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 #include <linux/sysctl.h>
  29
  30 #include <linux/uaccess.h>
  31 #include <asm/ioctls.h>
  32
  33 #include "internal.h"
  34
  35 /*
  36  * New pipe buffers will be restricted to this size while the user is exceeding
  37  * their pipe buffer quota. The general pipe use case needs at least two
  38  * buffers: one for data yet to be read, and one for new data. If this is less
  39  * than two, then a write to a non-empty pipe may block even if the pipe is not
  40  * full. This can occur with GNU make jobserver or similar uses of pipes as
  41  * semaphores: multiple processes may be waiting to write tokens back to the
  42  * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.
  43  *
  44  * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their
  45  * own risk, namely: pipe writes to non-full pipes may block until the pipe is
  46  * emptied.
  47  */
  48 #define PIPE_MIN_DEF_BUFFERS 2
  49
  50 /*
  51  * The max size that a non-root user is allowed to grow the pipe. Can
  52  * be set by root in /proc/sys/fs/pipe-max-size
  53  */
  54 static unsigned int pipe_max_size = 1048576;
  55
  56 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
  57  * matches default values.
  58  */
  59 static unsigned long pipe_user_pages_hard;
  60 static unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
  61
  62 /*
  63  * We use head and tail indices that aren't masked off, except at the point of
  64  * dereference, but rather they're allowed to wrap naturally.  This means there
  65  * isn't a dead spot in the buffer, but the ring has to be a power of two and
  66  * <= 2^31.
  67  * -- David Howells 2019-09-23.
  68  *
  69  * Reads with count = 0 should always return 0.
  70  * -- Julian Bradfield 1999-06-07.
  71  *
  72  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  73  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  74  *
  75  * pipe_read & write cleanup
  76  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  77  */
  78
  79 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  80 {
  81         if (pipe->files)
  82                 mutex_lock_nested(&pipe->mutex, subclass);
  83 }
  84
  85 void pipe_lock(struct pipe_inode_info *pipe)
  86 {
  87         /*
  88          * pipe_lock() nests non-pipe inode locks (for writing to a file)
  89          */
  90         pipe_lock_nested(pipe, I_MUTEX_PARENT);
  91 }
  92 EXPORT_SYMBOL(pipe_lock);
  93
  94 void pipe_unlock(struct pipe_inode_info *pipe)
  95 {
  96         if (pipe->files)
  97                 mutex_unlock(&pipe->mutex);
  98 }
  99 EXPORT_SYMBOL(pipe_unlock);
 100
 101 static inline void __pipe_lock(struct pipe_inode_info *pipe)
 102 {
 103         mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
 104 }
 105
 106 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
 107 {
 108         mutex_unlock(&pipe->mutex);
 109 }
 110
 111 void pipe_double_lock(struct pipe_inode_info *pipe1,
 112                       struct pipe_inode_info *pipe2)
 113 {
 114         BUG_ON(pipe1 == pipe2);
 115
 116         if (pipe1 < pipe2) {
 117                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
 118                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
 119         } else {
 120                 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
 121                 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
 122         }
 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 bool anon_pipe_buf_try_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                 return false;
 148         memcg_kmem_uncharge_page(page, 0);
 149         __SetPageLocked(page);
 150         return true;
 151 }
 152
 153 /**
 154  * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
 155  * @pipe:       the pipe that the buffer belongs to
 156  * @buf:        the buffer to attempt to steal
 157  *
 158  * Description:
 159  *      This function attempts to steal the &struct page attached to
 160  *      @buf. If successful, this function returns 0 and returns with
 161  *      the page locked. The caller may then reuse the page for whatever
 162  *      he wishes; the typical use is insertion into a different file
 163  *      page cache.
 164  */
 165 bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe,
 166                 struct pipe_buffer *buf)
 167 {
 168         struct page *page = buf->page;
 169
 170         /*
 171          * A reference of one is golden, that means that the owner of this
 172          * page is the only one holding a reference to it. lock the page
 173          * and return OK.
 174          */
 175         if (page_count(page) == 1) {
 176                 lock_page(page);
 177                 return true;
 178         }
 179         return false;
 180 }
 181 EXPORT_SYMBOL(generic_pipe_buf_try_steal);
 182
 183 /**
 184  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 185  * @pipe:       the pipe that the buffer belongs to
 186  * @buf:        the buffer to get a reference to
 187  *
 188  * Description:
 189  *      This function grabs an extra reference to @buf. It's used in
 190  *      the tee() system call, when we duplicate the buffers in one
 191  *      pipe into another.
 192  */
 193 bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 194 {
 195         return try_get_page(buf->page);
 196 }
 197 EXPORT_SYMBOL(generic_pipe_buf_get);
 198
 199 /**
 200  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 201  * @pipe:       the pipe that the buffer belongs to
 202  * @buf:        the buffer to put a reference to
 203  *
 204  * Description:
 205  *      This function releases a reference to @buf.
 206  */
 207 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 208                               struct pipe_buffer *buf)
 209 {
 210         put_page(buf->page);
 211 }
 212 EXPORT_SYMBOL(generic_pipe_buf_release);
 213
 214 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 215         .release        = anon_pipe_buf_release,
 216         .try_steal      = anon_pipe_buf_try_steal,
 217         .get            = generic_pipe_buf_get,
 218 };
 219
 220 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
 221 static inline bool pipe_readable(const struct pipe_inode_info *pipe)
 222 {
 223         unsigned int head = READ_ONCE(pipe->head);
 224         unsigned int tail = READ_ONCE(pipe->tail);
 225         unsigned int writers = READ_ONCE(pipe->writers);
 226
 227         return !pipe_empty(head, tail) || !writers;
 228 }
 229
 230 static ssize_t
 231 pipe_read(struct kiocb *iocb, struct iov_iter *to)
 232 {
 233         size_t total_len = iov_iter_count(to);
 234         struct file *filp = iocb->ki_filp;
 235         struct pipe_inode_info *pipe = filp->private_data;
 236         bool was_full, wake_next_reader = false;
 237         ssize_t ret;
 238
 239         /* Null read succeeds. */
 240         if (unlikely(total_len == 0))
 241                 return 0;
 242
 243         ret = 0;
 244         __pipe_lock(pipe);
 245
 246         /*
 247          * We only wake up writers if the pipe was full when we started
 248          * reading in order to avoid unnecessary wakeups.
