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) { 667 int err = file_update_time(filp); 668 if (err) 669 ret = err; 670 } 671 return ret; 672 } 673 674 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 675 { 676 struct pipe_inode_info *pipe = filp->private_data; 677 int count, buf, nrbufs; 678 679 switch (cmd) { 680 case FIONREAD: 681 __pipe_lock(pipe); 682 count = 0; 683 buf = pipe->curbuf; 684 nrbufs = pipe->nrbufs; 685 while (--nrbufs >= 0) { 686 count += pipe->bufs[buf].len; 687 buf = (buf+1) & (pipe->buffers - 1); 688 } 689 __pipe_unlock(pipe); 690 691 return put_user(count, (int __user *)arg); 692 default: 693 return -ENOIOCTLCMD; 694 } 695 } 696 697 /* No kernel lock held - fine */ 698 static unsigned int 699 pipe_poll(struct file *filp, poll_table *wait) 700 { 701 unsigned int mask; 702 struct pipe_inode_info *pipe = filp->private_data; 703 int nrbufs; 704 705 poll_wait(filp, &pipe->wait, wait); 706 707 /* Reading only -- no need for acquiring the semaphore. */ 708 nrbufs = pipe->nrbufs; 709 mask = 0; 710 if (filp->f_mode & FMODE_READ) { 711 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0; 712 if (!pipe->writers && filp->f_version != pipe->w_counter) 713 mask |= POLLHUP; 714 } 715 716 if (filp->f_mode & FMODE_WRITE) { 717 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0; 718 /* 719 * Most Unices do not set POLLERR for FIFOs but on Linux they 720 * behave exactly like pipes for poll(). 721 */ 722 if (!pipe->readers) 723 mask |= POLLERR; 724 } 725 726 return mask; 727 } 728 729 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe) 730 { 731 int kill = 0; 732 733 spin_lock(&inode->i_lock); 734 if (!--pipe->files) { 735 inode->i_pipe = NULL; 736 kill = 1; 737 } 738 spin_unlock(&inode->i_lock); 739 740 if (kill) 741 free_pipe_info(pipe); 742 } 743 744 static int 745 pipe_release(struct inode *inode, struct file *file) 746 { 747 struct pipe_inode_info *pipe = file->private_data; 748 749 __pipe_lock(pipe); 750 if (file->f_mode & FMODE_READ) 751 pipe->readers--; 752 if (file->f_mode & FMODE_WRITE) 753 pipe->writers--; 754 755 if (pipe->readers || pipe->writers) { 756 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP); 757 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 758 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); 759 } 760 __pipe_unlock(pipe); 761 762 put_pipe_info(inode, pipe); 763 return 0; 764 } 765 766 static int 767 pipe_fasync(int fd, struct file *filp, int on) 768 { 769 struct pipe_inode_info *pipe = filp->private_data; 770 int retval = 0; 771 772 __pipe_lock(pipe); 773 if (filp->f_mode & FMODE_READ) 774 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers); 775 if ((filp->f_mode & FMODE_WRITE) && retval >= 0) { 776 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers); 777 if (retval < 0 && (filp->f_mode & FMODE_READ)) 778 /* this can happen only if on == T */ 779 fasync_helper(-1, filp, 0, &pipe->fasync_readers); 780 } 781 __pipe_unlock(pipe); 782 return retval; 783 } 784 785 struct pipe_inode_info *alloc_pipe_info(void) 786 { 787 struct pipe_inode_info *pipe; 788 789 pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL); 790 if (pipe) { 791 pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL); 792 if (pipe->bufs) { 793 init_waitqueue_head(&pipe->wait); 794 pipe->r_counter = pipe->w_counter = 1; 795 pipe->buffers = PIPE_DEF_BUFFERS; 796 mutex_init(&pipe->mutex); 797 return pipe; 798 } 799 kfree(pipe); 800 } 801 802 return NULL; 803 } 804 805 void free_pipe_info(struct pipe_inode_info *pipe) 806 { 807 int i; 808 809 for (i = 0; i < pipe->buffers; i++) { 810 struct pipe_buffer *buf = pipe->bufs + i; 811 if (buf->ops) 812 buf->ops->release(pipe, buf); 813 } 814 if (pipe->tmp_page) 815 __free_page(pipe->tmp_page); 816 kfree(pipe->bufs); 817 kfree(pipe); 818 } 819 820 static struct vfsmount *pipe_mnt __read_mostly; 821 822 /* 823 * pipefs_dname() is called from d_path(). 