fs/pipe.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/fs/pipe.c
   4  *
   5  *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
   6  */
   7
   8 #include <linux/mm.h>
   9 #include <linux/file.h>
  10 #include <linux/poll.h>
  11 #include <linux/slab.h>
  12 #include <linux/module.h>
  13 #include <linux/init.h>
  14 #include <linux/fs.h>
  15 #include <linux/log2.h>
  16 #include <linux/mount.h>
  17 #include <linux/pseudo_fs.h>
  18 #include <linux/magic.h>
  19 #include <linux/pipe_fs_i.h>
  20 #include <linux/uio.h>
  21 #include <linux/highmem.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/audit.h>
  24 #include <linux/syscalls.h>
  25 #include <linux/fcntl.h>
  26 #include <linux/memcontrol.h>
  27 #include <linux/watch_queue.h>
  28 #include <linux/sysctl.h>
  29
  30 #include <linux/uaccess.h>
  31 #include <asm/ioctls.h>
  32
  33 #include "internal.h"
  34
  35 /*
  36  * New pipe buffers will be restricted to this size while the user is exceeding
  37  * their pipe buffer quota. The general pipe use case needs at least two
  38  * buffers: one for data yet to be read, and one for new data. If this is less
  39  * than two, then a write to a non-empty pipe may block even if the pipe is not
  40  * full. This can occur with GNU make jobserver or similar uses of pipes as
  41  * semaphores: multiple processes may be waiting to write tokens back to the
  42  * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.
  43  *
  44  * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their
  45  * own risk, namely: pipe writes to non-full pipes may block until the pipe is
  46  * emptied.
  47  */
  48 #define PIPE_MIN_DEF_BUFFERS 2
  49
  50 /*
  51  * The max size that a non-root user is allowed to grow the pipe. Can
  52  * be set by root in /proc/sys/fs/pipe-max-size
  53  */
  54 static unsigned int pipe_max_size = 1048576;
  55
  56 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
  57  * matches default values.
  58  */
  59 static unsigned long pipe_user_pages_hard;
  60 static unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
  61
  62 /*
  63  * We use head and tail indices that aren't masked off, except at the point of
  64  * dereference, but rather they're allowed to wrap naturally.  This means there
  65  * isn't a dead spot in the buffer, but the ring has to be a power of two and
  66  * <= 2^31.
  67  * -- David Howells 2019-09-23.
  68  *
  69  * Reads with count = 0 should always return 0.
  70  * -- Julian Bradfield 1999-06-07.
  71  *
  72  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  73  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  74  *
  75  * pipe_read & write cleanup
  76  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  77  */
  78
  79 #define cmp_int(l, r)           ((l > r) - (l < r))
  80
  81 #ifdef CONFIG_PROVE_LOCKING
  82 static int pipe_lock_cmp_fn(const struct lockdep_map *a,
  83                             const struct lockdep_map *b)
  84 {
  85         return cmp_int((unsigned long) a, (unsigned long) b);
  86 }
  87 #endif
  88
  89 void pipe_lock(struct pipe_inode_info *pipe)
  90 {
  91         if (pipe->files)
  92                 mutex_lock(&pipe->mutex);
  93 }
  94 EXPORT_SYMBOL(pipe_lock);
  95
  96 void pipe_unlock(struct pipe_inode_info *pipe)
  97 {
  98         if (pipe->files)
  99                 mutex_unlock(&pipe->mutex);
 100 }
 101 EXPORT_SYMBOL(pipe_unlock);
 102
 103 void pipe_double_lock(struct pipe_inode_info *pipe1,
 104                       struct pipe_inode_info *pipe2)
 105 {
 106         BUG_ON(pipe1 == pipe2);
 107
 108         if (pipe1 > pipe2)
 109                 swap(pipe1, pipe2);
 110
 111         pipe_lock(pipe1);
 112         pipe_lock(pipe2);
 113 }
 114
 115 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 116                                   struct pipe_buffer *buf)
 117 {
 118         struct page *page = buf->page;
 119
 120         /*
 121          * If nobody else uses this page, and we don't already have a
 122          * temporary page, let's keep track of it as a one-deep
 123          * allocation cache. (Otherwise just release our reference to it)
 124          */
 125         if (page_count(page) == 1 && !pipe->tmp_page)
 126                 pipe->tmp_page = page;
 127         else
 128                 put_page(page);
 129 }
 130
 131 static bool anon_pipe_buf_try_steal(struct pipe_inode_info *pipe,
 132                 struct pipe_buffer *buf)
 133 {
 134         struct page *page = buf->page;
 135
 136         if (page_count(page) != 1)
 137                 return false;
 138         memcg_kmem_uncharge_page(page, 0);
 139         __SetPageLocked(page);
 140         return true;
 141 }
 142
 143 /**
 144  * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
 145  * @pipe:       the pipe that the buffer belongs to
 146  * @buf:        the buffer to attempt to steal
 147  *
 148  * Description:
 149  *      This function attempts to steal the &struct page attached to
 150  *      @buf. If successful, this function returns 0 and returns with
 151  *      the page locked. The caller may then reuse the page for whatever
 152  *      he wishes; the typical use is insertion into a different file
 153  *      page cache.
 154  */
 155 bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe,
 156                 struct pipe_buffer *buf)
 157 {
 158         struct page *page = buf->page;
 159
 160         /*
 161          * A reference of one is golden, that means that the owner of this
 162          * page is the only one holding a reference to it. lock the page
 163          * and return OK.
 164          */
 165         if (page_count(page) == 1) {
 166                 lock_page(page);
 167                 return true;
 168         }
 169         return false;
 170 }
 171 EXPORT_SYMBOL(generic_pipe_buf_try_steal);
 172
 173 /**
 174  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 175  * @pipe:       the pipe that the buffer belongs to
 176  * @buf:        the buffer to get a reference to
 177  *
 178  * Description:
 179  *      This function grabs an extra reference to @buf. It's used in
 180  *      the tee() system call, when we duplicate the buffers in one
 181  *      pipe into another.
 182  */
 183 bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 184 {
 185         return try_get_page(buf->page);
 186 }
 187 EXPORT_SYMBOL(generic_pipe_buf_get);
 188
 189 /**
 190  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 191  * @pipe:       the pipe that the buffer belongs to
 192  * @buf:        the buffer to put a reference to
 193  *
 194  * Description:
 195  *      This function releases a reference to @buf.
