fs/pipe.c

   1 /*
   2  *  linux/fs/pipe.c
   3  *
   4  *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
   5  */
   6
   7 #include <linux/mm.h>
   8 #include <linux/file.h>
   9 #include <linux/poll.h>
  10 #include <linux/slab.h>
  11 #include <linux/module.h>
  12 #include <linux/init.h>
  13 #include <linux/fs.h>
  14 #include <linux/log2.h>
  15 #include <linux/mount.h>
  16 #include <linux/magic.h>
  17 #include <linux/pipe_fs_i.h>
  18 #include <linux/uio.h>
  19 #include <linux/highmem.h>
  20 #include <linux/pagemap.h>
  21 #include <linux/audit.h>
  22 #include <linux/syscalls.h>
  23 #include <linux/fcntl.h>
  24 #include <linux/aio.h>
  25
  26 #include <asm/uaccess.h>
  27 #include <asm/ioctls.h>
  28
  29 #include "internal.h"
  30
  31 /*
  32  * The max size that a non-root user is allowed to grow the pipe. Can
  33  * be set by root in /proc/sys/fs/pipe-max-size
  34  */
  35 unsigned int pipe_max_size = 1048576;
  36
  37 /*
  38  * Minimum pipe size, as required by POSIX
  39  */
  40 unsigned int pipe_min_size = PAGE_SIZE;
  41
  42 /*
  43  * We use a start+len construction, which provides full use of the
  44  * allocated memory.
  45  * -- Florian Coosmann (FGC)
  46  *
  47  * Reads with count = 0 should always return 0.
  48  * -- Julian Bradfield 1999-06-07.
  49  *
  50  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  51  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  52  *
  53  * pipe_read & write cleanup
  54  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  55  */
  56
  57 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  58 {
  59         if (pipe->files)
  60                 mutex_lock_nested(&pipe->mutex, subclass);
  61 }
  62
  63 void pipe_lock(struct pipe_inode_info *pipe)
  64 {
  65         /*
  66          * pipe_lock() nests non-pipe inode locks (for writing to a file)
  67          */
  68         pipe_lock_nested(pipe, I_MUTEX_PARENT);
  69 }
  70 EXPORT_SYMBOL(pipe_lock);
  71
  72 void pipe_unlock(struct pipe_inode_info *pipe)
  73 {
  74         if (pipe->files)
  75                 mutex_unlock(&pipe->mutex);
  76 }
  77 EXPORT_SYMBOL(pipe_unlock);
  78
  79 static inline void __pipe_lock(struct pipe_inode_info *pipe)
  80 {
  81         mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
  82 }
  83
  84 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
  85 {
  86         mutex_unlock(&pipe->mutex);
  87 }
  88
  89 void pipe_double_lock(struct pipe_inode_info *pipe1,
  90                       struct pipe_inode_info *pipe2)
  91 {
  92         BUG_ON(pipe1 == pipe2);
  93
  94         if (pipe1 < pipe2) {
  95                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
  96                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
  97         } else {
  98                 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
  99                 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
 100         }
 101 }
 102
 103 /* Drop the inode semaphore and wait for a pipe event, atomically */
 104 void pipe_wait(struct pipe_inode_info *pipe)
 105 {
 106         DEFINE_WAIT(wait);
 107
 108         /*
 109          * Pipes are system-local resources, so sleeping on them
 110          * is considered a noninteractive wait:
 111          */
 112         prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
 113         pipe_unlock(pipe);
 114         schedule();
 115         finish_wait(&pipe->wait, &wait);
 116         pipe_lock(pipe);
 117 }
 118
 119 static int
 120 pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
 121                         int atomic)
 122 {
 123         unsigned long copy;
 124
 125         while (len > 0) {
 126                 while (!iov->iov_len)
 127                         iov++;
 128                 copy = min_t(unsigned long, len, iov->iov_len);
 129
 130                 if (atomic) {
 131                         if (__copy_from_user_inatomic(to, iov->iov_base, copy))
 132                                 return -EFAULT;
 133                 } else {
 134                         if (copy_from_user(to, iov->iov_base, copy))
 135                                 return -EFAULT;
 136                 }
 137                 to += copy;
 138                 len -= copy;
 139                 iov->iov_base += copy;
 140                 iov->iov_len -= copy;
 141         }
 142         return 0;
 143 }
 144
 145 static int
 146 pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
 147                       int atomic)
 148 {
 149         unsigned long copy;
 150
 151         while (len > 0) {
 152                 while (!iov->iov_len)
 153                         iov++;
 154                 copy = min_t(unsigned long, len, iov->iov_len);
 155
 156                 if (atomic) {
 157                         if (__copy_to_user_inatomic(iov->iov_base, from, copy))
 158                                 return -EFAULT;
 159                 } else {
 160                         if (copy_to_user(iov->iov_base, from, copy))
 161                                 return -EFAULT;
 162                 }
 163                 from += copy;
 164                 len -= copy;
 165                 iov->iov_base += copy;
 166                 iov->iov_len -= copy;
 167         }
 168         return 0;
 169 }
 170
 171 /*
 172  * Attempt to pre-fault in the user memory, so we can use atomic copies.
