| 1 | // SPDX-License-Identifier: GPL-2.0 |
| 2 | /* |
| 3 | * linux/fs/pipe.c |
| 4 | * |
| 5 | * Copyright (C) 1991, 1992, 1999 Linus Torvalds |
| 6 | */ |
| 7 | |
| 8 | #include <linux/mm.h> |
| 9 | #include <linux/file.h> |
| 10 | #include <linux/poll.h> |
| 11 | #include <linux/slab.h> |
| 12 | #include <linux/module.h> |
| 13 | #include <linux/init.h> |
| 14 | #include <linux/fs.h> |
| 15 | #include <linux/log2.h> |
| 16 | #include <linux/mount.h> |
| 17 | #include <linux/magic.h> |
| 18 | #include <linux/pipe_fs_i.h> |
| 19 | #include <linux/uio.h> |
| 20 | #include <linux/highmem.h> |
| 21 | #include <linux/pagemap.h> |
| 22 | #include <linux/audit.h> |
| 23 | #include <linux/syscalls.h> |
| 24 | #include <linux/fcntl.h> |
| 25 | #include <linux/memcontrol.h> |
| 26 | |
| 27 | #include <linux/uaccess.h> |
| 28 | #include <asm/ioctls.h> |
| 29 | |
| 30 | #include "internal.h" |
| 31 | |
| 32 | /* |
| 33 | * The max size that a non-root user is allowed to grow the pipe. Can |
| 34 | * be set by root in /proc/sys/fs/pipe-max-size |
| 35 | */ |
| 36 | unsigned int pipe_max_size = 1048576; |
| 37 | |
| 38 | /* Maximum allocatable pages per user. Hard limit is unset by default, soft |
| 39 | * matches default values. |
| 40 | */ |
| 41 | unsigned long pipe_user_pages_hard; |
| 42 | unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR; |
| 43 | |
| 44 | /* |
| 45 | * We use a start+len construction, which provides full use of the |
| 46 | * allocated memory. |
| 47 | * -- Florian Coosmann (FGC) |
| 48 | * |
| 49 | * Reads with count = 0 should always return 0. |
| 50 | * -- Julian Bradfield 1999-06-07. |
| 51 | * |
| 52 | * FIFOs and Pipes now generate SIGIO for both readers and writers. |
| 53 | * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16 |
| 54 | * |
| 55 | * pipe_read & write cleanup |
| 56 | * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09 |
| 57 | */ |
| 58 | |
| 59 | static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass) |
| 60 | { |
| 61 | if (pipe->files) |
| 62 | mutex_lock_nested(&pipe->mutex, subclass); |
| 63 | } |
| 64 | |
| 65 | void pipe_lock(struct pipe_inode_info *pipe) |
| 66 | { |
| 67 | /* |
| 68 | * pipe_lock() nests non-pipe inode locks (for writing to a file) |
| 69 | */ |
| 70 | pipe_lock_nested(pipe, I_MUTEX_PARENT); |
| 71 | } |
| 72 | EXPORT_SYMBOL(pipe_lock); |
| 73 | |
| 74 | void pipe_unlock(struct pipe_inode_info *pipe) |
| 75 | { |
| 76 | if (pipe->files) |
| 77 | mutex_unlock(&pipe->mutex); |
| 78 | } |
| 79 | EXPORT_SYMBOL(pipe_unlock); |
| 80 | |
| 81 | static inline void __pipe_lock(struct pipe_inode_info *pipe) |
| 82 | { |
| 83 | mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT); |
| 84 | } |
| 85 | |
| 86 | static inline void __pipe_unlock(struct pipe_inode_info *pipe) |
| 87 | { |
| 88 | mutex_unlock(&pipe->mutex); |
| 89 | } |
| 90 | |
| 91 | void pipe_double_lock(struct pipe_inode_info *pipe1, |
| 92 | struct pipe_inode_info *pipe2) |
| 93 | { |
| 94 | BUG_ON(pipe1 == pipe2); |
| 95 | |
| 96 | if (pipe1 < pipe2) { |
| 97 | pipe_lock_nested(pipe1, I_MUTEX_PARENT); |
| 98 | pipe_lock_nested(pipe2, I_MUTEX_CHILD); |
| 99 | } else { |
| 100 | pipe_lock_nested(pipe2, I_MUTEX_PARENT); |
| 101 | pipe_lock_nested(pipe1, I_MUTEX_CHILD); |
| 102 | } |
| 103 | } |
| 104 | |
| 105 | /* Drop the inode semaphore and wait for a pipe event, atomically */ |
| 106 | void pipe_wait(struct pipe_inode_info *pipe) |
| 107 | { |
| 108 | DEFINE_WAIT(wait); |
| 109 | |
| 110 | /* |
| 111 | * Pipes are system-local resources, so sleeping on them |
| 112 | * is considered a noninteractive wait: |
| 113 | */ |
| 114 | prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE); |
| 115 | pipe_unlock(pipe); |
| 116 | schedule(); |
| 117 | finish_wait(&pipe->wait, &wait); |
| 118 | pipe_lock(pipe); |
| 119 | } |
| 120 | |
| 121 | static void anon_pipe_buf_release(struct pipe_inode_info *pipe, |
| 122 | struct pipe_buffer *buf) |
| 123 | { |
| 124 | struct page *page = buf->page; |
| 125 | |
| 126 | /* |
| 127 | * If nobody else uses this page, and we don't already have a |
| 128 | * temporary page, let's keep track of it as a one-deep |
| 129 | * allocation cache. (Otherwise just release our reference to it) |
| 130 | */ |
| 131 | if (page_count(page) == 1 && !pipe->tmp_page) |
| 132 | pipe->tmp_page = page; |
| 133 | else |
| 134 | put_page(page); |
| 135 | } |
| 136 | |
| 137 | static int anon_pipe_buf_steal(struct pipe_inode_info *pipe, |
| 138 | struct pipe_buffer *buf) |
| 139 | { |
| 140 | struct page *page = buf->page; |
| 141 | |
| 142 | if (page_count(page) == 1) { |
| 143 | if (memcg_kmem_enabled()) |
| 144 | memcg_kmem_uncharge(page, 0); |