 196  */
 197 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 198                               struct pipe_buffer *buf)
 199 {
 200         put_page(buf->page);
 201 }
 202 EXPORT_SYMBOL(generic_pipe_buf_release);
 203
 204 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 205         .release        = anon_pipe_buf_release,
 206         .try_steal      = anon_pipe_buf_try_steal,
 207         .get            = generic_pipe_buf_get,
 208 };
 209
 210 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
 211 static inline bool pipe_readable(const struct pipe_inode_info *pipe)
 212 {
 213         unsigned int head = READ_ONCE(pipe->head);
 214         unsigned int tail = READ_ONCE(pipe->tail);
 215         unsigned int writers = READ_ONCE(pipe->writers);
 216
 217         return !pipe_empty(head, tail) || !writers;
 218 }
 219
 220 static inline unsigned int pipe_update_tail(struct pipe_inode_info *pipe,
 221                                             struct pipe_buffer *buf,
 222                                             unsigned int tail)
 223 {
 224         pipe_buf_release(pipe, buf);
 225
 226         /*
 227          * If the pipe has a watch_queue, we need additional protection
 228          * by the spinlock because notifications get posted with only
 229          * this spinlock, no mutex
 230          */
 231         if (pipe_has_watch_queue(pipe)) {
 232                 spin_lock_irq(&pipe->rd_wait.lock);
 233 #ifdef CONFIG_WATCH_QUEUE
 234                 if (buf->flags & PIPE_BUF_FLAG_LOSS)
 235                         pipe->note_loss = true;
 236 #endif
 237                 pipe->tail = ++tail;
 238                 spin_unlock_irq(&pipe->rd_wait.lock);
 239                 return tail;
 240         }
 241
 242         /*
 243          * Without a watch_queue, we can simply increment the tail
 244          * without the spinlock - the mutex is enough.
 245          */
 246         pipe->tail = ++tail;
 247         return tail;
 248 }
 249
 250 static ssize_t
 251 pipe_read(struct kiocb *iocb, struct iov_iter *to)
 252 {
 253         size_t total_len = iov_iter_count(to);
 254         struct file *filp = iocb->ki_filp;
 255         struct pipe_inode_info *pipe = filp->private_data;
 256         bool was_full, wake_next_reader = false;
 257         ssize_t ret;
 258
 259         /* Null read succeeds. */
 260         if (unlikely(total_len == 0))
 261                 return 0;
 262
 263         ret = 0;
 264         mutex_lock(&pipe->mutex);
 265
 266         /*
 267          * We only wake up writers if the pipe was full when we started
 268          * reading in order to avoid unnecessary wakeups.
 269          *
 270          * But when we do wake up writers, we do so using a sync wakeup
 271          * (WF_SYNC), because we want them to get going and generate more
 272          * data for us.
 273          */
 274         was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
 275         for (;;) {
 276                 /* Read ->head with a barrier vs post_one_notification() */
 277                 unsigned int head = smp_load_acquire(&pipe->head);
 278                 unsigned int tail = pipe->tail;
 279                 unsigned int mask = pipe->ring_size - 1;
 280
 281 #ifdef CONFIG_WATCH_QUEUE
 282                 if (pipe->note_loss) {
 283                         struct watch_notification n;
 284
 285                         if (total_len < 8) {
 286                                 if (ret == 0)
 287                                         ret = -ENOBUFS;
 288                                 break;
 289                         }
 290
 291                         n.type = WATCH_TYPE_META;
 292                         n.subtype = WATCH_META_LOSS_NOTIFICATION;
 293                         n.info = watch_sizeof(n);
 294                         if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
 295                                 if (ret == 0)
 296                                         ret = -EFAULT;
 297                                 break;
 298                         }
 299                         ret += sizeof(n);
 300                         total_len -= sizeof(n);
 301                         pipe->note_loss = false;
 302                 }
 303 #endif
 304
 305                 if (!pipe_empty(head, tail)) {
 306                         struct pipe_buffer *buf = &pipe->bufs[tail & mask];
 307                         size_t chars = buf->len;
 308                         size_t written;
 309                         int error;
 310
 311                         if (chars > total_len) {
 312                                 if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
 313                                         if (ret == 0)
 314                                                 ret = -ENOBUFS;
 315                                         break;
 316                                 }
 317                                 chars = total_len;
 318                         }
 319
 320                         error = pipe_buf_confirm(pipe, buf);
 321                         if (error) {
 322                                 if (!ret)
 323                                         ret = error;
 324                                 break;
 325                         }
 326
 327                         written = copy_page_to_iter(buf->page, buf->offset, chars, to);
 328                         if (unlikely(written < chars)) {
 329                                 if (!ret)
 330                                         ret = -EFAULT;
 331                                 break;
 332                         }
 333                         ret += chars;
 334                         buf->offset += chars;
 335                         buf->len -= chars;
 336
 337                         /* Was it a packet buffer? Clean up and exit */
 338                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 339                                 total_len = chars;
 340                                 buf->len = 0;
 341                         }
 342
 343                         if (!buf->len)
 344                                 tail = pipe_update_tail(pipe, buf, tail);
 345                         total_len -= chars;
 346                         if (!total_len)
 347                                 break;  /* common path: read succeeded */
 348                         if (!pipe_empty(head, tail))    /* More to do? */
 349                                 continue;
 350                 }
 351
 352                 if (!pipe->writers)
 353                         break;
 354                 if (ret)
 355                         break;
 356                 if ((filp->f_flags & O_NONBLOCK) ||
 357                     (iocb->ki_flags & IOCB_NOWAIT)) {
 358                         ret = -EAGAIN;
 359                         break;
 360                 }
 361                 mutex_unlock(&pipe->mutex);
 362
 363                 /*
 364                  * We only get here if we didn't actually read anything.
 365                  *
 366                  * However, we could have seen (and removed) a zero-sized
 367                  * pipe buffer, and might have made space in the buffers
 368                  * that way.
 369                  *
 370                  * You can't make zero-sized pipe buffers by doing an empty
 371                  * write (not even in packet mode), but they can happen if
 372                  * the writer gets an EFAULT when trying to fill a buffer
 373                  * that already got allocated and inserted in the buffer
 374                  * array.