 173  * Returns the number of bytes not faulted in.
 174  */
 175 static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
 176 {
 177         while (!iov->iov_len)
 178                 iov++;
 179
 180         while (len > 0) {
 181                 unsigned long this_len;
 182
 183                 this_len = min_t(unsigned long, len, iov->iov_len);
 184                 if (fault_in_pages_writeable(iov->iov_base, this_len))
 185                         break;
 186
 187                 len -= this_len;
 188                 iov++;
 189         }
 190
 191         return len;
 192 }
 193
 194 /*
 195  * Pre-fault in the user memory, so we can use atomic copies.
 196  */
 197 static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
 198 {
 199         while (!iov->iov_len)
 200                 iov++;
 201
 202         while (len > 0) {
 203                 unsigned long this_len;
 204
 205                 this_len = min_t(unsigned long, len, iov->iov_len);
 206                 fault_in_pages_readable(iov->iov_base, this_len);
 207                 len -= this_len;
 208                 iov++;
 209         }
 210 }
 211
 212 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 213                                   struct pipe_buffer *buf)
 214 {
 215         struct page *page = buf->page;
 216
 217         /*
 218          * If nobody else uses this page, and we don't already have a
 219          * temporary page, let's keep track of it as a one-deep
 220          * allocation cache. (Otherwise just release our reference to it)
 221          */
 222         if (page_count(page) == 1 && !pipe->tmp_page)
 223                 pipe->tmp_page = page;
 224         else
 225                 page_cache_release(page);
 226 }
 227
 228 /**
 229  * generic_pipe_buf_map - virtually map a pipe buffer
 230  * @pipe:       the pipe that the buffer belongs to
 231  * @buf:        the buffer that should be mapped
 232  * @atomic:     whether to use an atomic map
 233  *
 234  * Description:
 235  *      This function returns a kernel virtual address mapping for the
 236  *      pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided
 237  *      and the caller has to be careful not to fault before calling
 238  *      the unmap function.
 239  *
 240  *      Note that this function calls kmap_atomic() if @atomic != 0.
 241  */
 242 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
 243                            struct pipe_buffer *buf, int atomic)
 244 {
 245         if (atomic) {
 246                 buf->flags |= PIPE_BUF_FLAG_ATOMIC;
 247                 return kmap_atomic(buf->page);
 248         }
 249
 250         return kmap(buf->page);
 251 }
 252 EXPORT_SYMBOL(generic_pipe_buf_map);
 253
 254 /**
 255  * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
 256  * @pipe:       the pipe that the buffer belongs to
 257  * @buf:        the buffer that should be unmapped
 258  * @map_data:   the data that the mapping function returned
 259  *
 260  * Description:
 261  *      This function undoes the mapping that ->map() provided.
 262  */
 263 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
 264                             struct pipe_buffer *buf, void *map_data)
 265 {
 266         if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
 267                 buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
 268                 kunmap_atomic(map_data);
 269         } else
 270                 kunmap(buf->page);
 271 }
 272 EXPORT_SYMBOL(generic_pipe_buf_unmap);
 273
 274 /**
 275  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
 276  * @pipe:       the pipe that the buffer belongs to
 277  * @buf:        the buffer to attempt to steal
 278  *
 279  * Description:
 280  *      This function attempts to steal the &struct page attached to
 281  *      @buf. If successful, this function returns 0 and returns with
 282  *      the page locked. The caller may then reuse the page for whatever
 283  *      he wishes; the typical use is insertion into a different file
 284  *      page cache.
 285  */
 286 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 287                            struct pipe_buffer *buf)
 288 {
 289         struct page *page = buf->page;
 290
 291         /*
 292          * A reference of one is golden, that means that the owner of this
 293          * page is the only one holding a reference to it. lock the page
 294          * and return OK.
 295          */
 296         if (page_count(page) == 1) {
 297                 lock_page(page);
 298                 return 0;
 299         }
 300
 301         return 1;
 302 }
 303 EXPORT_SYMBOL(generic_pipe_buf_steal);
 304
 305 /**
 306  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 307  * @pipe:       the pipe that the buffer belongs to
 308  * @buf:        the buffer to get a reference to
 309  *
 310  * Description:
 311  *      This function grabs an extra reference to @buf. It's used in
 312  *      in the tee() system call, when we duplicate the buffers in one
 313  *      pipe into another.
 314  */
 315 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 316 {
 317         page_cache_get(buf->page);
 318 }
 319 EXPORT_SYMBOL(generic_pipe_buf_get);
 320
 321 /**
 322  * generic_pipe_buf_confirm - verify contents of the pipe buffer
 323  * @info:       the pipe that the buffer belongs to
 324  * @buf:        the buffer to confirm
 325  *
 326  * Description:
 327  *      This function does nothing, because the generic pipe code uses
 328  *      pages that are always good when inserted into the pipe.