| 145 | __SetPageLocked(page); |
| 146 | return 0; |
| 147 | } |
| 148 | return 1; |
| 149 | } |
| 150 | |
| 151 | /** |
| 152 | * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer |
| 153 | * @pipe: the pipe that the buffer belongs to |
| 154 | * @buf: the buffer to attempt to steal |
| 155 | * |
| 156 | * Description: |
| 157 | * This function attempts to steal the &struct page attached to |
| 158 | * @buf. If successful, this function returns 0 and returns with |
| 159 | * the page locked. The caller may then reuse the page for whatever |
| 160 | * he wishes; the typical use is insertion into a different file |
| 161 | * page cache. |
| 162 | */ |
| 163 | int generic_pipe_buf_steal(struct pipe_inode_info *pipe, |
| 164 | struct pipe_buffer *buf) |
| 165 | { |
| 166 | struct page *page = buf->page; |
| 167 | |
| 168 | /* |
| 169 | * A reference of one is golden, that means that the owner of this |
| 170 | * page is the only one holding a reference to it. lock the page |
| 171 | * and return OK. |
| 172 | */ |
| 173 | if (page_count(page) == 1) { |
| 174 | lock_page(page); |
| 175 | return 0; |
| 176 | } |
| 177 | |
| 178 | return 1; |
| 179 | } |
| 180 | EXPORT_SYMBOL(generic_pipe_buf_steal); |
| 181 | |
| 182 | /** |
| 183 | * generic_pipe_buf_get - get a reference to a &struct pipe_buffer |
| 184 | * @pipe: the pipe that the buffer belongs to |
| 185 | * @buf: the buffer to get a reference to |
| 186 | * |
| 187 | * Description: |
| 188 | * This function grabs an extra reference to @buf. It's used in |
| 189 | * in the tee() system call, when we duplicate the buffers in one |
| 190 | * pipe into another. |
| 191 | */ |
| 192 | void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf) |
| 193 | { |
| 194 | get_page(buf->page); |
| 195 | } |
| 196 | EXPORT_SYMBOL(generic_pipe_buf_get); |
| 197 | |
| 198 | /** |
| 199 | * generic_pipe_buf_confirm - verify contents of the pipe buffer |
| 200 | * @info: the pipe that the buffer belongs to |
| 201 | * @buf: the buffer to confirm |
| 202 | * |
| 203 | * Description: |
| 204 | * This function does nothing, because the generic pipe code uses |
| 205 | * pages that are always good when inserted into the pipe. |
| 206 | */ |
| 207 | int generic_pipe_buf_confirm(struct pipe_inode_info *info, |
| 208 | struct pipe_buffer *buf) |
| 209 | { |
| 210 | return 0; |
| 211 | } |
| 212 | EXPORT_SYMBOL(generic_pipe_buf_confirm); |
| 213 | |
| 214 | /** |
| 215 | * generic_pipe_buf_release - put a reference to a &struct pipe_buffer |
| 216 | * @pipe: the pipe that the buffer belongs to |
| 217 | * @buf: the buffer to put a reference to |
| 218 | * |
| 219 | * Description: |
| 220 | * This function releases a reference to @buf. |
| 221 | */ |
| 222 | void generic_pipe_buf_release(struct pipe_inode_info *pipe, |
| 223 | struct pipe_buffer *buf) |
| 224 | { |
| 225 | put_page(buf->page); |
| 226 | } |
| 227 | EXPORT_SYMBOL(generic_pipe_buf_release); |
| 228 | |
| 229 | static const struct pipe_buf_operations anon_pipe_buf_ops = { |
| 230 | .can_merge = 1, |
| 231 | .confirm = generic_pipe_buf_confirm, |
| 232 | .release = anon_pipe_buf_release, |
| 233 | .steal = anon_pipe_buf_steal, |
| 234 | .get = generic_pipe_buf_get, |
| 235 | }; |
| 236 | |
| 237 | static const struct pipe_buf_operations packet_pipe_buf_ops = { |
| 238 | .can_merge = 0, |
| 239 | .confirm = generic_pipe_buf_confirm, |
| 240 | .release = anon_pipe_buf_release, |
| 241 | .steal = anon_pipe_buf_steal, |
| 242 | .get = generic_pipe_buf_get, |
| 243 | }; |
| 244 | |
| 245 | static ssize_t |
| 246 | pipe_read(struct kiocb *iocb, struct iov_iter *to) |
| 247 | { |
| 248 | size_t total_len = iov_iter_count(to); |
| 249 | struct file *filp = iocb->ki_filp; |
| 250 | struct pipe_inode_info *pipe = filp->private_data; |
| 251 | int do_wakeup; |
| 252 | ssize_t ret; |
| 253 | |
| 254 | /* Null read succeeds. */ |
| 255 | if (unlikely(total_len == 0)) |
| 256 | return 0; |
| 257 | |
| 258 | do_wakeup = 0; |
| 259 | ret = 0; |
| 260 | __pipe_lock(pipe); |
| 261 | for (;;) { |
| 262 | int bufs = pipe->nrbufs; |
| 263 | if (bufs) { |
| 264 | int curbuf = pipe->curbuf; |
| 265 | struct pipe_buffer *buf = pipe->bufs + curbuf; |
| 266 | size_t chars = buf->len; |
| 267 | size_t written; |
| 268 | int error; |
| 269 | |
| 270 | if (chars > total_len) |
| 271 | chars = total_len; |
| 272 | |
| 273 | error = pipe_buf_confirm(pipe, buf); |
| 274 | if (error) { |
| 275 | if (!ret) |
| 276 | ret = error; |
| 277 | break; |
| 278 | } |
| 279 | |
| 280 | written = copy_page_to_iter(buf->page, buf->offset, chars, to); |
| 281 | if (unlikely(written < chars)) { |
| 282 | if (!ret) |
| 283 | ret = -EFAULT; |
| 284 | break; |
| 285 | } |
