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