 329  */
 330 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
 331                              struct pipe_buffer *buf)
 332 {
 333         return 0;
 334 }
 335 EXPORT_SYMBOL(generic_pipe_buf_confirm);
 336
 337 /**
 338  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 339  * @pipe:       the pipe that the buffer belongs to
 340  * @buf:        the buffer to put a reference to
 341  *
 342  * Description:
 343  *      This function releases a reference to @buf.
 344  */
 345 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 346                               struct pipe_buffer *buf)
 347 {
 348         page_cache_release(buf->page);
 349 }
 350 EXPORT_SYMBOL(generic_pipe_buf_release);
 351
 352 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 353         .can_merge = 1,
 354         .map = generic_pipe_buf_map,
 355         .unmap = generic_pipe_buf_unmap,
 356         .confirm = generic_pipe_buf_confirm,
 357         .release = anon_pipe_buf_release,
 358         .steal = generic_pipe_buf_steal,
 359         .get = generic_pipe_buf_get,
 360 };
 361
 362 static const struct pipe_buf_operations packet_pipe_buf_ops = {
 363         .can_merge = 0,
 364         .map = generic_pipe_buf_map,
 365         .unmap = generic_pipe_buf_unmap,
 366         .confirm = generic_pipe_buf_confirm,
 367         .release = anon_pipe_buf_release,
 368         .steal = generic_pipe_buf_steal,
 369         .get = generic_pipe_buf_get,
 370 };
 371
 372 static ssize_t
 373 pipe_read(struct kiocb *iocb, const struct iovec *_iov,
 374            unsigned long nr_segs, loff_t pos)
 375 {
 376         struct file *filp = iocb->ki_filp;
 377         struct pipe_inode_info *pipe = filp->private_data;
 378         int do_wakeup;
 379         ssize_t ret;
 380         struct iovec *iov = (struct iovec *)_iov;
 381         size_t total_len;
 382
 383         total_len = iov_length(iov, nr_segs);
 384         /* Null read succeeds. */
 385         if (unlikely(total_len == 0))
 386                 return 0;
 387
 388         do_wakeup = 0;
 389         ret = 0;
 390         __pipe_lock(pipe);
 391         for (;;) {
 392                 int bufs = pipe->nrbufs;
 393                 if (bufs) {
 394                         int curbuf = pipe->curbuf;
 395                         struct pipe_buffer *buf = pipe->bufs + curbuf;
 396                         const struct pipe_buf_operations *ops = buf->ops;
 397                         void *addr;
 398                         size_t chars = buf->len;
 399                         int error, atomic;
 400
 401                         if (chars > total_len)
 402                                 chars = total_len;
 403
 404                         error = ops->confirm(pipe, buf);
 405                         if (error) {
 406                                 if (!ret)
 407                                         ret = error;
 408                                 break;
 409                         }
 410
 411                         atomic = !iov_fault_in_pages_write(iov, chars);
 412 redo:
 413                         addr = ops->map(pipe, buf, atomic);
 414                         error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
 415                         ops->unmap(pipe, buf, addr);
 416                         if (unlikely(error)) {
 417                                 /*
 418                                  * Just retry with the slow path if we failed.
 419                                  */
 420                                 if (atomic) {
 421                                         atomic = 0;
 422                                         goto redo;
 423                                 }
 424                                 if (!ret)
 425                                         ret = error;
 426                                 break;
 427                         }
 428                         ret += chars;
 429                         buf->offset += chars;
 430                         buf->len -= chars;
 431
 432                         /* Was it a packet buffer? Clean up and exit */
 433                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 434                                 total_len = chars;
 435                                 buf->len = 0;
 436                         }
 437
 438                         if (!buf->len) {
 439                                 buf->ops = NULL;
 440                                 ops->release(pipe, buf);
 441                                 curbuf = (curbuf + 1) & (pipe->buffers - 1);
 442                                 pipe->curbuf = curbuf;
 443                                 pipe->nrbufs = --bufs;
 444                                 do_wakeup = 1;
 445                         }
 446                         total_len -= chars;
 447                         if (!total_len)
 448                                 break;  /* common path: read succeeded */
 449                 }
 450                 if (bufs)       /* More to do? */
 451                         continue;
 452                 if (!pipe->writers)
 453                         break;
 454                 if (!pipe->waiting_writers) {
 455                         /* syscall merging: Usually we must not sleep
 456                          * if O_NONBLOCK is set, or if we got some data.
 457                          * But if a writer sleeps in kernel space, then
 458                          * we can wait for that data without violating POSIX.
