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  * New pipe buffers will be restricted to this size while the user is exceeding
  36  * their pipe buffer quota. The general pipe use case needs at least two
  37  * buffers: one for data yet to be read, and one for new data. If this is less
  38  * than two, then a write to a non-empty pipe may block even if the pipe is not
  39  * full. This can occur with GNU make jobserver or similar uses of pipes as
  40  * semaphores: multiple processes may be waiting to write tokens back to the
  41  * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.
  42  *
  43  * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their
  44  * own risk, namely: pipe writes to non-full pipes may block until the pipe is
  45  * emptied.
  46  */
  47 #define PIPE_MIN_DEF_BUFFERS 2
  48
  49 /*
  50  * The max size that a non-root user is allowed to grow the pipe. Can
  51  * be set by root in /proc/sys/fs/pipe-max-size
  52  */
  53 unsigned int pipe_max_size = 1048576;
  54
  55 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
  56  * matches default values.
  57  */
  58 unsigned long pipe_user_pages_hard;
  59 unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
  60
  61 /*
  62  * We use head and tail indices that aren't masked off, except at the point of
  63  * dereference, but rather they're allowed to wrap naturally.  This means there
  64  * isn't a dead spot in the buffer, but the ring has to be a power of two and
  65  * <= 2^31.
  66  * -- David Howells 2019-09-23.
  67  *
  68  * Reads with count = 0 should always return 0.
  69  * -- Julian Bradfield 1999-06-07.
  70  *
  71  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  72  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  73  *
  74  * pipe_read & write cleanup
  75  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  76  */
  77
  78 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  79 {
  80         if (pipe->files)
  81                 mutex_lock_nested(&pipe->mutex, subclass);
  82 }
  83
  84 void pipe_lock(struct pipe_inode_info *pipe)
  85 {
  86         /*
  87          * pipe_lock() nests non-pipe inode locks (for writing to a file)
  88          */
  89         pipe_lock_nested(pipe, I_MUTEX_PARENT);
  90 }
  91 EXPORT_SYMBOL(pipe_lock);
  92
  93 void pipe_unlock(struct pipe_inode_info *pipe)
  94 {
  95         if (pipe->files)
  96                 mutex_unlock(&pipe->mutex);
  97 }
  98 EXPORT_SYMBOL(pipe_unlock);
  99
 100 static inline void __pipe_lock(struct pipe_inode_info *pipe)
 101 {
 102         mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
 103 }
 104
 105 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
 106 {
 107         mutex_unlock(&pipe->mutex);
 108 }
 109
 110 void pipe_double_lock(struct pipe_inode_info *pipe1,
 111                       struct pipe_inode_info *pipe2)
 112 {
 113         BUG_ON(pipe1 == pipe2);
 114
 115         if (pipe1 < pipe2) {
 116                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
 117                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
 118         } else {
 119                 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
 120                 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
 121         }
 122 }
 123
 124 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 125                                   struct pipe_buffer *buf)
 126 {
 127         struct page *page = buf->page;
 128
 129         /*
 130          * If nobody else uses this page, and we don't already have a
 131          * temporary page, let's keep track of it as a one-deep
 132          * allocation cache. (Otherwise just release our reference to it)
 133          */
 134         if (page_count(page) == 1 && !pipe->tmp_page)
 135                 pipe->tmp_page = page;
 136         else
 137                 put_page(page);
 138 }
 139
 140 static bool anon_pipe_buf_try_steal(struct pipe_inode_info *pipe,
 141                 struct pipe_buffer *buf)
 142 {
 143         struct page *page = buf->page;
 144
 145         if (page_count(page) != 1)
 146                 return false;
 147         memcg_kmem_uncharge_page(page, 0);
 148         __SetPageLocked(page);
 149         return true;
 150 }
 151
 152 /**
 153  * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
 154  * @pipe:       the pipe that the buffer belongs to
 155  * @buf:        the buffer to attempt to steal
 156  *
 157  * Description:
 158  *      This function attempts to steal the &struct page attached to
 159  *      @buf. If successful, this function returns 0 and returns with
 160  *      the page locked. The caller may then reuse the page for whatever
 161  *      he wishes; the typical use is insertion into a different file
 162  *      page cache.
 163  */
 164 bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe,
 165                 struct pipe_buffer *buf)
 166 {
 167         struct page *page = buf->page;
 168
 169         /*
 170          * A reference of one is golden, that means that the owner of this
 171          * page is the only one holding a reference to it. lock the page
 172          * and return OK.
 173          */
 174         if (page_count(page) == 1) {
 175                 lock_page(page);
 176                 return true;
 177         }
 178         return false;
 179 }
 180 EXPORT_SYMBOL(generic_pipe_buf_try_steal);
 181
 182 /**
 183  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 184  * @pipe:       the pipe that the buffer belongs to
 185  * @buf:        the buffer to get a reference to
 186  *
 187  * Description:
 188  *      This function grabs an extra reference to @buf. It's used in
 189  *      the tee() system call, when we duplicate the buffers in one
 190  *      pipe into another.
 191  */
 192 bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 193 {
 194         return try_get_page(buf->page);
 195 }
 196 EXPORT_SYMBOL(generic_pipe_buf_get);
 197
 198 /**
 199  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 200  * @pipe:       the pipe that the buffer belongs to
 201  * @buf:        the buffer to put a reference to
 202  *
 203  * Description:
 204  *      This function releases a reference to @buf.