 249          *
 250          * But when we do wake up writers, we do so using a sync wakeup
 251          * (WF_SYNC), because we want them to get going and generate more
 252          * data for us.
 253          */
 254         was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
 255         for (;;) {
 256                 /* Read ->head with a barrier vs post_one_notification() */
 257                 unsigned int head = smp_load_acquire(&pipe->head);
 258                 unsigned int tail = pipe->tail;
 259                 unsigned int mask = pipe->ring_size - 1;
 260
 261 #ifdef CONFIG_WATCH_QUEUE
 262                 if (pipe->note_loss) {
 263                         struct watch_notification n;
 264
 265                         if (total_len < 8) {
 266                                 if (ret == 0)
 267                                         ret = -ENOBUFS;
 268                                 break;
 269                         }
 270
 271                         n.type = WATCH_TYPE_META;
 272                         n.subtype = WATCH_META_LOSS_NOTIFICATION;
 273                         n.info = watch_sizeof(n);
 274                         if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
 275                                 if (ret == 0)
 276                                         ret = -EFAULT;
 277                                 break;
 278                         }
 279                         ret += sizeof(n);
 280                         total_len -= sizeof(n);
 281                         pipe->note_loss = false;
 282                 }
 283 #endif
 284
 285                 if (!pipe_empty(head, tail)) {
 286                         struct pipe_buffer *buf = &pipe->bufs[tail & mask];
 287                         size_t chars = buf->len;
 288                         size_t written;
 289                         int error;
 290
 291                         if (chars > total_len) {
 292                                 if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
 293                                         if (ret == 0)
 294                                                 ret = -ENOBUFS;
 295                                         break;
 296                                 }
 297                                 chars = total_len;
 298                         }
 299
 300                         error = pipe_buf_confirm(pipe, buf);
 301                         if (error) {
 302                                 if (!ret)
 303                                         ret = error;
 304                                 break;
 305                         }
 306
 307                         written = copy_page_to_iter(buf->page, buf->offset, chars, to);
 308                         if (unlikely(written < chars)) {
 309                                 if (!ret)
 310                                         ret = -EFAULT;
 311                                 break;
 312                         }
 313                         ret += chars;
 314                         buf->offset += chars;
 315                         buf->len -= chars;
 316
 317                         /* Was it a packet buffer? Clean up and exit */
 318                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 319                                 total_len = chars;
 320                                 buf->len = 0;
 321                         }
 322
 323                         if (!buf->len) {
 324                                 pipe_buf_release(pipe, buf);
 325                                 spin_lock_irq(&pipe->rd_wait.lock);
 326 #ifdef CONFIG_WATCH_QUEUE
 327                                 if (buf->flags & PIPE_BUF_FLAG_LOSS)
 328                                         pipe->note_loss = true;
 329 #endif
 330                                 tail++;
 331                                 pipe->tail = tail;
 332                                 spin_unlock_irq(&pipe->rd_wait.lock);
 333                         }
 334                         total_len -= chars;
 335                         if (!total_len)
 336                                 break;  /* common path: read succeeded */
 337                         if (!pipe_empty(head, tail))    /* More to do? */
 338                                 continue;
 339                 }
 340
 341                 if (!pipe->writers)
 342                         break;
 343                 if (ret)
 344                         break;
 345                 if (filp->f_flags & O_NONBLOCK) {
 346                         ret = -EAGAIN;
 347                         break;
 348                 }
 349                 __pipe_unlock(pipe);
 350
 351                 /*
 352                  * We only get here if we didn't actually read anything.
 353                  *
 354                  * However, we could have seen (and removed) a zero-sized
 355                  * pipe buffer, and might have made space in the buffers
 356                  * that way.
 357                  *
 358                  * You can't make zero-sized pipe buffers by doing an empty
 359                  * write (not even in packet mode), but they can happen if
 360                  * the writer gets an EFAULT when trying to fill a buffer
 361                  * that already got allocated and inserted in the buffer
 362                  * array.
 363                  *
 364                  * So we still need to wake up any pending writers in the
 365                  * _very_ unlikely case that the pipe was full, but we got
 366                  * no data.
 367                  */
 368                 if (unlikely(was_full))
 369                         wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 370                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 371
 372                 /*
 373                  * But because we didn't read anything, at this point we can
 374                  * just return directly with -ERESTARTSYS if we're interrupted,
 375                  * since we've done any required wakeups and there's no need
 376                  * to mark anything accessed. And we've dropped the lock.
