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TOMOYO Linux Cross Reference
Linux/fs/pipe.c

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

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