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 <[email protected]> 2001-08-16
  74  *
  75  * pipe_read & write cleanup
  76  * -- Manfred Spraul <[email protected]> 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         /*
 450          * Reject writing to watch queue pipes before the point where we lock
 451          * the pipe.
 452          * Otherwise, lockdep would be unhappy if the caller already has another
 453          * pipe locked.
 454          * If we had to support locking a normal pipe and a notification pipe at
 455          * the same time, we could set up lockdep annotations for that, but
 456          * since we don't actually need that, it's simpler to just bail here.
 457          */
 458         if (pipe_has_watch_queue(pipe))
 459                 return -EXDEV;
 460
 461         /* Null write succeeds. */
 462         if (unlikely(total_len == 0))
 463                 return 0;
 464
 465         __pipe_lock(pipe);
 466
 467         if (!pipe->readers) {
 468                 send_sig(SIGPIPE, current, 0);
 469                 ret = -EPIPE;
 470                 goto out;
 471         }
 472
 473         /*
 474          * If it wasn't empty we try to merge new data into
 475          * the last buffer.
 476          *
 477          * That naturally merges small writes, but it also
 478          * page-aligns the rest of the writes for large writes
 479          * spanning multiple pages.
 480          */
 481         head = pipe->head;
 482         was_empty = pipe_empty(head, pipe->tail);
 483         chars = total_len & (PAGE_SIZE-1);
 484         if (chars && !was_empty) {
 485                 unsigned int mask = pipe->ring_size - 1;
 486                 struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
 487                 int offset = buf->offset + buf->len;
 488
 489                 if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
 490                     offset + chars <= PAGE_SIZE) {
 491                         ret = pipe_buf_confirm(pipe, buf);
 492                         if (ret)
 493                                 goto out;
 494
 495                         ret = copy_page_from_iter(buf->page, offset, chars, from);
 496                         if (unlikely(ret < chars)) {
 497                                 ret = -EFAULT;
 498                                 goto out;
 499                         }
 500
 501                         buf->len += ret;
 502                         if (!iov_iter_count(from))
 503                                 goto out;
 504                 }
 505         }
 506
 507         for (;;) {
 508                 if (!pipe->readers) {
 509                         send_sig(SIGPIPE, current, 0);
 510                         if (!ret)
 511                                 ret = -EPIPE;
 512                         break;
 513                 }
 514
 515                 head = pipe->head;
 516                 if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
 517                         unsigned int mask = pipe->ring_size - 1;
 518                         struct pipe_buffer *buf;
 519                         struct page *page = pipe->tmp_page;
 520                         int copied;
 521
 522                         if (!page) {
 523                                 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
 524                                 if (unlikely(!page)) {
 525                                         ret = ret ? : -ENOMEM;
 526                                         break;
 527                                 }
 528                                 pipe->tmp_page = page;
 529                         }
 530
 531                         /* Allocate a slot in the ring in advance and attach an
 532                          * empty buffer.  If we fault or otherwise fail to use
 533                          * it, either the reader will consume it or it'll still
 534                          * be there for the next write.
 535                          */
 536                         pipe->head = head + 1;
 537
 538                         /* Insert it into the buffer array */
 539                         buf = &pipe->bufs[head & mask];
 540                         buf->page = page;
 541                         buf->ops = &anon_pipe_buf_ops;
 542                         buf->offset = 0;
 543                         buf->len = 0;
 544                         if (is_packetized(filp))
 545                                 buf->flags = PIPE_BUF_FLAG_PACKET;
 546                         else
 547                                 buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
 548                         pipe->tmp_page = NULL;
 549
 550                         copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
 551                         if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
 552                                 if (!ret)
 553                                         ret = -EFAULT;
 554                                 break;
 555                         }
 556                         ret += copied;
 557                         buf->len = copied;
 558
 559                         if (!iov_iter_count(from))
 560                                 break;
 561                 }
 562
 563                 if (!pipe_full(head, pipe->tail, pipe->max_usage))
 564                         continue;
 565
 566                 /* Wait for buffer space to become available. */
 567                 if ((filp->f_flags & O_NONBLOCK) ||
 568                     (iocb->ki_flags & IOCB_NOWAIT)) {
 569                         if (!ret)
 570                                 ret = -EAGAIN;
 571                         break;
 572                 }
 573                 if (signal_pending(current)) {
 574                         if (!ret)
 575                                 ret = -ERESTARTSYS;
 576                         break;
 577                 }
 578
 579                 /*
 580                  * We're going to release the pipe lock and wait for more
 581                  * space. We wake up any readers if necessary, and then
 582                  * after waiting we need to re-check whether the pipe
 583                  * become empty while we dropped the lock.