 375                  *
 376                  * So we still need to wake up any pending writers in the
 377                  * _very_ unlikely case that the pipe was full, but we got
 378                  * no data.
 379                  */
 380                 if (unlikely(was_full))
 381                         wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 382                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 383
 384                 /*
 385                  * But because we didn't read anything, at this point we can
 386                  * just return directly with -ERESTARTSYS if we're interrupted,
 387                  * since we've done any required wakeups and there's no need
 388                  * to mark anything accessed. And we've dropped the lock.
 389                  */
 390                 if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0)
 391                         return -ERESTARTSYS;
 392
 393                 mutex_lock(&pipe->mutex);
 394                 was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
 395                 wake_next_reader = true;
 396         }
 397         if (pipe_empty(pipe->head, pipe->tail))
 398                 wake_next_reader = false;
 399         mutex_unlock(&pipe->mutex);
 400
 401         if (was_full)
 402                 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 403         if (wake_next_reader)
 404                 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 405         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 406         if (ret > 0)
 407                 file_accessed(filp);
 408         return ret;
 409 }
 410
 411 static inline int is_packetized(struct file *file)
 412 {
 413         return (file->f_flags & O_DIRECT) != 0;
 414 }
 415
 416 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
 417 static inline bool pipe_writable(const struct pipe_inode_info *pipe)
 418 {
 419         unsigned int head = READ_ONCE(pipe->head);
 420         unsigned int tail = READ_ONCE(pipe->tail);
 421         unsigned int max_usage = READ_ONCE(pipe->max_usage);
 422
 423         return !pipe_full(head, tail, max_usage) ||
 424                 !READ_ONCE(pipe->readers);
 425 }
 426
 427 static ssize_t
 428 pipe_write(struct kiocb *iocb, struct iov_iter *from)
 429 {
 430         struct file *filp = iocb->ki_filp;
 431         struct pipe_inode_info *pipe = filp->private_data;
 432         unsigned int head;
 433         ssize_t ret = 0;
 434         size_t total_len = iov_iter_count(from);
 435         ssize_t chars;
 436         bool was_empty = false;
 437         bool wake_next_writer = false;
 438
 439         /*
 440          * Reject writing to watch queue pipes before the point where we lock
 441          * the pipe.
 442          * Otherwise, lockdep would be unhappy if the caller already has another
 443          * pipe locked.
 444          * If we had to support locking a normal pipe and a notification pipe at
 445          * the same time, we could set up lockdep annotations for that, but
 446          * since we don't actually need that, it's simpler to just bail here.
 447          */
 448         if (pipe_has_watch_queue(pipe))
 449                 return -EXDEV;
 450
 451         /* Null write succeeds. */
 452         if (unlikely(total_len == 0))
 453                 return 0;
 454
 455         mutex_lock(&pipe->mutex);
 456
 457         if (!pipe->readers) {
 458                 send_sig(SIGPIPE, current, 0);
 459                 ret = -EPIPE;
 460                 goto out;
 461         }
 462
 463         /*
 464          * If it wasn't empty we try to merge new data into
 465          * the last buffer.
 466          *
 467          * That naturally merges small writes, but it also
 468          * page-aligns the rest of the writes for large writes
 469          * spanning multiple pages.
 470          */
 471         head = pipe->head;
 472         was_empty = pipe_empty(head, pipe->tail);
 473         chars = total_len & (PAGE_SIZE-1);
 474         if (chars && !was_empty) {
 475                 unsigned int mask = pipe->ring_size - 1;
 476                 struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
 477                 int offset = buf->offset + buf->len;
 478
 479                 if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
 480                     offset + chars <= PAGE_SIZE) {
 481                         ret = pipe_buf_confirm(pipe, buf);
 482                         if (ret)
 483                                 goto out;
 484
 485                         ret = copy_page_from_iter(buf->page, offset, chars, from);
 486                         if (unlikely(ret < chars)) {
 487                                 ret = -EFAULT;
 488                                 goto out;
 489                         }
 490
 491                         buf->len += ret;
 492                         if (!iov_iter_count(from))
 493                                 goto out;
 494                 }
 495         }
 496
 497         for (;;) {
 498                 if (!pipe->readers) {
 499                         send_sig(SIGPIPE, current, 0);
 500                         if (!ret)
 501                                 ret = -EPIPE;
 502                         break;
 503                 }
 504
 505                 head = pipe->head;
 506                 if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
 507                         unsigned int mask = pipe->ring_size - 1;
 508                         struct pipe_buffer *buf;
 509                         struct page *page = pipe->tmp_page;
 510                         int copied;
 511
 512                         if (!page) {
 513                                 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
 514                                 if (unlikely(!page)) {
 515                                         ret = ret ? : -ENOMEM;
 516                                         break;
 517                                 }
 518                                 pipe->tmp_page = page;
 519                         }
 520
 521                         /* Allocate a slot in the ring in advance and attach an
 522                          * empty buffer.  If we fault or otherwise fail to use
 523                          * it, either the reader will consume it or it'll still
 524                          * be there for the next write.
 525                          */
 526                         pipe->head = head + 1;
 527
 528                         /* Insert it into the buffer array */
 529                         buf = &pipe->bufs[head & mask];
 530                         buf->page = page;
 531                         buf->ops = &anon_pipe_buf_ops;
 532                         buf->offset = 0;
 533                         buf->len = 0;
 534                         if (is_packetized(filp))
 535                                 buf->flags = PIPE_BUF_FLAG_PACKET;
 536                         else
 537                                 buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
 538                         pipe->tmp_page = NULL;
 539
 540                         copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
 541                         if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
 542                                 if (!ret)
 543                                         ret = -EFAULT;
 544                                 break;
 545                         }
 546                         ret += copied;
 547                         buf->len = copied;
 548
 549                         if (!iov_iter_count(from))
 550                                 break;
 551                 }
 552
 553                 if (!pipe_full(head, pipe->tail, pipe->max_usage))
 554                         continue;
 555
 556                 /* Wait for buffer space to become available. */
 557                 if ((filp->f_flags & O_NONBLOCK) ||
 558                     (iocb->ki_flags & IOCB_NOWAIT)) {
 559                         if (!ret)
 560                                 ret = -EAGAIN;
 561                         break;
 562                 }
 563                 if (signal_pending(current)) {
 564                         if (!ret)
 565                                 ret = -ERESTARTSYS;
 566                         break;
 567                 }
 568
 569                 /*
 570                  * We're going to release the pipe lock and wait for more
 571                  * space. We wake up any readers if necessary, and then
 572                  * after waiting we need to re-check whether the pipe
 573                  * become empty while we dropped the lock.