 205  */
 206 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 207                               struct pipe_buffer *buf)
 208 {
 209         put_page(buf->page);
 210 }
 211 EXPORT_SYMBOL(generic_pipe_buf_release);
 212
 213 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 214         .release        = anon_pipe_buf_release,
 215         .try_steal      = anon_pipe_buf_try_steal,
 216         .get            = generic_pipe_buf_get,
 217 };
 218
 219 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
 220 static inline bool pipe_readable(const struct pipe_inode_info *pipe)
 221 {
 222         unsigned int head = READ_ONCE(pipe->head);
 223         unsigned int tail = READ_ONCE(pipe->tail);
 224         unsigned int writers = READ_ONCE(pipe->writers);
 225
 226         return !pipe_empty(head, tail) || !writers;
 227 }
 228
 229 static ssize_t
 230 pipe_read(struct kiocb *iocb, struct iov_iter *to)
 231 {
 232         size_t total_len = iov_iter_count(to);
 233         struct file *filp = iocb->ki_filp;
 234         struct pipe_inode_info *pipe = filp->private_data;
 235         bool was_full, wake_next_reader = false;
 236         ssize_t ret;
 237
 238         /* Null read succeeds. */
 239         if (unlikely(total_len == 0))
 240                 return 0;
 241
 242         ret = 0;
 243         __pipe_lock(pipe);
 244
 245         /*
 246          * We only wake up writers if the pipe was full when we started
 247          * reading in order to avoid unnecessary wakeups.
 248          *
 249          * But when we do wake up writers, we do so using a sync wakeup
 250          * (WF_SYNC), because we want them to get going and generate more
 251          * data for us.
 252          */
 253         was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
 254         for (;;) {
 255                 unsigned int head = pipe->head;
 256                 unsigned int tail = pipe->tail;
 257                 unsigned int mask = pipe->ring_size - 1;
 258
 259 #ifdef CONFIG_WATCH_QUEUE
 260                 if (pipe->note_loss) {
 261                         struct watch_notification n;
 262
 263                         if (total_len < 8) {
 264                                 if (ret == 0)
 265                                         ret = -ENOBUFS;
 266                                 break;
 267                         }
 268
 269                         n.type = WATCH_TYPE_META;
 270                         n.subtype = WATCH_META_LOSS_NOTIFICATION;
 271                         n.info = watch_sizeof(n);
 272                         if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
 273                                 if (ret == 0)
 274                                         ret = -EFAULT;
 275                                 break;
 276                         }
 277                         ret += sizeof(n);
 278                         total_len -= sizeof(n);
 279                         pipe->note_loss = false;
 280                 }
 281 #endif
 282
 283                 if (!pipe_empty(head, tail)) {
 284                         struct pipe_buffer *buf = &pipe->bufs[tail & mask];
 285                         size_t chars = buf->len;
 286                         size_t written;
 287                         int error;
 288
 289                         if (chars > total_len) {
 290                                 if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
 291                                         if (ret == 0)
 292                                                 ret = -ENOBUFS;
 293                                         break;
 294                                 }
 295                                 chars = total_len;
 296                         }
 297
 298                         error = pipe_buf_confirm(pipe, buf);
 299                         if (error) {
 300                                 if (!ret)
 301                                         ret = error;
 302                                 break;
 303                         }
 304
 305                         written = copy_page_to_iter(buf->page, buf->offset, chars, to);
 306                         if (unlikely(written < chars)) {
 307                                 if (!ret)
 308                                         ret = -EFAULT;
 309                                 break;
 310                         }
 311                         ret += chars;
 312                         buf->offset += chars;
 313                         buf->len -= chars;
 314
 315                         /* Was it a packet buffer? Clean up and exit */
 316                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 317                                 total_len = chars;
 318                                 buf->len = 0;
 319                         }
 320
 321                         if (!buf->len) {
 322                                 pipe_buf_release(pipe, buf);
 323                                 spin_lock_irq(&pipe->rd_wait.lock);
 324 #ifdef CONFIG_WATCH_QUEUE
 325                                 if (buf->flags & PIPE_BUF_FLAG_LOSS)
 326                                         pipe->note_loss = true;
 327 #endif
 328                                 tail++;
 329                                 pipe->tail = tail;
 330                                 spin_unlock_irq(&pipe->rd_wait.lock);
 331                         }
 332                         total_len -= chars;
 333                         if (!total_len)
 334                                 break;  /* common path: read succeeded */
 335                         if (!pipe_empty(head, tail))    /* More to do? */
 336                                 continue;
 337                 }
 338
 339                 if (!pipe->writers)
 340                         break;
 341                 if (ret)
 342                         break;
 343                 if (filp->f_flags & O_NONBLOCK) {
 344                         ret = -EAGAIN;
 345                         break;
 346                 }
 347                 __pipe_unlock(pipe);
 348
 349                 /*
 350                  * We only get here if we didn't actually read anything.
 351                  *
 352                  * However, we could have seen (and removed) a zero-sized
 353                  * pipe buffer, and might have made space in the buffers
 354                  * that way.
 355                  *
 356                  * You can't make zero-sized pipe buffers by doing an empty
 357                  * write (not even in packet mode), but they can happen if
 358                  * the writer gets an EFAULT when trying to fill a buffer
 359                  * that already got allocated and inserted in the buffer
 360                  * array.
 361                  *
 362                  * So we still need to wake up any pending writers in the
 363                  * _very_ unlikely case that the pipe was full, but we got
 364                  * no data.
 365                  */
 366                 if (unlikely(was_full))
 367                         wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 368                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 369
 370                 /*
 371                  * But because we didn't read anything, at this point we can
 372                  * just return directly with -ERESTARTSYS if we're interrupted,
 373                  * since we've done any required wakeups and there's no need
 374                  * to mark anything accessed. And we've dropped the lock.