 584                  */
 585                 __pipe_unlock(pipe);
 586                 if (was_empty)
 587                         wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 588                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 589                 wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
 590                 __pipe_lock(pipe);
 591                 was_empty = pipe_empty(pipe->head, pipe->tail);
 592                 wake_next_writer = true;
 593         }
 594 out:
 595         if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
 596                 wake_next_writer = false;
 597         __pipe_unlock(pipe);
 598
 599         /*
 600          * If we do do a wakeup event, we do a 'sync' wakeup, because we
 601          * want the reader to start processing things asap, rather than
 602          * leave the data pending.
 603          *
 604          * This is particularly important for small writes, because of
 605          * how (for example) the GNU make jobserver uses small writes to
 606          * wake up pending jobs
 607          *
 608          * Epoll nonsensically wants a wakeup whether the pipe
 609          * was already empty or not.
 610          */
 611         if (was_empty || pipe->poll_usage)
 612                 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 613         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 614         if (wake_next_writer)
 615                 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 616         if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
 617                 int err = file_update_time(filp);
 618                 if (err)
 619                         ret = err;
 620                 sb_end_write(file_inode(filp)->i_sb);
 621         }
 622         return ret;
 623 }
 624
 625 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 626 {
 627         struct pipe_inode_info *pipe = filp->private_data;
 628         unsigned int count, head, tail, mask;
 629
 630         switch (cmd) {
 631         case FIONREAD:
 632                 __pipe_lock(pipe);
 633                 count = 0;
 634                 head = pipe->head;
 635                 tail = pipe->tail;
 636                 mask = pipe->ring_size - 1;
 637
 638                 while (tail != head) {
 639                         count += pipe->bufs[tail & mask].len;
 640                         tail++;
 641                 }
 642                 __pipe_unlock(pipe);
 643
 644                 return put_user(count, (int __user *)arg);
 645
 646 #ifdef CONFIG_WATCH_QUEUE
 647         case IOC_WATCH_QUEUE_SET_SIZE: {
 648                 int ret;
 649                 __pipe_lock(pipe);
 650                 ret = watch_queue_set_size(pipe, arg);
 651                 __pipe_unlock(pipe);
 652                 return ret;
 653         }
 654
 655         case IOC_WATCH_QUEUE_SET_FILTER:
 656                 return watch_queue_set_filter(
 657                         pipe, (struct watch_notification_filter __user *)arg);
 658 #endif
 659
 660         default:
 661                 return -ENOIOCTLCMD;
 662         }
 663 }
 664
 665 /* No kernel lock held - fine */
 666 static __poll_t
 667 pipe_poll(struct file *filp, poll_table *wait)
 668 {
 669         __poll_t mask;
 670         struct pipe_inode_info *pipe = filp->private_data;
 671         unsigned int head, tail;
 672
 673         /* Epoll has some historical nasty semantics, this enables them */
 674         WRITE_ONCE(pipe->poll_usage, true);
 675
 676         /*
 677          * Reading pipe state only -- no need for acquiring the semaphore.
 678          *
 679          * But because this is racy, the code has to add the
 680          * entry to the poll table _first_ ..
 681          */
 682         if (filp->f_mode & FMODE_READ)
 683                 poll_wait(filp, &pipe->rd_wait, wait);
 684         if (filp->f_mode & FMODE_WRITE)
 685                 poll_wait(filp, &pipe->wr_wait, wait);
 686
 687         /*
 688          * .. and only then can you do the racy tests. That way,
 689          * if something changes and you got it wrong, the poll
 690          * table entry will wake you up and fix it.
 691          */
 692         head = READ_ONCE(pipe->head);
 693         tail = READ_ONCE(pipe->tail);
 694
 695         mask = 0;
 696         if (filp->f_mode & FMODE_READ) {
 697                 if (!pipe_empty(head, tail))
 698                         mask |= EPOLLIN | EPOLLRDNORM;
 699                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 700                         mask |= EPOLLHUP;
 701         }
 702
 703         if (filp->f_mode & FMODE_WRITE) {
 704                 if (!pipe_full(head, tail, pipe->max_usage))
 705                         mask |= EPOLLOUT | EPOLLWRNORM;
 706                 /*
 707                  * Most Unices do not set EPOLLERR for FIFOs but on Linux they
 708                  * behave exactly like pipes for poll().