| 286 | ret += chars; |
| 287 | buf->offset += chars; |
| 288 | buf->len -= chars; |
| 289 | |
| 290 | /* Was it a packet buffer? Clean up and exit */ |
| 291 | if (buf->flags & PIPE_BUF_FLAG_PACKET) { |
| 292 | total_len = chars; |
| 293 | buf->len = 0; |
| 294 | } |
| 295 | |
| 296 | if (!buf->len) { |
| 297 | pipe_buf_release(pipe, buf); |
| 298 | curbuf = (curbuf + 1) & (pipe->buffers - 1); |
| 299 | pipe->curbuf = curbuf; |
| 300 | pipe->nrbufs = --bufs; |
| 301 | do_wakeup = 1; |
| 302 | } |
| 303 | total_len -= chars; |
| 304 | if (!total_len) |
| 305 | break; /* common path: read succeeded */ |
| 306 | } |
| 307 | if (bufs) /* More to do? */ |
| 308 | continue; |
| 309 | if (!pipe->writers) |
| 310 | break; |
| 311 | if (!pipe->waiting_writers) { |
| 312 | /* syscall merging: Usually we must not sleep |
| 313 | * if O_NONBLOCK is set, or if we got some data. |
| 314 | * But if a writer sleeps in kernel space, then |
| 315 | * we can wait for that data without violating POSIX. |
| 316 | */ |
| 317 | if (ret) |
| 318 | break; |
| 319 | if (filp->f_flags & O_NONBLOCK) { |
| 320 | ret = -EAGAIN; |
| 321 | break; |
| 322 | } |
| 323 | } |
| 324 | if (signal_pending(current)) { |
| 325 | if (!ret) |
| 326 | ret = -ERESTARTSYS; |
| 327 | break; |
| 328 | } |
| 329 | if (do_wakeup) { |
| 330 | wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM); |
| 331 | kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); |
| 332 | } |
| 333 | pipe_wait(pipe); |
| 334 | } |
| 335 | __pipe_unlock(pipe); |
| 336 | |
| 337 | /* Signal writers asynchronously that there is more room. */ |
| 338 | if (do_wakeup) { |
| 339 | wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM); |
| 340 | kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); |
| 341 | } |
| 342 | if (ret > 0) |
| 343 | file_accessed(filp); |
| 344 | return ret; |
| 345 | } |
| 346 | |
| 347 | static inline int is_packetized(struct file *file) |
| 348 | { |
| 349 | return (file->f_flags & O_DIRECT) != 0; |
| 350 | } |
| 351 | |
| 352 | static ssize_t |
| 353 | pipe_write(struct kiocb *iocb, struct iov_iter *from) |
| 354 | { |
| 355 | struct file *filp = iocb->ki_filp; |
| 356 | struct pipe_inode_info *pipe = filp->private_data; |
| 357 | ssize_t ret = 0; |
| 358 | int do_wakeup = 0; |
| 359 | size_t total_len = iov_iter_count(from); |
| 360 | ssize_t chars; |
| 361 | |
| 362 | /* Null write succeeds. */ |
| 363 | if (unlikely(total_len == 0)) |
| 364 | return 0; |
| 365 | |
| 366 | __pipe_lock(pipe); |
| 367 | |
| 368 | if (!pipe->readers) { |
| 369 | send_sig(SIGPIPE, current, 0); |
| 370 | ret = -EPIPE; |
| 371 | goto out; |
| 372 | } |
| 373 | |
| 374 | /* We try to merge small writes */ |
| 375 | chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */ |
| 376 | if (pipe->nrbufs && chars != 0) { |
| 377 | int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) & |
| 378 | (pipe->buffers - 1); |
| 379 | struct pipe_buffer *buf = pipe->bufs + lastbuf; |
| 380 | int offset = buf->offset + buf->len; |
| 381 | |
| 382 | if (buf->ops->can_merge && offset + chars <= PAGE_SIZE) { |
| 383 | ret = pipe_buf_confirm(pipe, buf); |
| 384 | if (ret) |
| 385 | goto out; |
| 386 | |
| 387 | ret = copy_page_from_iter(buf->page, offset, chars, from); |
| 388 | if (unlikely(ret < chars)) { |
| 389 | ret = -EFAULT; |
| 390 | goto out; |
| 391 | } |
| 392 | do_wakeup = 1; |
| 393 | buf->len += ret; |
| 394 | if (!iov_iter_count(from)) |
| 395 | goto out; |
| 396 | } |
| 397 | } |
| 398 | |
| 399 | for (;;) { |
| 400 | int bufs; |
| 401 | |
| 402 | if (!pipe->readers) { |
| 403 | send_sig(SIGPIPE, current, 0); |
| 404 | if (!ret) |
| 405 | ret = -EPIPE; |
| 406 | break; |
| 407 | } |
| 408 | bufs = pipe->nrbufs; |
| 409 | if (bufs < pipe->buffers) { |
| 410 | int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1); |
| 411 | struct pipe_buffer *buf = pipe->bufs + newbuf; |
| 412 | struct page *page = pipe->tmp_page; |
| 413 | int copied; |
| 414 | |
| 415 | if (!page) { |
| 416 | page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT); |
| 417 | if (unlikely(!page)) { |
| 418 | ret = ret ? : -ENOMEM; |
| 419 | break; |
| 420 | } |
| 421 | pipe->tmp_page = page; |
| 422 | } |
| 423 | /* Always wake up, even if the copy fails. Otherwise |
| 424 | * we lock up (O_NONBLOCK-)readers that sleep due to |
| 425 | * syscall merging. |
| 426 | * FIXME! Is this really true? |
| 427 | */ |
| 428 | do_wakeup = 1; |
| 429 | copied = copy_page_from_iter(page, 0, PAGE_SIZE, from); |
| 430 | if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) { |
| 431 | if (!ret) |
| 432 | ret = -EFAULT; |
| 433 | break; |
| 434 | } |
| 435 | ret += copied; |
| 436 | |