 459                          */
 460                         if (ret)
 461                                 break;
 462                         if (filp->f_flags & O_NONBLOCK) {
 463                                 ret = -EAGAIN;
 464                                 break;
 465                         }
 466                 }
 467                 if (signal_pending(current)) {
 468                         if (!ret)
 469                                 ret = -ERESTARTSYS;
 470                         break;
 471                 }
 472                 if (do_wakeup) {
 473                         wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 474                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 475                 }
 476                 pipe_wait(pipe);
 477         }
 478         __pipe_unlock(pipe);
 479
 480         /* Signal writers asynchronously that there is more room. */
 481         if (do_wakeup) {
 482                 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 483                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 484         }
 485         if (ret > 0)
 486                 file_accessed(filp);
 487         return ret;
 488 }
 489
 490 static inline int is_packetized(struct file *file)
 491 {
 492         return (file->f_flags & O_DIRECT) != 0;
 493 }
 494
 495 static ssize_t
 496 pipe_write(struct kiocb *iocb, const struct iovec *_iov,
 497             unsigned long nr_segs, loff_t ppos)
 498 {
 499         struct file *filp = iocb->ki_filp;
 500         struct pipe_inode_info *pipe = filp->private_data;
 501         ssize_t ret;
 502         int do_wakeup;
 503         struct iovec *iov = (struct iovec *)_iov;
 504         size_t total_len;
 505         ssize_t chars;
 506
 507         total_len = iov_length(iov, nr_segs);
 508         /* Null write succeeds. */
 509         if (unlikely(total_len == 0))
 510                 return 0;
 511
 512         do_wakeup = 0;
 513         ret = 0;
 514         __pipe_lock(pipe);
 515
 516         if (!pipe->readers) {
 517                 send_sig(SIGPIPE, current, 0);
 518                 ret = -EPIPE;
 519                 goto out;
 520         }
 521
 522         /* We try to merge small writes */
 523         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 524         if (pipe->nrbufs && chars != 0) {
 525                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 526                                                         (pipe->buffers - 1);
 527                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
 528                 const struct pipe_buf_operations *ops = buf->ops;
 529                 int offset = buf->offset + buf->len;
 530
 531                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 532                         int error, atomic = 1;
 533                         void *addr;
 534
 535                         error = ops->confirm(pipe, buf);
 536                         if (error)
 537                                 goto out;
 538
 539                         iov_fault_in_pages_read(iov, chars);
 540 redo1:
 541                         addr = ops->map(pipe, buf, atomic);
 542                         error = pipe_iov_copy_from_user(offset + addr, iov,
 543                                                         chars, atomic);
 544                         ops->unmap(pipe, buf, addr);
 545                         ret = error;
 546                         do_wakeup = 1;
 547                         if (error) {
 548                                 if (atomic) {
 549                                         atomic = 0;
 550                                         goto redo1;
 551                                 }
 552                                 goto out;
 553                         }
 554                         buf->len += chars;
 555                         total_len -= chars;
 556                         ret = chars;
 557                         if (!total_len)
 558                                 goto out;
 559                 }
 560         }
 561
 562         for (;;) {
 563                 int bufs;
 564
 565                 if (!pipe->readers) {
 566                         send_sig(SIGPIPE, current, 0);
 567                         if (!ret)
 568                                 ret = -EPIPE;
 569                         break;
 570                 }
 571                 bufs = pipe->nrbufs;
 572                 if (bufs < pipe->buffers) {
 573                         int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
 574                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 575                         struct page *page = pipe->tmp_page;
 576                         char *src;
 577                         int error, atomic = 1;
 578
 579                         if (!page) {
 580                                 page = alloc_page(GFP_HIGHUSER);
 581                                 if (unlikely(!page)) {
 582                                         ret = ret ? : -ENOMEM;
 583                                         break;
 584                                 }
 585                                 pipe->tmp_page = page;
 586                         }
 587                         /* Always wake up, even if the copy fails. Otherwise
 588                          * we lock up (O_NONBLOCK-)readers that sleep due to
 589                          * syscall merging.
 590                          * FIXME! Is this really true?
 591                          */
 592                         do_wakeup = 1;
 593                         chars = PAGE_SIZE;
 594                         if (chars > total_len)
 595                                 chars = total_len;
 596
 597                         iov_fault_in_pages_read(iov, chars);
 598 redo2:
 599                         if (atomic)
 600                                 src = kmap_atomic(page);
 601                         else
 602                                 src = kmap(page);
 603
 604                         error = pipe_iov_copy_from_user(src, iov, chars,
 605                                                         atomic);
 606                         if (atomic)
 607                                 kunmap_atomic(src);
 608                         else
 609                                 kunmap(page);
 610
 611                         if (unlikely(error)) {
 612                                 if (atomic) {
 613                                         atomic = 0;
 614                                         goto redo2;
 615                                 }
 616                                 if (!ret)
 617                                         ret = error;
 618                                 break;
 619                         }
 620                         ret += chars;
 621
 622                         /* Insert it into the buffer array */
 623                         buf->page = page;
 624                         buf->ops = &anon_pipe_buf_ops;
 625                         buf->offset = 0;
 626                         buf->len = chars;
 627                         buf->flags = 0;