 709                  */
 710                 if (!pipe->readers)
 711                         mask |= EPOLLERR;
 712         }
 713
 714         return mask;
 715 }
 716
 717 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
 718 {
 719         int kill = 0;
 720
 721         spin_lock(&inode->i_lock);
 722         if (!--pipe->files) {
 723                 inode->i_pipe = NULL;
 724                 kill = 1;
 725         }
 726         spin_unlock(&inode->i_lock);
 727
 728         if (kill)
 729                 free_pipe_info(pipe);
 730 }
 731
 732 static int
 733 pipe_release(struct inode *inode, struct file *file)
 734 {
 735         struct pipe_inode_info *pipe = file->private_data;
 736
 737         __pipe_lock(pipe);
 738         if (file->f_mode & FMODE_READ)
 739                 pipe->readers--;
 740         if (file->f_mode & FMODE_WRITE)
 741                 pipe->writers--;
 742
 743         /* Was that the last reader or writer, but not the other side? */
 744         if (!pipe->readers != !pipe->writers) {
 745                 wake_up_interruptible_all(&pipe->rd_wait);
 746                 wake_up_interruptible_all(&pipe->wr_wait);
 747                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 748                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 749         }
 750         __pipe_unlock(pipe);
 751
 752         put_pipe_info(inode, pipe);
 753         return 0;
 754 }
 755
 756 static int
 757 pipe_fasync(int fd, struct file *filp, int on)
 758 {
 759         struct pipe_inode_info *pipe = filp->private_data;
 760         int retval = 0;
 761
 762         __pipe_lock(pipe);
 763         if (filp->f_mode & FMODE_READ)
 764                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 765         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 766                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 767                 if (retval < 0 && (filp->f_mode & FMODE_READ))
 768                         /* this can happen only if on == T */
 769                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 770         }
 771         __pipe_unlock(pipe);
 772         return retval;
 773 }
 774
 775 unsigned long account_pipe_buffers(struct user_struct *user,
 776                                    unsigned long old, unsigned long new)
 777 {
 778         return atomic_long_add_return(new - old, &user->pipe_bufs);
 779 }
 780
 781 bool too_many_pipe_buffers_soft(unsigned long user_bufs)
 782 {
 783         unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
 784
 785         return soft_limit && user_bufs > soft_limit;
 786 }
 787
 788 bool too_many_pipe_buffers_hard(unsigned long user_bufs)
 789 {
 790         unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
 791
 792         return hard_limit && user_bufs > hard_limit;
 793 }
 794
 795 bool pipe_is_unprivileged_user(void)
 796 {
 797         return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
 798 }
 799
 800 struct pipe_inode_info *alloc_pipe_info(void)
 801 {
 802         struct pipe_inode_info *pipe;
 803         unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
 804         struct user_struct *user = get_current_user();
 805         unsigned long user_bufs;
 806         unsigned int max_size = READ_ONCE(pipe_max_size);
 807
 808         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
 809         if (pipe == NULL)
 810                 goto out_free_uid;
 811
 812         if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
 813                 pipe_bufs = max_size >> PAGE_SHIFT;
 814
 815         user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
 816
 817         if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
 818                 user_bufs = account_pipe_buffers(user, pipe_bufs, PIPE_MIN_DEF_BUFFERS);
 819                 pipe_bufs = PIPE_MIN_DEF_BUFFERS;
 820         }
 821
 822         if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
 823                 goto out_revert_acct;
 824
 825         pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
 826                              GFP_KERNEL_ACCOUNT);
 827
 828         if (pipe->bufs) {
 829                 init_waitqueue_head(&pipe->rd_wait);
 830                 init_waitqueue_head(&pipe->wr_wait);
 831                 pipe->r_counter = pipe->w_counter = 1;
 832                 pipe->max_usage = pipe_bufs;
 833                 pipe->ring_size = pipe_bufs;
 834                 pipe->nr_accounted = pipe_bufs;
 835                 pipe->user = user;
 836                 mutex_init(&pipe->mutex);
 837                 return pipe;
 838         }
 839
 840 out_revert_acct:
 841         (void) account_pipe_buffers(user, pipe_bufs, 0);
 842         kfree(pipe);
 843 out_free_uid:
 844         free_uid(user);
 845         return NULL;
 846 }
 847
 848 void free_pipe_info(struct pipe_inode_info *pipe)
 849 {
 850         unsigned int i;
 851
 852 #ifdef CONFIG_WATCH_QUEUE
 853         if (pipe->watch_queue)
 854                 watch_queue_clear(pipe->watch_queue);
 855 #endif
 856
 857         (void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
 858         free_uid(pipe->user);
 859         for (i = 0; i < pipe->ring_size; i++) {
 860                 struct pipe_buffer *buf = pipe->bufs + i;
 861                 if (buf->ops)
 862                         pipe_buf_release(pipe, buf);
 863         }
 864 #ifdef CONFIG_WATCH_QUEUE
 865         if (pipe->watch_queue)
 866                 put_watch_queue(pipe->watch_queue);
 867 #endif
 868         if (pipe->tmp_page)
 869                 __free_page(pipe->tmp_page);
 870         kfree(pipe->bufs);
 871         kfree(pipe);
 872 }
 873
 874 static struct vfsmount *pipe_mnt __ro_after_init;
 875
 876 /*
 877  * pipefs_dname() is called from d_path().