| 437 | /* Insert it into the buffer array */ |
| 438 | buf->page = page; |
| 439 | buf->ops = &anon_pipe_buf_ops; |
| 440 | buf->offset = 0; |
| 441 | buf->len = copied; |
| 442 | buf->flags = 0; |
| 443 | if (is_packetized(filp)) { |
| 444 | buf->ops = &packet_pipe_buf_ops; |
| 445 | buf->flags = PIPE_BUF_FLAG_PACKET; |
| 446 | } |
| 447 | pipe->nrbufs = ++bufs; |
| 448 | pipe->tmp_page = NULL; |
| 449 | |
| 450 | if (!iov_iter_count(from)) |
| 451 | break; |
| 452 | } |
| 453 | if (bufs < pipe->buffers) |
| 454 | continue; |
| 455 | if (filp->f_flags & O_NONBLOCK) { |
| 456 | if (!ret) |
| 457 | ret = -EAGAIN; |
| 458 | break; |
| 459 | } |
| 460 | if (signal_pending(current)) { |
| 461 | if (!ret) |
| 462 | ret = -ERESTARTSYS; |
| 463 | break; |
| 464 | } |
| 465 | if (do_wakeup) { |
| 466 | wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLRDNORM); |
| 467 | kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); |
| 468 | do_wakeup = 0; |
| 469 | } |
| 470 | pipe->waiting_writers++; |
| 471 | pipe_wait(pipe); |
| 472 | pipe->waiting_writers--; |
| 473 | } |
| 474 | out: |
| 475 | __pipe_unlock(pipe); |
| 476 | if (do_wakeup) { |
| 477 | wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLRDNORM); |
| 478 | kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); |
| 479 | } |
| 480 | if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) { |
| 481 | int err = file_update_time(filp); |
| 482 | if (err) |
| 483 | ret = err; |
| 484 | sb_end_write(file_inode(filp)->i_sb); |
| 485 | } |
| 486 | return ret; |
| 487 | } |
| 488 | |
| 489 | static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) |
| 490 | { |
| 491 | struct pipe_inode_info *pipe = filp->private_data; |
| 492 | int count, buf, nrbufs; |
| 493 | |
| 494 | switch (cmd) { |
| 495 | case FIONREAD: |
| 496 | __pipe_lock(pipe); |
| 497 | count = 0; |
| 498 | buf = pipe->curbuf; |
| 499 | nrbufs = pipe->nrbufs; |
| 500 | while (--nrbufs >= 0) { |
| 501 | count += pipe->bufs[buf].len; |
| 502 | buf = (buf+1) & (pipe->buffers - 1); |
| 503 | } |
| 504 | __pipe_unlock(pipe); |
| 505 | |
| 506 | return put_user(count, (int __user *)arg); |
| 507 | default: |
| 508 | return -ENOIOCTLCMD; |
| 509 | } |
| 510 | } |
| 511 | |
| 512 | /* No kernel lock held - fine */ |
| 513 | static __poll_t |
| 514 | pipe_poll(struct file *filp, poll_table *wait) |
| 515 | { |
| 516 | __poll_t mask; |
| 517 | struct pipe_inode_info *pipe = filp->private_data; |
| 518 | int nrbufs; |
| 519 | |
| 520 | poll_wait(filp, &pipe->wait, wait); |
| 521 | |
| 522 | /* Reading only -- no need for acquiring the semaphore. */ |
| 523 | nrbufs = pipe->nrbufs; |
| 524 | mask = 0; |
| 525 | if (filp->f_mode & FMODE_READ) { |
| 526 | mask = (nrbufs > 0) ? EPOLLIN | EPOLLRDNORM : 0; |
| 527 | if (!pipe->writers && filp->f_version != pipe->w_counter) |
| 528 | mask |= EPOLLHUP; |
| 529 | } |
| 530 | |
| 531 | if (filp->f_mode & FMODE_WRITE) { |
| 532 | mask |= (nrbufs < pipe->buffers) ? EPOLLOUT | EPOLLWRNORM : 0; |
| 533 | /* |
| 534 | * Most Unices do not set EPOLLERR for FIFOs but on Linux they |
| 535 | * behave exactly like pipes for poll(). |
| 536 | */ |
| 537 | if (!pipe->readers) |
| 538 | mask |= EPOLLERR; |
| 539 | } |
| 540 | |
| 541 | return mask; |
| 542 | } |
| 543 | |
| 544 | static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe) |
| 545 | { |
| 546 | int kill = 0; |
| 547 | |
| 548 | spin_lock(&inode->i_lock); |
| 549 | if (!--pipe->files) { |
| 550 | inode->i_pipe = NULL; |
| 551 | kill = 1; |
| 552 | } |
| 553 | spin_unlock(&inode->i_lock); |
| 554 | |
| 555 | if (kill) |
| 556 | free_pipe_info(pipe); |
| 557 | } |
| 558 | |
| 559 | static int |
| 560 | pipe_release(struct inode *inode, struct file *file) |
| 561 | { |
| 562 | struct pipe_inode_info *pipe = file->private_data; |
| 563 | |
| 564 | __pipe_lock(pipe); |
| 565 | if (file->f_mode & FMODE_READ) |
| 566 | pipe->readers--; |
| 567 | if (file->f_mode & FMODE_WRITE) |
| 568 | pipe->writers--; |
| 569 | |
| 570 | if (pipe->readers || pipe->writers) { |
| 571 | wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLOUT | EPOLLRDNORM | EPOLLWRNORM | EPOLLERR | EPOLLHUP); |
| 572 | kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); |
| 573 | kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); |
| 574 | } |
| 575 | __pipe_unlock(pipe); |
| 576 | |
| 577 | put_pipe_info(inode, pipe); |
| 578 | return 0; |
| 579 | } |
| 580 | |
| 581 | static int |
| 582 | pipe_fasync(int fd, struct file *filp, int on) |
| 583 | { |
| 584 | struct pipe_inode_info *pipe = filp->private_data; |
| 585 | int retval = 0; |
| 586 | |
| 587 | __pipe_lock(pipe); |
| 588 | if (filp->f_mode & FMODE_READ) |