 375                  */
 376                 if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0)
 377                         return -ERESTARTSYS;
 378
 379                 __pipe_lock(pipe);
 380                 was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
 381                 wake_next_reader = true;
 382         }
 383         if (pipe_empty(pipe->head, pipe->tail))
 384                 wake_next_reader = false;
 385         __pipe_unlock(pipe);
 386
 387         if (was_full)
 388                 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 389         if (wake_next_reader)
 390                 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 391         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 392         if (ret > 0)
 393                 file_accessed(filp);
 394         return ret;
 395 }
 396
 397 static inline int is_packetized(struct file *file)
 398 {
 399         return (file->f_flags & O_DIRECT) != 0;
 400 }
 401
 402 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
 403 static inline bool pipe_writable(const struct pipe_inode_info *pipe)
 404 {
 405         unsigned int head = READ_ONCE(pipe->head);
 406         unsigned int tail = READ_ONCE(pipe->tail);
 407         unsigned int max_usage = READ_ONCE(pipe->max_usage);
 408
 409         return !pipe_full(head, tail, max_usage) ||
 410                 !READ_ONCE(pipe->readers);
 411 }
 412
 413 static ssize_t
 414 pipe_write(struct kiocb *iocb, struct iov_iter *from)
 415 {
 416         struct file *filp = iocb->ki_filp;
 417         struct pipe_inode_info *pipe = filp->private_data;
 418         unsigned int head;
 419         ssize_t ret = 0;
 420         size_t total_len = iov_iter_count(from);
 421         ssize_t chars;
 422         bool was_empty = false;
 423         bool wake_next_writer = false;
 424
 425         /* Null write succeeds. */
 426         if (unlikely(total_len == 0))
 427                 return 0;
 428
 429         __pipe_lock(pipe);
 430
 431         if (!pipe->readers) {
 432                 send_sig(SIGPIPE, current, 0);
 433                 ret = -EPIPE;
 434                 goto out;
 435         }
 436
 437 #ifdef CONFIG_WATCH_QUEUE
 438         if (pipe->watch_queue) {
 439                 ret = -EXDEV;
 440                 goto out;
 441         }
 442 #endif
 443
 444         /*
 445          * If it wasn't empty we try to merge new data into
 446          * the last buffer.
 447          *
 448          * That naturally merges small writes, but it also
 449          * page-aligns the rest of the writes for large writes
 450          * spanning multiple pages.
 451          */
 452         head = pipe->head;
 453         was_empty = pipe_empty(head, pipe->tail);
 454         chars = total_len & (PAGE_SIZE-1);
 455         if (chars && !was_empty) {
 456                 unsigned int mask = pipe->ring_size - 1;
 457                 struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
 458                 int offset = buf->offset + buf->len;
 459
 460                 if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
 461                     offset + chars <= PAGE_SIZE) {
 462                         ret = pipe_buf_confirm(pipe, buf);
 463                         if (ret)
 464                                 goto out;
 465
 466                         ret = copy_page_from_iter(buf->page, offset, chars, from);
 467                         if (unlikely(ret < chars)) {
 468                                 ret = -EFAULT;
 469                                 goto out;
 470                         }
 471
 472                         buf->len += ret;
 473                         if (!iov_iter_count(from))
 474                                 goto out;
 475                 }
 476         }
 477
 478         for (;;) {
 479                 if (!pipe->readers) {
 480                         send_sig(SIGPIPE, current, 0);
 481                         if (!ret)
 482                                 ret = -EPIPE;
 483                         break;
 484                 }
 485
 486                 head = pipe->head;
 487                 if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
 488                         unsigned int mask = pipe->ring_size - 1;
 489                         struct pipe_buffer *buf = &pipe->bufs[head & mask];
 490                         struct page *page = pipe->tmp_page;
 491                         int copied;
 492
 493                         if (!page) {
 494                                 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
 495                                 if (unlikely(!page)) {
 496                                         ret = ret ? : -ENOMEM;
 497                                         break;
 498                                 }
 499                                 pipe->tmp_page = page;
 500                         }
 501
 502                         /* Allocate a slot in the ring in advance and attach an
 503                          * empty buffer.  If we fault or otherwise fail to use
 504                          * it, either the reader will consume it or it'll still
 505                          * be there for the next write.
 506                          */
 507                         spin_lock_irq(&pipe->rd_wait.lock);
 508
 509                         head = pipe->head;
 510                         if (pipe_full(head, pipe->tail, pipe->max_usage)) {
 511                                 spin_unlock_irq(&pipe->rd_wait.lock);
 512                                 continue;
 513                         }
 514
 515                         pipe->head = head + 1;
 516                         spin_unlock_irq(&pipe->rd_wait.lock);
 517
 518                         /* Insert it into the buffer array */
 519                         buf = &pipe->bufs[head & mask];
 520                         buf->page = page;
 521                         buf->ops = &anon_pipe_buf_ops;
 522                         buf->offset = 0;
 523                         buf->len = 0;
 524                         if (is_packetized(filp))
 525                                 buf->flags = PIPE_BUF_FLAG_PACKET;
 526                         else
 527                                 buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
 528                         pipe->tmp_page = NULL;
 529
 530                         copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
 531                         if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
 532                                 if (!ret)
 533                                         ret = -EFAULT;
 534                                 break;
 535                         }
 536                         ret += copied;
 537                         buf->offset = 0;
 538                         buf->len = copied;
 539
 540                         if (!iov_iter_count(from))
 541                                 break;
 542                 }
 543
 544                 if (!pipe_full(head, pipe->tail, pipe->max_usage))
 545                         continue;
 546
 547                 /* Wait for buffer space to become available. */
 548                 if (filp->f_flags & O_NONBLOCK) {
 549                         if (!ret)
 550                                 ret = -EAGAIN;
 551                         break;
 552                 }
 553                 if (signal_pending(current)) {
 554                         if (!ret)
 555                                 ret = -ERESTARTSYS;
 556                         break;
 557                 }
 558
 559                 /*
 560                  * We're going to release the pipe lock and wait for more
 561                  * space. We wake up any readers if necessary, and then
 562                  * after waiting we need to re-check whether the pipe
 563                  * become empty while we dropped the lock.