 878  */
 879 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 880 {
 881         return dynamic_dname(buffer, buflen, "pipe:[%lu]",
 882                                 d_inode(dentry)->i_ino);
 883 }
 884
 885 static const struct dentry_operations pipefs_dentry_operations = {
 886         .d_dname        = pipefs_dname,
 887 };
 888
 889 static struct inode * get_pipe_inode(void)
 890 {
 891         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 892         struct pipe_inode_info *pipe;
 893
 894         if (!inode)
 895                 goto fail_inode;
 896
 897         inode->i_ino = get_next_ino();
 898
 899         pipe = alloc_pipe_info();
 900         if (!pipe)
 901                 goto fail_iput;
 902
 903         inode->i_pipe = pipe;
 904         pipe->files = 2;
 905         pipe->readers = pipe->writers = 1;
 906         inode->i_fop = &pipefifo_fops;
 907
 908         /*
 909          * Mark the inode dirty from the very beginning,
 910          * that way it will never be moved to the dirty
 911          * list because "mark_inode_dirty()" will think
 912          * that it already _is_ on the dirty list.
 913          */
 914         inode->i_state = I_DIRTY;
 915         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 916         inode->i_uid = current_fsuid();
 917         inode->i_gid = current_fsgid();
 918         simple_inode_init_ts(inode);
 919
 920         return inode;
 921
 922 fail_iput:
 923         iput(inode);
 924
 925 fail_inode:
 926         return NULL;
 927 }
 928
 929 int create_pipe_files(struct file **res, int flags)
 930 {
 931         struct inode *inode = get_pipe_inode();
 932         struct file *f;
 933         int error;
 934
 935         if (!inode)
 936                 return -ENFILE;
 937
 938         if (flags & O_NOTIFICATION_PIPE) {
 939                 error = watch_queue_init(inode->i_pipe);
 940                 if (error) {
 941                         free_pipe_info(inode->i_pipe);
 942                         iput(inode);
 943                         return error;
 944                 }
 945         }
 946
 947         f = alloc_file_pseudo(inode, pipe_mnt, "",
 948                                 O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
 949                                 &pipefifo_fops);
 950         if (IS_ERR(f)) {
 951                 free_pipe_info(inode->i_pipe);
 952                 iput(inode);
 953                 return PTR_ERR(f);
 954         }
 955
 956         f->private_data = inode->i_pipe;
 957
 958         res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
 959                                   &pipefifo_fops);
 960         if (IS_ERR(res[0])) {
 961                 put_pipe_info(inode, inode->i_pipe);
 962                 fput(f);
 963                 return PTR_ERR(res[0]);
 964         }
 965         res[0]->private_data = inode->i_pipe;
 966         res[1] = f;
 967         stream_open(inode, res[0]);
 968         stream_open(inode, res[1]);
 969         return 0;
 970 }
 971
 972 static int __do_pipe_flags(int *fd, struct file **files, int flags)
 973 {
 974         int error;
 975         int fdw, fdr;
 976
 977         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
 978                 return -EINVAL;
 979
 980         error = create_pipe_files(files, flags);
 981         if (error)
 982                 return error;
 983
 984         error = get_unused_fd_flags(flags);
 985         if (error < 0)
 986                 goto err_read_pipe;
 987         fdr = error;
 988
 989         error = get_unused_fd_flags(flags);
 990         if (error < 0)
 991                 goto err_fdr;
 992         fdw = error;
 993
 994         audit_fd_pair(fdr, fdw);
 995         fd[0] = fdr;
 996         fd[1] = fdw;
 997         /* pipe groks IOCB_NOWAIT */
 998         files[0]->f_mode |= FMODE_NOWAIT;
 999         files[1]->f_mode |= FMODE_NOWAIT;
1000         return 0;
1001
1002  err_fdr:
1003         put_unused_fd(fdr);
1004  err_read_pipe:
1005         fput(files[0]);
1006         fput(files[1]);
1007         return error;
1008 }
1009
1010 int do_pipe_flags(int *fd, int flags)
1011 {
1012         struct file *files[2];
1013         int error = __do_pipe_flags(fd, files, flags);
1014         if (!error) {
1015                 fd_install(fd[0], files[0]);
1016                 fd_install(fd[1], files[1]);
1017         }
1018         return error;
1019 }
1020
1021 /*
1022  * sys_pipe() is the normal C calling standard for creating
1023  * a pipe. It's not the way Unix traditionally does this, though.