| 589 | retval = fasync_helper(fd, filp, on, &pipe->fasync_readers); |
| 590 | if ((filp->f_mode & FMODE_WRITE) && retval >= 0) { |
| 591 | retval = fasync_helper(fd, filp, on, &pipe->fasync_writers); |
| 592 | if (retval < 0 && (filp->f_mode & FMODE_READ)) |
| 593 | /* this can happen only if on == T */ |
| 594 | fasync_helper(-1, filp, 0, &pipe->fasync_readers); |
| 595 | } |
| 596 | __pipe_unlock(pipe); |
| 597 | return retval; |
| 598 | } |
| 599 | |
| 600 | static unsigned long account_pipe_buffers(struct user_struct *user, |
| 601 | unsigned long old, unsigned long new) |
| 602 | { |
| 603 | return atomic_long_add_return(new - old, &user->pipe_bufs); |
| 604 | } |
| 605 | |
| 606 | static bool too_many_pipe_buffers_soft(unsigned long user_bufs) |
| 607 | { |
| 608 | unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft); |
| 609 | |
| 610 | return soft_limit && user_bufs > soft_limit; |
| 611 | } |
| 612 | |
| 613 | static bool too_many_pipe_buffers_hard(unsigned long user_bufs) |
| 614 | { |
| 615 | unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard); |
| 616 | |
| 617 | return hard_limit && user_bufs > hard_limit; |
| 618 | } |
| 619 | |
| 620 | static bool is_unprivileged_user(void) |
| 621 | { |
| 622 | return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN); |
| 623 | } |
| 624 | |
| 625 | struct pipe_inode_info *alloc_pipe_info(void) |
| 626 | { |
| 627 | struct pipe_inode_info *pipe; |
| 628 | unsigned long pipe_bufs = PIPE_DEF_BUFFERS; |
| 629 | struct user_struct *user = get_current_user(); |
| 630 | unsigned long user_bufs; |
| 631 | unsigned int max_size = READ_ONCE(pipe_max_size); |
| 632 | |
| 633 | pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT); |
| 634 | if (pipe == NULL) |
| 635 | goto out_free_uid; |
| 636 | |
| 637 | if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE)) |
| 638 | pipe_bufs = max_size >> PAGE_SHIFT; |
| 639 | |
| 640 | user_bufs = account_pipe_buffers(user, 0, pipe_bufs); |
| 641 | |
| 642 | if (too_many_pipe_buffers_soft(user_bufs) && is_unprivileged_user()) { |
| 643 | user_bufs = account_pipe_buffers(user, pipe_bufs, 1); |
| 644 | pipe_bufs = 1; |
| 645 | } |
| 646 | |
| 647 | if (too_many_pipe_buffers_hard(user_bufs) && is_unprivileged_user()) |
| 648 | goto out_revert_acct; |
| 649 | |
| 650 | pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer), |
| 651 | GFP_KERNEL_ACCOUNT); |
| 652 | |
| 653 | if (pipe->bufs) { |
| 654 | init_waitqueue_head(&pipe->wait); |
| 655 | pipe->r_counter = pipe->w_counter = 1; |
| 656 | pipe->buffers = pipe_bufs; |
| 657 | pipe->user = user; |
| 658 | mutex_init(&pipe->mutex); |
| 659 | return pipe; |
| 660 | } |
| 661 | |
| 662 | out_revert_acct: |
| 663 | (void) account_pipe_buffers(user, pipe_bufs, 0); |
| 664 | kfree(pipe); |
| 665 | out_free_uid: |
| 666 | free_uid(user); |
| 667 | return NULL; |
| 668 | } |
| 669 | |
| 670 | void free_pipe_info(struct pipe_inode_info *pipe) |
| 671 | { |
| 672 | int i; |
| 673 | |
| 674 | (void) account_pipe_buffers(pipe->user, pipe->buffers, 0); |
| 675 | free_uid(pipe->user); |
| 676 | for (i = 0; i < pipe->buffers; i++) { |
| 677 | struct pipe_buffer *buf = pipe->bufs + i; |
| 678 | if (buf->ops) |
| 679 | pipe_buf_release(pipe, buf); |
| 680 | } |
| 681 | if (pipe->tmp_page) |
| 682 | __free_page(pipe->tmp_page); |
| 683 | kfree(pipe->bufs); |
| 684 | kfree(pipe); |
| 685 | } |
| 686 | |
| 687 | static struct vfsmount *pipe_mnt __read_mostly; |
| 688 | |
| 689 | /* |
| 690 | * pipefs_dname() is called from d_path(). |
| 691 | */ |
| 692 | static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen) |
| 693 | { |
| 694 | return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]", |
| 695 | d_inode(dentry)->i_ino); |
| 696 | } |
| 697 | |
| 698 | static const struct dentry_operations pipefs_dentry_operations = { |
| 699 | .d_dname = pipefs_dname, |
| 700 | }; |
| 701 | |
| 702 | static struct inode * get_pipe_inode(void) |
| 703 | { |
| 704 | struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb); |
| 705 | struct pipe_inode_info *pipe; |
| 706 | |
| 707 | if (!inode) |
| 708 | goto fail_inode; |
| 709 | |
| 710 | inode->i_ino = get_next_ino(); |
| 711 | |
| 712 | pipe = alloc_pipe_info(); |
| 713 | if (!pipe) |
| 714 | goto fail_iput; |
| 715 | |
| 716 | inode->i_pipe = pipe; |
| 717 | pipe->files = 2; |
| 718 | pipe->readers = pipe->writers = 1; |
| 719 | inode->i_fop = &pipefifo_fops; |
| 720 | |
| 721 | /* |
| 722 | * Mark the inode dirty from the very beginning, |
| 723 | * that way it will never be moved to the dirty |
| 724 | * list because "mark_inode_dirty()" will think |
| 725 | * that it already _is_ on the dirty list. |
| 726 | */ |