 377                  */
 378                 if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0)
 379                         return -ERESTARTSYS;
 380
 381                 __pipe_lock(pipe);
 382                 was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
 383                 wake_next_reader = true;
 384         }
 385         if (pipe_empty(pipe->head, pipe->tail))
 386                 wake_next_reader = false;
 387         __pipe_unlock(pipe);
 388
 389         if (was_full)
 390                 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 391         if (wake_next_reader)
 392                 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 393         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 394         if (ret > 0)
 395                 file_accessed(filp);
 396         return ret;
 397 }
 398
 399 static inline int is_packetized(struct file *file)
 400 {
 401         return (file->f_flags & O_DIRECT) != 0;
 402 }
 403
 404 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
 405 static inline bool pipe_writable(const struct pipe_inode_info *pipe)
 406 {
 407         unsigned int head = READ_ONCE(pipe->head);
 408         unsigned int tail = READ_ONCE(pipe->tail);
 409         unsigned int max_usage = READ_ONCE(pipe->max_usage);
 410
 411         return !pipe_full(head, tail, max_usage) ||
 412                 !READ_ONCE(pipe->readers);
 413 }
 414
 415 static ssize_t
 416 pipe_write(struct kiocb *iocb, struct iov_iter *from)
 417 {
 418         struct file *filp = iocb->ki_filp;
 419         struct pipe_inode_info *pipe = filp->private_data;
 420         unsigned int head;
 421         ssize_t ret = 0;
 422         size_t total_len = iov_iter_count(from);
 423         ssize_t chars;
 424         bool was_empty = false;
 425         bool wake_next_writer = false;
 426
 427         /* Null write succeeds. */
 428         if (unlikely(total_len == 0))
 429                 return 0;
 430
 431         __pipe_lock(pipe);
 432
 433         if (!pipe->readers) {
 434                 send_sig(SIGPIPE, current, 0);
 435                 ret = -EPIPE;
 436                 goto out;
 437         }
 438
 439 #ifdef CONFIG_WATCH_QUEUE
 440         if (pipe->watch_queue) {
 441                 ret = -EXDEV;
 442                 goto out;
 443         }
 444 #endif
 445
 446         /*
 447          * If it wasn't empty we try to merge new data into
 448          * the last buffer.
 449          *
 450          * That naturally merges small writes, but it also
 451          * page-aligns the rest of the writes for large writes
 452          * spanning multiple pages.
 453          */
 454         head = pipe->head;
 455         was_empty = pipe_empty(head, pipe->tail);
 456         chars = total_len & (PAGE_SIZE-1);
 457         if (chars && !was_empty) {
 458                 unsigned int mask = pipe->ring_size - 1;
 459                 struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
 460                 int offset = buf->offset + buf->len;
 461
 462                 if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
 463                     offset + chars <= PAGE_SIZE) {
 464                         ret = pipe_buf_confirm(pipe, buf);
 465                         if (ret)
 466                                 goto out;
 467
 468                         ret = copy_page_from_iter(buf->page, offset, chars, from);
 469                         if (unlikely(ret < chars)) {
 470                                 ret = -EFAULT;
 471                                 goto out;
 472                         }
 473
 474                         buf->len += ret;
 475                         if (!iov_iter_count(from))
 476                                 goto out;
 477                 }
 478         }
 479
 480         for (;;) {
 481                 if (!pipe->readers) {
 482                         send_sig(SIGPIPE, current, 0);
 483                         if (!ret)
 484                                 ret = -EPIPE;
 485                         break;
 486                 }
 487
 488                 head = pipe->head;
 489                 if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
 490                         unsigned int mask = pipe->ring_size - 1;
 491                         struct pipe_buffer *buf = &pipe->bufs[head & mask];
 492                         struct page *page = pipe->tmp_page;
 493                         int copied;
 494
 495                         if (!page) {
 496                                 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
 497                                 if (unlikely(!page)) {
 498                                         ret = ret ? : -ENOMEM;
 499                                         break;
 500                                 }
 501                                 pipe->tmp_page = page;
 502                         }
 503
 504                         /* Allocate a slot in the ring in advance and attach an
 505                          * empty buffer.  If we fault or otherwise fail to use
 506                          * it, either the reader will consume it or it'll still
 507                          * be there for the next write.
 508                          */
 509                         spin_lock_irq(&pipe->rd_wait.lock);
 510
 511                         head = pipe->head;
 512                         if (pipe_full(head, pipe->tail, pipe->max_usage)) {
 513                                 spin_unlock_irq(&pipe->rd_wait.lock);
 514                                 continue;
 515                         }
 516
 517                         pipe->head = head + 1;
 518                         spin_unlock_irq(&pipe->rd_wait.lock);
 519
 520                         /* Insert it into the buffer array */
 521                         buf = &pipe->bufs[head & mask];
 522                         buf->page = page;
 523                         buf->ops = &anon_pipe_buf_ops;
 524                         buf->offset = 0;
 525                         buf->len = 0;
 526                         if (is_packetized(filp))
 527                                 buf->flags = PIPE_BUF_FLAG_PACKET;
 528                         else
 529                                 buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
 530                         pipe->tmp_page = NULL;
 531
 532                         copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
 533                         if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
 534                                 if (!ret)
 535                                         ret = -EFAULT;
 536                                 break;
 537                         }
 538                         ret += copied;
 539                         buf->offset = 0;
 540                         buf->len = copied;
 541
 542                         if (!iov_iter_count(from))
 543                                 break;
 544                 }
 545
 546                 if (!pipe_full(head, pipe->tail, pipe->max_usage))
 547                         continue;
 548
 549                 /* Wait for buffer space to become available. */
 550                 if (filp->f_flags & O_NONBLOCK) {
 551                         if (!ret)
 552                                 ret = -EAGAIN;
 553                         break;
 554                 }
 555                 if (signal_pending(current)) {
 556                         if (!ret)
 557                                 ret = -ERESTARTSYS;
 558                         break;
 559                 }
 560
 561                 /*
 562                  * We're going to release the pipe lock and wait for more
 563                  * space. We wake up any readers if necessary, and then
 564                  * after waiting we need to re-check whether the pipe
 565                  * become empty while we dropped the lock.
 566                  */
 567                 __pipe_unlock(pipe);
 568                 if (was_empty)
 569                         wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 570                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 571                 wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
 572                 __pipe_lock(pipe);
 573                 was_empty = pipe_empty(pipe->head, pipe->tail);
 574                 wake_next_writer = true;
 575         }
 576 out:
 577         if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
 578                 wake_next_writer = false;
 579         __pipe_unlock(pipe);
 580
 581         /*
 582          * If we do do a wakeup event, we do a 'sync' wakeup, because we
 583          * want the reader to start processing things asap, rather than
 584          * leave the data pending.
 585          *
 586          * This is particularly important for small writes, because of
 587          * how (for example) the GNU make jobserver uses small writes to
 588          * wake up pending jobs
 589          *
 590          * Epoll nonsensically wants a wakeup whether the pipe
 591          * was already empty or not.
