fs/pipe.c

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