fs/pipe.c

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