1024  */
1025 static int do_pipe2(int __user *fildes, int flags)
1026 {
1027         struct file *files[2];
1028         int fd[2];
1029         int error;
1030
1031         error = __do_pipe_flags(fd, files, flags);
1032         if (!error) {
1033                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
1034                         fput(files[0]);
1035                         fput(files[1]);
1036                         put_unused_fd(fd[0]);
1037                         put_unused_fd(fd[1]);
1038                         error = -EFAULT;
1039                 } else {
1040                         fd_install(fd[0], files[0]);
1041                         fd_install(fd[1], files[1]);
1042                 }
1043         }
1044         return error;
1045 }
1046
1047 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1048 {
1049         return do_pipe2(fildes, flags);
1050 }
1051
1052 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1053 {
1054         return do_pipe2(fildes, 0);
1055 }
1056
1057 /*
1058  * This is the stupid "wait for pipe to be readable or writable"
1059  * model.
1060  *
1061  * See pipe_read/write() for the proper kind of exclusive wait,
1062  * but that requires that we wake up any other readers/writers
1063  * if we then do not end up reading everything (ie the whole
1064  * "wake_next_reader/writer" logic in pipe_read/write()).
1065  */
1066 void pipe_wait_readable(struct pipe_inode_info *pipe)
1067 {
1068         pipe_unlock(pipe);
1069         wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
1070         pipe_lock(pipe);
1071 }
1072
1073 void pipe_wait_writable(struct pipe_inode_info *pipe)
1074 {
1075         pipe_unlock(pipe);
1076         wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
1077         pipe_lock(pipe);
1078 }
1079
1080 /*
1081  * This depends on both the wait (here) and the wakeup (wake_up_partner)
1082  * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
1083  * race with the count check and waitqueue prep.
1084  *
1085  * Normally in order to avoid races, you'd do the prepare_to_wait() first,
1086  * then check the condition you're waiting for, and only then sleep. But
1087  * because of the pipe lock, we can check the condition before being on
1088  * the wait queue.
1089  *
1090  * We use the 'rd_wait' waitqueue for pipe partner waiting.
1091  */
1092 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1093 {
1094         DEFINE_WAIT(rdwait);
1095         int cur = *cnt;
1096
1097         while (cur == *cnt) {
1098                 prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
1099                 pipe_unlock(pipe);
1100                 schedule();
1101                 finish_wait(&pipe->rd_wait, &rdwait);
1102                 pipe_lock(pipe);
1103                 if (signal_pending(current))
1104                         break;
1105         }
1106         return cur == *cnt ? -ERESTARTSYS : 0;
1107 }
1108
1109 static void wake_up_partner(struct pipe_inode_info *pipe)
1110 {
1111         wake_up_interruptible_all(&pipe->rd_wait);
1112 }
1113
1114 static int fifo_open(struct inode *inode, struct file *filp)
1115 {
1116         struct pipe_inode_info *pipe;
1117         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1118         int ret;
1119
1120         filp->f_version = 0;
1121
1122         spin_lock(&inode->i_lock);
1123         if (inode->i_pipe) {
1124                 pipe = inode->i_pipe;
1125                 pipe->files++;
1126                 spin_unlock(&inode->i_lock);
1127         } else {
1128                 spin_unlock(&inode->i_lock);
1129                 pipe = alloc_pipe_info();
1130                 if (!pipe)
1131                         return -ENOMEM;
1132                 pipe->files = 1;
1133                 spin_lock(&inode->i_lock);
1134                 if (unlikely(inode->i_pipe)) {
1135                         inode->i_pipe->files++;
1136                         spin_unlock(&inode->i_lock);
1137                         free_pipe_info(pipe);
1138                         pipe = inode->i_pipe;
1139                 } else {
1140                         inode->i_pipe = pipe;
1141                         spin_unlock(&inode->i_lock);
1142                 }
1143         }
1144         filp->private_data = pipe;
1145         /* OK, we have a pipe and it's pinned down */
1146
1147         __pipe_lock(pipe);
1148
1149         /* We can only do regular read/write on fifos */
1150         stream_open(inode, filp);
1151
1152         switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
1153         case FMODE_READ:
1154         /*
1155          *  O_RDONLY
1156          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
1157          *  opened, even when there is no process writing the FIFO.