 564                  */
 565                 __pipe_unlock(pipe);
 566                 if (was_empty)
 567                         wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 568                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 569                 wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
 570                 __pipe_lock(pipe);
 571                 was_empty = pipe_empty(pipe->head, pipe->tail);
 572                 wake_next_writer = true;
 573         }
 574 out:
 575         if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
 576                 wake_next_writer = false;
 577         __pipe_unlock(pipe);
 578
 579         /*
 580          * If we do do a wakeup event, we do a 'sync' wakeup, because we
 581          * want the reader to start processing things asap, rather than
 582          * leave the data pending.
 583          *
 584          * This is particularly important for small writes, because of
 585          * how (for example) the GNU make jobserver uses small writes to
 586          * wake up pending jobs
 587          *
 588          * Epoll nonsensically wants a wakeup whether the pipe
 589          * was already empty or not.
 590          */
 591         if (was_empty || pipe->poll_usage)
 592                 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 593         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 594         if (wake_next_writer)
 595                 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 596         if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
 597                 int err = file_update_time(filp);
 598                 if (err)
 599                         ret = err;
 600                 sb_end_write(file_inode(filp)->i_sb);
 601         }
 602         return ret;
 603 }
 604
 605 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 606 {
 607         struct pipe_inode_info *pipe = filp->private_data;
 608         int count, head, tail, mask;
 609
 610         switch (cmd) {
 611         case FIONREAD:
 612                 __pipe_lock(pipe);
 613                 count = 0;
 614                 head = pipe->head;
 615                 tail = pipe->tail;
 616                 mask = pipe->ring_size - 1;
 617
 618                 while (tail != head) {
 619                         count += pipe->bufs[tail & mask].len;
 620                         tail++;
 621                 }
 622                 __pipe_unlock(pipe);
 623
 624                 return put_user(count, (int __user *)arg);
 625
 626 #ifdef CONFIG_WATCH_QUEUE
 627         case IOC_WATCH_QUEUE_SET_SIZE: {
 628                 int ret;
 629                 __pipe_lock(pipe);
 630                 ret = watch_queue_set_size(pipe, arg);
 631                 __pipe_unlock(pipe);
 632                 return ret;
 633         }
 634
 635         case IOC_WATCH_QUEUE_SET_FILTER:
 636                 return watch_queue_set_filter(
 637                         pipe, (struct watch_notification_filter __user *)arg);
 638 #endif
 639
 640         default:
 641                 return -ENOIOCTLCMD;
 642         }
 643 }
 644
 645 /* No kernel lock held - fine */
 646 static __poll_t
 647 pipe_poll(struct file *filp, poll_table *wait)
 648 {
 649         __poll_t mask;
 650         struct pipe_inode_info *pipe = filp->private_data;
 651         unsigned int head, tail;
 652
 653         /* Epoll has some historical nasty semantics, this enables them */
 654         pipe->poll_usage = 1;
 655
 656         /*
 657          * Reading pipe state only -- no need for acquiring the semaphore.
 658          *
 659          * But because this is racy, the code has to add the
 660          * entry to the poll table _first_ ..
 661          */
 662         if (filp->f_mode & FMODE_READ)
 663                 poll_wait(filp, &pipe->rd_wait, wait);
 664         if (filp->f_mode & FMODE_WRITE)
 665                 poll_wait(filp, &pipe->wr_wait, wait);
 666
 667         /*
 668          * .. and only then can you do the racy tests. That way,
 669          * if something changes and you got it wrong, the poll
 670          * table entry will wake you up and fix it.
 671          */
 672         head = READ_ONCE(pipe->head);
 673         tail = READ_ONCE(pipe->tail);
 674
 675         mask = 0;
 676         if (filp->f_mode & FMODE_READ) {
 677                 if (!pipe_empty(head, tail))
 678                         mask |= EPOLLIN | EPOLLRDNORM;
 679                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 680                         mask |= EPOLLHUP;
 681         }
 682
 683         if (filp->f_mode & FMODE_WRITE) {
 684                 if (!pipe_full(head, tail, pipe->max_usage))
 685                         mask |= EPOLLOUT | EPOLLWRNORM;
 686                 /*
 687                  * Most Unices do not set EPOLLERR for FIFOs but on Linux they
 688                  * behave exactly like pipes for poll().