 628                         if (is_packetized(filp)) {
 629                                 buf->ops = &packet_pipe_buf_ops;
 630                                 buf->flags = PIPE_BUF_FLAG_PACKET;
 631                         }
 632                         pipe->nrbufs = ++bufs;
 633                         pipe->tmp_page = NULL;
 634
 635                         total_len -= chars;
 636                         if (!total_len)
 637                                 break;
 638                 }
 639                 if (bufs < pipe->buffers)
 640                         continue;
 641                 if (filp->f_flags & O_NONBLOCK) {
 642                         if (!ret)
 643                                 ret = -EAGAIN;
 644                         break;
 645                 }
 646                 if (signal_pending(current)) {
 647                         if (!ret)
 648                                 ret = -ERESTARTSYS;
 649                         break;
 650                 }
 651                 if (do_wakeup) {
 652                         wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 653                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 654                         do_wakeup = 0;
 655                 }
 656                 pipe->waiting_writers++;
 657                 pipe_wait(pipe);
 658                 pipe->waiting_writers--;
 659         }
 660 out:
 661         __pipe_unlock(pipe);
 662         if (do_wakeup) {
 663                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 664                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 665         }
 666         if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
 667                 int err = file_update_time(filp);
 668                 if (err)
 669                         ret = err;
 670                 sb_end_write(file_inode(filp)->i_sb);
 671         }
 672         return ret;
 673 }
 674
 675 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 676 {
 677         struct pipe_inode_info *pipe = filp->private_data;
 678         int count, buf, nrbufs;
 679
 680         switch (cmd) {
 681                 case FIONREAD:
 682                         __pipe_lock(pipe);
 683                         count = 0;
 684                         buf = pipe->curbuf;
 685                         nrbufs = pipe->nrbufs;
 686                         while (--nrbufs >= 0) {
 687                                 count += pipe->bufs[buf].len;
 688                                 buf = (buf+1) & (pipe->buffers - 1);
 689                         }
 690                         __pipe_unlock(pipe);
 691
 692                         return put_user(count, (int __user *)arg);
 693                 default:
 694                         return -ENOIOCTLCMD;
 695         }
 696 }
 697
 698 /* No kernel lock held - fine */
 699 static unsigned int
 700 pipe_poll(struct file *filp, poll_table *wait)
 701 {
 702         unsigned int mask;
 703         struct pipe_inode_info *pipe = filp->private_data;
 704         int nrbufs;
 705
 706         poll_wait(filp, &pipe->wait, wait);
 707
 708         /* Reading only -- no need for acquiring the semaphore.  */
 709         nrbufs = pipe->nrbufs;
 710         mask = 0;
 711         if (filp->f_mode & FMODE_READ) {
 712                 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 713                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 714                         mask |= POLLHUP;
 715         }
 716
 717         if (filp->f_mode & FMODE_WRITE) {
 718                 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
 719                 /*
 720                  * Most Unices do not set POLLERR for FIFOs but on Linux they
 721                  * behave exactly like pipes for poll().
 722                  */
 723                 if (!pipe->readers)
 724                         mask |= POLLERR;
 725         }
 726
 727         return mask;
 728 }
 729
 730 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
 731 {
 732         int kill = 0;
 733
 734         spin_lock(&inode->i_lock);
 735         if (!--pipe->files) {
 736                 inode->i_pipe = NULL;
 737                 kill = 1;
 738         }
 739         spin_unlock(&inode->i_lock);
 740
 741         if (kill)
 742                 free_pipe_info(pipe);
 743 }
 744
 745 static int
 746 pipe_release(struct inode *inode, struct file *file)
 747 {
 748         struct pipe_inode_info *pipe = file->private_data;
 749
 750         __pipe_lock(pipe);
 751         if (file->f_mode & FMODE_READ)
 752                 pipe->readers--;
 753         if (file->f_mode & FMODE_WRITE)
 754                 pipe->writers--;
 755
 756         if (pipe->readers || pipe->writers) {
 757                 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
 758                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 759                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 760         }
 761         __pipe_unlock(pipe);
 762
 763         put_pipe_info(inode, pipe);
 764         return 0;
 765 }
 766
 767 static int
 768 pipe_fasync(int fd, struct file *filp, int on)
 769 {
 770         struct pipe_inode_info *pipe = filp->private_data;
 771         int retval = 0;
 772
 773         __pipe_lock(pipe);
 774         if (filp->f_mode & FMODE_READ)
 775                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 776         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 777                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 778                 if (retval < 0 && (filp->f_mode & FMODE_READ))
 779                         /* this can happen only if on == T */
 780                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 781         }
 782         __pipe_unlock(pipe);
 783         return retval;
 784 }
 785
 786 struct pipe_inode_info *alloc_pipe_info(void)
 787 {
 788         struct pipe_inode_info *pipe;
 789
 790         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 791         if (pipe) {
 792                 pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
 793                 if (pipe->bufs) {
 794                         init_waitqueue_head(&pipe->wait);
 795                         pipe->r_counter = pipe->w_counter = 1;
 796                         pipe->buffers = PIPE_DEF_BUFFERS;
 797                         mutex_init(&pipe->mutex);
 798                         return pipe;
 799                 }
 800                 kfree(pipe);
 801         }
 802
 803         return NULL;
 804 }
 805
 806 void free_pipe_info(struct pipe_inode_info *pipe)
 807 {
 808         int i;
 809
 810         for (i = 0; i < pipe->buffers; i++) {
 811                 struct pipe_buffer *buf = pipe->bufs + i;
 812                 if (buf->ops)
 813                         buf->ops->release(pipe, buf);
 814         }
 815         if (pipe->tmp_page)
 816                 __free_page(pipe->tmp_page);
 817         kfree(pipe->bufs);
 818         kfree(pipe);
 819 }
 820
 821 static struct vfsmount *pipe_mnt __read_mostly;
 822
 823 /*
 824  * pipefs_dname() is called from d_path().