 592          */
 593         if (was_empty || pipe->poll_usage)
 594                 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 595         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 596         if (wake_next_writer)
 597                 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 598         if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
 599                 int err = file_update_time(filp);
 600                 if (err)
 601                         ret = err;
 602                 sb_end_write(file_inode(filp)->i_sb);
 603         }
 604         return ret;
 605 }
 606
 607 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 608 {
 609         struct pipe_inode_info *pipe = filp->private_data;
 610         unsigned int count, head, tail, mask;
 611
 612         switch (cmd) {
 613         case FIONREAD:
 614                 __pipe_lock(pipe);
 615                 count = 0;
 616                 head = pipe->head;
 617                 tail = pipe->tail;
 618                 mask = pipe->ring_size - 1;
 619
 620                 while (tail != head) {
 621                         count += pipe->bufs[tail & mask].len;
 622                         tail++;
 623                 }
 624                 __pipe_unlock(pipe);
 625
 626                 return put_user(count, (int __user *)arg);
 627
 628 #ifdef CONFIG_WATCH_QUEUE
 629         case IOC_WATCH_QUEUE_SET_SIZE: {
 630                 int ret;
 631                 __pipe_lock(pipe);
 632                 ret = watch_queue_set_size(pipe, arg);
 633                 __pipe_unlock(pipe);
 634                 return ret;
 635         }
 636
 637         case IOC_WATCH_QUEUE_SET_FILTER:
 638                 return watch_queue_set_filter(
 639                         pipe, (struct watch_notification_filter __user *)arg);
 640 #endif
 641
 642         default:
 643                 return -ENOIOCTLCMD;
 644         }
 645 }
 646
 647 /* No kernel lock held - fine */
 648 static __poll_t
 649 pipe_poll(struct file *filp, poll_table *wait)
 650 {
 651         __poll_t mask;
 652         struct pipe_inode_info *pipe = filp->private_data;
 653         unsigned int head, tail;
 654
 655         /* Epoll has some historical nasty semantics, this enables them */
 656         WRITE_ONCE(pipe->poll_usage, true);
 657
 658         /*
 659          * Reading pipe state only -- no need for acquiring the semaphore.
 660          *
 661          * But because this is racy, the code has to add the
 662          * entry to the poll table _first_ ..
 663          */
 664         if (filp->f_mode & FMODE_READ)
 665                 poll_wait(filp, &pipe->rd_wait, wait);
 666         if (filp->f_mode & FMODE_WRITE)
 667                 poll_wait(filp, &pipe->wr_wait, wait);
 668
 669         /*
 670          * .. and only then can you do the racy tests. That way,
 671          * if something changes and you got it wrong, the poll
 672          * table entry will wake you up and fix it.
 673          */
 674         head = READ_ONCE(pipe->head);
 675         tail = READ_ONCE(pipe->tail);
 676
 677         mask = 0;
 678         if (filp->f_mode & FMODE_READ) {
 679                 if (!pipe_empty(head, tail))
 680                         mask |= EPOLLIN | EPOLLRDNORM;
 681                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 682                         mask |= EPOLLHUP;
 683         }
 684
 685         if (filp->f_mode & FMODE_WRITE) {
 686                 if (!pipe_full(head, tail, pipe->max_usage))
 687                         mask |= EPOLLOUT | EPOLLWRNORM;
 688                 /*
 689                  * Most Unices do not set EPOLLERR for FIFOs but on Linux they
 690                  * behave exactly like pipes for poll().
 691                  */
 692                 if (!pipe->readers)
 693                         mask |= EPOLLERR;
 694         }
 695
 696         return mask;
 697 }
 698
 699 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
 700 {
 701         int kill = 0;
 702
 703         spin_lock(&inode->i_lock);
 704         if (!--pipe->files) {
 705                 inode->i_pipe = NULL;
 706                 kill = 1;
 707         }
 708         spin_unlock(&inode->i_lock);
 709
 710         if (kill)
 711                 free_pipe_info(pipe);
 712 }
 713
 714 static int
 715 pipe_release(struct inode *inode, struct file *file)
 716 {
 717         struct pipe_inode_info *pipe = file->private_data;
 718
 719         __pipe_lock(pipe);
 720         if (file->f_mode & FMODE_READ)
 721                 pipe->readers--;
 722         if (file->f_mode & FMODE_WRITE)
 723                 pipe->writers--;
 724
 725         /* Was that the last reader or writer, but not the other side? */
 726         if (!pipe->readers != !pipe->writers) {
 727                 wake_up_interruptible_all(&pipe->rd_wait);
 728                 wake_up_interruptible_all(&pipe->wr_wait);
 729                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 730                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 731         }
 732         __pipe_unlock(pipe);
 733
 734         put_pipe_info(inode, pipe);
 735         return 0;
 736 }
 737
 738 static int
 739 pipe_fasync(int fd, struct file *filp, int on)
 740 {
 741         struct pipe_inode_info *pipe = filp->private_data;
 742         int retval = 0;
 743
 744         __pipe_lock(pipe);
 745         if (filp->f_mode & FMODE_READ)
 746                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 747         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 748                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 749                 if (retval < 0 && (filp->f_mode & FMODE_READ))
 750                         /* this can happen only if on == T */
 751                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 752         }
 753         __pipe_unlock(pipe);
 754         return retval;
 755 }
 756
 757 unsigned long account_pipe_buffers(struct user_struct *user,
 758                                    unsigned long old, unsigned long new)
 759 {
 760         return atomic_long_add_return(new - old, &user->pipe_bufs);
 761 }
 762
 763 bool too_many_pipe_buffers_soft(unsigned long user_bufs)
 764 {
 765         unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
 766
 767         return soft_limit && user_bufs > soft_limit;
 768 }
 769
 770 bool too_many_pipe_buffers_hard(unsigned long user_bufs)
 771 {
 772         unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
 773
 774         return hard_limit && user_bufs > hard_limit;
 775 }
 776
 777 bool pipe_is_unprivileged_user(void)
 778 {
 779         return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
 780 }
 781
 782 struct pipe_inode_info *alloc_pipe_info(void)
 783 {
 784         struct pipe_inode_info *pipe;
 785         unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
 786         struct user_struct *user = get_current_user();
 787         unsigned long user_bufs;
