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 int 730 pipe_release(struct inode *inode, struct file *file) 731 { 732 struct pipe_inode_info *pipe = inode->i_pipe; 733 int kill = 0; 734 735 __pipe_lock(pipe); 736 if (file->f_mode & FMODE_READ) 737 pipe->readers--; 738 if (file->f_mode & FMODE_WRITE) 739 pipe->writers--; 740 741 if (pipe->readers || pipe->writers) { 742 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP); 743 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 744 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); 745 } 746 spin_lock(&inode->i_lock); 747 if (!--pipe->files) { 748 inode->i_pipe = NULL; 749 kill = 1; 750 } 751 spin_unlock(&inode->i_lock); 752 __pipe_unlock(pipe); 753 754 if (kill) 755 free_pipe_info(pipe); 756 757 return 0; 758 } 759 760 static int 761 pipe_fasync(int fd, struct file *filp, int on) 762 { 763 struct pipe_inode_info *pipe = filp->private_data; 764 int retval = 0; 765 766 __pipe_lock(pipe); 767 if (filp->f_mode & FMODE_READ) 768 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers); 769 if ((filp->f_mode & FMODE_WRITE) && retval >= 0) { 770 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers); 771 if (retval < 0 && (filp->f_mode & FMODE_READ)) 772 /* this can happen only if on == T */ 773 fasync_helper(-1, filp, 0, &pipe->fasync_readers); 774 } 775 __pipe_unlock(pipe); 776 return retval; 777 } 778 779 struct pipe_inode_info *alloc_pipe_info(void) 780 { 781 struct pipe_inode_info *pipe; 782 783 pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL); 784 if (pipe) { 785 pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL); 786 if (pipe->bufs) { 787 init_waitqueue_head(&pipe->wait); 788 pipe->r_counter = pipe->w_counter = 1; 789 pipe->buffers = PIPE_DEF_BUFFERS; 790 mutex_init(&pipe->mutex); 791 return pipe; 792 } 793 kfree(pipe); 794 } 795 796 return NULL; 797 } 798 799 void free_pipe_info(struct pipe_inode_info *pipe) 800 { 801 int i; 802 803 for (i = 0; i < pipe->buffers; i++) { 804 struct pipe_buffer *buf = pipe->bufs + i; 805 if (buf->ops) 806 buf->ops->release(pipe, buf); 807 } 808 if (pipe->tmp_page) 809 __free_page(pipe->tmp_page); 810 kfree(pipe->bufs); 811 kfree(pipe); 812 } 813 814 static struct vfsmount *pipe_mnt __read_mostly; 815 816 /* 817 * pipefs_dname() is called from d_path(). 818 */ 819 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen) 820 { 821 return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]", 822 dentry->d_inode->i_ino); 823 } 824 825 static const struct dentry_operations pipefs_dentry_operations = { 826 .d_dname = pipefs_dname, 827 }; 828 829 static struct inode * get_pipe_inode(void) 830 { 831 struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb); 832 struct pipe_inode_info *pipe; 833 834 if (!inode) 835 goto fail_inode; 836 837 inode->i_ino = get_next_ino(); 838 839 pipe = alloc_pipe_info(); 840 if (!pipe) 841 goto fail_iput; 842 843 inode->i_pipe = pipe; 844 pipe->files = 2; 845 pipe->readers = pipe->writers = 1; 846 inode->i_fop = &pipefifo_fops; 847 848 /* 849 * Mark the inode dirty from the very beginning, 850 * that way it will never be moved to the dirty 851 * list because "mark_inode_dirty()" will think 852 * that it already _is_ on the dirty list. 853 */ 854 inode->i_state = I_DIRTY; 855 inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR; 