 825  */
 826 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 827 {
 828         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 829                                 dentry->d_inode->i_ino);
 830 }
 831
 832 static const struct dentry_operations pipefs_dentry_operations = {
 833         .d_dname        = pipefs_dname,
 834 };
 835
 836 static struct inode * get_pipe_inode(void)
 837 {
 838         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 839         struct pipe_inode_info *pipe;
 840
 841         if (!inode)
 842                 goto fail_inode;
 843
 844         inode->i_ino = get_next_ino();
 845
 846         pipe = alloc_pipe_info();
 847         if (!pipe)
 848                 goto fail_iput;
 849
 850         inode->i_pipe = pipe;
 851         pipe->files = 2;
 852         pipe->readers = pipe->writers = 1;
 853         inode->i_fop = &pipefifo_fops;
 854
 855         /*
 856          * Mark the inode dirty from the very beginning,
 857          * that way it will never be moved to the dirty
 858          * list because "mark_inode_dirty()" will think
 859          * that it already _is_ on the dirty list.
 860          */
 861         inode->i_state = I_DIRTY;
 862         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 863         inode->i_uid = current_fsuid();
 864         inode->i_gid = current_fsgid();
 865         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 866
 867         return inode;
 868
 869 fail_iput:
 870         iput(inode);
 871
 872 fail_inode:
 873         return NULL;
 874 }
 875
 876 int create_pipe_files(struct file **res, int flags)
 877 {
 878         int err;
 879         struct inode *inode = get_pipe_inode();
 880         struct file *f;
 881         struct path path;
 882         static struct qstr name = { .name = "" };
 883
 884         if (!inode)
 885                 return -ENFILE;
 886
 887         err = -ENOMEM;
 888         path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
 889         if (!path.dentry)
 890                 goto err_inode;
 891         path.mnt = mntget(pipe_mnt);
 892
 893         d_instantiate(path.dentry, inode);
 894
 895         err = -ENFILE;
 896         f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops);
 897         if (IS_ERR(f))
 898                 goto err_dentry;
 899
 900         f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
 901         f->private_data = inode->i_pipe;
 902
 903         res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
 904         if (IS_ERR(res[0]))
 905                 goto err_file;
 906
 907         path_get(&path);
 908         res[0]->private_data = inode->i_pipe;
 909         res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
 910         res[1] = f;
 911         return 0;
 912
 913 err_file:
 914         put_filp(f);
 915 err_dentry:
 916         free_pipe_info(inode->i_pipe);
 917         path_put(&path);
 918         return err;
 919
 920 err_inode:
 921         free_pipe_info(inode->i_pipe);
 922         iput(inode);
 923         return err;
 924 }
 925
 926 static int __do_pipe_flags(int *fd, struct file **files, int flags)
 927 {
 928         int error;
 929         int fdw, fdr;
 930
 931         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
 932                 return -EINVAL;
 933
 934         error = create_pipe_files(files, flags);
 935         if (error)
 936                 return error;
 937
 938         error = get_unused_fd_flags(flags);
 939         if (error < 0)
 940                 goto err_read_pipe;
 941         fdr = error;
 942
 943         error = get_unused_fd_flags(flags);
 944         if (error < 0)
 945                 goto err_fdr;
 946         fdw = error;
 947
 948         audit_fd_pair(fdr, fdw);
 949         fd[0] = fdr;
 950         fd[1] = fdw;
 951         return 0;
 952
 953  err_fdr:
 954         put_unused_fd(fdr);
 955  err_read_pipe:
 956         fput(files[0]);
 957         fput(files[1]);
 958         return error;
 959 }
 960
 961 int do_pipe_flags(int *fd, int flags)
 962 {
 963         struct file *files[2];
 964         int error = __do_pipe_flags(fd, files, flags);
 965         if (!error) {
 966                 fd_install(fd[0], files[0]);
 967                 fd_install(fd[1], files[1]);
 968         }
 969         return error;
 970 }
 971
 972 /*
 973  * sys_pipe() is the normal C calling standard for creating
 974  * a pipe. It's not the way Unix traditionally does this, though.