1158          */
1159                 pipe->r_counter++;
1160                 if (pipe->readers++ == 0)
1161                         wake_up_partner(pipe);
1162
1163                 if (!is_pipe && !pipe->writers) {
1164                         if ((filp->f_flags & O_NONBLOCK)) {
1165                                 /* suppress EPOLLHUP until we have
1166                                  * seen a writer */
1167                                 filp->f_version = pipe->w_counter;
1168                         } else {
1169                                 if (wait_for_partner(pipe, &pipe->w_counter))
1170                                         goto err_rd;
1171                         }
1172                 }
1173                 break;
1174
1175         case FMODE_WRITE:
1176         /*
1177          *  O_WRONLY
1178          *  POSIX.1 says that O_NONBLOCK means return -1 with
1179          *  errno=ENXIO when there is no process reading the FIFO.
1180          */
1181                 ret = -ENXIO;
1182                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1183                         goto err;
1184
1185                 pipe->w_counter++;
1186                 if (!pipe->writers++)
1187                         wake_up_partner(pipe);
1188
1189                 if (!is_pipe && !pipe->readers) {
1190                         if (wait_for_partner(pipe, &pipe->r_counter))
1191                                 goto err_wr;
1192                 }
1193                 break;
1194
1195         case FMODE_READ | FMODE_WRITE:
1196         /*
1197          *  O_RDWR
1198          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1199          *  This implementation will NEVER block on a O_RDWR open, since
1200          *  the process can at least talk to itself.
1201          */
1202
1203                 pipe->readers++;
1204                 pipe->writers++;
1205                 pipe->r_counter++;
1206                 pipe->w_counter++;
1207                 if (pipe->readers == 1 || pipe->writers == 1)
1208                         wake_up_partner(pipe);
1209                 break;
1210
1211         default:
1212                 ret = -EINVAL;
1213                 goto err;
1214         }
1215
1216         /* Ok! */
1217         __pipe_unlock(pipe);
1218         return 0;
1219
1220 err_rd:
1221         if (!--pipe->readers)
1222                 wake_up_interruptible(&pipe->wr_wait);
1223         ret = -ERESTARTSYS;
1224         goto err;
1225
1226 err_wr:
1227         if (!--pipe->writers)
1228                 wake_up_interruptible_all(&pipe->rd_wait);
1229         ret = -ERESTARTSYS;
1230         goto err;
1231
1232 err:
1233         __pipe_unlock(pipe);
1234
1235         put_pipe_info(inode, pipe);
1236         return ret;
1237 }
1238
1239 const struct file_operations pipefifo_fops = {
1240         .open           = fifo_open,
1241         .llseek         = no_llseek,
1242         .read_iter      = pipe_read,
1243         .write_iter     = pipe_write,
1244         .poll           = pipe_poll,
1245         .unlocked_ioctl = pipe_ioctl,
1246         .release        = pipe_release,
1247         .fasync         = pipe_fasync,
1248         .splice_write   = iter_file_splice_write,
1249 };
1250
1251 /*
1252  * Currently we rely on the pipe array holding a power-of-2 number
1253  * of pages. Returns 0 on error.
1254  */
1255 unsigned int round_pipe_size(unsigned int size)
1256 {
1257         if (size > (1U << 31))
1258                 return 0;
1259
1260         /* Minimum pipe size, as required by POSIX */
1261         if (size < PAGE_SIZE)
1262                 return PAGE_SIZE;
1263
1264         return roundup_pow_of_two(size);
1265 }
1266
1267 /*
1268  * Resize the pipe ring to a number of slots.
