~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/fs/pipe.c

Version: ~ [ linux-5.11-rc3 ] ~ [ linux-5.10.7 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.89 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.167 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.215 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.251 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.251 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.85 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

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

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp