fs/pipe.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/fs/pipe.c
   4  *
   5  *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
   6  */
   7
   8 #include <linux/mm.h>
   9 #include <linux/file.h>
  10 #include <linux/poll.h>
  11 #include <linux/slab.h>
  12 #include <linux/module.h>
  13 #include <linux/init.h>
  14 #include <linux/fs.h>
  15 #include <linux/log2.h>
  16 #include <linux/mount.h>
  17 #include <linux/pseudo_fs.h>
  18 #include <linux/magic.h>
  19 #include <linux/pipe_fs_i.h>
  20 #include <linux/uio.h>
  21 #include <linux/highmem.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/audit.h>
  24 #include <linux/syscalls.h>
  25 #include <linux/fcntl.h>
  26 #include <linux/memcontrol.h>
  27 #include <linux/watch_queue.h>
  28
  29 #include <linux/uaccess.h>
  30 #include <asm/ioctls.h>
  31
  32 #include "internal.h"
  33
  34 /*
  35  * The max size that a non-root user is allowed to grow the pipe. Can
  36  * be set by root in /proc/sys/fs/pipe-max-size
  37  */
  38 unsigned int pipe_max_size = 1048576;
  39
  40 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
  41  * matches default values.
  42  */
  43 unsigned long pipe_user_pages_hard;
  44 unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
  45
  46 /*
  47  * We use head and tail indices that aren't masked off, except at the point of
  48  * dereference, but rather they're allowed to wrap naturally.  This means there
  49  * isn't a dead spot in the buffer, but the ring has to be a power of two and
  50  * <= 2^31.
  51  * -- David Howells 2019-09-23.
  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 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 110                                   struct pipe_buffer *buf)
 111 {
 112         struct page *page = buf->page;
 113
 114         /*
 115          * If nobody else uses this page, and we don't already have a
 116          * temporary page, let's keep track of it as a one-deep
 117          * allocation cache. (Otherwise just release our reference to it)
 118          */
 119         if (page_count(page) == 1 && !pipe->tmp_page)
 120                 pipe->tmp_page = page;
 121         else
 122                 put_page(page);
 123 }
 124
 125 static bool anon_pipe_buf_try_steal(struct pipe_inode_info *pipe,
 126                 struct pipe_buffer *buf)
 127 {
 128         struct page *page = buf->page;
 129
 130         if (page_count(page) != 1)
 131                 return false;
 132         memcg_kmem_uncharge_page(page, 0);
 133         __SetPageLocked(page);
 134         return true;
 135 }
 136
 137 /**
 138  * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
 139  * @pipe:       the pipe that the buffer belongs to
 140  * @buf:        the buffer to attempt to steal
 141  *
 142  * Description:
 143  *      This function attempts to steal the &struct page attached to
 144  *      @buf. If successful, this function returns 0 and returns with
 145  *      the page locked. The caller may then reuse the page for whatever
 146  *      he wishes; the typical use is insertion into a different file
 147  *      page cache.
 148  */
 149 bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe,
 150                 struct pipe_buffer *buf)
 151 {
 152         struct page *page = buf->page;
 153
 154         /*
 155          * A reference of one is golden, that means that the owner of this
 156          * page is the only one holding a reference to it. lock the page
 157          * and return OK.
 158          */
 159         if (page_count(page) == 1) {
 160                 lock_page(page);
 161                 return true;
 162         }
 163         return false;
 164 }
 165 EXPORT_SYMBOL(generic_pipe_buf_try_steal);
 166
 167 /**
 168  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 169  * @pipe:       the pipe that the buffer belongs to
 170  * @buf:        the buffer to get a reference to
 171  *
 172  * Description:
 173  *      This function grabs an extra reference to @buf. It's used in
 174  *      the tee() system call, when we duplicate the buffers in one
 175  *      pipe into another.
 176  */
 177 bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 178 {
 179         return try_get_page(buf->page);
 180 }
 181 EXPORT_SYMBOL(generic_pipe_buf_get);
 182
 183 /**
 184  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 185  * @pipe:       the pipe that the buffer belongs to
 186  * @buf:        the buffer to put a reference to
 187  *
 188  * Description:
 189  *      This function releases a reference to @buf.
 190  */
 191 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 192                               struct pipe_buffer *buf)
 193 {
 194         put_page(buf->page);
 195 }
 196 EXPORT_SYMBOL(generic_pipe_buf_release);
 197
 198 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 199         .release        = anon_pipe_buf_release,
 200         .try_steal      = anon_pipe_buf_try_steal,
 201         .get            = generic_pipe_buf_get,
 202 };
 203
 204 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
 205 static inline bool pipe_readable(const struct pipe_inode_info *pipe)
 206 {
 207         unsigned int head = READ_ONCE(pipe->head);
 208         unsigned int tail = READ_ONCE(pipe->tail);
 209         unsigned int writers = READ_ONCE(pipe->writers);
 210
 211         return !pipe_empty(head, tail) || !writers;
 212 }
 213
 214 static ssize_t
 215 pipe_read(struct kiocb *iocb, struct iov_iter *to)
 216 {
 217         size_t total_len = iov_iter_count(to);
 218         struct file *filp = iocb->ki_filp;
 219         struct pipe_inode_info *pipe = filp->private_data;
 220         bool was_full, wake_next_reader = false;
 221         ssize_t ret;
 222
 223         /* Null read succeeds. */
 224         if (unlikely(total_len == 0))
 225                 return 0;
 226
 227         ret = 0;
 228         __pipe_lock(pipe);
 229
 230         /*
 231          * We only wake up writers if the pipe was full when we started
 232          * reading in order to avoid unnecessary wakeups.
 233          *
 234          * But when we do wake up writers, we do so using a sync wakeup
 235          * (WF_SYNC), because we want them to get going and generate more
 236          * data for us.
 237          */
 238         was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
 239         for (;;) {
 240                 unsigned int head = pipe->head;
 241                 unsigned int tail = pipe->tail;
 242                 unsigned int mask = pipe->ring_size - 1;
 243
 244 #ifdef CONFIG_WATCH_QUEUE
 245                 if (pipe->note_loss) {
 246                         struct watch_notification n;
 247
 248                         if (total_len < 8) {
 249                                 if (ret == 0)
 250                                         ret = -ENOBUFS;
 251                                 break;
 252                         }
 253
 254                         n.type = WATCH_TYPE_META;
 255                         n.subtype = WATCH_META_LOSS_NOTIFICATION;
 256                         n.info = watch_sizeof(n);
 257                         if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
 258                                 if (ret == 0)
 259                                         ret = -EFAULT;
 260                                 break;
 261                         }
 262                         ret += sizeof(n);
 263                         total_len -= sizeof(n);
 264                         pipe->note_loss = false;
 265                 }
 266 #endif
 267
 268                 if (!pipe_empty(head, tail)) {
 269                         struct pipe_buffer *buf = &pipe->bufs[tail & mask];
 270                         size_t chars = buf->len;
 271                         size_t written;
 272                         int error;
 273
 274                         if (chars > total_len) {
 275                                 if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
 276                                         if (ret == 0)
 277                                                 ret = -ENOBUFS;
 278                                         break;
 279                                 }
 280                                 chars = total_len;
 281                         }
 282
 283                         error = pipe_buf_confirm(pipe, buf);
 284                         if (error) {
 285                                 if (!ret)
 286                                         ret = error;
 287                                 break;
 288                         }
 289
 290                         written = copy_page_to_iter(buf->page, buf->offset, chars, to);
 291                         if (unlikely(written < chars)) {
 292                                 if (!ret)
 293                                         ret = -EFAULT;
 294                                 break;
 295                         }
 296                         ret += chars;
 297                         buf->offset += chars;
 298                         buf->len -= chars;
 299
 300                         /* Was it a packet buffer? Clean up and exit */
 301                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 302                                 total_len = chars;
 303                                 buf->len = 0;
 304                         }
 305
 306                         if (!buf->len) {
 307                                 pipe_buf_release(pipe, buf);
 308                                 spin_lock_irq(&pipe->rd_wait.lock);
 309 #ifdef CONFIG_WATCH_QUEUE
 310                                 if (buf->flags & PIPE_BUF_FLAG_LOSS)
 311                                         pipe->note_loss = true;
 312 #endif
 313                                 tail++;
 314                                 pipe->tail = tail;
 315                                 spin_unlock_irq(&pipe->rd_wait.lock);
 316                         }
 317                         total_len -= chars;
 318                         if (!total_len)
 319                                 break;  /* common path: read succeeded */
 320                         if (!pipe_empty(head, tail))    /* More to do? */
 321                                 continue;
 322                 }
 323
 324                 if (!pipe->writers)
 325                         break;
 326                 if (ret)
 327                         break;
 328                 if (filp->f_flags & O_NONBLOCK) {
 329                         ret = -EAGAIN;
 330                         break;
 331                 }
 332                 __pipe_unlock(pipe);
 333
 334                 /*
 335                  * We only get here if we didn't actually read anything.
 336                  *
 337                  * However, we could have seen (and removed) a zero-sized
 338                  * pipe buffer, and might have made space in the buffers
 339                  * that way.
 340                  *
 341                  * You can't make zero-sized pipe buffers by doing an empty
 342                  * write (not even in packet mode), but they can happen if
 343                  * the writer gets an EFAULT when trying to fill a buffer
 344                  * that already got allocated and inserted in the buffer
 345                  * array.
 346                  *
 347                  * So we still need to wake up any pending writers in the
 348                  * _very_ unlikely case that the pipe was full, but we got
 349                  * no data.
 350                  */
 351                 if (unlikely(was_full)) {
 352                         wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 353                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 354                 }
 355
 356                 /*
 357                  * But because we didn't read anything, at this point we can
 358                  * just return directly with -ERESTARTSYS if we're interrupted,
 359                  * since we've done any required wakeups and there's no need
 360                  * to mark anything accessed. And we've dropped the lock.
 361                  */
 362                 if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0)
 363                         return -ERESTARTSYS;
 364
 365                 __pipe_lock(pipe);
 366                 was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
 367                 wake_next_reader = true;
 368         }
 369         if (pipe_empty(pipe->head, pipe->tail))
 370                 wake_next_reader = false;
 371         __pipe_unlock(pipe);
 372
 373         if (was_full) {
 374                 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 375                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 376         }
 377         if (wake_next_reader)
 378                 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 379         if (ret > 0)
 380                 file_accessed(filp);
 381         return ret;
 382 }
 383
 384 static inline int is_packetized(struct file *file)
 385 {
 386         return (file->f_flags & O_DIRECT) != 0;
 387 }
 388
 389 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
 390 static inline bool pipe_writable(const struct pipe_inode_info *pipe)
 391 {
 392         unsigned int head = READ_ONCE(pipe->head);
 393         unsigned int tail = READ_ONCE(pipe->tail);
 394         unsigned int max_usage = READ_ONCE(pipe->max_usage);
 395
 396         return !pipe_full(head, tail, max_usage) ||
 397                 !READ_ONCE(pipe->readers);
 398 }
 399
 400 static ssize_t
 401 pipe_write(struct kiocb *iocb, struct iov_iter *from)
 402 {
 403         struct file *filp = iocb->ki_filp;
 404         struct pipe_inode_info *pipe = filp->private_data;
 405         unsigned int head;
 406         ssize_t ret = 0;
 407         size_t total_len = iov_iter_count(from);
 408         ssize_t chars;
 409         bool was_empty = false;
 410         bool wake_next_writer = false;
 411
 412         /* Null write succeeds. */
 413         if (unlikely(total_len == 0))
 414                 return 0;
 415
 416         __pipe_lock(pipe);
 417
 418         if (!pipe->readers) {
 419                 send_sig(SIGPIPE, current, 0);
 420                 ret = -EPIPE;
 421                 goto out;
 422         }
 423
 424 #ifdef CONFIG_WATCH_QUEUE
 425         if (pipe->watch_queue) {
 426                 ret = -EXDEV;
 427                 goto out;
 428         }
 429 #endif
 430
 431         /*
 432          * Only wake up if the pipe started out empty, since
 433          * otherwise there should be no readers waiting.
 434          *
 435          * If it wasn't empty we try to merge new data into
 436          * the last buffer.
 437          *
 438          * That naturally merges small writes, but it also
 439          * page-aligs the rest of the writes for large writes
 440          * spanning multiple pages.
 441          */
 442         head = pipe->head;
 443         was_empty = pipe_empty(head, pipe->tail);
 444         chars = total_len & (PAGE_SIZE-1);
 445         if (chars && !was_empty) {
 446                 unsigned int mask = pipe->ring_size - 1;
 447                 struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
 448                 int offset = buf->offset + buf->len;
 449
 450                 if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
 451                     offset + chars <= PAGE_SIZE) {
 452                         ret = pipe_buf_confirm(pipe, buf);
 453                         if (ret)
 454                                 goto out;
 455
 456                         ret = copy_page_from_iter(buf->page, offset, chars, from);
 457                         if (unlikely(ret < chars)) {
 458                                 ret = -EFAULT;
 459                                 goto out;
 460                         }
 461
 462                         buf->len += ret;
 463                         if (!iov_iter_count(from))
 464                                 goto out;
 465                 }
 466         }
 467
 468         for (;;) {
 469                 if (!pipe->readers) {
 470                         send_sig(SIGPIPE, current, 0);
 471                         if (!ret)
 472                                 ret = -EPIPE;
 473                         break;
 474                 }
 475
 476                 head = pipe->head;
 477                 if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
 478                         unsigned int mask = pipe->ring_size - 1;
 479                         struct pipe_buffer *buf = &pipe->bufs[head & mask];
 480                         struct page *page = pipe->tmp_page;
 481                         int copied;
 482
 483                         if (!page) {
 484                                 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
 485                                 if (unlikely(!page)) {
 486                                         ret = ret ? : -ENOMEM;
 487                                         break;
 488                                 }
 489                                 pipe->tmp_page = page;
 490                         }
 491
 492                         /* Allocate a slot in the ring in advance and attach an
 493                          * empty buffer.  If we fault or otherwise fail to use
 494                          * it, either the reader will consume it or it'll still
 495                          * be there for the next write.
 496                          */
 497                         spin_lock_irq(&pipe->rd_wait.lock);
 498
 499                         head = pipe->head;
 500                         if (pipe_full(head, pipe->tail, pipe->max_usage)) {
 501                                 spin_unlock_irq(&pipe->rd_wait.lock);
 502                                 continue;
 503                         }
 504
 505                         pipe->head = head + 1;
 506                         spin_unlock_irq(&pipe->rd_wait.lock);
 507
 508                         /* Insert it into the buffer array */
 509                         buf = &pipe->bufs[head & mask];
 510                         buf->page = page;
 511                         buf->ops = &anon_pipe_buf_ops;
 512                         buf->offset = 0;
 513                         buf->len = 0;
 514                         if (is_packetized(filp))
 515                                 buf->flags = PIPE_BUF_FLAG_PACKET;
 516                         else
 517                                 buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
 518                         pipe->tmp_page = NULL;
 519
 520                         copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
 521                         if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
 522                                 if (!ret)
 523                                         ret = -EFAULT;
 524                                 break;
 525                         }
 526                         ret += copied;
 527                         buf->offset = 0;
 528                         buf->len = copied;
 529
 530                         if (!iov_iter_count(from))
 531                                 break;
 532                 }
 533
 534                 if (!pipe_full(head, pipe->tail, pipe->max_usage))
 535                         continue;
 536
 537                 /* Wait for buffer space to become available. */
 538                 if (filp->f_flags & O_NONBLOCK) {
 539                         if (!ret)
 540                                 ret = -EAGAIN;
 541                         break;
 542                 }
 543                 if (signal_pending(current)) {
 544                         if (!ret)
 545                                 ret = -ERESTARTSYS;
 546                         break;
 547                 }
 548
 549                 /*
 550                  * We're going to release the pipe lock and wait for more
 551                  * space. We wake up any readers if necessary, and then
 552                  * after waiting we need to re-check whether the pipe
 553                  * become empty while we dropped the lock.
 554                  */
 555                 __pipe_unlock(pipe);
 556                 if (was_empty) {
 557                         wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 558                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 559                 }
 560                 wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
 561                 __pipe_lock(pipe);
 562                 was_empty = pipe_empty(pipe->head, pipe->tail);
 563                 wake_next_writer = true;
 564         }
 565 out:
 566         if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
 567                 wake_next_writer = false;
 568         __pipe_unlock(pipe);
 569
 570         /*
 571          * If we do do a wakeup event, we do a 'sync' wakeup, because we
 572          * want the reader to start processing things asap, rather than
 573          * leave the data pending.
 574          *
 575          * This is particularly important for small writes, because of
 576          * how (for example) the GNU make jobserver uses small writes to
 577          * wake up pending jobs
 578          */
 579         if (was_empty) {
 580                 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 581                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 582         }
 583         if (wake_next_writer)
 584                 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 585         if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
 586                 int err = file_update_time(filp);
 587                 if (err)
 588                         ret = err;
 589                 sb_end_write(file_inode(filp)->i_sb);
 590         }
 591         return ret;
 592 }
 593
 594 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 595 {
 596         struct pipe_inode_info *pipe = filp->private_data;
 597         int count, head, tail, mask;
 598
 599         switch (cmd) {
 600         case FIONREAD:
 601                 __pipe_lock(pipe);
 602                 count = 0;
 603                 head = pipe->head;
 604                 tail = pipe->tail;
 605                 mask = pipe->ring_size - 1;
 606
 607                 while (tail != head) {
 608                         count += pipe->bufs[tail & mask].len;
 609                         tail++;
 610                 }
 611                 __pipe_unlock(pipe);
 612
 613                 return put_user(count, (int __user *)arg);
 614
 615 #ifdef CONFIG_WATCH_QUEUE
 616         case IOC_WATCH_QUEUE_SET_SIZE: {
 617                 int ret;
 618                 __pipe_lock(pipe);
 619                 ret = watch_queue_set_size(pipe, arg);
 620                 __pipe_unlock(pipe);
 621                 return ret;
 622         }
 623
 624         case IOC_WATCH_QUEUE_SET_FILTER:
 625                 return watch_queue_set_filter(
 626                         pipe, (struct watch_notification_filter __user *)arg);
 627 #endif
 628
 629         default:
 630                 return -ENOIOCTLCMD;
 631         }
 632 }
 633
 634 /* No kernel lock held - fine */
 635 static __poll_t
 636 pipe_poll(struct file *filp, poll_table *wait)
 637 {
 638         __poll_t mask;
 639         struct pipe_inode_info *pipe = filp->private_data;
 640         unsigned int head, tail;
 641
 642         /*
 643          * Reading pipe state only -- no need for acquiring the semaphore.
 644          *
 645          * But because this is racy, the code has to add the
 646          * entry to the poll table _first_ ..
 647          */
 648         if (filp->f_mode & FMODE_READ)
 649                 poll_wait(filp, &pipe->rd_wait, wait);
 650         if (filp->f_mode & FMODE_WRITE)
 651                 poll_wait(filp, &pipe->wr_wait, wait);
 652
 653         /*
 654          * .. and only then can you do the racy tests. That way,
 655          * if something changes and you got it wrong, the poll
 656          * table entry will wake you up and fix it.
 657          */
 658         head = READ_ONCE(pipe->head);
 659         tail = READ_ONCE(pipe->tail);
 660
 661         mask = 0;
 662         if (filp->f_mode & FMODE_READ) {
 663                 if (!pipe_empty(head, tail))
 664                         mask |= EPOLLIN | EPOLLRDNORM;
 665                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 666                         mask |= EPOLLHUP;
 667         }
 668
 669         if (filp->f_mode & FMODE_WRITE) {
 670                 if (!pipe_full(head, tail, pipe->max_usage))
 671                         mask |= EPOLLOUT | EPOLLWRNORM;
 672                 /*
 673                  * Most Unices do not set EPOLLERR for FIFOs but on Linux they
 674                  * behave exactly like pipes for poll().
 675                  */
 676                 if (!pipe->readers)
 677                         mask |= EPOLLERR;
 678         }
 679
 680         return mask;
 681 }
 682
 683 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
 684 {
 685         int kill = 0;
 686
 687         spin_lock(&inode->i_lock);
 688         if (!--pipe->files) {
 689                 inode->i_pipe = NULL;
 690                 kill = 1;
 691         }
 692         spin_unlock(&inode->i_lock);
 693
 694         if (kill)
 695                 free_pipe_info(pipe);
 696 }
 697
 698 static int
 699 pipe_release(struct inode *inode, struct file *file)
 700 {
 701         struct pipe_inode_info *pipe = file->private_data;
 702
 703         __pipe_lock(pipe);
 704         if (file->f_mode & FMODE_READ)
 705                 pipe->readers--;
 706         if (file->f_mode & FMODE_WRITE)
 707                 pipe->writers--;
 708
 709         /* Was that the last reader or writer, but not the other side? */
 710         if (!pipe->readers != !pipe->writers) {