856 inode->i_uid = current_fsuid(); 857 inode->i_gid = current_fsgid(); 858 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 859 860 return inode; 861 862 fail_iput: 863 iput(inode); 864 865 fail_inode: 866 return NULL; 867 } 868 869 int create_pipe_files(struct file **res, int flags) 870 { 871 int err; 872 struct inode *inode = get_pipe_inode(); 873 struct file *f; 874 struct path path; 875 static struct qstr name = { .name = "" }; 876 877 if (!inode) 878 return -ENFILE; 879 880 err = -ENOMEM; 881 path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name); 882 if (!path.dentry) 883 goto err_inode; 884 path.mnt = mntget(pipe_mnt); 885 886 d_instantiate(path.dentry, inode); 887 888 err = -ENFILE; 889 f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops); 890 if (IS_ERR(f)) 891 goto err_dentry; 892 893 f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)); 894 f->private_data = inode->i_pipe; 895 896 res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops); 897 if (IS_ERR(res[0])) 898 goto err_file; 899 900 path_get(&path); 901 res[0]->private_data = inode->i_pipe; 902 res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK); 903 res[1] = f; 904 return 0; 905 906 err_file: 907 put_filp(f); 908 err_dentry: 909 free_pipe_info(inode->i_pipe); 910 path_put(&path); 911 return err; 912 913 err_inode: 914 free_pipe_info(inode->i_pipe); 915 iput(inode); 916 return err; 917 } 918 919 static int __do_pipe_flags(int *fd, struct file **files, int flags) 920 { 921 int error; 922 int fdw, fdr; 923 924 if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT)) 925 return -EINVAL; 926 927 error = create_pipe_files(files, flags); 928 if (error) 929 return error; 930 931 error = get_unused_fd_flags(flags); 932 if (error < 0) 933 goto err_read_pipe; 934 fdr = error; 935 936 error = get_unused_fd_flags(flags); 937 if (error < 0) 938 goto err_fdr; 939 fdw = error; 940 941 audit_fd_pair(fdr, fdw); 942 fd[0] = fdr; 943 fd[1] = fdw; 944 return 0; 945 946 err_fdr: 947 put_unused_fd(fdr); 948 err_read_pipe: 949 fput(files[0]); 950 fput(files[1]); 951 return error; 952 } 953 954 int do_pipe_flags(int *fd, int flags) 955 { 956 struct file *files[2]; 957 int error = __do_pipe_flags(fd, files, flags); 958 if (!error) { 959 fd_install(fd[0], files[0]); 960 fd_install(fd[1], files[1]); 961 } 962 return error; 963 } 964 965 /* 966 * sys_pipe() is the normal C calling standard for creating 967 * a pipe. It's not the way Unix traditionally does this, though. 968 */ 969 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags) 970 { 971 struct file *files[2]; 972 int fd[2]; 973 int error; 974 975 error = __do_pipe_flags(fd, files, flags); 976 if (!error) { 977 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) { 978 fput(files[0]); 979 fput(files[1]); 980 put_unused_fd(fd[0]); 981 put_unused_fd(fd[1]); 982 error = -EFAULT; 983 } else { 984 fd_install(fd[0], files[0]); 985 fd_install(fd[1], files[1]); 986 } 987 } 988 return error; 989 } 990 991 SYSCALL_DEFINE1(pipe, int __user *, fildes) 992 { 993 return sys_pipe2(fildes, 0); 994 } 995 996 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt) 997 { 998 int cur = *cnt; 999 1000 while (cur == *cnt) { 1001 pipe_wait(pipe); 1002 if (signal_pending(current)) 1003 break; 1004 } 1005 return cur == *cnt ? -ERESTARTSYS : 