 574                  */
 575                 mutex_unlock(&pipe->mutex);
 576                 if (was_empty)
 577                         wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 578                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 579                 wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
 580                 mutex_lock(&pipe->mutex);
 581                 was_empty = pipe_empty(pipe->head, pipe->tail);
 582                 wake_next_writer = true;
 583         }
 584 out:
 585         if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
 586                 wake_next_writer = false;
 587         mutex_unlock(&pipe->mutex);
 588
 589         /*
 590          * If we do do a wakeup event, we do a 'sync' wakeup, because we
 591          * want the reader to start processing things asap, rather than
 592          * leave the data pending.
 593          *
 594          * This is particularly important for small writes, because of
 595          * how (for example) the GNU make jobserver uses small writes to
 596          * wake up pending jobs
 597          *
 598          * Epoll nonsensically wants a wakeup whether the pipe
 599          * was already empty or not.
 600          */
 601         if (was_empty || pipe->poll_usage)
 602                 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 603         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 604         if (wake_next_writer)
 605                 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 606         if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
 607                 int err = file_update_time(filp);
 608                 if (err)
 609                         ret = err;
 610                 sb_end_write(file_inode(filp)->i_sb);
 611         }
 612         return ret;
 613 }
 614
 615 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 616 {
 617         struct pipe_inode_info *pipe = filp->private_data;
 618         unsigned int count, head, tail, mask;
 619
 620         switch (cmd) {
 621         case FIONREAD:
 622                 mutex_lock(&pipe->mutex);
 623                 count = 0;
 624                 head = pipe->head;
 625                 tail = pipe->tail;
 626                 mask = pipe->ring_size - 1;
 627
 628                 while (tail != head) {
 629                         count += pipe->bufs[tail & mask].len;
 630                         tail++;
 631                 }
 632                 mutex_unlock(&pipe->mutex);
 633
 634                 return put_user(count, (int __user *)arg);
 635
 636 #ifdef CONFIG_WATCH_QUEUE
 637         case IOC_WATCH_QUEUE_SET_SIZE: {
 638                 int ret;
 639                 mutex_lock(&pipe->mutex);
 640                 ret = watch_queue_set_size(pipe, arg);
 641                 mutex_unlock(&pipe->mutex);
 642                 return ret;
 643         }
 644
 645         case IOC_WATCH_QUEUE_SET_FILTER:
 646                 return watch_queue_set_filter(
 647                         pipe, (struct watch_notification_filter __user *)arg);
 648 #endif
 649
 650         default:
 651                 return -ENOIOCTLCMD;
 652         }
 653 }
 654
 655 /* No kernel lock held - fine */
 656 static __poll_t
 657 pipe_poll(struct file *filp, poll_table *wait)
 658 {
 659         __poll_t mask;
 660         struct pipe_inode_info *pipe = filp->private_data;
 661         unsigned int head, tail;
 662
 663         /* Epoll has some historical nasty semantics, this enables them */
 664         WRITE_ONCE(pipe->poll_usage, true);
 665
 666         /*
 667          * Reading pipe state only -- no need for acquiring the semaphore.
 668          *
 669          * But because this is racy, the code has to add the
 670          * entry to the poll table _first_ ..
 671          */
 672         if (filp->f_mode & FMODE_READ)
 673                 poll_wait(filp, &pipe->rd_wait, wait);
 674         if (filp->f_mode & FMODE_WRITE)
 675                 poll_wait(filp, &pipe->wr_wait, wait);
 676
 677         /*
 678          * .. and only then can you do the racy tests. That way,
 679          * if something changes and you got it wrong, the poll
 680          * table entry will wake you up and fix it.
 681          */
 682         head = READ_ONCE(pipe->head);
 683         tail = READ_ONCE(pipe->tail);
 684
 685         mask = 0;
 686         if (filp->f_mode & FMODE_READ) {
 687                 if (!pipe_empty(head, tail))
 688                         mask |= EPOLLIN | EPOLLRDNORM;
 689                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 690                         mask |= EPOLLHUP;
 691         }
 692
 693         if (filp->f_mode & FMODE_WRITE) {
 694                 if (!pipe_full(head, tail, pipe->max_usage))
 695                         mask |= EPOLLOUT | EPOLLWRNORM;
 696                 /*
 697                  * Most Unices do not set EPOLLERR for FIFOs but on Linux they
 698                  * behave exactly like pipes for poll().