 788         unsigned int max_size = READ_ONCE(pipe_max_size);
 789
 790         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
 791         if (pipe == NULL)
 792                 goto out_free_uid;
 793
 794         if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
 795                 pipe_bufs = max_size >> PAGE_SHIFT;
 796
 797         user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
 798
 799         if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
 800                 user_bufs = account_pipe_buffers(user, pipe_bufs, PIPE_MIN_DEF_BUFFERS);
 801                 pipe_bufs = PIPE_MIN_DEF_BUFFERS;
 802         }
 803
 804         if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
 805                 goto out_revert_acct;
 806
 807         pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
 808                              GFP_KERNEL_ACCOUNT);
 809
 810         if (pipe->bufs) {
 811                 init_waitqueue_head(&pipe->rd_wait);
 812                 init_waitqueue_head(&pipe->wr_wait);
 813                 pipe->r_counter = pipe->w_counter = 1;
 814                 pipe->max_usage = pipe_bufs;
 815                 pipe->ring_size = pipe_bufs;
 816                 pipe->nr_accounted = pipe_bufs;
 817                 pipe->user = user;
 818                 mutex_init(&pipe->mutex);
 819                 return pipe;
 820         }
 821
 822 out_revert_acct:
 823         (void) account_pipe_buffers(user, pipe_bufs, 0);
 824         kfree(pipe);
 825 out_free_uid:
 826         free_uid(user);
 827         return NULL;
 828 }
 829
 830 void free_pipe_info(struct pipe_inode_info *pipe)
 831 {
 832         unsigned int i;
 833
 834 #ifdef CONFIG_WATCH_QUEUE
 835         if (pipe->watch_queue)
 836                 watch_queue_clear(pipe->watch_queue);
 837 #endif
 838
 839         (void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
 840         free_uid(pipe->user);
 841         for (i = 0; i < pipe->ring_size; i++) {
 842                 struct pipe_buffer *buf = pipe->bufs + i;
 843                 if (buf->ops)
 844                         pipe_buf_release(pipe, buf);
 845         }
 846 #ifdef CONFIG_WATCH_QUEUE
 847         if (pipe->watch_queue)
 848                 put_watch_queue(pipe->watch_queue);
 849 #endif
 850         if (pipe->tmp_page)
 851                 __free_page(pipe->tmp_page);
 852         kfree(pipe->bufs);
 853         kfree(pipe);
 854 }
 855
 856 static struct vfsmount *pipe_mnt __read_mostly;
 857
 858 /*
 859  * pipefs_dname() is called from d_path().
 860  */
 861 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 862 {
 863         return dynamic_dname(buffer, buflen, "pipe:[%lu]",
 864                                 d_inode(dentry)->i_ino);
 865 }
 866
 867 static const struct dentry_operations pipefs_dentry_operations = {
 868         .d_dname        = pipefs_dname,
 869 };
 870
 871 static struct inode * get_pipe_inode(void)
 872 {
 873         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 874         struct pipe_inode_info *pipe;
 875
 876         if (!inode)
 877                 goto fail_inode;
 878
 879         inode->i_ino = get_next_ino();
 880
 881         pipe = alloc_pipe_info();
 882         if (!pipe)
 883                 goto fail_iput;
 884
 885         inode->i_pipe = pipe;
 886         pipe->files = 2;
 887         pipe->readers = pipe->writers = 1;
 888         inode->i_fop = &pipefifo_fops;
 889
 890         /*
 891          * Mark the inode dirty from the very beginning,
 892          * that way it will never be moved to the dirty
 893          * list because "mark_inode_dirty()" will think
 894          * that it already _is_ on the dirty list.
 895          */
 896         inode->i_state = I_DIRTY;
 897         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 898         inode->i_uid = current_fsuid();
 899         inode->i_gid = current_fsgid();
 900         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 901
 902         return inode;
 903
 904 fail_iput:
 905         iput(inode);
 906
 907 fail_inode:
 908         return NULL;
 909 }
 910
 911 int create_pipe_files(struct file **res, int flags)
 912 {
 913         struct inode *inode = get_pipe_inode();
 914         struct file *f;
 915         int error;
 916
 917         if (!inode)
 918                 return -ENFILE;
 919
 920         if (flags & O_NOTIFICATION_PIPE) {
 921                 error = watch_queue_init(inode->i_pipe);
 922                 if (error) {
 923                         free_pipe_info(inode->i_pipe);
 924                         iput(inode);
 925                         return error;
 926                 }
 927         }
 928
 929         f = alloc_file_pseudo(inode, pipe_mnt, "",
 930                                 O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
 931                                 &pipefifo_fops);
 932         if (IS_ERR(f)) {
 933                 free_pipe_info(inode->i_pipe);
 934                 iput(inode);
 935                 return PTR_ERR(f);
 936         }
 937
 938         f->private_data = inode->i_pipe;
 939
 940         res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
 941                                   &pipefifo_fops);
 942         if (IS_ERR(res[0])) {
 943                 put_pipe_info(inode, inode->i_pipe);
 944                 fput(f);
 945                 return PTR_ERR(res[0]);
 946         }
 947         res[0]->private_data = inode->i_pipe;
 948         res[1] = f;
 949         stream_open(inode, res[0]);
 950         stream_open(inode, res[1]);
 951         return 0;
 952 }
 953
 954 static int __do_pipe_flags(int *fd, struct file **files, int flags)
 955 {
 956         int error;
 957         int fdw, fdr;
 958
 959         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
 960                 return -EINVAL;
 961
 962         error = create_pipe_files(files, flags);
 963         if (error)
 964                 return error;
 965
 966         error = get_unused_fd_flags(flags);
 967         if (error < 0)
 968                 goto err_read_pipe;
 969         fdr = error;
 970
 971         error = get_unused_fd_flags(flags);
 972         if (error < 0)
 973                 goto err_fdr;
 974         fdw = error;
 975
 976         audit_fd_pair(fdr, fdw);
 977         fd[0] = fdr;
 978         fd[1] = fdw;
 979         return 0;
 980
 981  err_fdr:
 982         put_unused_fd(fdr);
 983  err_read_pipe:
 984         fput(files[0]);
 985         fput(files[1]);
 986         return error;
 987 }
 988
 989 int do_pipe_flags(int *fd, int flags)
 990 {
 991         struct file *files[2];
 992         int error = __do_pipe_flags(fd, files, flags);
 993         if (!error) {
 994                 fd_install(fd[0], files[0]);
 995                 fd_install(fd[1], files[1]);
 996         }
 997         return error;
 998 }
 999
1000 /*
1001  * sys_pipe() is the normal C calling standard for creating
1002  * a pipe. It's not the way Unix traditionally does this, though.
