock(&inode->i_lock);
575         if (!--pipe->files) {
576                 inode->i_pipe = NULL;
577                 kill = 1;
578         }
579         spin_unlock(&inode->i_lock);
580
581         if (kill)
582                 free_pipe_info(pipe);
583 }
584
585 static int
586 pipe_release(struct inode *inode, struct file *file)
587 {
588         struct pipe_inode_info *pipe = file->private_data;
589
590         __pipe_lock(pipe);
591         if (file->f_mode & FMODE_READ)
592                 pipe->readers--;
593         if (file->f_mode & FMODE_WRITE)
594                 pipe->writers--;
595
596         if (pipe->readers || pipe->writers) {
597                 wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLOUT | EPOLLRDNORM | EPOLLWRNORM | EPOLLERR | EPOLLHUP);
598                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
599                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
600         }
601         __pipe_unlock(pipe);
602
603         put_pipe_info(inode, pipe);
604         return 0;
605 }
606
607 static int
608 pipe_fasync(int fd, struct file *filp, int on)
609 {
610         struct pipe_inode_info *pipe = filp->private_data;
611         int retval = 0;
612
613         __pipe_lock(pipe);
614         if (filp->f_mode & FMODE_READ)
615                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
616         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
617                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
618                 if (retval < 0 && (filp->f_mode & FMODE_READ))
619                         /* this can happen only if on == T */
620                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
621         }
622         __pipe_unlock(pipe);
623         return retval;
624 }
625
626 static unsigned long account_pipe_buffers(struct user_struct *user,
627                                  unsigned long old, unsigned long new)
628 {
629         return atomic_long_add_return(new - old, &user->pipe_bufs);
630 }
631
632 static bool too_many_pipe_buffers_soft(unsigned long user_bufs)
633 {
634         unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
635
636         return soft_limit && user_bufs > soft_limit;
637 }
638
639 static bool too_many_pipe_buffers_hard(unsigned long user_bufs)
640 {
641         unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
642
643         return hard_limit && user_bufs > hard_limit;
644 }
645
646 static bool is_unprivileged_user(void)
647 {
648         return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
649 }
650
651 struct pipe_inode_info *alloc_pipe_info(void)
652 {
653         struct pipe_inode_info *pipe;
654         unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
655         struct user_struct *user = get_current_user();
656         unsigned long user_bufs;
657         unsigned int max_size = READ_ONCE(pipe_max_size);
658
659         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
660         if (pipe == NULL)
661                 goto out_free_uid;
662
663         if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
664                 pipe_bufs = max_size >> PAGE_SHIFT;
665
666         user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
667
668         if (too_many_pipe_buffers_soft(user_bufs) && is_unprivileged_user()) {
669                 user_bufs = account_pipe_buffers(user, pipe_bufs, 1);
670                 pipe_bufs = 1;
671         }
672
673         if (too_many_pipe_buffers_hard(user_bufs) && is_unprivileged_user())
674                 goto out_revert_acct;
675
676         pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
677                              GFP_KERNEL_ACCOUNT);
678
679         if (pipe->bufs) {
680                 init_waitqueue_head(&pipe->wait);
681                 pipe->r_counter = pipe->w_counter = 1;
682                 pipe->buffers = pipe_bufs;
683                 pipe->user = user;
684                 mutex_init(&pipe->mutex);
685                 return pipe;
686         }
687
688 out_revert_acct:
689         (void) account_pipe_buffers(user, pipe_bufs, 0);
690         kfree(pipe);
691 out_free_uid:
692         free_uid(user);
693         return NULL;
694 }
695
696 void free_pipe_info(struct pipe_inode_info *pipe)
697 {
698         int i;
699
700         (void) account_pipe_buffers(pipe->user, pipe->buffers, 0);
701         free_uid(pipe->user);
702         for (i = 0; i < pipe->buffers; i++) {
703                 struct pipe_buffer *buf = pipe->bufs + i;
704                 if (buf->ops)
705                         pipe_buf_release(pipe, buf);
706         }
707         if (pipe->tmp_page)
708                 __free_page(pipe->tmp_page);
709         kfree(pipe->bufs);
710         kfree(pipe);
711 }
712
713 static struct vfsmount *pipe_mnt __read_mostly;
714
715 /*
716  * pipefs_dname() is called from d_path().