824 */ 825 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen) 826 { 827 return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]", 828 dentry->d_inode->i_ino); 829 } 830 831 static const struct dentry_operations pipefs_dentry_operations = { 832 .d_dname = pipefs_dname, 833 }; 834 835 static struct inode * get_pipe_inode(void) 836 { 837 struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb); 838 struct pipe_inode_info *pipe; 839 840 if (!inode) 841 goto fail_inode; 842 843 inode->i_ino = get_next_ino(); 844 845 pipe = alloc_pipe_info(); 846 if (!pipe) 847 goto fail_iput; 848 849 inode->i_pipe = pipe; 850 pipe->files = 2; 851 pipe->readers = pipe->writers = 1; 852 inode->i_fop = &pipefifo_fops; 853 854 /* 855 * Mark the inode dirty from the very beginning, 856 * that way it will never be moved to the dirty 857 * list because "mark_inode_dirty()" will think 858 * that it already _is_ on the dirty list. 859 */ 860 inode->i_state = I_DIRTY; 861 inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR; 862 inode->i_uid = current_fsuid(); 863 inode->i_gid = current_fsgid(); 864 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 865 866 return inode; 867 868 fail_iput: 869 iput(inode); 870 871 fail_inode: 872 return NULL; 873 } 874 875 int create_pipe_files(struct file **res, int flags) 876 { 877 int err; 878 struct inode *inode = get_pipe_inode(); 879 struct file *f; 880 struct path path; 881 static struct qstr name = { .name = "" }; 882 883 if (!inode) 884 return -ENFILE; 885 886 err = -ENOMEM; 887 path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name); 888 if (!path.dentry) 889 goto err_inode; 890 path.mnt = mntget(pipe_mnt); 891 892 d_instantiate(path.dentry, inode); 893 894 err = -ENFILE; 895 f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops); 896 if (IS_ERR(f)) 897 goto err_dentry; 898 899 f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)); 900 f->private_data = inode->i_pipe; 901 902 res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops); 903 if (IS_ERR(res[0])) 904 goto err_file; 905 906 path_get(&path); 907 res[0]->private_data = inode->i_pipe; 908 res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK); 909 res[1] = f; 910 return 0; 911 912 err_file: 913 put_filp(f); 914 err_dentry: 915 free_pipe_info(inode->i_pipe); 916 path_put(&path); 917 return err; 918 919 err_inode: 920 free_pipe_info(inode->i_pipe); 921 iput(inode); 922 return err; 923 } 924 925 static int __do_pipe_flags(int *fd, struct file **files, int flags) 926 { 927 int error; 928 int fdw, fdr; 929 930 if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT)) 931 return -EINVAL; 932 933 error = create_pipe_files(files, flags); 934 if (error) 935 return error; 936 937 error = get_unused_fd_flags(flags); 938 if (error < 0) 939 goto err_read_pipe; 940 fdr = error; 941 942 error = get_unused_fd_flags(flags); 943 if (error < 0) 944 goto err_fdr; 945 fdw = error; 946 947 audit_fd_pair(fdr, fdw); 948 fd[0] = fdr; 949 fd[1] = fdw; 950 return 0; 951 952 err_fdr: 953 put_unused_fd(fdr); 954 err_read_pipe: 955 fput(files[0]); 956 fput(files[1]); 957 return error; 958 } 959 960 int do_pipe_flags(int *fd, int flags) 961 { 962 struct file *files[2]; 963 int error = __do_pipe_flags(fd, files, flags); 964 if (!error) { 965 fd_install(fd[0], files[0]); 966 fd_install(fd[1], files[1]); 967 } 968 return error; 969 } 970 971 /* 972 * sys_pipe() is the normal C calling standard for creating 973 * a pipe. It's not the way Unix traditionally does this, though. 974 */ 975 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags) 976 { 977 struct file *files[2]; 978 int fd[2]; 979 int error; 980 981 error = __do_pipe_flags(fd, files, flags); 982 if (!error) { 983 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) { 984 fput(files[0]); 985 fput(files[1]); 986 put_unused_fd(fd[0]); 987 put_unused_fd(fd[1]); 988 error = -EFAULT; 989 } else { 990 fd_install(fd[0], files[0]); 991 fd_install(fd[1], files[1]); 992 } 993 } 994 return error; 995 } 996 997 SYSCALL_DEFINE1(pipe, int __user *, fildes) 998 { 999 return sys_pipe2(fildes, 0); 1000 } 1001 1002 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt) 1003 { 1004 int cur = *cnt; 1005 1006 