1003  */
1004 static int do_pipe2(int __user *fildes, int flags)
1005 {
1006         struct file *files[2];
1007         int fd[2];
1008         int error;
1009
1010         error = __do_pipe_flags(fd, files, flags);
1011         if (!error) {
1012                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
1013                         fput(files[0]);
1014                         fput(files[1]);
1015                         put_unused_fd(fd[0]);
1016                         put_unused_fd(fd[1]);
1017                         error = -EFAULT;
1018                 } else {
1019                         fd_install(fd[0], files[0]);
1020                         fd_install(fd[1], files[1]);
1021                 }
1022         }
1023         return error;
1024 }
1025
1026 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1027 {
1028         return do_pipe2(fildes, flags);
1029 }
1030
1031 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1032 {
1033         return do_pipe2(fildes, 0);
1034 }
1035
1036 /*
1037  * This is the stupid "wait for pipe to be readable or writable"
1038  * model.
1039  *
1040  * See pipe_read/write() for the proper kind of exclusive wait,
1041  * but that requires that we wake up any other readers/writers
1042  * if we then do not end up reading everything (ie the whole
1043  * "wake_next_reader/writer" logic in pipe_read/write()).
1044  */
1045 void pipe_wait_readable(struct pipe_inode_info *pipe)
1046 {
1047         pipe_unlock(pipe);
1048         wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
1049         pipe_lock(pipe);
1050 }
1051
1052 void pipe_wait_writable(struct pipe_inode_info *pipe)
1053 {
1054         pipe_unlock(pipe);
1055         wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
1056         pipe_lock(pipe);
1057 }
1058
1059 /*
1060  * This depends on both the wait (here) and the wakeup (wake_up_partner)
1061  * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
1062  * race with the count check and waitqueue prep.
1063  *
1064  * Normally in order to avoid races, you'd do the prepare_to_wait() first,
1065  * then check the condition you're waiting for, and only then sleep. But
1066  * because of the pipe lock, we can check the condition before being on
1067  * the wait queue.
1068  *
1069  * We use the 'rd_wait' waitqueue for pipe partner waiting.
1070  */
1071 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1072 {
1073         DEFINE_WAIT(rdwait);
1074         int cur = *cnt;
1075
1076         while (cur == *cnt) {
1077                 prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
1078                 pipe_unlock(pipe);
1079                 schedule();
1080                 finish_wait(&pipe->rd_wait, &rdwait);
1081                 pipe_lock(pipe);
1082                 if (signal_pending(current))
1083                         break;
1084         }
1085         return cur == *cnt ? -ERESTARTSYS : 0;
1086 }
1087
1088 static void wake_up_partner(struct pipe_inode_info *pipe)
1089 {
1090         wake_up_interruptible_all(&pipe->rd_wait);
1091 }
1092
1093 static int fifo_open(struct inode *inode, struct file *filp)
1094 {
1095         struct pipe_inode_info *pipe;
1096         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1097         int ret;
1098
1099         filp->f_version = 0;
1100
1101         spin_lock(&inode->i_lock);
1102         if (inode->i_pipe) {
1103                 pipe = inode->i_pipe;
1104                 pipe->files++;
1105                 spin_unlock(&inode->i_lock);
1106         } else {
1107                 spin_unlock(&inode->i_lock);
1108                 pipe = alloc_pipe_info();
1109                 if (!pipe)
1110                         return -ENOMEM;
1111                 pipe->files = 1;
1112                 spin_lock(&inode->i_lock);
1113                 if (unlikely(inode->i_pipe)) {
1114                         inode->i_pipe->files++;
1115                         spin_unlock(&inode->i_lock);
1116                         free_pipe_info(pipe);
1117                         pipe = inode->i_pipe;
1118                 } else {
1119                         inode->i_pipe = pipe;
1120                         spin_unlock(&inode->i_lock);
1121                 }
1122         }
1123         filp->private_data = pipe;
1124         /* OK, we have a pipe and it's pinned down */
1125
1126         __pipe_lock(pipe);
1127
1128         /* We can only do regular read/write on fifos */
1129         stream_open(inode, filp);
1130
1131         switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
1132         case FMODE_READ:
1133         /*
1134          *  O_RDONLY
1135          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
1136          *  opened, even when there is no process writing the FIFO.
1137          */
1138                 pipe->r_counter++;
1139                 if (pipe->readers++ == 0)
1140                         wake_up_partner(pipe);
1141
1142                 if (!is_pipe && !pipe->writers) {
1143                         if ((filp->f_flags & O_NONBLOCK)) {
1144                                 /* suppress EPOLLHUP until we have
1145                                  * seen a writer */
1146                                 filp->f_version = pipe->w_counter;
1147                         } else {
1148                                 if (wait_for_partner(pipe, &pipe->w_counter))
1149                                         goto err_rd;
1150                         }
1151                 }
1152                 break;
1153
1154         case FMODE_WRITE:
1155         /*
1156          *  O_WRONLY
1157          *  POSIX.1 says that O_NONBLOCK means return -1 with
1158          *  errno=ENXIO when there is no process reading the FIFO.