1269  *
1270  * Note the pipe can be reduced in capacity, but only if the current
1271  * occupancy doesn't exceed nr_slots; if it does, EBUSY will be
1272  * returned instead.
1273  */
1274 int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
1275 {
1276         struct pipe_buffer *bufs;
1277         unsigned int head, tail, mask, n;
1278
1279         bufs = kcalloc(nr_slots, sizeof(*bufs),
1280                        GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1281         if (unlikely(!bufs))
1282                 return -ENOMEM;
1283
1284         spin_lock_irq(&pipe->rd_wait.lock);
1285         mask = pipe->ring_size - 1;
1286         head = pipe->head;
1287         tail = pipe->tail;
1288
1289         n = pipe_occupancy(head, tail);
1290         if (nr_slots < n) {
1291                 spin_unlock_irq(&pipe->rd_wait.lock);
1292                 kfree(bufs);
1293                 return -EBUSY;
1294         }
1295
1296         /*
1297          * The pipe array wraps around, so just start the new one at zero
1298          * and adjust the indices.
1299          */
1300         if (n > 0) {
1301                 unsigned int h = head & mask;
1302                 unsigned int t = tail & mask;
1303                 if (h > t) {
1304                         memcpy(bufs, pipe->bufs + t,
1305                                n * sizeof(struct pipe_buffer));
1306                 } else {
1307                         unsigned int tsize = pipe->ring_size - t;
1308                         if (h > 0)
1309                                 memcpy(bufs + tsize, pipe->bufs,
1310                                        h * sizeof(struct pipe_buffer));
1311                         memcpy(bufs, pipe->bufs + t,
1312                                tsize * sizeof(struct pipe_buffer));
1313                 }
1314         }
1315
1316         head = n;
1317         tail = 0;
1318
1319         kfree(pipe->bufs);
1320         pipe->bufs = bufs;
1321         pipe->ring_size = nr_slots;
1322         if (pipe->max_usage > nr_slots)
1323                 pipe->max_usage = nr_slots;
1324         pipe->tail = tail;
1325         pipe->head = head;
1326
1327         if (!pipe_has_watch_queue(pipe)) {
1328                 pipe->max_usage = nr_slots;
1329                 pipe->nr_accounted = nr_slots;
1330         }
1331
1332         spin_unlock_irq(&pipe->rd_wait.lock);
1333
1334         /* This might have made more room for writers */
1335         wake_up_interruptible(&pipe->wr_wait);
1336         return 0;
1337 }
1338
1339 /*
1340  * Allocate a new array of pipe buffers and copy the info over. Returns the
1341  * pipe size if successful, or return -ERROR on error.
1342  */
1343 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned int arg)
1344 {
1345         unsigned long user_bufs;
1346         unsigned int nr_slots, size;
1347         long ret = 0;
1348
1349         if (pipe_has_watch_queue(pipe))
1350                 return -EBUSY;
1351
1352         size = round_pipe_size(arg);
1353         nr_slots = size >> PAGE_SHIFT;
1354
1355         if (!nr_slots)
1356                 return -EINVAL;
1357
1358         /*
1359          * If trying to increase the pipe capacity, check that an
1360          * unprivileged user is not trying to exceed various limits
1361          * (soft limit check here, hard limit check just below).
1362          * Decreasing the pipe capacity is always permitted, even
1363          * if the user is currently over a limit.
1364          */
1365         if (nr_slots > pipe->max_usage &&
1366                         size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1367                 return -EPERM;
1368
1369         user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
1370
1371         if (nr_slots > pipe->max_usage &&
1372                         (too_many_pipe_buffers_hard(user_bufs) ||
1373                          too_many_pipe_buffers_soft(user_bufs)) &&
1374                         pipe_is_unprivileged_user()) {
1375                 ret = -EPERM;
1376                 goto out_revert_acct;
1377         }
1378
1379         ret = pipe_resize_ring(pipe, nr_slots);
1380         if (ret < 0)
1381                 goto out_revert_acct;
1382
1383         return pipe->max_usage * PAGE_SIZE;
1384
1385 out_revert_acct:
1386         (void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
1387         return ret;
1388 }
1389
1390 /*
1391  * Note that i_pipe and i_cdev share the same location, so checking ->i_pipe is
1392  * not enough to verify that this is a pipe.