while (cur == *cnt) { 1007 pipe_wait(pipe); 1008 if (signal_pending(current)) 1009 break; 1010 } 1011 return cur == *cnt ? -ERESTARTSYS : 0; 1012 } 1013 1014 static void wake_up_partner(struct pipe_inode_info *pipe) 1015 { 1016 wake_up_interruptible(&pipe->wait); 1017 } 1018 1019 static int fifo_open(struct inode *inode, struct file *filp) 1020 { 1021 struct pipe_inode_info *pipe; 1022 bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC; 1023 int ret; 1024 1025 filp->f_version = 0; 1026 1027 spin_lock(&inode->i_lock); 1028 if (inode->i_pipe) { 1029 pipe = inode->i_pipe; 1030 pipe->files++; 1031 spin_unlock(&inode->i_lock); 1032 } else { 1033 spin_unlock(&inode->i_lock); 1034 pipe = alloc_pipe_info(); 1035 if (!pipe) 1036 return -ENOMEM; 1037 pipe->files = 1; 1038 spin_lock(&inode->i_lock); 1039 if (unlikely(inode->i_pipe)) { 1040 inode->i_pipe->files++; 1041 spin_unlock(&inode->i_lock); 1042 free_pipe_info(pipe); 1043 pipe = inode->i_pipe; 1044 } else { 1045 inode->i_pipe = pipe; 1046 spin_unlock(&inode->i_lock); 1047 } 1048 } 1049 filp->private_data = pipe; 1050 /* OK, we have a pipe and it's pinned down */ 1051 1052 __pipe_lock(pipe); 1053 1054 /* We can only do regular read/write on fifos */ 1055 filp->f_mode &= (FMODE_READ | FMODE_WRITE); 1056 1057 switch (filp->f_mode) { 1058 case FMODE_READ: 1059 /* 1060 * O_RDONLY 1061 * POSIX.1 says that O_NONBLOCK means return with the FIFO 1062 * opened, even when there is no process writing the FIFO. 1063 */ 1064 pipe->r_counter++; 1065 if (pipe->readers++ == 0) 1066 wake_up_partner(pipe); 1067 1068 if (!is_pipe && !pipe->writers) { 1069 if ((filp->f_flags & O_NONBLOCK)) { 1070 /* suppress POLLHUP until we have 1071 * seen a writer */ 1072 filp->f_version = pipe->w_counter; 1073 } else { 1074 if (wait_for_partner(pipe, &pipe->w_counter)) 1075 goto err_rd; 1076 } 1077 } 1078 break; 1079 1080 case FMODE_WRITE: 1081 /* 1082 * O_WRONLY 1083 * POSIX.1 says that O_NONBLOCK means return -1 with 1084 * errno=ENXIO when there is no process reading the FIFO. 1085 */ 1086 ret = -ENXIO; 1087 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers) 1088 goto err; 1089 1090 pipe->w_counter++; 1091 if (!pipe->writers++) 1092 wake_up_partner(pipe); 1093 1094 if (!is_pipe && !pipe->readers) { 1095 if (wait_for_partner(pipe, &pipe->r_counter)) 1096 goto err_wr; 1097 } 1098 break; 1099 1100 case FMODE_READ | FMODE_WRITE: 1101 /* 1102 * O_RDWR 1103 * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set. 1104 * This implementation will NEVER block on a O_RDWR open, since 1105 * the process can at least talk to itself. 1106 */ 1107 1108 pipe->readers++; 1109 pipe->writers++; 1110 pipe->r_counter++; 1111 pipe->w_counter++; 1112 if (pipe->readers == 1 || pipe->writers == 1) 1113 wake_up_partner(pipe); 1114 break; 1115 1116 default: 1117 ret = -EINVAL; 1118 goto err; 1119 } 1120 1121 /* Ok! */ 1122 __pipe_unlock(pipe); 1123 return 0; 1124 1125 err_rd: 1126 if (!--pipe->readers) 1127 wake_up_interruptible(&pipe->wait); 1128 ret = -ERESTARTSYS; 1129 goto err; 1130 1131 err_wr: 1132 if (!--pipe->writers) 1133 wake_up_interruptible(&pipe->wait); 1134 ret = -ERESTARTSYS; 1135 goto err; 1136 1137 err: 1138 __pipe_unlock(pipe); 1139 1140 put_pipe_info(inode, pipe); 1141 return ret; 1142 } 1143 1144 const struct file_operations pipefifo_fops = { 1145 .open = fifo_open, 1146 .llseek = no_llseek, 1147 .read = do_sync_read, 1148 .aio_read = pipe_read, 1149 .write = do_sync_write, 1150 .aio_write = pipe_write, 1151 .poll = pipe_poll, 1152 .unlocked_ioctl = pipe_ioctl, 1153 .release = pipe_release, 1154 .fasync = pipe_fasync, 1155 }; 1156 1157 /* 1158 * Allocate a new array of pipe buffers and copy the info over. Returns the 1159 * pipe size if successful, or return -ERROR on error. 