0; 1006 } 1007 1008 static void wake_up_partner(struct pipe_inode_info *pipe) 1009 { 1010 wake_up_interruptible(&pipe->wait); 1011 } 1012 1013 static int fifo_open(struct inode *inode, struct file *filp) 1014 { 1015 struct pipe_inode_info *pipe; 1016 bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC; 1017 int kill = 0; 1018 int ret; 1019 1020 filp->f_version = 0; 1021 1022 spin_lock(&inode->i_lock); 1023 if (inode->i_pipe) { 1024 pipe = inode->i_pipe; 1025 pipe->files++; 1026 spin_unlock(&inode->i_lock); 1027 } else { 1028 spin_unlock(&inode->i_lock); 1029 pipe = alloc_pipe_info(); 1030 if (!pipe) 1031 return -ENOMEM; 1032 pipe->files = 1; 1033 spin_lock(&inode->i_lock); 1034 if (unlikely(inode->i_pipe)) { 1035 inode->i_pipe->files++; 1036 spin_unlock(&inode->i_lock); 1037 free_pipe_info(pipe); 1038 pipe = inode->i_pipe; 1039 } else { 1040 inode->i_pipe = pipe; 1041 spin_unlock(&inode->i_lock); 1042 } 1043 } 1044 filp->private_data = pipe; 1045 /* OK, we have a pipe and it's pinned down */ 1046 1047 __pipe_lock(pipe); 1048 1049 /* We can only do regular read/write on fifos */ 1050 filp->f_mode &= (FMODE_READ | FMODE_WRITE); 1051 1052 switch (filp->f_mode) { 1053 case FMODE_READ: 1054 /* 1055 * O_RDONLY 1056 * POSIX.1 says that O_NONBLOCK means return with the FIFO 1057 * opened, even when there is no process writing the FIFO. 1058 */ 1059 pipe->r_counter++; 1060 if (pipe->readers++ == 0) 1061 wake_up_partner(pipe); 1062 1063 if (!is_pipe && !pipe->writers) { 1064 if ((filp->f_flags & O_NONBLOCK)) { 1065 /* suppress POLLHUP until we have 1066 * seen a writer */ 1067 filp->f_version = pipe->w_counter; 1068 } else { 1069 if (wait_for_partner(pipe, &pipe->w_counter)) 1070 goto err_rd; 1071 } 1072 } 1073 break; 1074 1075 case FMODE_WRITE: 1076 /* 1077 * O_WRONLY 1078 * POSIX.1 says that O_NONBLOCK means return -1 with 1079 * errno=ENXIO when there is no process reading the FIFO. 1080 */ 1081 ret = -ENXIO; 1082 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers) 1083 goto err; 1084 1085 pipe->w_counter++; 1086 if (!pipe->writers++) 1087 wake_up_partner(pipe); 1088 1089 if (!is_pipe && !pipe->readers) { 1090 if (wait_for_partner(pipe, &pipe->r_counter)) 1091 goto err_wr; 1092 } 1093 break; 1094 1095 case FMODE_READ | FMODE_WRITE: 1096 /* 1097 * O_RDWR 1098 * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set. 1099 * This implementation will NEVER block on a O_RDWR open, since 1100 * the process can at least talk to itself. 1101 */ 1102 1103 pipe->readers++; 1104 pipe->writers++; 1105 pipe->r_counter++; 1106 pipe->w_counter++; 1107 if (pipe->readers == 1 || pipe->writers == 1) 1108 wake_up_partner(pipe); 1109 break; 1110 1111 default: 1112 ret = -EINVAL; 1113 goto err; 1114 } 1115 1116 /* Ok! */ 1117 __pipe_unlock(pipe); 1118 return 0; 1119 1120 err_rd: 1121 if (!--pipe->readers) 1122 wake_up_interruptible(&pipe->wait); 1123 ret = -ERESTARTSYS; 1124 goto err; 1125 1126 err_wr: 1127 if (!--pipe->writers) 1128 wake_up_interruptible(&pipe->wait); 1129 ret = -ERESTARTSYS; 1130 goto err; 1131 1132 err: 1133 spin_lock(&inode->i_lock); 1134 if (!--pipe->files) { 1135 inode->i_pipe = NULL; 1136 kill = 1; 1137 } 1138 spin_unlock(&inode->i_lock); 1139 __pipe_unlock(pipe); 1140 if (kill) 1141 free_pipe_info(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); 1327