 975  */
 976 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
 977 {
 978         struct file *files[2];
 979         int fd[2];
 980         int error;
 981
 982         error = __do_pipe_flags(fd, files, flags);
 983         if (!error) {
 984                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
 985                         fput(files[0]);
 986                         fput(files[1]);
 987                         put_unused_fd(fd[0]);
 988                         put_unused_fd(fd[1]);
 989                         error = -EFAULT;
 990                 } else {
 991                         fd_install(fd[0], files[0]);
 992                         fd_install(fd[1], files[1]);
 993                 }
 994         }
 995         return error;
 996 }
 997
 998 SYSCALL_DEFINE1(pipe, int __user *, fildes)
 999 {
1000         return sys_pipe2(fildes, 0);
1001 }
1002
1003 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1004 {
1005         int cur = *cnt;
1006
1007         while (cur == *cnt) {
1008                 pipe_wait(pipe);
1009                 if (signal_pending(current))
1010                         break;
1011         }
1012         return cur == *cnt ? -ERESTARTSYS : 0;
1013 }
1014
1015 static void wake_up_partner(struct pipe_inode_info *pipe)
1016 {
1017         wake_up_interruptible(&pipe->wait);
1018 }
1019
1020 static int fifo_open(struct inode *inode, struct file *filp)
1021 {
1022         struct pipe_inode_info *pipe;
1023         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1024         int ret;
1025
1026         filp->f_version = 0;
1027
1028         spin_lock(&inode->i_lock);
1029         if (inode->i_pipe) {
1030                 pipe = inode->i_pipe;
1031                 pipe->files++;
1032                 spin_unlock(&inode->i_lock);
1033         } else {
1034                 spin_unlock(&inode->i_lock);
1035                 pipe = alloc_pipe_info();
1036                 if (!pipe)
1037                         return -ENOMEM;
1038                 pipe->files = 1;
1039                 spin_lock(&inode->i_lock);
1040                 if (unlikely(inode->i_pipe)) {
1041                         inode->i_pipe->files++;
1042                         spin_unlock(&inode->i_lock);
1043                         free_pipe_info(pipe);
1044                         pipe = inode->i_pipe;
1045                 } else {
1046                         inode->i_pipe = pipe;
1047                         spin_unlock(&inode->i_lock);
1048                 }
1049         }
1050         filp->private_data = pipe;
1051         /* OK, we have a pipe and it's pinned down */
1052
1053         __pipe_lock(pipe);
1054
1055         /* We can only do regular read/write on fifos */
1056         filp->f_mode &= (FMODE_READ | FMODE_WRITE);
1057
1058         switch (filp->f_mode) {
1059         case FMODE_READ:
1060         /*
1061          *  O_RDONLY
1062          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
1063          *  opened, even when there is no process writing the FIFO.
1064          */
1065                 pipe->r_counter++;
1066                 if (pipe->readers++ == 0)
1067                         wake_up_partner(pipe);
1068
1069                 if (!is_pipe && !pipe->writers) {
1070                         if ((filp->f_flags & O_NONBLOCK)) {
1071                                 /* suppress POLLHUP until we have
1072                                  * seen a writer */
1073                                 filp->f_version = pipe->w_counter;
1074                         } else {
1075                                 if (wait_for_partner(pipe, &pipe->w_counter))
1076                                         goto err_rd;
1077                         }
1078                 }
1079                 break;
1080
1081         case FMODE_WRITE:
1082         /*
1083          *  O_WRONLY
1084          *  POSIX.1 says that O_NONBLOCK means return -1 with
1085          *  errno=ENXIO when there is no process reading the FIFO.
1086          */
1087                 ret = -ENXIO;
1088                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1089                         goto err;
1090
1091                 pipe->w_counter++;
1092                 if (!pipe->writers++)
1093                         wake_up_partner(pipe);
1094
1095                 if (!is_pipe && !pipe->readers) {
1096                         if (wait_for_partner(pipe, &pipe->r_counter))
1097                                 goto err_wr;
1098                 }
1099                 break;
1100
1101         case FMODE_READ | FMODE_WRITE:
1102         /*
1103          *  O_RDWR
1104          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1105          *  This implementation will NEVER block on a O_RDWR open, since
1106          *  the process can at least talk to itself.
1107          */
1108
1109                 pipe->readers++;
1110                 pipe->writers++;
1111                 pipe->r_counter++;
1112                 pipe->w_counter++;
1113                 if (pipe->readers == 1 || pipe->writers == 1)
1114                         wake_up_partner(pipe);
1115                 break;
1116
1117         default:
1118                 ret = -EINVAL;
1119                 goto err;
1120         }
1121
1122         /* Ok! */
1123         __pipe_unlock(pipe);
1124         return 0;
1125
1126 err_rd:
1127         if (!--pipe->readers)
1128                 wake_up_interruptible(&pipe->wait);
1129         ret = -ERESTARTSYS;
1130         goto err;
1131
1132 err_wr:
1133         if (!--pipe->writers)
1134                 wake_up_interruptible(&pipe->wait);
1135         ret = -ERESTARTSYS;
1136         goto err;
1137
1138 err:
1139         __pipe_unlock(pipe);
1140
1141         put_pipe_info(inode, pipe);
1142         return ret;
1143 }
1144
1145 const struct file_operations pipefifo_fops = {
1146         .open           = fifo_open,
1147         .llseek         = no_llseek,
1148         .read           = do_sync_read,
1149         .aio_read       = pipe_read,
1150         .write          = do_sync_write,
1151         .aio_write      = pipe_write,
1152         .poll           = pipe_poll,
1153         .unlocked_ioctl = pipe_ioctl,
1154         .release        = pipe_release,
1155         .fasync         = pipe_fasync,
1156 };
1157
1158 /*
1159  * Allocate a new array of pipe buffers and copy the info over. Returns the
1160  * pipe size if successful, or return -ERROR on error.