1393  */
1394 struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
1395 {
1396         struct pipe_inode_info *pipe = file->private_data;
1397
1398         if (file->f_op != &pipefifo_fops || !pipe)
1399                 return NULL;
1400         if (for_splice && pipe_has_watch_queue(pipe))
1401                 return NULL;
1402         return pipe;
1403 }
1404
1405 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
1406 {
1407         struct pipe_inode_info *pipe;
1408         long ret;
1409
1410         pipe = get_pipe_info(file, false);
1411         if (!pipe)
1412                 return -EBADF;
1413
1414         __pipe_lock(pipe);
1415
1416         switch (cmd) {
1417         case F_SETPIPE_SZ:
1418                 ret = pipe_set_size(pipe, arg);
1419                 break;
1420         case F_GETPIPE_SZ:
1421                 ret = pipe->max_usage * PAGE_SIZE;
1422                 break;
1423         default:
1424                 ret = -EINVAL;
1425                 break;
1426         }
1427
1428         __pipe_unlock(pipe);
1429         return ret;
1430 }
1431
1432 static const struct super_operations pipefs_ops = {
1433         .destroy_inode = free_inode_nonrcu,
1434         .statfs = simple_statfs,
1435 };
1436
1437 /*
1438  * pipefs should _never_ be mounted by userland - too much of security hassle,
1439  * no real gain from having the whole whorehouse mounted. So we don't need
1440  * any operations on the root directory. However, we need a non-trivial
1441  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1442  */
1443
1444 static int pipefs_init_fs_context(struct fs_context *fc)
1445 {
1446         struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
1447         if (!ctx)
1448                 return -ENOMEM;
1449         ctx->ops = &pipefs_ops;
1450         ctx->dops = &pipefs_dentry_operations;
1451         return 0;
1452 }
1453
1454 static struct file_system_type pipe_fs_type = {
1455         .name           = "pipefs",
1456         .init_fs_context = pipefs_init_fs_context,
1457         .kill_sb        = kill_anon_super,
1458 };
1459
1460 #ifdef CONFIG_SYSCTL
1461 static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
1462                                         unsigned int *valp,
1463                                         int write, void *data)
1464 {
1465         if (write) {
1466                 unsigned int val;
1467
1468                 val = round_pipe_size(*lvalp);
1469                 if (val == 0)
1470                         return -EINVAL;
1471
1472                 *valp = val;
1473         } else {
1474                 unsigned int val = *valp;
1475                 *lvalp = (unsigned long) val;
1476         }
1477
1478         return 0;
1479 }
1480
1481 static int proc_dopipe_max_size(struct ctl_table *table, int write,
1482                                 void *buffer, size_t *lenp, loff_t *ppos)
1483 {
1484         return do_proc_douintvec(table, write, buffer, lenp, ppos,
1485                                  do_proc_dopipe_max_size_conv, NULL);
1486 }
1487
1488 static struct ctl_table fs_pipe_sysctls[] = {
1489         {
1490                 .procname       = "pipe-max-size",
1491                 .data           = &pipe_max_size,
1492                 .maxlen         = sizeof(pipe_max_size),
1493                 .mode           = 0644,
1494                 .proc_handler   = proc_dopipe_max_size,
1495         },
1496         {
1497                 .procname       = "pipe-user-pages-hard",
1498                 .data           = &pipe_user_pages_hard,
1499                 .maxlen         = sizeof(pipe_user_pages_hard),
1500                 .mode           = 0644,
1501                 .proc_handler   = proc_doulongvec_minmax,
1502         },
1503         {
1504                 .procname       = "pipe-user-pages-soft",
1505                 .data           = &pipe_user_pages_soft,
1506                 .maxlen         = sizeof(pipe_user_pages_soft),
1507                 .mode           = 0644,
1508                 .proc_handler   = proc_doulongvec_minmax,
1509         },
1510 };
1511 #endif
1512
1513 static int __init init_pipe_fs(void)
1514 {
1515         int err = register_filesystem(&pipe_fs_type);
1516
1517         if (!err) {
1518                 pipe_mnt = kern_mount(&pipe_fs_type);
1519                 if (IS_ERR(pipe_mnt)) {
1520                         err = PTR_ERR(pipe_mnt);
1521                         unregister_filesystem(&pipe_fs_type);
1522                 }
1523         }
1524 #ifdef CONFIG_SYSCTL
1525         register_sysctl_init("fs", fs_pipe_sysctls);
1526 #endif
1527         return err;
1528 }
1529
1530 fs_initcall(init_pipe_fs);