 699                  */
 700                 if (!pipe->readers)
 701                         mask |= EPOLLERR;
 702         }
 703
 704         return mask;
 705 }
 706
 707 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
 708 {
 709         int kill = 0;
 710
 711         spin_lock(&inode->i_lock);
 712         if (!--pipe->files) {
 713                 inode->i_pipe = NULL;
 714                 kill = 1;
 715         }
 716         spin_unlock(&inode->i_lock);
 717
 718         if (kill)
 719                 free_pipe_info(pipe);
 720 }
 721
 722 static int
 723 pipe_release(struct inode *inode, struct file *file)
 724 {
 725         struct pipe_inode_info *pipe = file->private_data;
 726
 727         mutex_lock(&pipe->mutex);
 728         if (file->f_mode & FMODE_READ)
 729                 pipe->readers--;
 730         if (file->f_mode & FMODE_WRITE)
 731                 pipe->writers--;
 732
 733         /* Was that the last reader or writer, but not the other side? */
 734         if (!pipe->readers != !pipe->writers) {
 735                 wake_up_interruptible_all(&pipe->rd_wait);
 736                 wake_up_interruptible_all(&pipe->wr_wait);
 737                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 738                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 739         }
 740         mutex_unlock(&pipe->mutex);
 741
 742         put_pipe_info(inode, pipe);
 743         return 0;
 744 }
 745
 746 static int
 747 pipe_fasync(int fd, struct file *filp, int on)
 748 {
 749         struct pipe_inode_info *pipe = filp->private_data;
 750         int retval = 0;
 751
 752         mutex_lock(&pipe->mutex);
 753         if (filp->f_mode & FMODE_READ)
 754                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 755         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 756                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 757                 if (retval < 0 && (filp->f_mode & FMODE_READ))
 758                         /* this can happen only if on == T */
 759                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 760         }
 761         mutex_unlock(&pipe->mutex);
 762         return retval;
 763 }
 764
 765 unsigned long account_pipe_buffers(struct user_struct *user,
 766                                    unsigned long old, unsigned long new)
 767 {
 768         return atomic_long_add_return(new - old, &user->pipe_bufs);
 769 }
 770
 771 bool too_many_pipe_buffers_soft(unsigned long user_bufs)
 772 {
 773         unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
 774
 775         return soft_limit && user_bufs > soft_limit;
 776 }
 777
 778 bool too_many_pipe_buffers_hard(unsigned long user_bufs)
 779 {
 780         unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
 781
 782         return hard_limit && user_bufs > hard_limit;
 783 }
 784
 785 bool pipe_is_unprivileged_user(void)
 786 {
 787         return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
 788 }
 789
 790 struct pipe_inode_info *alloc_pipe_info(void)
 791 {
 792         struct pipe_inode_info *pipe;
 793         unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
 794         struct user_struct *user = get_current_user();
 795         unsigned long user_bufs;
 796         unsigned int max_size = READ_ONCE(pipe_max_size);
 797
 798         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
 799         if (pipe == NULL)
 800                 goto out_free_uid;
 801
 802         if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
 803                 pipe_bufs = max_size >> PAGE_SHIFT;
 804
 805         user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
 806
 807         if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
 808                 user_bufs = account_pipe_buffers(user, pipe_bufs, PIPE_MIN_DEF_BUFFERS);
 809                 pipe_bufs = PIPE_MIN_DEF_BUFFERS;
 810         }
 811
 812         if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
 813                 goto out_revert_acct;
 814
 815         pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
 816                              GFP_KERNEL_ACCOUNT);
 817
 818         if (pipe->bufs) {
 819                 init_waitqueue_head(&pipe->rd_wait);
 820                 init_waitqueue_head(&pipe->wr_wait);
 821                 pipe->r_counter = pipe->w_counter = 1;
 822                 pipe->max_usage = pipe_bufs;
 823                 pipe->ring_size = pipe_bufs;
 824                 pipe->nr_accounted = pipe_bufs;
 825                 pipe->user = user;
 826                 mutex_init(&pipe->mutex);
 827                 lock_set_cmp_fn(&pipe->mutex, pipe_lock_cmp_fn, NULL);
 828                 return pipe;
 829         }
 830
 831 out_revert_acct:
 832         (void) account_pipe_buffers(user, pipe_bufs, 0);
 833         kfree(pipe);
 834 out_free_uid:
 835         free_uid(user);
 836         return NULL;
 837 }
 838
 839 void free_pipe_info(struct pipe_inode_info *pipe)
 840 {
 841         unsigned int i;
 842
 843 #ifdef CONFIG_WATCH_QUEUE
 844         if (pipe->watch_queue)
 845                 watch_queue_clear(pipe->watch_queue);
 846 #endif
 847
 848         (void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
 849         free_uid(pipe->user);
 850         for (i = 0; i < pipe->ring_size; i++) {
 851                 struct pipe_buffer *buf = pipe->bufs + i;
 852                 if (buf->ops)
 853                         pipe_buf_release(pipe, buf);
 854         }
 855 #ifdef CONFIG_WATCH_QUEUE
 856         if (pipe->watch_queue)
 857                 put_watch_queue(pipe->watch_queue);
 858 #endif
 859         if (pipe->tmp_page)
 860                 __free_page(pipe->tmp_page);
 861         kfree(pipe->bufs);
 862         kfree(pipe);
 863 }
 864
 865 static struct vfsmount *pipe_mnt __ro_after_init;
 866
 867 /*
 868  * pipefs_dname() is called from d_path().
 869  */
 870 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 871 {
 872         return dynamic_dname(buffer, buflen, "pipe:[%lu]",
 873                                 d_inode(dentry)->i_ino);
 874 }
 875
 876 static const struct dentry_operations pipefs_dentry_operations = {
 877         .d_dname        = pipefs_dname,
 878 };
 879
 880 static struct inode * get_pipe_inode(void)
 881 {
 882         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 883         struct pipe_inode_info *pipe;
 884
 885         if (!inode)
 886                 goto fail_inode;
 887
 888         inode->i_ino = get_next_ino();
 889
 890         pipe = alloc_pipe_info();
 891         if (!pipe)
 892                 goto fail_iput;
 893
 894         inode->i_pipe = pipe;
 895         pipe->files = 2;
 896         pipe->readers = pipe->writers = 1;
 897         inode->i_fop = &pipefifo_fops;
 898
 899         /*
 900          * Mark the inode dirty from the very beginning,
 901          * that way it will never be moved to the dirty
 902          * list because "mark_inode_dirty()" will think
 903          * that it already _is_ on the dirty list.