 689                  */
 690                 if (!pipe->readers)
 691                         mask |= EPOLLERR;
 692         }
 693
 694         return mask;
 695 }
 696
 697 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
 698 {
 699         int kill = 0;
 700
 701         spin_lock(&inode->i_lock);
 702         if (!--pipe->files) {
 703                 inode->i_pipe = NULL;
 704                 kill = 1;
 705         }
 706         spin_unlock(&inode->i_lock);
 707
 708         if (kill)
 709                 free_pipe_info(pipe);
 710 }
 711
 712 static int
 713 pipe_release(struct inode *inode, struct file *file)
 714 {
 715         struct pipe_inode_info *pipe = file->private_data;
 716
 717         __pipe_lock(pipe);
 718         if (file->f_mode & FMODE_READ)
 719                 pipe->readers--;
 720         if (file->f_mode & FMODE_WRITE)
 721                 pipe->writers--;
 722
 723         /* Was that the last reader or writer, but not the other side? */
 724         if (!pipe->readers != !pipe->writers) {
 725                 wake_up_interruptible_all(&pipe->rd_wait);
 726                 wake_up_interruptible_all(&pipe->wr_wait);
 727                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 728                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 729         }
 730         __pipe_unlock(pipe);
 731
 732         put_pipe_info(inode, pipe);
 733         return 0;
 734 }
 735
 736 static int
 737 pipe_fasync(int fd, struct file *filp, int on)
 738 {
 739         struct pipe_inode_info *pipe = filp->private_data;
 740         int retval = 0;
 741
 742         __pipe_lock(pipe);
 743         if (filp->f_mode & FMODE_READ)
 744                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 745         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 746                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 747                 if (retval < 0 && (filp->f_mode & FMODE_READ))
 748                         /* this can happen only if on == T */
 749                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 750         }
 751         __pipe_unlock(pipe);
 752         return retval;
 753 }
 754
 755 unsigned long account_pipe_buffers(struct user_struct *user,
 756                                    unsigned long old, unsigned long new)
 757 {
 758         return atomic_long_add_return(new - old, &user->pipe_bufs);
 759 }
 760
 761 bool too_many_pipe_buffers_soft(unsigned long user_bufs)
 762 {
 763         unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
 764
 765         return soft_limit && user_bufs > soft_limit;
 766 }
 767
 768 bool too_many_pipe_buffers_hard(unsigned long user_bufs)
 769 {
 770         unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
 771
 772         return hard_limit && user_bufs > hard_limit;
 773 }
 774
 775 bool pipe_is_unprivileged_user(void)
 776 {
 777         return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
 778 }
 779
 780 struct pipe_inode_info *alloc_pipe_info(void)
 781 {
 782         struct pipe_inode_info *pipe;
 783         unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
 784         struct user_struct *user = get_current_user();
 785         unsigned long user_bufs;
 786         unsigned int max_size = READ_ONCE(pipe_max_size);
 787
 788         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
 789         if (pipe == NULL)
 790                 goto out_free_uid;
 791
 792         if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
 793                 pipe_bufs = max_size >> PAGE_SHIFT;
 794
 795         user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
 796
 797         if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
 798                 user_bufs = account_pipe_buffers(user, pipe_bufs, PIPE_MIN_DEF_BUFFERS);
 799                 pipe_bufs = PIPE_MIN_DEF_BUFFERS;
 800         }
 801
 802         if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
 803                 goto out_revert_acct;
 804
 805         pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
 806                              GFP_KERNEL_ACCOUNT);
 807
 808         if (pipe->bufs) {
 809                 init_waitqueue_head(&pipe->rd_wait);
 810                 init_waitqueue_head(&pipe->wr_wait);
 811                 pipe->r_counter = pipe->w_counter = 1;
 812                 pipe->max_usage = pipe_bufs;
 813                 pipe->ring_size = pipe_bufs;
 814                 pipe->nr_accounted = pipe_bufs;
 815                 pipe->user = user;
 816                 mutex_init(&pipe->mutex);
 817                 return pipe;
 818         }
 819
 820 out_revert_acct:
 821         (void) account_pipe_buffers(user, pipe_bufs, 0);
 822         kfree(pipe);
 823 out_free_uid:
 824         free_uid(user);
 825         return NULL;
 826 }
 827
 828 void free_pipe_info(struct pipe_inode_info *pipe)
 829 {
 830         int i;
 831
 832 #ifdef CONFIG_WATCH_QUEUE
 833         if (pipe->watch_queue) {
 834                 watch_queue_clear(pipe->watch_queue);
 835                 put_watch_queue(pipe->watch_queue);
 836         }
 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         if (pipe->tmp_page)
 847                 __free_page(pipe->tmp_page);
 848         kfree(pipe->bufs);
 849         kfree(pipe);
 850 }
 851
 852 static struct vfsmount *pipe_mnt __read_mostly;
 853
 854 /*
 855  * pipefs_dname() is called from d_path().
 856  */
 857 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 858 {
 859         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 860                                 d_inode(dentry)->i_ino);
 861 }
 862
 863 static const struct dentry_operations pipefs_dentry_operations = {
 864         .d_dname        = pipefs_dname,
 865 };
 866
 867 static struct inode * get_pipe_inode(void)
 868 {
 869         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 870         struct pipe_inode_info *pipe;
 871
 872         if (!inode)
 873                 goto fail_inode;
 874
 875         inode->i_ino = get_next_ino();
 876
 877         pipe = alloc_pipe_info();
 878         if (!pipe)
 879                 goto fail_iput;
 880
 881         inode->i_pipe = pipe;
 882         pipe->files = 2;
 883         pipe->readers = pipe->writers = 1;
 884         inode->i_fop = &pipefifo_fops;
 885
 886         /*
 887          * Mark the inode dirty from the very beginning,
 888          * that way it will never be moved to the dirty
 889          * list because "mark_inode_dirty()" will think
 890          * that it already _is_ on the dirty list.
