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TOMOYO Linux Cross Reference
Linux/fs/pipe.c

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

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