 904          */
 905         inode->i_state = I_DIRTY;
 906         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 907         inode->i_uid = current_fsuid();
 908         inode->i_gid = current_fsgid();
 909         simple_inode_init_ts(inode);
 910
 911         return inode;
 912
 913 fail_iput:
 914         iput(inode);
 915
 916 fail_inode:
 917         return NULL;
 918 }
 919
 920 int create_pipe_files(struct file **res, int flags)
 921 {
 922         struct inode *inode = get_pipe_inode();
 923         struct file *f;
 924         int error;
 925
 926         if (!inode)
 927                 return -ENFILE;
 928
 929         if (flags & O_NOTIFICATION_PIPE) {
 930                 error = watch_queue_init(inode->i_pipe);
 931                 if (error) {
 932                         free_pipe_info(inode->i_pipe);
 933                         iput(inode);
 934                         return error;
 935                 }
 936         }
 937
 938         f = alloc_file_pseudo(inode, pipe_mnt, "",
 939                                 O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
 940                                 &pipefifo_fops);
 941         if (IS_ERR(f)) {
 942                 free_pipe_info(inode->i_pipe);
 943                 iput(inode);
 944                 return PTR_ERR(f);
 945         }
 946
 947         f->private_data = inode->i_pipe;
 948
 949         res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
 950                                   &pipefifo_fops);
 951         if (IS_ERR(res[0])) {
 952                 put_pipe_info(inode, inode->i_pipe);
 953                 fput(f);
 954                 return PTR_ERR(res[0]);
 955         }
 956         res[0]->private_data = inode->i_pipe;
 957         res[1] = f;
 958         stream_open(inode, res[0]);
 959         stream_open(inode, res[1]);
 960         return 0;
 961 }
 962
 963 static int __do_pipe_flags(int *fd, struct file **files, int flags)
 964 {
 965         int error;
 966         int fdw, fdr;
 967
 968         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
 969                 return -EINVAL;
 970
 971         error = create_pipe_files(files, flags);
 972         if (error)
 973                 return error;
 974
 975         error = get_unused_fd_flags(flags);
 976         if (error < 0)
 977                 goto err_read_pipe;
 978         fdr = error;
 979
 980         error = get_unused_fd_flags(flags);
 981         if (error < 0)
 982                 goto err_fdr;
 983         fdw = error;
 984
 985         audit_fd_pair(fdr, fdw);
 986         fd[0] = fdr;
 987         fd[1] = fdw;
 988         /* pipe groks IOCB_NOWAIT */
 989         files[0]->f_mode |= FMODE_NOWAIT;
 990         files[1]->f_mode |= FMODE_NOWAIT;
 991         return 0;
 992
 993  err_fdr:
 994         put_unused_fd(fdr);
 995  err_read_pipe:
 996         fput(files[0]);
 997         fput(files[1]);
 998         return error;
 999 }
1000
1001 int do_pipe_flags(int *fd, int flags)
1002 {
1003         struct file *files[2];
1004         int error = __do_pipe_flags(fd, files, flags);
1005         if (!error) {
1006                 fd_install(fd[0], files[0]);
1007                 fd_install(fd[1], files[1]);
1008         }
1009         return error;
1010 }
1011
1012 /*
1013  * sys_pipe() is the normal C calling standard for creating
1014  * a pipe. It's not the way Unix traditionally does this, though.
1015  */
1016 static int do_pipe2(int __user *fildes, int flags)
1017 {
1018         struct file *files[2];
1019         int fd[2];
1020         int error;
1021
1022         error = __do_pipe_flags(fd, files, flags);
1023         if (!error) {
1024                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
1025                         fput(files[0]);
1026                         fput(files[1]);
1027                         put_unused_fd(fd[0]);
1028                         put_unused_fd(fd[1]);
1029                         error = -EFAULT;
1030                 } else {
1031                         fd_install(fd[0], files[0]);
1032                         fd_install(fd[1], files[1]);
1033                 }
1034         }
1035         return error;
1036 }
1037
1038 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1039 {
1040         return do_pipe2(fildes, flags);
1041 }
1042
1043 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1044 {
1045         return do_pipe2(fildes, 0);
1046 }
1047
1048 /*
1049  * This is the stupid "wait for pipe to be readable or writable"
1050  * model.
1051  *
1052  * See pipe_read/write() for the proper kind of exclusive wait,
1053  * but that requires that we wake up any other readers/writers
1054  * if we then do not end up reading everything (ie the whole
1055  * "wake_next_reader/writer" logic in pipe_read/write()).
1056  */
1057 void pipe_wait_readable(struct pipe_inode_info *pipe)
1058 {
1059         pipe_unlock(pipe);
1060         wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
1061         pipe_lock(pipe);
1062 }
1063
1064 void pipe_wait_writable(struct pipe_inode_info *pipe)
1065 {
1066         pipe_unlock(pipe);
1067         wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
1068         pipe_lock(pipe);
1069 }
1070
1071 /*
1072  * This depends on both the wait (here) and the wakeup (wake_up_partner)
1073  * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
1074  * race with the count check and waitqueue prep.
1075  *
1076  * Normally in order to avoid races, you'd do the prepare_to_wait() first,
1077  * then check the condition you're waiting for, and only then sleep. But
1078  * because of the pipe lock, we can check the condition before being on
1079  * the wait queue.
1080  *
1081  * We use the 'rd_wait' waitqueue for pipe partner waiting.
1082  */
1083 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1084 {
1085         DEFINE_WAIT(rdwait);
1086         int cur = *cnt;
1087
1088         while (cur == *cnt) {
1089                 prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
1090                 pipe_unlock(pipe);
1091                 schedule();
1092                 finish_wait(&pipe->rd_wait, &rdwait);
1093                 pipe_lock(pipe);
1094                 if (signal_pending(current))
1095                         break;
1096         }
1097         return cur == *cnt ? -ERESTARTSYS : 0;
1098 }
1099
1100 static void wake_up_partner(struct pipe_inode_info *pipe)
1101 {
1102         wake_up_interruptible_all(&pipe->rd_wait);
1103 }
1104
1105 static int fifo_open(struct inode *inode, struct file *filp)
1106 {
1107         struct pipe_inode_info *pipe;
1108         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1109         int ret;
1110
1111         filp->f_version = 0;
1112
1113         spin_lock(&inode->i_lock);
1114         if (inode->i_pipe) {
1115                 pipe = inode->i_pipe;
1116                 pipe->files++;
1117                 spin_unlock(&inode->i_lock);
1118         } else {
1119                 spin_unlock(&inode->i_lock);
1120                 pipe = alloc_pipe_info();
1121                 if (!pipe)
1122                         return -ENOMEM;
1123                 pipe->files = 1;
1124                 spin_lock(&inode->i_lock);
1125                 if (unlikely(inode->i_pipe)) {
1126                         inode->i_pipe->files++;
1127                         spin_unlock(&inode->i_lock);
1128                         free_pipe_info(pipe);
1129                         pipe = inode->i_pipe;
1130                 } else {
1131                         inode->i_pipe = pipe;
1132                         spin_unlock(&inode->i_lock);
1133                 }
1134         }
1135         filp->private_data = pipe;
1136         /* OK, we have a pipe and it's pinned down */
1137
1138         mutex_lock(&pipe->mutex);
1139
1140         /* We can only do regular read/write on fifos */
1141         stream_open(inode, filp);
1142
1143         switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
1144         case FMODE_READ:
1145         /*
1146          *  O_RDONLY
1147          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
1148          *  opened, even when there is no process writing the FIFO.