717  */
718 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
719 {
720         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
721                                 d_inode(dentry)->i_ino);
722 }
723
724 static const struct dentry_operations pipefs_dentry_operations = {
725         .d_dname        = pipefs_dname,
726 };
727
728 static struct inode * get_pipe_inode(void)
729 {
730         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
731         struct pipe_inode_info *pipe;
732
733         if (!inode)
734                 goto fail_inode;
735
736         inode->i_ino = get_next_ino();
737
738         pipe = alloc_pipe_info();
739         if (!pipe)
740                 goto fail_iput;
741
742         inode->i_pipe = pipe;
743         pipe->files = 2;
744         pipe->readers = pipe->writers = 1;
745         inode->i_fop = &pipefifo_fops;
746
747         /*
748          * Mark the inode dirty from the very beginning,
749          * that way it will never be moved to the dirty
750          * list because "mark_inode_dirty()" will think
751          * that it already _is_ on the dirty list.
752          */
753         inode->i_state = I_DIRTY;
754         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
755         inode->i_uid = current_fsuid();
756         inode->i_gid = current_fsgid();
757         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
758
759         return inode;
760
761 fail_iput:
762         iput(inode);
763
764 fail_inode:
765         return NULL;
766 }
767
768 int create_pipe_files(struct file **res, int flags)
769 {
770         struct inode *inode = get_pipe_inode();
771         struct file *f;
772
773         if (!inode)
774                 return -ENFILE;
775
776         f = alloc_file_pseudo(inode, pipe_mnt, "",
777                                 O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
778                                 &pipefifo_fops);
779         if (IS_ERR(f)) {
780                 free_pipe_info(inode->i_pipe);
781                 iput(inode);
782                 return PTR_ERR(f);
783         }
784
785         f->private_data = inode->i_pipe;
786
787         res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
788                                   &pipefifo_fops);
789         if (IS_ERR(res[0])) {
790                 put_pipe_info(inode, inode->i_pipe);
791                 fput(f);
792                 return PTR_ERR(res[0]);
793         }
794         res[0]->private_data = inode->i_pipe;
795         res[1] = f;
796         return 0;
797 }
798
799 static int __do_pipe_flags(int *fd, struct file **files, int flags)
800 {
801         int error;
802         int fdw, fdr;
803
804         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
805                 return -EINVAL;
806
807         error = create_pipe_files(files, flags);
808         if (error)
809                 return error;
810
811         error = get_unused_fd_flags(flags);
812         if (error < 0)
813                 goto err_read_pipe;
814         fdr = error;
815
816         error = get_unused_fd_flags(flags);
817         if (error < 0)
818                 goto err_fdr;
819         fdw = error;
820
821         audit_fd_pair(fdr, fdw);
822         fd[0] = fdr;
823         fd[1] = fdw;
824         return 0;
825
826  err_fdr:
827         put_unused_fd(fdr);
828  err_read_pipe:
829         fput(files[0]);
830         fput(files[1]);
831         return error;
832 }
833
834 int do_pipe_flags(int *fd, int flags)
835 {
836         struct file *files[2];
837         int error = __do_pipe_flags(fd, files, flags);
838         if (!error) {
839                 fd_install(fd[0], files[0]);
840                 fd_install(fd[1], files[1]);
841         }
842         return error;
843 }
844
845 /*
846  * sys_pipe() is the normal C calling standard for creating
847  * a pipe. It's not the way Unix traditionally does this, though.
848  */
849 static int do_pipe2(int __user *fildes, int flags)
850 {
851         struct file *files[2];
852         int fd[2];
853         int error;
854
855         error = __do_pipe_flags(fd, files, flags);
856         if (!error) {
857                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
858                         fput(files[0]);
859                         fput(files[1]);
860                         put_unused_fd(fd[0]);
861                         put_unused_fd(fd[1]);
862                         error = -EFAULT;
863                 } else {
864                         fd_install(fd[0], files[0]);
865                         fd_install(fd[1], files[1]);
866                 }
867         }
868         return error;
869 }
870
871 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
872 {
873         return do_pipe2(fildes, flags);
874 }
875
876 SYSCALL_DEFINE1(pipe, int __user *, fildes)
877 {
878         return do_pipe2(fildes, 0);
879 }
880
881 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
882 {
883         int cur = *cnt; 
884
885         while (cur == *cnt) {
886                 pipe_wait(pipe);
887                 if (signal_pending(current))
888                         break;
889         }
890         return cur == *cnt ? -ERESTARTSYS : 0;
891 }
892
893 static void wake_up_partner(struct pipe_inode_info *pipe)
894 {
895         wake_up_interruptible(&pipe->wait);
896 }
897
898 static int fifo_open(struct inode *inode, struct file *filp)
899 {
900         struct pipe_inode_info *pipe;
901         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
902         int ret;
903
904         filp->f_version = 0;
905
906         spin_lock(&inode->i_lock);
907         if (inode->i_pipe) {
908                 pipe = inode->i_pipe;
909                 pipe->files++;
910                 spin_unlock(&inode->i_lock);
911         } else {
912                 spin_unlock(&inode->i_lock);
913                 pipe = alloc_pipe_info();
914                 if (!pipe)
915                         return -ENOMEM;
916                 pipe->files = 1;
917                 spin_lock(&inode->i_lock);
918                 if (unlikely(inode->i_pipe)) {
919                         inode->i_pipe->files++;
920                         spin_unlock(&inode->i_lock);
921                         free_pipe_info(pipe);
922                         pipe = inode->i_pipe;
923                 } else {
924                         inode->i_pipe = pipe;
925                         spin_unlock(&inode->i_lock);
926                 }
927         }
928         filp->private_data = pipe;
929         /* OK, we have a pipe and it's pinned down */
930
931         __pipe_lock(pipe);
932
933         /* We can only do regular read/write on fifos */
934         filp->f_mode &= (FMODE_READ | FMODE_WRITE);
935
936         switch (filp->f_mode) {
937         case FMODE_READ:
938         /*
939          *  O_RDONLY
940          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
941          *  opened, even when there is no process writing the FIFO.