 711                 wake_up_interruptible_all(&pipe->rd_wait);
 712                 wake_up_interruptible_all(&pipe->wr_wait);
 713                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 714                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 715         }
 716         __pipe_unlock(pipe);
 717
 718         put_pipe_info(inode, pipe);
 719         return 0;
 720 }
 721
 722 static int
 723 pipe_fasync(int fd, struct file *filp, int on)
 724 {
 725         struct pipe_inode_info *pipe = filp->private_data;
 726         int retval = 0;
 727
 728         __pipe_lock(pipe);
 729         if (filp->f_mode & FMODE_READ)
 730                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 731         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 732                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 733                 if (retval < 0 && (filp->f_mode & FMODE_READ))
 734                         /* this can happen only if on == T */
 735                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 736         }
 737         __pipe_unlock(pipe);
 738         return retval;
 739 }
 740
 741 unsigned long account_pipe_buffers(struct user_struct *user,
 742                                    unsigned long old, unsigned long new)
 743 {
 744         return atomic_long_add_return(new - old, &user->pipe_bufs);
 745 }
 746
 747 bool too_many_pipe_buffers_soft(unsigned long user_bufs)
 748 {
 749         unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
 750
 751         return soft_limit && user_bufs > soft_limit;
 752 }
 753
 754 bool too_many_pipe_buffers_hard(unsigned long user_bufs)
 755 {
 756         unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
 757
 758         return hard_limit && user_bufs > hard_limit;
 759 }
 760
 761 bool pipe_is_unprivileged_user(void)
 762 {
 763         return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
 764 }
 765
 766 struct pipe_inode_info *alloc_pipe_info(void)
 767 {
 768         struct pipe_inode_info *pipe;
 769         unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
 770         struct user_struct *user = get_current_user();
 771         unsigned long user_bufs;
 772         unsigned int max_size = READ_ONCE(pipe_max_size);
 773
 774         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
 775         if (pipe == NULL)
 776                 goto out_free_uid;
 777
 778         if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
 779                 pipe_bufs = max_size >> PAGE_SHIFT;
 780
 781         user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
 782
 783         if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
 784                 user_bufs = account_pipe_buffers(user, pipe_bufs, 1);
 785                 pipe_bufs = 1;
 786         }
 787
 788         if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
 789                 goto out_revert_acct;
 790
 791         pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
 792                              GFP_KERNEL_ACCOUNT);
 793
 794         if (pipe->bufs) {
 795                 init_waitqueue_head(&pipe->rd_wait);
 796                 init_waitqueue_head(&pipe->wr_wait);
 797                 pipe->r_counter = pipe->w_counter = 1;
 798                 pipe->max_usage = pipe_bufs;
 799                 pipe->ring_size = pipe_bufs;
 800                 pipe->nr_accounted = pipe_bufs;
 801                 pipe->user = user;
 802                 mutex_init(&pipe->mutex);
 803                 return pipe;
 804         }
 805
 806 out_revert_acct:
 807         (void) account_pipe_buffers(user, pipe_bufs, 0);
 808         kfree(pipe);
 809 out_free_uid:
 810         free_uid(user);
 811         return NULL;
 812 }
 813
 814 void free_pipe_info(struct pipe_inode_info *pipe)
 815 {
 816         int i;
 817
 818 #ifdef CONFIG_WATCH_QUEUE
 819         if (pipe->watch_queue) {
 820                 watch_queue_clear(pipe->watch_queue);
 821                 put_watch_queue(pipe->watch_queue);
 822         }
 823 #endif
 824
 825         (void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
 826         free_uid(pipe->user);
 827         for (i = 0; i < pipe->ring_size; i++) {
 828                 struct pipe_buffer *buf = pipe->bufs + i;
 829                 if (buf->ops)
 830                         pipe_buf_release(pipe, buf);
 831         }
 832         if (pipe->tmp_page)
 833                 __free_page(pipe->tmp_page);
 834         kfree(pipe->bufs);
 835         kfree(pipe);
 836 }
 837
 838 static struct vfsmount *pipe_mnt __read_mostly;
 839
 840 /*
 841  * pipefs_dname() is called from d_path().
 842  */
 843 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 844 {
 845         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 846                                 d_inode(dentry)->i_ino);
 847 }
 848
 849 static const struct dentry_operations pipefs_dentry_operations = {
 850         .d_dname        = pipefs_dname,
 851 };
 852
 853 static struct inode * get_pipe_inode(void)
 854 {
 855         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 856         struct pipe_inode_info *pipe;
 857
 858         if (!inode)
 859                 goto fail_inode;
 860
 861         inode->i_ino = get_next_ino();
 862
 863         pipe = alloc_pipe_info();
 864         if (!pipe)
 865                 goto fail_iput;
 866
 867         inode->i_pipe = pipe;
 868         pipe->files = 2;
 869         pipe->readers = pipe->writers = 1;
 870         inode->i_fop = &pipefifo_fops;
 871
 872         /*
 873          * Mark the inode dirty from the very beginning,
 874          * that way it will never be moved to the dirty
 875          * list because "mark_inode_dirty()" will think
 876          * that it already _is_ on the dirty list.