1149          */
1150                 pipe->r_counter++;
1151                 if (pipe->readers++ == 0)
1152                         wake_up_partner(pipe);
1153
1154                 if (!is_pipe && !pipe->writers) {
1155                         if ((filp->f_flags & O_NONBLOCK)) {
1156                                 /* suppress EPOLLHUP until we have
1157                                  * seen a writer */
1158                                 filp->f_version = pipe->w_counter;
1159                         } else {
1160                                 if (wait_for_partner(pipe, &pipe->w_counter))
1161                                         goto err_rd;
1162                         }
1163                 }
1164                 break;
1165
1166         case FMODE_WRITE:
1167         /*
1168          *  O_WRONLY
1169          *  POSIX.1 says that O_NONBLOCK means return -1 with
1170          *  errno=ENXIO when there is no process reading the FIFO.
1171          */
1172                 ret = -ENXIO;
1173                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1174                         goto err;
1175
1176                 pipe->w_counter++;
1177                 if (!pipe->writers++)
1178                         wake_up_partner(pipe);
1179
1180                 if (!is_pipe && !pipe->readers) {
1181                         if (wait_for_partner(pipe, &pipe->r_counter))
1182                                 goto err_wr;
1183                 }
1184                 break;
1185
1186         case FMODE_READ | FMODE_WRITE:
1187         /*
1188          *  O_RDWR
1189          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1190          *  This implementation will NEVER block on a O_RDWR open, since
1191          *  the process can at least talk to itself.
1192          */
1193
1194                 pipe->readers++;
1195                 pipe->writers++;
1196                 pipe->r_counter++;
1197                 pipe->w_counter++;
1198                 if (pipe->readers == 1 || pipe->writers == 1)
1199                         wake_up_partner(pipe);
1200                 break;
1201
1202         default:
1203                 ret = -EINVAL;
1204                 goto err;
1205         }
1206
1207         /* Ok! */
1208         mutex_unlock(&pipe->mutex);
1209         return 0;
1210
1211 err_rd:
1212         if (!--pipe->readers)
1213                 wake_up_interruptible(&pipe->wr_wait);
1214         ret = -ERESTARTSYS;
1215         goto err;
1216
1217 err_wr:
1218         if (!--pipe->writers)
1219                 wake_up_interruptible_all(&pipe->rd_wait);
1220         ret = -ERESTARTSYS;
1221         goto err;
1222
1223 err:
1224         mutex_unlock(&pipe->mutex);
1225
1226         put_pipe_info(inode, pipe);
1227         return ret;
1228 }
1229
1230 const struct file_operations pipefifo_fops = {
1231         .open           = fifo_open,
1232         .llseek         = no_llseek,
1233         .read_iter      = pipe_read,
1234         .write_iter     = pipe_write,
1235         .poll           = pipe_poll,
1236         .unlocked_ioctl = pipe_ioctl,
1237         .release        = pipe_release,
1238         .fasync         = pipe_fasync,
1239         .splice_write   = iter_file_splice_write,
1240 };
1241
1242 /*
1243  * Currently we rely on the pipe array holding a power-of-2 number
1244  * of pages. Returns 0 on error.
1245  */
1246 unsigned int round_pipe_size(unsigned int size)
1247 {
1248         if (size > (1U << 31))
1249                 return 0;
1250
1251         /* Minimum pipe size, as required by POSIX */
1252         if (size < PAGE_SIZE)
1253                 return PAGE_SIZE;
1254
1255         return roundup_pow_of_two(size);
1256 }
1257
1258 /*
1259  * Resize the pipe ring to a number of slots.
1260  *
1261  * Note the pipe can be reduced in capacity, but only if the current
1262  * occupancy doesn't exceed nr_slots; if it does, EBUSY will be
1263  * returned instead.
1264  */
1265 int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
1266 {
1267         struct pipe_buffer *bufs;
1268         unsigned int head, tail, mask, n;
1269
1270         bufs = kcalloc(nr_slots, sizeof(*bufs),
1271                        GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1272         if (unlikely(!bufs))
1273                 return -ENOMEM;
1274
1275         spin_lock_irq(&pipe->rd_wait.lock);
1276         mask = pipe->ring_size - 1;
1277         head = pipe->head;
1278         tail = pipe->tail;
1279
1280         n = pipe_occupancy(head, tail);
1281         if (nr_slots < n) {
1282                 spin_unlock_irq(&pipe->rd_wait.lock);
1283                 kfree(bufs);
1284                 return -EBUSY;
1285         }
1286
1287         /*
1288          * The pipe array wraps around, so just start the new one at zero
1289          * and adjust the indices.
1290          */
1291         if (n > 0) {
1292                 unsigned int h = head & mask;
1293                 unsigned int t = tail & mask;
1294                 if (h > t) {
1295                         memcpy(bufs, pipe->bufs + t,
1296                                n * sizeof(struct pipe_buffer));
1297                 } else {
1298                         unsigned int tsize = pipe->ring_size - t;
1299                         if (h > 0)
1300                                 memcpy(bufs + tsize, pipe->bufs,
1301                                        h * sizeof(struct pipe_buffer));
1302                         memcpy(bufs, pipe->bufs + t,
1303                                tsize * sizeof(struct pipe_buffer));
1304                 }
1305         }
1306
1307         head = n;
1308         tail = 0;
1309
1310         kfree(pipe->bufs);
1311         pipe->bufs = bufs;
1312         pipe->ring_size = nr_slots;
1313         if (pipe->max_usage > nr_slots)
1314                 pipe->max_usage = nr_slots;
1315         pipe->tail = tail;
1316         pipe->head = head;
1317
1318         if (!pipe_has_watch_queue(pipe)) {
1319                 pipe->max_usage = nr_slots;
1320                 pipe->nr_accounted = nr_slots;
1321         }
1322
1323         spin_unlock_irq(&pipe->rd_wait.lock);
1324
1325         /* This might have made more room for writers */
1326         wake_up_interruptible(&pipe->wr_wait);
1327         return 0;
1328 }
1329
1330 /*
1331  * Allocate a new array of pipe buffers and copy the info over. Returns the
1332  * pipe size if successful, or return -ERROR on error.