| 727 | inode->i_state = I_DIRTY; |
| 728 | inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR; |
| 729 | inode->i_uid = current_fsuid(); |
| 730 | inode->i_gid = current_fsgid(); |
| 731 | inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); |
| 732 | |
| 733 | return inode; |
| 734 | |
| 735 | fail_iput: |
| 736 | iput(inode); |
| 737 | |
| 738 | fail_inode: |
| 739 | return NULL; |
| 740 | } |
| 741 | |
| 742 | int create_pipe_files(struct file **res, int flags) |
| 743 | { |
| 744 | struct inode *inode = get_pipe_inode(); |
| 745 | struct file *f; |
| 746 | |
| 747 | if (!inode) |
| 748 | return -ENFILE; |
| 749 | |
| 750 | f = alloc_file_pseudo(inode, pipe_mnt, "", |
| 751 | O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)), |
| 752 | &pipefifo_fops); |
| 753 | if (IS_ERR(f)) { |
| 754 | free_pipe_info(inode->i_pipe); |
| 755 | iput(inode); |
| 756 | return PTR_ERR(f); |
| 757 | } |
| 758 | |
| 759 | f->private_data = inode->i_pipe; |
| 760 | |
| 761 | res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK), |
| 762 | &pipefifo_fops); |
| 763 | if (IS_ERR(res[0])) { |
| 764 | put_pipe_info(inode, inode->i_pipe); |
| 765 | fput(f); |
| 766 | return PTR_ERR(res[0]); |
| 767 | } |
| 768 | res[0]->private_data = inode->i_pipe; |
| 769 | res[1] = f; |
| 770 | return 0; |
| 771 | } |
| 772 | |
| 773 | static int __do_pipe_flags(int *fd, struct file **files, int flags) |
| 774 | { |
| 775 | int error; |
| 776 | int fdw, fdr; |
| 777 | |
| 778 | if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT)) |
| 779 | return -EINVAL; |
| 780 | |
| 781 | error = create_pipe_files(files, flags); |
| 782 | if (error) |
| 783 | return error; |
| 784 | |
| 785 | error = get_unused_fd_flags(flags); |
| 786 | if (error < 0) |
| 787 | goto err_read_pipe; |
| 788 | fdr = error; |
| 789 | |
| 790 | error = get_unused_fd_flags(flags); |
| 791 | if (error < 0) |
| 792 | goto err_fdr; |
| 793 | fdw = error; |
| 794 | |
| 795 | audit_fd_pair(fdr, fdw); |
| 796 | fd[0] = fdr; |
| 797 | fd[1] = fdw; |
| 798 | return 0; |
| 799 | |
| 800 | err_fdr: |
| 801 | put_unused_fd(fdr); |
| 802 | err_read_pipe: |
| 803 | fput(files[0]); |
| 804 | fput(files[1]); |
| 805 | return error; |
| 806 | } |
| 807 | |
| 808 | int do_pipe_flags(int *fd, int flags) |
| 809 | { |
| 810 | struct file *files[2]; |
| 811 | int error = __do_pipe_flags(fd, files, flags); |
| 812 | if (!error) { |
| 813 | fd_install(fd[0], files[0]); |
| 814 | fd_install(fd[1], files[1]); |
| 815 | } |
| 816 | return error; |
| 817 | } |
| 818 | |
| 819 | /* |
| 820 | * sys_pipe() is the normal C calling standard for creating |
| 821 | * a pipe. It's not the way Unix traditionally does this, though. |
| 822 | */ |
| 823 | static int do_pipe2(int __user *fildes, int flags) |
| 824 | { |
| 825 | struct file *files[2]; |
| 826 | int fd[2]; |
| 827 | int error; |
| 828 | |
| 829 | error = __do_pipe_flags(fd, files, flags); |
| 830 | if (!error) { |
| 831 | if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) { |
| 832 | fput(files[0]); |
| 833 | fput(files[1]); |
| 834 | put_unused_fd(fd[0]); |
| 835 | put_unused_fd(fd[1]); |
| 836 | error = -EFAULT; |
| 837 | } else { |
| 838 | fd_install(fd[0], files[0]); |
| 839 | fd_install(fd[1], files[1]); |
| 840 | } |
| 841 | } |
| 842 | return error; |
| 843 | } |
| 844 | |
| 845 | SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags) |
| 846 | { |
| 847 | return do_pipe2(fildes, flags); |
| 848 | } |
| 849 | |
| 850 | SYSCALL_DEFINE1(pipe, int __user *, fildes) |
| 851 | { |
| 852 | return do_pipe2(fildes, 0); |
| 853 | } |
| 854 | |
| 855 | static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt) |
| 856 | { |
| 857 | int cur = *cnt; |
| 858 | |
| 859 | while (cur == *cnt) { |
| 860 | pipe_wait(pipe); |
| 861 | if (signal_pending(current)) |
| 862 | break; |
| 863 | } |
| 864 | return cur == *cnt ? -ERESTARTSYS : 0; |
| 865 | } |
| 866 | |
| 867 | static void wake_up_partner(struct pipe_inode_info *pipe) |
| 868 | { |
| 869 | wake_up_interruptible(&pipe->wait); |
| 870 | } |
| 871 | |
| 872 | static int fifo_open(struct inode *inode, struct file *filp) |
| 873 | { |
| 874 | struct pipe_inode_info *pipe; |
| 875 | bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC; |
| 876 | int ret; |
| 877 | |
| 878 | filp->f_version = 0; |
| 879 | |
| 880 | spin_lock(&inode->i_lock); |
| 881 | if (inode->i_pipe) { |
| 882 | pipe = inode->i_pipe; |
| 883 | pipe->files++; |
| 884 | spin_unlock(&inode->i_lock); |
| 885 | } else { |
| 886 | spin_unlock(&inode->i_lock); |
| 887 | pipe = alloc_pipe_info(); |
| 888 | if (!pipe) |
| 889 | return -ENOMEM; |
| 890 | pipe->files = 1; |
| 891 | spin_lock(&inode->i_lock); |