1161  */
1162 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
1163 {
1164         struct pipe_buffer *bufs;
1165
1166         /*
1167          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1168          * expect a lot of shrink+grow operations, just free and allocate
1169          * again like we would do for growing. If the pipe currently
1170          * contains more buffers than arg, then return busy.
1171          */
1172         if (nr_pages < pipe->nrbufs)
1173                 return -EBUSY;
1174
1175         bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN);
1176         if (unlikely(!bufs))
1177                 return -ENOMEM;
1178
1179         /*
1180          * The pipe array wraps around, so just start the new one at zero
1181          * and adjust the indexes.
1182          */
1183         if (pipe->nrbufs) {
1184                 unsigned int tail;
1185                 unsigned int head;
1186
1187                 tail = pipe->curbuf + pipe->nrbufs;
1188                 if (tail < pipe->buffers)
1189                         tail = 0;
1190                 else
1191                         tail &= (pipe->buffers - 1);
1192
1193                 head = pipe->nrbufs - tail;
1194                 if (head)
1195                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1196                 if (tail)
1197                         memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1198         }
1199
1200         pipe->curbuf = 0;
1201         kfree(pipe->bufs);
1202         pipe->bufs = bufs;
1203         pipe->buffers = nr_pages;
1204         return nr_pages * PAGE_SIZE;
1205 }
1206
1207 /*
1208  * Currently we rely on the pipe array holding a power-of-2 number
1209  * of pages.
1210  */
1211 static inline unsigned int round_pipe_size(unsigned int size)
1212 {
1213         unsigned long nr_pages;
1214
1215         nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1216         return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1217 }
1218
1219 /*
1220  * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1221  * will return an error.
1222  */
1223 int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1224                  size_t *lenp, loff_t *ppos)
1225 {
1226         int ret;
1227
1228         ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1229         if (ret < 0 || !write)
1230                 return ret;
1231
1232         pipe_max_size = round_pipe_size(pipe_max_size);
1233         return ret;
1234 }
1235
1236 /*
1237  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1238  * location, so checking ->i_pipe is not enough to verify that this is a
1239  * pipe.
1240  */
1241 struct pipe_inode_info *get_pipe_info(struct file *file)
1242 {
1243         return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1244 }
1245
1246 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1247 {
1248         struct pipe_inode_info *pipe;
1249         long ret;
1250
1251         pipe = get_pipe_info(file);
1252         if (!pipe)
1253                 return -EBADF;
1254
1255         __pipe_lock(pipe);
1256
1257         switch (cmd) {
1258         case F_SETPIPE_SZ: {
1259                 unsigned int size, nr_pages;
1260
1261                 size = round_pipe_size(arg);
1262                 nr_pages = size >> PAGE_SHIFT;
1263
1264                 ret = -EINVAL;
1265                 if (!nr_pages)
1266                         goto out;
1267
1268                 if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1269                         ret = -EPERM;
1270                         goto out;
1271                 }
1272                 ret = pipe_set_size(pipe, nr_pages);
1273                 break;
1274                 }
1275         case F_GETPIPE_SZ:
1276                 ret = pipe->buffers * PAGE_SIZE;
1277                 break;
1278         default:
1279                 ret = -EINVAL;
1280                 break;
1281         }
1282
1283 out:
1284         __pipe_unlock(pipe);
1285         return ret;
1286 }
1287
1288 static const struct super_operations pipefs_ops = {
1289         .destroy_inode = free_inode_nonrcu,
1290         .statfs = simple_statfs,
1291 };
1292
1293 /*
1294  * pipefs should _never_ be mounted by userland - too much of security hassle,
1295  * no real gain from having the whole whorehouse mounted. So we don't need
1296  * any operations on the root directory. However, we need a non-trivial
1297  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1298  */
1299 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1300                          int flags, const char *dev_name, void *data)
1301 {
1302         return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1303                         &pipefs_dentry_operations, PIPEFS_MAGIC);
1304 }
1305
1306 static struct file_system_type pipe_fs_type = {
1307         .name           = "pipefs",
1308         .mount          = pipefs_mount,
1309         .kill_sb        = kill_anon_super,
1310 };
1311
1312 static int __init init_pipe_fs(void)
1313 {
1314         int err = register_filesystem(&pipe_fs_type);
1315
1316         if (!err) {
1317                 pipe_mnt = kern_mount(&pipe_fs_type);
1318                 if (IS_ERR(pipe_mnt)) {
1319                         err = PTR_ERR(pipe_mnt);
1320                         unregister_filesystem(&pipe_fs_type);
1321                 }
1322         }
1323         return err;
1324 }
1325
1326 fs_initcall(init_pipe_fs);