1333  */
1334 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned int arg)
1335 {
1336         unsigned long user_bufs;
1337         unsigned int nr_slots, size;
1338         long ret = 0;
1339
1340         if (pipe_has_watch_queue(pipe))
1341                 return -EBUSY;
1342
1343         size = round_pipe_size(arg);
1344         nr_slots = size >> PAGE_SHIFT;
1345
1346         if (!nr_slots)
1347                 return -EINVAL;
1348
1349         /*
1350          * If trying to increase the pipe capacity, check that an
1351          * unprivileged user is not trying to exceed various limits
1352          * (soft limit check here, hard limit check just below).
1353          * Decreasing the pipe capacity is always permitted, even
1354          * if the user is currently over a limit.
1355          */
1356         if (nr_slots > pipe->max_usage &&
1357                         size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1358                 return -EPERM;
1359
1360         user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
1361
1362         if (nr_slots > pipe->max_usage &&
1363                         (too_many_pipe_buffers_hard(user_bufs) ||
1364                          too_many_pipe_buffers_soft(user_bufs)) &&
1365                         pipe_is_unprivileged_user()) {
1366                 ret = -EPERM;
1367                 goto out_revert_acct;
1368         }
1369
1370         ret = pipe_resize_ring(pipe, nr_slots);
1371         if (ret < 0)
1372                 goto out_revert_acct;
1373
1374         return pipe->max_usage * PAGE_SIZE;
1375
1376 out_revert_acct:
1377         (void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
1378         return ret;
1379 }
1380
1381 /*
1382  * Note that i_pipe and i_cdev share the same location, so checking ->i_pipe is
1383  * not enough to verify that this is a pipe.
1384  */
1385 struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
1386 {
1387         struct pipe_inode_info *pipe = file->private_data;
1388
1389         if (file->f_op != &pipefifo_fops || !pipe)
1390                 return NULL;
1391         if (for_splice && pipe_has_watch_queue(pipe))
1392                 return NULL;
1393         return pipe;
1394 }
1395
1396 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
1397 {
1398         struct pipe_inode_info *pipe;
1399         long ret;
1400
1401         pipe = get_pipe_info(file, false);
1402         if (!pipe)
1403                 return -EBADF;
1404
1405         mutex_lock(&pipe->mutex);
1406
1407         switch (cmd) {
1408         case F_SETPIPE_SZ:
1409                 ret = pipe_set_size(pipe, arg);
1410                 break;
1411         case F_GETPIPE_SZ:
1412                 ret = pipe->max_usage * PAGE_SIZE;
1413                 break;
1414         default:
1415                 ret = -EINVAL;
1416                 break;
1417         }
1418
1419         mutex_unlock(&pipe->mutex);
1420         return ret;
1421 }
1422
1423 static const struct super_operations pipefs_ops = {
1424         .destroy_inode = free_inode_nonrcu,
1425         .statfs = simple_statfs,
1426 };
1427
1428 /*
1429  * pipefs should _never_ be mounted by userland - too much of security hassle,
1430  * no real gain from having the whole whorehouse mounted. So we don't need
1431  * any operations on the root directory. However, we need a non-trivial
1432  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1433  */
1434
1435 static int pipefs_init_fs_context(struct fs_context *fc)
1436 {
1437         struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
1438         if (!ctx)
1439                 return -ENOMEM;
1440         ctx->ops = &pipefs_ops;
1441         ctx->dops = &pipefs_dentry_operations;
1442         return 0;
1443 }
1444
1445 static struct file_system_type pipe_fs_type = {
1446         .name           = "pipefs",
1447         .init_fs_context = pipefs_init_fs_context,
1448         .kill_sb        = kill_anon_super,
1449 };
1450
1451 #ifdef CONFIG_SYSCTL
1452 static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
1453                                         unsigned int *valp,
1454                                         int write, void *data)
1455 {
1456         if (write) {
1457                 unsigned int val;
1458
1459                 val = round_pipe_size(*lvalp);
1460                 if (val == 0)
1461                         return -EINVAL;
1462
1463                 *valp = val;
1464         } else {
1465                 unsigned int val = *valp;
1466                 *lvalp = (unsigned long) val;
1467         }
1468
1469         return 0;
1470 }
1471
1472 static int proc_dopipe_max_size(struct ctl_table *table, int write,
1473                                 void *buffer, size_t *lenp, loff_t *ppos)
1474 {
1475         return do_proc_douintvec(table, write, buffer, lenp, ppos,
1476                                  do_proc_dopipe_max_size_conv, NULL);
1477 }
1478
1479 static struct ctl_table fs_pipe_sysctls[] = {
1480         {
1481                 .procname       = "pipe-max-size",
1482                 .data           = &pipe_max_size,
1483                 .maxlen         = sizeof(pipe_max_size),
1484                 .mode           = 0644,
1485                 .proc_handler   = proc_dopipe_max_size,
1486         },
1487         {
1488                 .procname       = "pipe-user-pages-hard",
1489                 .data           = &pipe_user_pages_hard,
1490                 .maxlen         = sizeof(pipe_user_pages_hard),
1491                 .mode           = 0644,
1492                 .proc_handler   = proc_doulongvec_minmax,
1493         },
1494         {
1495                 .procname       = "pipe-user-pages-soft",
1496                 .data           = &pipe_user_pages_soft,
1497                 .maxlen         = sizeof(pipe_user_pages_soft),
1498                 .mode           = 0644,
1499                 .proc_handler   = proc_doulongvec_minmax,
1500         },
1501 };
1502 #endif
1503
1504 static int __init init_pipe_fs(void)
1505 {
1506         int err = register_filesystem(&pipe_fs_type);
1507
1508         if (!err) {
1509                 pipe_mnt = kern_mount(&pipe_fs_type);
1510                 if (IS_ERR(pipe_mnt)) {
1511                         err = PTR_ERR(pipe_mnt);
1512                         unregister_filesystem(&pipe_fs_type);
1513                 }
1514         }
1515 #ifdef CONFIG_SYSCTL
1516         register_sysctl_init("fs", fs_pipe_sysctls);
1517 #endif
1518         return err;
1519 }
1520
1521 fs_initcall(init_pipe_fs);