942          */
943                 pipe->r_counter++;
944                 if (pipe->readers++ == 0)
945                         wake_up_partner(pipe);
946
947                 if (!is_pipe && !pipe->writers) {
948                         if ((filp->f_flags & O_NONBLOCK)) {
949                                 /* suppress EPOLLHUP until we have
950                                  * seen a writer */
951                                 filp->f_version = pipe->w_counter;
952                         } else {
953                                 if (wait_for_partner(pipe, &pipe->w_counter))
954                                         goto err_rd;
955                         }
956                 }
957                 break;
958         
959         case FMODE_WRITE:
960         /*
961          *  O_WRONLY
962          *  POSIX.1 says that O_NONBLOCK means return -1 with
963          *  errno=ENXIO when there is no process reading the FIFO.
964          */
965                 ret = -ENXIO;
966                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
967                         goto err;
968
969                 pipe->w_counter++;
970                 if (!pipe->writers++)
971                         wake_up_partner(pipe);
972
973                 if (!is_pipe && !pipe->readers) {
974                         if (wait_for_partner(pipe, &pipe->r_counter))
975                                 goto err_wr;
976                 }
977                 break;
978         
979         case FMODE_READ | FMODE_WRITE:
980         /*
981          *  O_RDWR
982          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
983          *  This implementation will NEVER block on a O_RDWR open, since
984          *  the process can at least talk to itself.
985          */
986
987                 pipe->readers++;
988                 pipe->writers++;
989                 pipe->r_counter++;
990                 pipe->w_counter++;
991                 if (pipe->readers == 1 || pipe->writers == 1)
992                         wake_up_partner(pipe);
993                 break;
994
995         default:
996                 ret = -EINVAL;
997                 goto err;
998         }
999
1000         /* Ok! */
1001         __pipe_unlock(pipe);
1002         return 0;
1003
1004 err_rd:
1005         if (!--pipe->readers)
1006                 wake_up_interruptible(&pipe->wait);
1007         ret = -ERESTARTSYS;
1008         goto err;
1009
1010 err_wr:
1011         if (!--pipe->writers)
1012                 wake_up_interruptible(&pipe->wait);
1013         ret = -ERESTARTSYS;
1014         goto err;
1015
1016 err:
1017         __pipe_unlock(pipe);
1018
1019         put_pipe_info(inode, pipe);
1020         return ret;
1021 }
1022
1023 const struct file_operations pipefifo_fops = {
1024         .open           = fifo_open,
1025         .llseek         = no_llseek,
1026         .read_iter      = pipe_read,
1027         .write_iter     = pipe_write,
1028         .poll           = pipe_poll,
1029         .unlocked_ioctl = pipe_ioctl,
1030         .release        = pipe_release,
1031         .fasync         = pipe_fasync,
1032 };
1033
1034 /*
1035  * Currently we rely on the pipe array holding a power-of-2 number
1036  * of pages. Returns 0 on error.
1037  */
1038 unsigned int round_pipe_size(unsigned long size)
1039 {
1040         if (size > (1U << 31))
1041                 return 0;
1042
1043         /* Minimum pipe size, as required by POSIX */
1044         if (size < PAGE_SIZE)
1045                 return PAGE_SIZE;
1046
1047         return roundup_pow_of_two(size);
1048 }
1049
1050 /*
1051  * Allocate a new array of pipe buffers and copy the info over. Returns the
1052  * pipe size if successful, or return -ERROR on error.
1053  */
1054 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1055 {
1056         struct pipe_buffer *bufs;
1057         unsigned int size, nr_pages;
1058         unsigned long user_bufs;
1059         long ret = 0;
1060
1061         size = round_pipe_size(arg);
1062         nr_pages = size >> PAGE_SHIFT;
1063
1064         if (!nr_pages)
1065                 return -EINVAL;
1066
1067         /*
1068          * If trying to increase the pipe capacity, check that an
1069          * unprivileged user is not trying to exceed various limits
1070          * (soft limit check here, hard limit check just below).