 877          */
 878         inode->i_state = I_DIRTY;
 879         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 880         inode->i_uid = current_fsuid();
 881         inode->i_gid = current_fsgid();
 882         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 883
 884         return inode;
 885
 886 fail_iput:
 887         iput(inode);
 888
 889 fail_inode:
 890         return NULL;
 891 }
 892
 893 int create_pipe_files(struct file **res, int flags)
 894 {
 895         struct inode *inode = get_pipe_inode();
 896         struct file *f;
 897         int error;
 898
 899         if (!inode)
 900                 return -ENFILE;
 901
 902         if (flags & O_NOTIFICATION_PIPE) {
 903                 error = watch_queue_init(inode->i_pipe);
 904                 if (error) {
 905                         free_pipe_info(inode->i_pipe);
 906                         iput(inode);
 907                         return error;
 908                 }
 909         }
 910
 911         f = alloc_file_pseudo(inode, pipe_mnt, "",
 912                                 O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
 913                                 &pipefifo_fops);
 914         if (IS_ERR(f)) {
 915                 free_pipe_info(inode->i_pipe);
 916                 iput(inode);
 917                 return PTR_ERR(f);
 918         }
 919
 920         f->private_data = inode->i_pipe;
 921
 922         res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
 923                                   &pipefifo_fops);
 924         if (IS_ERR(res[0])) {
 925                 put_pipe_info(inode, inode->i_pipe);
 926                 fput(f);
 927                 return PTR_ERR(res[0]);
 928         }
 929         res[0]->private_data = inode->i_pipe;
 930         res[1] = f;
 931         stream_open(inode, res[0]);
 932         stream_open(inode, res[1]);
 933         return 0;
 934 }
 935
 936 static int __do_pipe_flags(int *fd, struct file **files, int flags)
 937 {
 938         int error;
 939         int fdw, fdr;
 940
 941         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
 942                 return -EINVAL;
 943
 944         error = create_pipe_files(files, flags);
 945         if (error)
 946                 return error;
 947
 948         error = get_unused_fd_flags(flags);
 949         if (error < 0)
 950                 goto err_read_pipe;
 951         fdr = error;
 952
 953         error = get_unused_fd_flags(flags);
 954         if (error < 0)
 955                 goto err_fdr;
 956         fdw = error;
 957
 958         audit_fd_pair(fdr, fdw);
 959         fd[0] = fdr;
 960         fd[1] = fdw;
 961         return 0;
 962
 963  err_fdr:
 964         put_unused_fd(fdr);
 965  err_read_pipe:
 966         fput(files[0]);
 967         fput(files[1]);
 968         return error;
 969 }
 970
 971 int do_pipe_flags(int *fd, int flags)
 972 {
 973         struct file *files[2];
 974         int error = __do_pipe_flags(fd, files, flags);
 975         if (!error) {
 976                 fd_install(fd[0], files[0]);
 977                 fd_install(fd[1], files[1]);
 978         }
 979         return error;
 980 }
 981
 982 /*
 983  * sys_pipe() is the normal C calling standard for creating
 984  * a pipe. It's not the way Unix traditionally does this, though.
 985  */
 986 static int do_pipe2(int __user *fildes, int flags)
 987 {
 988         struct file *files[2];
 989         int fd[2];
 990         int error;
 991
 992         error = __do_pipe_flags(fd, files, flags);
 993         if (!error) {
 994                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
 995                         fput(files[0]);
 996                         fput(files[1]);
 997                         put_unused_fd(fd[0]);
 998                         put_unused_fd(fd[1]);
 999                         error = -EFAULT;
1000                 } else {
1001                         fd_install(fd[0], files[0]);
1002                         fd_install(fd[1], files[1]);
1003                 }
1004         }
1005         return error;
1006 }
1007
1008 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1009 {
1010         return do_pipe2(fildes, flags);
1011 }
1012
1013 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1014 {
1015         return do_pipe2(fildes, 0);
1016 }
1017
1018 /*
1019  * This is the stupid "wait for pipe to be readable or writable"
1020  * model.
1021  *
1022  * See pipe_read/write() for the proper kind of exclusive wait,
1023  * but that requires that we wake up any other readers/writers
1024  * if we then do not end up reading everything (ie the whole
1025  * "wake_next_reader/writer" logic in pipe_read/write()).
1026  */
1027 void pipe_wait_readable(struct pipe_inode_info *pipe)
1028 {
1029         pipe_unlock(pipe);
1030         wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
1031         pipe_lock(pipe);
1032 }
1033
1034 void pipe_wait_writable(struct pipe_inode_info *pipe)
1035 {
1036         pipe_unlock(pipe);
1037         wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
1038         pipe_lock(pipe);
1039 }
1040
1041 /*
1042  * This depends on both the wait (here) and the wakeup (wake_up_partner)
1043  * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
1044  * race with the count check and waitqueue prep.
1045  *
1046  * Normally in order to avoid races, you'd do the prepare_to_wait() first,
1047  * then check the condition you're waiting for, and only then sleep. But
1048  * because of the pipe lock, we can check the condition before being on
1049  * the wait queue.
1050  *
1051  * We use the 'rd_wait' waitqueue for pipe partner waiting.
1052  */
1053 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1054 {
1055         DEFINE_WAIT(rdwait);
1056         int cur = *cnt;
1057
1058         while (cur == *cnt) {
1059                 prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
1060                 pipe_unlock(pipe);
1061                 schedule();
1062                 finish_wait(&pipe->rd_wait, &rdwait);
1063                 pipe_lock(pipe);
1064                 if (signal_pending(current))
1065                         break;
1066         }
1067         return cur == *cnt ? -ERESTARTSYS : 0;
1068 }
1069
1070 static void wake_up_partner(struct pipe_inode_info *pipe)
1071 {
1072         wake_up_interruptible_all(&pipe->rd_wait);
1073 }
1074
1075 static int fifo_open(struct inode *inode, struct file *filp)
1076 {
1077         struct pipe_inode_info *pipe;
1078         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1079         int ret;
1080
1081         filp->f_version = 0;
1082
1083         spin_lock(&inode->i_lock);
1084         if (inode->i_pipe) {
1085                 pipe = inode->i_pipe;
1086                 pipe->files++;
1087                 spin_unlock(&inode->i_lock);
1088         } else {
1089                 spin_unlock(&inode->i_lock);
1090                 pipe = alloc_pipe_info();
1091                 if (!pipe)
1092                         return -ENOMEM;
1093                 pipe->files = 1;
1094                 spin_lock(&inode->i_lock);
1095                 if (unlikely(inode->i_pipe)) {
1096                         inode->i_pipe->files++;
1097                         spin_unlock(&inode->i_lock);
1098                         free_pipe_info(pipe);
1099                         pipe = inode->i_pipe;
1100                 } else {
1101                         inode->i_pipe = pipe;
1102                         spin_unlock(&inode->i_lock);
1103                 }
1104         }
1105         filp->private_data = pipe;
1106         /* OK, we have a pipe and it's pinned down */
1107
1108         __pipe_lock(pipe);
1109
1110         /* We can only do regular read/write on fifos */
1111         stream_open(inode, filp);
1112
1113         switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
1114         case FMODE_READ:
1115         /*
1116          *  O_RDONLY
1117          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
1118          *  opened, even when there is no process writing the FIFO.