| 892 | if (unlikely(inode->i_pipe)) { |
| 893 | inode->i_pipe->files++; |
| 894 | spin_unlock(&inode->i_lock); |
| 895 | free_pipe_info(pipe); |
| 896 | pipe = inode->i_pipe; |
| 897 | } else { |
| 898 | inode->i_pipe = pipe; |
| 899 | spin_unlock(&inode->i_lock); |
| 900 | } |
| 901 | } |
| 902 | filp->private_data = pipe; |
| 903 | /* OK, we have a pipe and it's pinned down */ |
| 904 | |
| 905 | __pipe_lock(pipe); |
| 906 | |
| 907 | /* We can only do regular read/write on fifos */ |
| 908 | filp->f_mode &= (FMODE_READ | FMODE_WRITE); |
| 909 | |
| 910 | switch (filp->f_mode) { |
| 911 | case FMODE_READ: |
| 912 | /* |
| 913 | * O_RDONLY |
| 914 | * POSIX.1 says that O_NONBLOCK means return with the FIFO |
| 915 | * opened, even when there is no process writing the FIFO. |
| 916 | */ |
| 917 | pipe->r_counter++; |
| 918 | if (pipe->readers++ == 0) |
| 919 | wake_up_partner(pipe); |
| 920 | |
| 921 | if (!is_pipe && !pipe->writers) { |
| 922 | if ((filp->f_flags & O_NONBLOCK)) { |
| 923 | /* suppress EPOLLHUP until we have |
| 924 | * seen a writer */ |
| 925 | filp->f_version = pipe->w_counter; |
| 926 | } else { |
| 927 | if (wait_for_partner(pipe, &pipe->w_counter)) |
| 928 | goto err_rd; |
| 929 | } |
| 930 | } |
| 931 | break; |
| 932 | |
| 933 | case FMODE_WRITE: |
| 934 | /* |
| 935 | * O_WRONLY |
| 936 | * POSIX.1 says that O_NONBLOCK means return -1 with |
| 937 | * errno=ENXIO when there is no process reading the FIFO. |
| 938 | */ |
| 939 | ret = -ENXIO; |
| 940 | if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers) |
| 941 | goto err; |
| 942 | |
| 943 | pipe->w_counter++; |
| 944 | if (!pipe->writers++) |
| 945 | wake_up_partner(pipe); |
| 946 | |
| 947 | if (!is_pipe && !pipe->readers) { |
| 948 | if (wait_for_partner(pipe, &pipe->r_counter)) |
| 949 | goto err_wr; |
| 950 | } |
| 951 | break; |
| 952 | |
| 953 | case FMODE_READ | FMODE_WRITE: |
| 954 | /* |
| 955 | * O_RDWR |
| 956 | * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set. |
| 957 | * This implementation will NEVER block on a O_RDWR open, since |
| 958 | * the process can at least talk to itself. |
| 959 | */ |
| 960 | |
| 961 | pipe->readers++; |
| 962 | pipe->writers++; |
| 963 | pipe->r_counter++; |
| 964 | pipe->w_counter++; |
| 965 | if (pipe->readers == 1 || pipe->writers == 1) |
| 966 | wake_up_partner(pipe); |
| 967 | break; |
| 968 | |
| 969 | default: |
| 970 | ret = -EINVAL; |
| 971 | goto err; |
| 972 | } |
| 973 | |
| 974 | /* Ok! */ |
| 975 | __pipe_unlock(pipe); |
| 976 | return 0; |
| 977 | |
| 978 | err_rd: |
| 979 | if (!--pipe->readers) |
| 980 | wake_up_interruptible(&pipe->wait); |
| 981 | ret = -ERESTARTSYS; |
| 982 | goto err; |
| 983 | |
| 984 | err_wr: |
| 985 | if (!--pipe->writers) |
| 986 | wake_up_interruptible(&pipe->wait); |
| 987 | ret = -ERESTARTSYS; |
| 988 | goto err; |
| 989 | |
| 990 | err: |
| 991 | __pipe_unlock(pipe); |
| 992 | |
| 993 | put_pipe_info(inode, pipe); |
| 994 | return ret; |
| 995 | } |
| 996 | |
| 997 | const struct file_operations pipefifo_fops = { |
| 998 | .open = fifo_open, |
| 999 | .llseek = no_llseek, |
| 1000 | .read_iter = pipe_read, |
| 1001 | .write_iter = pipe_write, |
| 1002 | .poll = pipe_poll, |
| 1003 | .unlocked_ioctl = pipe_ioctl, |
| 1004 | .release = pipe_release, |
| 1005 | .fasync = pipe_fasync, |
| 1006 | }; |
| 1007 | |
| 1008 | /* |
| 1009 | * Currently we rely on the pipe array holding a power-of-2 number |
| 1010 | * of pages. Returns 0 on error. |
| 1011 | */ |
| 1012 | unsigned int round_pipe_size(unsigned long size) |
| 1013 | { |
| 1014 | if (size > (1U << 31)) |
| 1015 | return 0; |
| 1016 | |
| 1017 | /* Minimum pipe size, as required by POSIX */ |
| 1018 | if (size < PAGE_SIZE) |
| 1019 | return PAGE_SIZE; |
| 1020 | |
| 1021 | return roundup_pow_of_two(size); |
| 1022 | } |
| 1023 | |
| 1024 | /* |
| 1025 | * Allocate a new array of pipe buffers and copy the info over. Returns the |
| 1026 | * pipe size if successful, or return -ERROR on error. |
| 1027 | */ |
| 1028 | static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg) |
| 1029 | { |
| 1030 | struct pipe_buffer *bufs; |
| 1031 | unsigned int size, nr_pages; |
| 1032 | unsigned long user_bufs; |
| 1033 | long ret = 0; |
| 1034 | |
| 1035 | size = round_pipe_size(arg); |
| 1036 | nr_pages = size >> PAGE_SHIFT; |
| 1037 | |
| 1038 | if (!nr_pages) |
| 1039 | return -EINVAL; |
| 1040 | |
| 1041 | /* |
| 1042 | * If trying to increase the pipe capacity, check that an |
| 1043 | * unprivileged user is not trying to exceed various limits |
| 1044 | * (soft limit check here, hard limit check just below). |
| 1045 | * Decreasing the pipe capacity is always permitted, even |