1159          */
1160                 ret = -ENXIO;
1161                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1162                         goto err;
1163
1164                 pipe->w_counter++;
1165                 if (!pipe->writers++)
1166                         wake_up_partner(pipe);
1167
1168                 if (!is_pipe && !pipe->readers) {
1169                         if (wait_for_partner(pipe, &pipe->r_counter))
1170                                 goto err_wr;
1171                 }
1172                 break;
1173
1174         case FMODE_READ | FMODE_WRITE:
1175         /*
1176          *  O_RDWR
1177          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1178          *  This implementation will NEVER block on a O_RDWR open, since
1179          *  the process can at least talk to itself.
1180          */
1181
1182                 pipe->readers++;
1183                 pipe->writers++;
1184                 pipe->r_counter++;
1185                 pipe->w_counter++;
1186                 if (pipe->readers == 1 || pipe->writers == 1)
1187                         wake_up_partner(pipe);
1188                 break;
1189
1190         default:
1191                 ret = -EINVAL;
1192                 goto err;
1193         }
1194
1195         /* Ok! */
1196         __pipe_unlock(pipe);
1197         return 0;
1198
1199 err_rd:
1200         if (!--pipe->readers)
1201                 wake_up_interruptible(&pipe->wr_wait);
1202         ret = -ERESTARTSYS;
1203         goto err;
1204
1205 err_wr:
1206         if (!--pipe->writers)
1207                 wake_up_interruptible_all(&pipe->rd_wait);
1208         ret = -ERESTARTSYS;
1209         goto err;
1210
1211 err:
1212         __pipe_unlock(pipe);
1213
1214         put_pipe_info(inode, pipe);
1215         return ret;
1216 }
1217
1218 const struct file_operations pipefifo_fops = {
1219         .open           = fifo_open,
1220         .llseek         = no_llseek,
1221         .read_iter      = pipe_read,
1222         .write_iter     = pipe_write,
1223         .poll           = pipe_poll,
1224         .unlocked_ioctl = pipe_ioctl,
1225         .release        = pipe_release,
1226         .fasync         = pipe_fasync,
1227         .splice_write   = iter_file_splice_write,
1228 };
1229
1230 /*
1231  * Currently we rely on the pipe array holding a power-of-2 number
1232  * of pages. Returns 0 on error.
1233  */
1234 unsigned int round_pipe_size(unsigned long size)
1235 {
1236         if (size > (1U << 31))
1237                 return 0;
1238
1239         /* Minimum pipe size, as required by POSIX */
1240         if (size < PAGE_SIZE)
1241                 return PAGE_SIZE;
1242
1243         return roundup_pow_of_two(size);
1244 }
1245
1246 /*
1247  * Resize the pipe ring to a number of slots.
1248  *
1249  * Note the pipe can be reduced in capacity, but only if the current
1250  * occupancy doesn't exceed nr_slots; if it does, EBUSY will be
1251  * returned instead.
1252  */
1253 int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
1254 {
1255         struct pipe_buffer *bufs;
1256         unsigned int head, tail, mask, n;
1257
1258         bufs = kcalloc(nr_slots, sizeof(*bufs),
1259                        GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1260         if (unlikely(!bufs))
1261                 return -ENOMEM;
1262
1263         spin_lock_irq(&pipe->rd_wait.lock);
1264         mask = pipe->ring_size - 1;
1265         head = pipe->head;
1266         tail = pipe->tail;
1267
1268         n = pipe_occupancy(head, tail);
1269         if (nr_slots < n) {
1270                 spin_unlock_irq(&pipe->rd_wait.lock);
1271                 kfree(bufs);
1272                 return -EBUSY;
1273         }
1274
1275         /*
1276          * The pipe array wraps around, so just start the new one at zero
1277          * and adjust the indices.
1278          */
1279         if (n > 0) {
1280                 unsigned int h = head & mask;
1281                 unsigned int t = tail & mask;
1282                 if (h > t) {
1283                         memcpy(bufs, pipe->bufs + t,
1284                                n * sizeof(struct pipe_buffer));
1285                 } else {
1286                         unsigned int tsize = pipe->ring_size - t;
1287                         if (h > 0)
1288                                 memcpy(bufs + tsize, pipe->bufs,
1289                                        h * sizeof(struct pipe_buffer));
1290                         memcpy(bufs, pipe->bufs + t,
1291                                tsize * sizeof(struct pipe_buffer));
1292                 }
1293         }
1294
1295         head = n;
1296         tail = 0;
1297
1298         kfree(pipe->bufs);
1299         pipe->bufs = bufs;
1300         pipe->ring_size = nr_slots;
1301         if (pipe->max_usage > nr_slots)
1302                 pipe->max_usage = nr_slots;
1303         pipe->tail = tail;
1304         pipe->head = head;
1305
1306         spin_unlock_irq(&pipe->rd_wait.lock);
1307
1308         /* This might have made more room for writers */
1309         wake_up_interruptible(&pipe->wr_wait);
1310         return 0;
1311 }
1312
1313 /*
1314  * Allocate a new array of pipe buffers and copy the info over. Returns the
1315  * pipe size if successful, or return -ERROR on error.
1316  */
1317 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1318 {
1319         unsigned long user_bufs;
1320         unsigned int nr_slots, size;
1321         long ret = 0;
1322
1323 #ifdef CONFIG_WATCH_QUEUE
1324         if (pipe->watch_queue)
1325                 return -EBUSY;
1326 #endif
1327
1328         size = round_pipe_size(arg);
1329         nr_slots = size >> PAGE_SHIFT;
1330
1331         if (!nr_slots)
1332                 return -EINVAL;
1333
1334         /*
1335          * If trying to increase the pipe capacity, check that an
1336          * unprivileged user is not trying to exceed various limits
1337          * (soft limit check here, hard limit check just below).