1119          */
1120                 pipe->r_counter++;
1121                 if (pipe->readers++ == 0)
1122                         wake_up_partner(pipe);
1123
1124                 if (!is_pipe && !pipe->writers) {
1125                         if ((filp->f_flags & O_NONBLOCK)) {
1126                                 /* suppress EPOLLHUP until we have
1127                                  * seen a writer */
1128                                 filp->f_version = pipe->w_counter;
1129                         } else {
1130                                 if (wait_for_partner(pipe, &pipe->w_counter))
1131                                         goto err_rd;
1132                         }
1133                 }
1134                 break;
1135
1136         case FMODE_WRITE:
1137         /*
1138          *  O_WRONLY
1139          *  POSIX.1 says that O_NONBLOCK means return -1 with
1140          *  errno=ENXIO when there is no process reading the FIFO.
1141          */
1142                 ret = -ENXIO;
1143                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1144                         goto err;
1145
1146                 pipe->w_counter++;
1147                 if (!pipe->writers++)
1148                         wake_up_partner(pipe);
1149
1150                 if (!is_pipe && !pipe->readers) {
1151                         if (wait_for_partner(pipe, &pipe->r_counter))
1152                                 goto err_wr;
1153                 }
1154                 break;
1155
1156         case FMODE_READ | FMODE_WRITE:
1157         /*
1158          *  O_RDWR
1159          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1160          *  This implementation will NEVER block on a O_RDWR open, since
1161          *  the process can at least talk to itself.
1162          */
1163
1164                 pipe->readers++;
1165                 pipe->writers++;
1166                 pipe->r_counter++;
1167                 pipe->w_counter++;
1168                 if (pipe->readers == 1 || pipe->writers == 1)
1169                         wake_up_partner(pipe);
1170                 break;
1171
1172         default:
1173                 ret = -EINVAL;
1174                 goto err;
1175         }
1176
1177         /* Ok! */
1178         __pipe_unlock(pipe);
1179         return 0;
1180
1181 err_rd:
1182         if (!--pipe->readers)
1183                 wake_up_interruptible(&pipe->wr_wait);
1184         ret = -ERESTARTSYS;
1185         goto err;
1186
1187 err_wr:
1188         if (!--pipe->writers)
1189                 wake_up_interruptible_all(&pipe->rd_wait);
1190         ret = -ERESTARTSYS;
1191         goto err;
1192
1193 err:
1194         __pipe_unlock(pipe);
1195
1196         put_pipe_info(inode, pipe);
1197         return ret;
1198 }
1199
1200 const struct file_operations pipefifo_fops = {
1201         .open           = fifo_open,
1202         .llseek         = no_llseek,
1203         .read_iter      = pipe_read,
1204         .write_iter     = pipe_write,
1205         .poll           = pipe_poll,
1206         .unlocked_ioctl = pipe_ioctl,
1207         .release        = pipe_release,
1208         .fasync         = pipe_fasync,
1209         .splice_write   = iter_file_splice_write,
1210 };
1211
1212 /*
1213  * Currently we rely on the pipe array holding a power-of-2 number
1214  * of pages. Returns 0 on error.
1215  */
1216 unsigned int round_pipe_size(unsigned long size)
1217 {
1218         if (size > (1U << 31))
1219                 return 0;
1220
1221         /* Minimum pipe size, as required by POSIX */
1222         if (size < PAGE_SIZE)
1223                 return PAGE_SIZE;
1224
1225         return roundup_pow_of_two(size);
1226 }
1227
1228 /*
1229  * Resize the pipe ring to a number of slots.
1230  */
1231 int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
1232 {
1233         struct pipe_buffer *bufs;
1234         unsigned int head, tail, mask, n;
1235
1236         /*
1237          * We can shrink the pipe, if arg is greater than the ring occupancy.
1238          * Since we don't expect a lot of shrink+grow operations, just free and
1239          * allocate again like we would do for growing.  If the pipe currently
1240          * contains more buffers than arg, then return busy.
1241          */
1242         mask = pipe->ring_size - 1;
1243         head = pipe->head;
1244         tail = pipe->tail;
1245         n = pipe_occupancy(pipe->head, pipe->tail);
1246         if (nr_slots < n)
1247                 return -EBUSY;
1248
1249         bufs = kcalloc(nr_slots, sizeof(*bufs),
1250                        GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1251         if (unlikely(!bufs))
1252                 return -ENOMEM;
1253
1254         /*
1255          * The pipe array wraps around, so just start the new one at zero
1256          * and adjust the indices.