1071          * Decreasing the pipe capacity is always permitted, even
1072          * if the user is currently over a limit.
1073          */
1074         if (nr_pages > pipe->buffers &&
1075                         size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1076                 return -EPERM;
1077
1078         user_bufs = account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
1079
1080         if (nr_pages > pipe->buffers &&
1081                         (too_many_pipe_buffers_hard(user_bufs) ||
1082                          too_many_pipe_buffers_soft(user_bufs)) &&
1083                         is_unprivileged_user()) {
1084                 ret = -EPERM;
1085                 goto out_revert_acct;
1086         }
1087
1088         /*
1089          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1090          * expect a lot of shrink+grow operations, just free and allocate
1091          * again like we would do for growing. If the pipe currently
1092          * contains more buffers than arg, then return busy.
1093          */
1094         if (nr_pages < pipe->nrbufs) {
1095                 ret = -EBUSY;
1096                 goto out_revert_acct;
1097         }
1098
1099         bufs = kcalloc(nr_pages, sizeof(*bufs),
1100                        GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1101         if (unlikely(!bufs)) {
1102                 ret = -ENOMEM;
1103                 goto out_revert_acct;
1104         }
1105
1106         /*
1107          * The pipe array wraps around, so just start the new one at zero
1108          * and adjust the indexes.
1109          */
1110         if (pipe->nrbufs) {
1111                 unsigned int tail;
1112                 unsigned int head;
1113
1114                 tail = pipe->curbuf + pipe->nrbufs;
1115                 if (tail < pipe->buffers)
1116                         tail = 0;
1117                 else
1118                         tail &= (pipe->buffers - 1);
1119
1120                 head = pipe->nrbufs - tail;
1121                 if (head)
1122                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1123                 if (tail)
1124                         memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1125         }
1126
1127         pipe->curbuf = 0;
1128         kfree(pipe->bufs);
1129         pipe->bufs = bufs;
1130         pipe->buffers = nr_pages;
1131         return nr_pages * PAGE_SIZE;
1132
1133 out_revert_acct:
1134         (void) account_pipe_buffers(pipe->user, nr_pages, pipe->buffers);
1135         return ret;
1136 }
1137
1138 /*
1139  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1140  * location, so checking ->i_pipe is not enough to verify that this is a
1141  * pipe.
1142  */
1143 struct pipe_inode_info *get_pipe_info(struct file *file)
1144 {
1145         return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1146 }
1147
1148 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1149 {
1150         struct pipe_inode_info *pipe;
1151         long ret;
1152
1153         pipe = get_pipe_info(file);
1154         if (!pipe)
1155                 return -EBADF;
1156
1157         __pipe_lock(pipe);
1158
1159         switch (cmd) {
1160         case F_SETPIPE_SZ:
1161                 ret = pipe_set_size(pipe, arg);
1162                 break;
1163         case F_GETPIPE_SZ:
1164                 ret = pipe->buffers * PAGE_SIZE;
1165                 break;
1166         default:
1167                 ret = -EINVAL;
1168                 break;
1169         }
1170
1171         __pipe_unlock(pipe);
1172         return ret;
1173 }
1174
1175 static const struct super_operations pipefs_ops = {
1176         .destroy_inode = free_inode_nonrcu,
1177         .statfs = simple_statfs,
1178 };
1179
1180 /*
1181  * pipefs should _never_ be mounted by userland - too much of security hassle,
1182  * no real gain from having the whole whorehouse mounted. So we don't need
1183  * any operations on the root directory. However, we need a non-trivial
1184  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1185  */
1186
1187 static int pipefs_init_fs_context(struct fs_context *fc)
1188 {
1189         struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
1190         if (!ctx)
1191                 return -ENOMEM;
1192         ctx->ops = &pipefs_ops;
1193         ctx->dops = &pipefs_dentry_operations;
1194         return 0;
1195 }
1196
1197 static struct file_system_type pipe_fs_type = {
1198         .name           = "pipefs",
1199         .init_fs_context = pipefs_init_fs_context,
1200         .kill_sb        = kill_anon_super,
1201 };
1202
1203 static int __init init_pipe_fs(void)
1204 {
1205         int err = register_filesystem(&pipe_fs_type);
1206
1207         if (!err) {
1208                 pipe_mnt = kern_mount(&pipe_fs_type);
1209                 if (IS_ERR(pipe_mnt)) {
1210                         err = PTR_ERR(pipe_mnt);
1211                         unregister_filesystem(&pipe_fs_type);
1212                 }
1213         }
1214         return err;
1215 }
1216
1217 fs_initcall(init_pipe_fs);