| 1046 | * if the user is currently over a limit. |
| 1047 | */ |
| 1048 | if (nr_pages > pipe->buffers && |
| 1049 | size > pipe_max_size && !capable(CAP_SYS_RESOURCE)) |
| 1050 | return -EPERM; |
| 1051 | |
| 1052 | user_bufs = account_pipe_buffers(pipe->user, pipe->buffers, nr_pages); |
| 1053 | |
| 1054 | if (nr_pages > pipe->buffers && |
| 1055 | (too_many_pipe_buffers_hard(user_bufs) || |
| 1056 | too_many_pipe_buffers_soft(user_bufs)) && |
| 1057 | is_unprivileged_user()) { |
| 1058 | ret = -EPERM; |
| 1059 | goto out_revert_acct; |
| 1060 | } |
| 1061 | |
| 1062 | /* |
| 1063 | * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't |
| 1064 | * expect a lot of shrink+grow operations, just free and allocate |
| 1065 | * again like we would do for growing. If the pipe currently |
| 1066 | * contains more buffers than arg, then return busy. |
| 1067 | */ |
| 1068 | if (nr_pages < pipe->nrbufs) { |
| 1069 | ret = -EBUSY; |
| 1070 | goto out_revert_acct; |
| 1071 | } |
| 1072 | |
| 1073 | bufs = kcalloc(nr_pages, sizeof(*bufs), |
| 1074 | GFP_KERNEL_ACCOUNT | __GFP_NOWARN); |
| 1075 | if (unlikely(!bufs)) { |
| 1076 | ret = -ENOMEM; |
| 1077 | goto out_revert_acct; |
| 1078 | } |
| 1079 | |
| 1080 | /* |
| 1081 | * The pipe array wraps around, so just start the new one at zero |
| 1082 | * and adjust the indexes. |
| 1083 | */ |
| 1084 | if (pipe->nrbufs) { |
| 1085 | unsigned int tail; |
| 1086 | unsigned int head; |
| 1087 | |
| 1088 | tail = pipe->curbuf + pipe->nrbufs; |
| 1089 | if (tail < pipe->buffers) |
| 1090 | tail = 0; |
| 1091 | else |
| 1092 | tail &= (pipe->buffers - 1); |
| 1093 | |
| 1094 | head = pipe->nrbufs - tail; |
| 1095 | if (head) |
| 1096 | memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer)); |
| 1097 | if (tail) |
| 1098 | memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer)); |
| 1099 | } |
| 1100 | |
| 1101 | pipe->curbuf = 0; |
| 1102 | kfree(pipe->bufs); |
| 1103 | pipe->bufs = bufs; |
| 1104 | pipe->buffers = nr_pages; |
| 1105 | return nr_pages * PAGE_SIZE; |
| 1106 | |
| 1107 | out_revert_acct: |
| 1108 | (void) account_pipe_buffers(pipe->user, nr_pages, pipe->buffers); |
| 1109 | return ret; |
| 1110 | } |
| 1111 | |
| 1112 | /* |
| 1113 | * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same |
| 1114 | * location, so checking ->i_pipe is not enough to verify that this is a |
| 1115 | * pipe. |
| 1116 | */ |
| 1117 | struct pipe_inode_info *get_pipe_info(struct file *file) |
| 1118 | { |
| 1119 | return file->f_op == &pipefifo_fops ? file->private_data : NULL; |
| 1120 | } |
| 1121 | |
| 1122 | long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg) |
| 1123 | { |
| 1124 | struct pipe_inode_info *pipe; |
| 1125 | long ret; |
| 1126 | |
| 1127 | pipe = get_pipe_info(file); |
| 1128 | if (!pipe) |
| 1129 | return -EBADF; |
| 1130 | |
| 1131 | __pipe_lock(pipe); |
| 1132 | |
| 1133 | switch (cmd) { |
| 1134 | case F_SETPIPE_SZ: |
| 1135 | ret = pipe_set_size(pipe, arg); |
| 1136 | break; |
| 1137 | case F_GETPIPE_SZ: |
| 1138 | ret = pipe->buffers * PAGE_SIZE; |
| 1139 | break; |
| 1140 | default: |
| 1141 | ret = -EINVAL; |
| 1142 | break; |
| 1143 | } |
| 1144 | |
| 1145 | __pipe_unlock(pipe); |
| 1146 | return ret; |
| 1147 | } |
| 1148 | |
| 1149 | static const struct super_operations pipefs_ops = { |
| 1150 | .destroy_inode = free_inode_nonrcu, |
| 1151 | .statfs = simple_statfs, |
| 1152 | }; |
| 1153 | |
| 1154 | /* |
| 1155 | * pipefs should _never_ be mounted by userland - too much of security hassle, |
| 1156 | * no real gain from having the whole whorehouse mounted. So we don't need |
| 1157 | * any operations on the root directory. However, we need a non-trivial |
| 1158 | * d_name - pipe: will go nicely and kill the special-casing in procfs. |
| 1159 | */ |
| 1160 | static struct dentry *pipefs_mount(struct file_system_type *fs_type, |
| 1161 | int flags, const char *dev_name, void *data) |
| 1162 | { |
| 1163 | return mount_pseudo(fs_type, "pipe:", &pipefs_ops, |
| 1164 | &pipefs_dentry_operations, PIPEFS_MAGIC); |
| 1165 | } |
| 1166 | |
| 1167 | static struct file_system_type pipe_fs_type = { |
| 1168 | .name = "pipefs", |
| 1169 | .mount = pipefs_mount, |
| 1170 | .kill_sb = kill_anon_super, |
| 1171 | }; |
| 1172 | |
| 1173 | static int __init init_pipe_fs(void) |
| 1174 | { |
| 1175 | int err = register_filesystem(&pipe_fs_type); |
| 1176 | |
| 1177 | if (!err) { |
| 1178 | pipe_mnt = kern_mount(&pipe_fs_type); |
| 1179 | if (IS_ERR(pipe_mnt)) { |
| 1180 | err = PTR_ERR(pipe_mnt); |
| 1181 | unregister_filesystem(&pipe_fs_type); |
| 1182 | } |
| 1183 | } |
| 1184 | return err; |
| 1185 | } |
| 1186 | |
| 1187 | fs_initcall(init_pipe_fs); |