1257          */
1258         if (n > 0) {
1259                 unsigned int h = head & mask;
1260                 unsigned int t = tail & mask;
1261                 if (h > t) {
1262                         memcpy(bufs, pipe->bufs + t,
1263                                n * sizeof(struct pipe_buffer));
1264                 } else {
1265                         unsigned int tsize = pipe->ring_size - t;
1266                         if (h > 0)
1267                                 memcpy(bufs + tsize, pipe->bufs,
1268                                        h * sizeof(struct pipe_buffer));
1269                         memcpy(bufs, pipe->bufs + t,
1270                                tsize * sizeof(struct pipe_buffer));
1271                 }
1272         }
1273
1274         head = n;
1275         tail = 0;
1276
1277         kfree(pipe->bufs);
1278         pipe->bufs = bufs;
1279         pipe->ring_size = nr_slots;
1280         if (pipe->max_usage > nr_slots)
1281                 pipe->max_usage = nr_slots;
1282         pipe->tail = tail;
1283         pipe->head = head;
1284
1285         /* This might have made more room for writers */
1286         wake_up_interruptible(&pipe->wr_wait);
1287         return 0;
1288 }
1289
1290 /*
1291  * Allocate a new array of pipe buffers and copy the info over. Returns the
1292  * pipe size if successful, or return -ERROR on error.
1293  */
1294 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1295 {
1296         unsigned long user_bufs;
1297         unsigned int nr_slots, size;
1298         long ret = 0;
1299
1300 #ifdef CONFIG_WATCH_QUEUE
1301         if (pipe->watch_queue)
1302                 return -EBUSY;
1303 #endif
1304
1305         size = round_pipe_size(arg);
1306         nr_slots = size >> PAGE_SHIFT;
1307
1308         if (!nr_slots)
1309                 return -EINVAL;
1310
1311         /*
1312          * If trying to increase the pipe capacity, check that an
1313          * unprivileged user is not trying to exceed various limits
1314          * (soft limit check here, hard limit check just below).
1315          * Decreasing the pipe capacity is always permitted, even
1316          * if the user is currently over a limit.
1317          */
1318         if (nr_slots > pipe->max_usage &&
1319                         size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1320                 return -EPERM;
1321
1322         user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
1323
1324         if (nr_slots > pipe->max_usage &&
1325                         (too_many_pipe_buffers_hard(user_bufs) ||
1326                          too_many_pipe_buffers_soft(user_bufs)) &&
1327                         pipe_is_unprivileged_user()) {
1328                 ret = -EPERM;
1329                 goto out_revert_acct;
1330         }
1331
1332         ret = pipe_resize_ring(pipe, nr_slots);
1333         if (ret < 0)
1334                 goto out_revert_acct;
1335
1336         pipe->max_usage = nr_slots;
1337         pipe->nr_accounted = nr_slots;
1338         return pipe->max_usage * PAGE_SIZE;
1339
1340 out_revert_acct:
1341         (void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
1342         return ret;
1343 }
1344
1345 /*
1346  * Note that i_pipe and i_cdev share the same location, so checking ->i_pipe is
1347  * not enough to verify that this is a pipe.
1348  */
1349 struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
1350 {
1351         struct pipe_inode_info *pipe = file->private_data;
1352
1353         if (file->f_op != &pipefifo_fops || !pipe)
1354                 return NULL;
1355 #ifdef CONFIG_WATCH_QUEUE
1356         if (for_splice && pipe->watch_queue)
1357                 return NULL;
1358 #endif
1359         return pipe;
1360 }
1361
1362 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1363 {
1364         struct pipe_inode_info *pipe;
1365         long ret;
1366
1367         pipe = get_pipe_info(file, false);
1368         if (!pipe)
1369                 return -EBADF;
1370
1371         __pipe_lock(pipe);
1372
1373         switch (cmd) {
1374         case F_SETPIPE_SZ:
1375                 ret = pipe_set_size(pipe, arg);
1376                 break;
1377         case F_GETPIPE_SZ:
1378                 ret = pipe->max_usage * PAGE_SIZE;
1379                 break;
1380         default:
1381                 ret = -EINVAL;
1382                 break;
1383         }
1384
1385         __pipe_unlock(pipe);
1386         return ret;
1387 }
1388
1389 static const struct super_operations pipefs_ops = {
1390         .destroy_inode = free_inode_nonrcu,
1391         .statfs = simple_statfs,
1392 };
1393
1394 /*
1395  * pipefs should _never_ be mounted by userland - too much of security hassle,
1396  * no real gain from having the whole whorehouse mounted. So we don't need
1397  * any operations on the root directory. However, we need a non-trivial
1398  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1399  */
1400
1401 static int pipefs_init_fs_context(struct fs_context *fc)
1402 {
1403         struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
1404         if (!ctx)
1405                 return -ENOMEM;
1406         ctx->ops = &pipefs_ops;
1407         ctx->dops = &pipefs_dentry_operations;
1408         return 0;
1409 }
1410
1411 static struct file_system_type pipe_fs_type = {
1412         .name           = "pipefs",
1413         .init_fs_context = pipefs_init_fs_context,
1414         .kill_sb        = kill_anon_super,
1415 };
1416
1417 static int __init init_pipe_fs(void)
1418 {
1419         int err = register_filesystem(&pipe_fs_type);
1420
1421         if (!err) {
1422                 pipe_mnt = kern_mount(&pipe_fs_type);
1423                 if (IS_ERR(pipe_mnt)) {
1424                         err = PTR_ERR(pipe_mnt);
1425                         unregister_filesystem(&pipe_fs_type);
1426                 }
1427         }
1428         return err;
1429 }
1430
1431 fs_initcall(init_pipe_fs);