1338          * Decreasing the pipe capacity is always permitted, even
1339          * if the user is currently over a limit.
1340          */
1341         if (nr_slots > pipe->max_usage &&
1342                         size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1343                 return -EPERM;
1344
1345         user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
1346
1347         if (nr_slots > pipe->max_usage &&
1348                         (too_many_pipe_buffers_hard(user_bufs) ||
1349                          too_many_pipe_buffers_soft(user_bufs)) &&
1350                         pipe_is_unprivileged_user()) {
1351                 ret = -EPERM;
1352                 goto out_revert_acct;
1353         }
1354
1355         ret = pipe_resize_ring(pipe, nr_slots);
1356         if (ret < 0)
1357                 goto out_revert_acct;
1358
1359         pipe->max_usage = nr_slots;
1360         pipe->nr_accounted = nr_slots;
1361         return pipe->max_usage * PAGE_SIZE;
1362
1363 out_revert_acct:
1364         (void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
1365         return ret;
1366 }
1367
1368 /*
1369  * Note that i_pipe and i_cdev share the same location, so checking ->i_pipe is
1370  * not enough to verify that this is a pipe.
1371  */
1372 struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
1373 {
1374         struct pipe_inode_info *pipe = file->private_data;
1375
1376         if (file->f_op != &pipefifo_fops || !pipe)
1377                 return NULL;
1378 #ifdef CONFIG_WATCH_QUEUE
1379         if (for_splice && pipe->watch_queue)
1380                 return NULL;
1381 #endif
1382         return pipe;
1383 }
1384
1385 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1386 {
1387         struct pipe_inode_info *pipe;
1388         long ret;
1389
1390         pipe = get_pipe_info(file, false);
1391         if (!pipe)
1392                 return -EBADF;
1393
1394         __pipe_lock(pipe);
1395
1396         switch (cmd) {
1397         case F_SETPIPE_SZ:
1398                 ret = pipe_set_size(pipe, arg);
1399                 break;
1400         case F_GETPIPE_SZ:
1401                 ret = pipe->max_usage * PAGE_SIZE;
1402                 break;
1403         default:
1404                 ret = -EINVAL;
1405                 break;
1406         }
1407
1408         __pipe_unlock(pipe);
1409         return ret;
1410 }
1411
1412 static const struct super_operations pipefs_ops = {
1413         .destroy_inode = free_inode_nonrcu,
1414         .statfs = simple_statfs,
1415 };
1416
1417 /*
1418  * pipefs should _never_ be mounted by userland - too much of security hassle,
1419  * no real gain from having the whole whorehouse mounted. So we don't need
1420  * any operations on the root directory. However, we need a non-trivial
1421  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1422  */
1423
1424 static int pipefs_init_fs_context(struct fs_context *fc)
1425 {
1426         struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
1427         if (!ctx)
1428                 return -ENOMEM;
1429         ctx->ops = &pipefs_ops;
1430         ctx->dops = &pipefs_dentry_operations;
1431         return 0;
1432 }
1433
1434 static struct file_system_type pipe_fs_type = {
1435         .name           = "pipefs",
1436         .init_fs_context = pipefs_init_fs_context,
1437         .kill_sb        = kill_anon_super,
1438 };
1439
1440 #ifdef CONFIG_SYSCTL
1441 static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
1442                                         unsigned int *valp,
1443                                         int write, void *data)
1444 {
1445         if (write) {
1446                 unsigned int val;
1447
1448                 val = round_pipe_size(*lvalp);
1449                 if (val == 0)
1450                         return -EINVAL;
1451
1452                 *valp = val;
1453         } else {
1454                 unsigned int val = *valp;
1455                 *lvalp = (unsigned long) val;
1456         }
1457
1458         return 0;
1459 }
1460
1461 static int proc_dopipe_max_size(struct ctl_table *table, int write,
1462                                 void *buffer, size_t *lenp, loff_t *ppos)
1463 {
1464         return do_proc_douintvec(table, write, buffer, lenp, ppos,
1465                                  do_proc_dopipe_max_size_conv, NULL);
1466 }
1467
1468 static struct ctl_table fs_pipe_sysctls[] = {
1469         {
1470                 .procname       = "pipe-max-size",
1471                 .data           = &pipe_max_size,
1472                 .maxlen         = sizeof(pipe_max_size),
1473                 .mode           = 0644,
1474                 .proc_handler   = proc_dopipe_max_size,
1475         },
1476         {
1477                 .procname       = "pipe-user-pages-hard",
1478                 .data           = &pipe_user_pages_hard,
1479                 .maxlen         = sizeof(pipe_user_pages_hard),
1480                 .mode           = 0644,
1481                 .proc_handler   = proc_doulongvec_minmax,
1482         },
1483         {
1484                 .procname       = "pipe-user-pages-soft",
1485                 .data           = &pipe_user_pages_soft,
1486                 .maxlen         = sizeof(pipe_user_pages_soft),
1487                 .mode           = 0644,
1488                 .proc_handler   = proc_doulongvec_minmax,
1489         },
1490         { }
1491 };
1492 #endif
1493
1494 static int __init init_pipe_fs(void)
1495 {
1496         int err = register_filesystem(&pipe_fs_type);
1497
1498         if (!err) {
1499                 pipe_mnt = kern_mount(&pipe_fs_type);
1500                 if (IS_ERR(pipe_mnt)) {
1501                         err = PTR_ERR(pipe_mnt);
1502                         unregister_filesystem(&pipe_fs_type);
1503                 }
1504         }
1505 #ifdef CONFIG_SYSCTL
1506         register_sysctl_init("fs", fs_pipe_sysctls);
1507 #endif
1508         return err;
1509 }
1510
1511 fs_initcall(init_pipe_fs);