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