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