 891          */
 892         inode->i_state = I_DIRTY;
 893         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 894         inode->i_uid = current_fsuid();
 895         inode->i_gid = current_fsgid();
 896         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 897
 898         return inode;
 899
 900 fail_iput:
 901         iput(inode);
 902
 903 fail_inode:
 904         return NULL;
 905 }
 906
 907 int create_pipe_files(struct file **res, int flags)
 908 {
 909         struct inode *inode = get_pipe_inode();
 910         struct file *f;
 911         int error;
 912
 913         if (!inode)
 914                 return -ENFILE;
 915
 916         if (flags & O_NOTIFICATION_PIPE) {
 917                 error = watch_queue_init(inode->i_pipe);
 918                 if (error) {
 919                         free_pipe_info(inode->i_pipe);
 920                         iput(inode);
 921                         return error;
 922                 }
 923         }
 924
 925         f = alloc_file_pseudo(inode, pipe_mnt, "",
 926                                 O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
 927                                 &pipefifo_fops);
 928         if (IS_ERR(f)) {
 929                 free_pipe_info(inode->i_pipe);
 930                 iput(inode);
 931                 return PTR_ERR(f);
 932         }
 933
 934         f->private_data = inode->i_pipe;
 935
 936         res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
 937                                   &pipefifo_fops);
 938         if (IS_ERR(res[0])) {
 939                 put_pipe_info(inode, inode->i_pipe);
 940                 fput(f);
 941                 return PTR_ERR(res[0]);
 942         }
 943         res[0]->private_data = inode->i_pipe;
 944         res[1] = f;
 945         stream_open(inode, res[0]);
 946         stream_open(inode, res[1]);
 947         return 0;
 948 }
 949
 950 static int __do_pipe_flags(int *fd, struct file **files, int flags)
 951 {
 952         int error;
 953         int fdw, fdr;
 954
 955         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
 956                 return -EINVAL;
 957
 958         error = create_pipe_files(files, flags);
 959         if (error)
 960                 return error;
 961
 962         error = get_unused_fd_flags(flags);
 963         if (error < 0)
 964                 goto err_read_pipe;
 965         fdr = error;
 966
 967         error = get_unused_fd_flags(flags);
 968         if (error < 0)
 969                 goto err_fdr;
 970         fdw = error;
 971
 972         audit_fd_pair(fdr, fdw);
 973         fd[0] = fdr;
 974         fd[1] = fdw;
 975         return 0;
 976
 977  err_fdr:
 978         put_unused_fd(fdr);
 979  err_read_pipe:
 980         fput(files[0]);
 981         fput(files[1]);
 982         return error;
 983 }
 984
 985 int do_pipe_flags(int *fd, int flags)
 986 {
 987         struct file *files[2];
 988         int error = __do_pipe_flags(fd, files, flags);
 989         if (!error) {
 990                 fd_install(fd[0], files[0]);
 991                 fd_install(fd[1], files[1]);
 992         }
 993         return error;
 994 }
 995
 996 /*
 997  * sys_pipe() is the normal C calling standard for creating
 998  * a pipe. It's not the way Unix traditionally does this, though.
 999  */
1000 static int do_pipe2(int __user *fildes, int flags)
1001 {
1002         struct file *files[2];
1003         int fd[2];
1004         int error;
1005
1006         error = __do_pipe_flags(fd, files, flags);
1007         if (!error) {
1008                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
1009                         fput(files[0]);
1010                         fput(files[1]);
1011                         put_unused_fd(fd[0]);
1012                         put_unused_fd(fd[1]);
1013                         error = -EFAULT;
1014                 } else {
1015                         fd_install(fd[0], files[0]);
1016                         fd_install(fd[1], files[1]);
1017                 }
1018         }
1019         return error;
1020 }
1021
1022 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1023 {
1024         return do_pipe2(fildes, flags);
1025 }
1026
1027 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1028 {
1029         return do_pipe2(fildes, 0);
1030 }
1031
1032 /*
1033  * This is the stupid "wait for pipe to be readable or writable"
1034  * model.
1035  *
1036  * See pipe_read/write() for the proper kind of exclusive wait,
1037  * but that requires that we wake up any other readers/writers
1038  * if we then do not end up reading everything (ie the whole
1039  * "wake_next_reader/writer" logic in pipe_read/write()).
1040  */
1041 void pipe_wait_readable(struct pipe_inode_info *pipe)
1042 {
1043         pipe_unlock(pipe);
1044         wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
1045         pipe_lock(pipe);
1046 }
1047
1048 void pipe_wait_writable(struct pipe_inode_info *pipe)
1049 {
1050         pipe_unlock(pipe);
1051         wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
1052         pipe_lock(pipe);
1053 }
1054
1055 /*
1056  * This depends on both the wait (here) and the wakeup (wake_up_partner)
1057  * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
1058  * race with the count check and waitqueue prep.
1059  *
1060  * Normally in order to avoid races, you'd do the prepare_to_wait() first,
1061  * then check the condition you're waiting for, and only then sleep. But
1062  * because of the pipe lock, we can check the condition before being on
1063  * the wait queue.
1064  *
1065  * We use the 'rd_wait' waitqueue for pipe partner waiting.