1160 */ 1161 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages) 1162 { 1163 struct pipe_buffer *bufs; 1164 1165 /* 1166 * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't 1167 * expect a lot of shrink+grow operations, just free and allocate 1168 * again like we would do for growing. If the pipe currently 1169 * contains more buffers than arg, then return busy. 1170 */ 1171 if (nr_pages < pipe->nrbufs) 1172 return -EBUSY; 1173 1174 bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN); 1175 if (unlikely(!bufs)) 1176 return -ENOMEM; 1177 1178 /* 1179 * The pipe array wraps around, so just start the new one at zero 1180 * and adjust the indexes. 1181 */ 1182 if (pipe->nrbufs) { 1183 unsigned int tail; 1184 unsigned int head; 1185 1186 tail = pipe->curbuf + pipe->nrbufs; 1187 if (tail < pipe->buffers) 1188 tail = 0; 1189 else 1190 tail &= (pipe->buffers - 1); 1191 1192 head = pipe->nrbufs - tail; 1193 if (head) 1194 memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer)); 1195 if (tail) 1196 memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer)); 1197 } 1198 1199 pipe->curbuf = 0; 1200 kfree(pipe->bufs); 1201 pipe->bufs = bufs; 1202 pipe->buffers = nr_pages; 1203 return nr_pages * PAGE_SIZE; 1204 } 1205 1206 /* 1207 * Currently we rely on the pipe array holding a power-of-2 number 1208 * of pages. 1209 */ 1210 static inline unsigned int round_pipe_size(unsigned int size) 1211 { 1212 unsigned long nr_pages; 1213 1214 nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; 1215 return roundup_pow_of_two(nr_pages) << PAGE_SHIFT; 1216 } 1217 1218 /* 1219 * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax 1220 * will return an error. 1221 */ 1222 int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf, 1223 size_t *lenp, loff_t *ppos) 1224 { 1225 int ret; 1226 1227 ret = proc_dointvec_minmax(table, write, buf, lenp, ppos); 1228 if (ret < 0 || !write) 1229 return ret; 1230 1231 pipe_max_size = round_pipe_size(pipe_max_size); 1232 return ret; 1233 } 1234 1235 /* 1236 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same 1237 * location, so checking ->i_pipe is not enough to verify that this is a 1238 * pipe. 1239 */ 1240 struct pipe_inode_info *get_pipe_info(struct file *file) 1241 { 1242 return file->f_op == &pipefifo_fops ? file->private_data : NULL; 1243 } 1244 1245 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg) 1246 { 1247 struct pipe_inode_info *pipe; 1248 long ret; 1249 1250 pipe = get_pipe_info(file); 1251 if (!pipe) 1252 return -EBADF; 1253 1254 __pipe_lock(pipe); 1255 1256 switch (cmd) { 1257 case F_SETPIPE_SZ: { 1258 unsigned int size, nr_pages; 1259 1260 size = round_pipe_size(arg); 1261 nr_pages = size >> PAGE_SHIFT; 1262 1263 ret = -EINVAL; 1264 if (!nr_pages) 1265 goto out; 1266 1267 if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) { 1268 ret = -EPERM; 1269 goto out; 1270 } 1271 ret = pipe_set_size(pipe, nr_pages); 1272 break; 1273 } 1274 case F_GETPIPE_SZ: 1275 ret = pipe->buffers * PAGE_SIZE; 1276 break; 1277 default: 1278 ret = -EINVAL; 1279 break; 1280 } 1281 1282 out: 1283 __pipe_unlock(pipe); 1284 return ret; 1285 } 1286 1287 static const struct super_operations pipefs_ops = { 1288 .destroy_inode = free_inode_nonrcu, 1289 .statfs = simple_statfs, 1290 }; 1291 1292 /* 1293 * pipefs should _never_ be mounted by userland - too much of security hassle, 1294 * no real gain from having the whole whorehouse mounted. So we don't need 1295 * any operations on the root directory. However, we need a non-trivial 1296 * d_name - pipe: will go nicely and kill the special-casing in procfs. 1297 */ 1298 static struct dentry *pipefs_mount(struct file_system_type *fs_type, 1299 int flags, const char *dev_name, void *data) 1300 { 1301 return mount_pseudo(fs_type, "pipe:", &pipefs_ops, 1302 &pipefs_dentry_operations, PIPEFS_MAGIC); 1303 } 1304 1305 static struct file_system_type pipe_fs_type = { 1306 .name = "pipefs", 1307 .mount = pipefs_mount, 1308 .kill_sb = kill_anon_super, 1309 }; 1310 1311 static int __init init_pipe_fs(void) 1312 { 1313 int err = register_filesystem(&pipe_fs_type); 1314 1315 if (!err) { 1316 pipe_mnt = kern_mount(&pipe_fs_type); 1317 if (IS_ERR(pipe_mnt)) { 1318 err = PTR_ERR(pipe_mnt); 1319 unregister_filesystem(&pipe_fs_type); 1320 } 1321 } 1322 return err; 1323 } 1324 1325 fs_initcall(init_pipe_fs); 1326