1066  */
1067 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1068 {
1069         DEFINE_WAIT(rdwait);
1070         int cur = *cnt;
1071
1072         while (cur == *cnt) {
1073                 prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
1074                 pipe_unlock(pipe);
1075                 schedule();
1076                 finish_wait(&pipe->rd_wait, &rdwait);
1077                 pipe_lock(pipe);
1078                 if (signal_pending(current))
1079                         break;
1080         }
1081         return cur == *cnt ? -ERESTARTSYS : 0;
1082 }
1083
1084 static void wake_up_partner(struct pipe_inode_info *pipe)
1085 {
1086         wake_up_interruptible_all(&pipe->rd_wait);
1087 }
1088
1089 static int fifo_open(struct inode *inode, struct file *filp)
1090 {
1091         struct pipe_inode_info *pipe;
1092         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1093         int ret;
1094
1095         filp->f_version = 0;
1096
1097         spin_lock(&inode->i_lock);
1098         if (inode->i_pipe) {
1099                 pipe = inode->i_pipe;
1100                 pipe->files++;
1101                 spin_unlock(&inode->i_lock);
1102         } else {
1103                 spin_unlock(&inode->i_lock);
1104                 pipe = alloc_pipe_info();
1105                 if (!pipe)
1106                         return -ENOMEM;
1107                 pipe->files = 1;
1108                 spin_lock(&inode->i_lock);
1109                 if (unlikely(inode->i_pipe)) {
1110                         inode->i_pipe->files++;
1111                         spin_unlock(&inode->i_lock);
1112                         free_pipe_info(pipe);
1113                         pipe = inode->i_pipe;
1114                 } else {
1115                         inode->i_pipe = pipe;
1116                         spin_unlock(&inode->i_lock);
1117                 }
1118         }
1119         filp->private_data = pipe;
1120         /* OK, we have a pipe and it's pinned down */
1121
1122         __pipe_lock(pipe);
1123
1124         /* We can only do regular read/write on fifos */
1125         stream_open(inode, filp);
1126
1127         switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
1128         case FMODE_READ:
1129         /*
1130          *  O_RDONLY
1131          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
1132          *  opened, even when there is no process writing the FIFO.
1133          */
1134                 pipe->r_counter++;
1135                 if (pipe->readers++ == 0)
1136                         wake_up_partner(pipe);
1137
1138                 if (!is_pipe && !pipe->writers) {
1139                         if ((filp->f_flags & O_NONBLOCK)) {
1140                                 /* suppress EPOLLHUP until we have
1141                                  * seen a writer */
1142                                 filp->f_version = pipe->w_counter;
1143                         } else {
1144                                 if (wait_for_partner(pipe, &pipe->w_counter))
1145                                         goto err_rd;
1146                         }
1147                 }
1148                 break;
1149
1150         case FMODE_WRITE:
1151         /*
1152          *  O_WRONLY
1153          *  POSIX.1 says that O_NONBLOCK means return -1 with
1154          *  errno=ENXIO when there is no process reading the FIFO.
1155          */
1156                 ret = -ENXIO;
1157                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1158                         goto err;
1159
1160                 pipe->w_counter++;
1161                 if (!pipe->writers++)
1162                         wake_up_partner(pipe);
1163
1164                 if (!is_pipe && !pipe->readers) {
1165                         if (wait_for_partner(pipe, &pipe->r_counter))
1166                                 goto err_wr;
1167                 }
1168                 break;
1169
1170         case FMODE_READ | FMODE_WRITE:
1171         /*
1172          *  O_RDWR
1173          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1174          *  This implementation will NEVER block on a O_RDWR open, since
1175          *  the process can at least talk to itself.
1176          */
1177
1178                 pipe->readers++;
1179                 pipe->writers++;
1180                 pipe->r_counter++;
1181                 pipe->w_counter++;
1182                 if (pipe->readers == 1 || pipe->writers == 1)
1183                         wake_up_partner(pipe);
1184                 break;
1185
1186         default:
1187                 ret = -EINVAL;
1188                 goto err;
1189         }
1190
1191         /* Ok! */
1192         __pipe_unlock(pipe);
1193         return 0;
1194
1195 err_rd:
1196         if (!--pipe->readers)
1197                 wake_up_interruptible(&pipe->wr_wait);
1198         ret = -ERESTARTSYS;
1199         goto err;
1200
1201 err_wr:
1202         if (!--pipe->writers)
1203                 wake_up_interruptible_all(&pipe->rd_wait);
1204         ret = -ERESTARTSYS;
1205         goto err;
1206
1207 err:
1208         __pipe_unlock(pipe);
1209
1210         put_pipe_info(inode, pipe);
1211         return ret;
1212 }
1213
1214 const struct file_operations pipefifo_fops = {
1215         .open           = fifo_open,
1216         .llseek         = no_llseek,
1217         .read_iter      = pipe_read,
1218         .write_iter     = pipe_write,
1219         .poll           = pipe_poll,
1220         .unlocked_ioctl = pipe_ioctl,
1221         .release        = pipe_release,
1222         .fasync         = pipe_fasync,
1223         .splice_write   = iter_file_splice_write,
1224 };
1225
1226 /*
1227  * Currently we rely on the pipe array holding a power-of-2 number
1228  * of pages. Returns 0 on error.
1229  */
1230 unsigned int round_pipe_size(unsigned long size)
1231 {
1232         if (size > (1U << 31))
1233                 return 0;
1234
1235         /* Minimum pipe size, as required by POSIX */
1236         if (size < PAGE_SIZE)
1237                 return PAGE_SIZE;
1238
1239         return roundup_pow_of_two(size);
1240 }
1241
1242 /*
1243  * Resize the pipe ring to a number of slots.
1244  */
1245 int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
1246 {
1247         struct pipe_buffer *bufs;
1248         unsigned int head, tail, mask, n;
1249
1250         /*
1251          * We can shrink the pipe, if arg is greater than the ring occupancy.
1252          * Since we don't expect a lot of shrink+grow operations, just free and
1253          * allocate again like we would do for growing.  If the pipe currently
1254          * contains more buffers than arg, then return busy.
1255          */
1256         mask = pipe->ring_size - 1;
1257         head = pipe->head;
1258         tail = pipe->tail;
1259         n = pipe_occupancy(pipe->head, pipe->tail);
1260         if (nr_slots < n)
1261                 return -EBUSY;
1262
1263         bufs = kcalloc(nr_slots, sizeof(*bufs),
1264                        GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1265         if (unlikely(!bufs))
1266                 return -ENOMEM;
1267
1268         /*
1269          * The pipe array wraps around, so just start the new one at zero
1270          * and adjust the indices.
1271          */
1272         if (n > 0) {
1273                 unsigned int h = head & mask;
1274                 unsigned int t = tail & mask;
1275                 if (h > t) {
1276                         memcpy(bufs, pipe->bufs + t,
1277                                n * sizeof(struct pipe_buffer));
1278                 } else {
1279                         unsigned int tsize = pipe->ring_size - t;
1280                         if (h > 0)
1281                                 memcpy(bufs + tsize, pipe->bufs,
1282                                        h * sizeof(struct pipe_buffer));
1283                         memcpy(bufs, pipe->bufs + t,
1284                                tsize * sizeof(struct pipe_buffer));
1285                 }
1286         }
1287
1288         head = n;
1289         tail = 0;
1290
1291         kfree(pipe->bufs);
1292         pipe->bufs = bufs;
1293         pipe->ring_size = nr_slots;
1294         if (pipe->max_usage > nr_slots)
1295                 pipe->max_usage = nr_slots;
1296         pipe->tail = tail;
1297         pipe->head = head;
1298
1299         /* This might have made more room for writers */
1300         wake_up_interruptible(&pipe->wr_wait);
1301         return 0;
1302 }
1303
1304 /*
1305  * Allocate a new array of pipe buffers and copy the info over. Returns the
1306  * pipe size if successful, or return -ERROR on error.
1307  */
1308 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1309 {
1310         unsigned long user_bufs;
1311         unsigned int nr_slots, size;
1312         long ret = 0;
1313
1314 #ifdef CONFIG_WATCH_QUEUE
1315         if (pipe->watch_queue)
1316                 return -EBUSY;
1317 #endif
1318
1319         size = round_pipe_size(arg);
1320         nr_slots = size >> PAGE_SHIFT;
1321
1322         if (!nr_slots)
1323                 return -EINVAL;
1324
1325         /*
1326          * If trying to increase the pipe capacity, check that an
1327          * unprivileged user is not trying to exceed various limits
1328          * (soft limit check here, hard limit check just below).
1329          * Decreasing the pipe capacity is always permitted, even
1330          * if the user is currently over a limit.
1331          */
1332         if (nr_slots > pipe->max_usage &&
1333                         size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1334                 return -EPERM;
1335
1336         user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
1337
1338         if (nr_slots > pipe->max_usage &&
1339                         (too_many_pipe_buffers_hard(user_bufs) ||
1340                          too_many_pipe_buffers_soft(user_bufs)) &&
1341                         pipe_is_unprivileged_user()) {
1342                 ret = -EPERM;
1343                 goto out_revert_acct;
1344         }
1345
1346         ret = pipe_resize_ring(pipe, nr_slots);
1347         if (ret < 0)
1348                 goto out_revert_acct;
1349
1350         pipe->max_usage = nr_slots;
1351         pipe->nr_accounted = nr_slots;
1352         return pipe->max_usage * PAGE_SIZE;
1353
1354 out_revert_acct:
1355         (void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
1356         return ret;
1357 }
1358
1359 /*
1360  * Note that i_pipe and i_cdev share the same location, so checking ->i_pipe is
1361  * not enough to verify that this is a pipe.
1362  */
1363 struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
1364 {
1365         struct pipe_inode_info *pipe = file->private_data;
1366
1367         if (file->f_op != &pipefifo_fops || !pipe)
1368                 return NULL;
1369 #ifdef CONFIG_WATCH_QUEUE
1370         if (for_splice && pipe->watch_queue)
1371                 return NULL;
1372 #endif
1373         return pipe;
1374 }
1375
1376 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1377 {
1378         struct pipe_inode_info *pipe;
1379         long ret;
1380
1381         pipe = get_pipe_info(file, false);
1382         if (!pipe)
1383                 return -EBADF;
1384
1385         __pipe_lock(pipe);
1386
1387         switch (cmd) {
1388         case F_SETPIPE_SZ:
1389                 ret = pipe_set_size(pipe, arg);
1390                 break;
1391         case F_GETPIPE_SZ:
1392                 ret = pipe->max_usage * PAGE_SIZE;
1393                 break;
1394         default:
1395                 ret = -EINVAL;
1396                 break;
1397         }
1398
1399         __pipe_unlock(pipe);
1400         return ret;
1401 }
1402
1403 static const struct super_operations pipefs_ops = {
1404         .destroy_inode = free_inode_nonrcu,
1405         .statfs = simple_statfs,
1406 };
1407
1408 /*
1409  * pipefs should _never_ be mounted by userland - too much of security hassle,
1410  * no real gain from having the whole whorehouse mounted. So we don't need
1411  * any operations on the root directory. However, we need a non-trivial
1412  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1413  */
1414
1415 static int pipefs_init_fs_context(struct fs_context *fc)
1416 {
1417         struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
1418         if (!ctx)
1419                 return -ENOMEM;
1420         ctx->ops = &pipefs_ops;
1421         ctx->dops = &pipefs_dentry_operations;
1422         return 0;
1423 }
1424
1425 static struct file_system_type pipe_fs_type = {
1426         .name           = "pipefs",
1427         .init_fs_context = pipefs_init_fs_context,
1428         .kill_sb        = kill_anon_super,
1429 };
1430
1431 static int __init init_pipe_fs(void)
1432 {
1433         int err = register_filesystem(&pipe_fs_type);
1434
1435         if (!err) {
1436                 pipe_mnt = kern_mount(&pipe_fs_type);
1437                 if (IS_ERR(pipe_mnt)) {
1438                         err = PTR_ERR(pipe_mnt);
1439                         unregister_filesystem(&pipe_fs_type);
1440                 }
1441         }
1442         return err;
1443 }
1444
1445 fs_initcall(init_pipe_fs);