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 <jelson@circlemud.org> 2001-08-16
  58  *
  59  * pipe_read & write cleanup
  60  * -- Manfred Spraul <manfred@colorfullife.com> 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 user_struct *user,
 605                                  unsigned long old, unsigned long new)
 606 {
 607         atomic_long_add(new - old, &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         unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
 626         struct user_struct *user = get_current_user();
 627
 628         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
 629         if (pipe == NULL)
 630                 goto out_free_uid;
 631
 632         if (!too_many_pipe_buffers_hard(user)) {
 633                 if (too_many_pipe_buffers_soft(user))
 634                         pipe_bufs = 1;
 635                 pipe->bufs = kcalloc(pipe_bufs,
 636                                      sizeof(struct pipe_buffer),
 637                                      GFP_KERNEL_ACCOUNT);
 638         }
 639
 640         if (pipe->bufs) {
 641                 init_waitqueue_head(&pipe->wait);
 642                 pipe->r_counter = pipe->w_counter = 1;
 643                 pipe->buffers = pipe_bufs;
 644                 pipe->user = user;
 645                 account_pipe_buffers(user, 0, pipe_bufs);
 646                 mutex_init(&pipe->mutex);
 647                 return pipe;
 648         }
 649
 650         kfree(pipe);
 651 out_free_uid:
 652         free_uid(user);
 653         return NULL;
 654 }
 655
 656 void free_pipe_info(struct pipe_inode_info *pipe)
 657 {
 658         int i;
 659
 660         account_pipe_buffers(pipe->user, pipe->buffers, 0);
 661         free_uid(pipe->user);
 662         for (i = 0; i < pipe->buffers; i++) {
 663                 struct pipe_buffer *buf = pipe->bufs + i;
 664                 if (buf->ops)
 665                         pipe_buf_release(pipe, buf);
 666         }
 667         if (pipe->tmp_page)
 668                 __free_page(pipe->tmp_page);
 669         kfree(pipe->bufs);
 670         kfree(pipe);
 671 }
 672
 673 static struct vfsmount *pipe_mnt __read_mostly;
 674
 675 /*
 676  * pipefs_dname() is called from d_path().
 677  */
 678 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 679 {
 680         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 681                                 d_inode(dentry)->i_ino);
 682 }
 683
 684 static const struct dentry_operations pipefs_dentry_operations = {
 685         .d_dname        = pipefs_dname,
 686 };
 687
 688 static struct inode * get_pipe_inode(void)
 689 {
 690         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 691         struct pipe_inode_info *pipe;
 692
 693         if (!inode)
 694                 goto fail_inode;
 695
 696         inode->i_ino = get_next_ino();
 697
 698         pipe = alloc_pipe_info();
 699         if (!pipe)
 700                 goto fail_iput;
 701
 702         inode->i_pipe = pipe;
 703         pipe->files = 2;
 704         pipe->readers = pipe->writers = 1;
 705         inode->i_fop = &pipefifo_fops;
 706
 707         /*
 708          * Mark the inode dirty from the very beginning,
 709          * that way it will never be moved to the dirty
 710          * list because "mark_inode_dirty()" will think
 711          * that it already _is_ on the dirty list.
 712          */
 713         inode->i_state = I_DIRTY;
 714         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 715         inode->i_uid = current_fsuid();
 716         inode->i_gid = current_fsgid();
 717         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 718
 719         return inode;
 720
 721 fail_iput:
 722         iput(inode);
 723
 724 fail_inode:
 725         return NULL;
 726 }
 727
 728 int create_pipe_files(struct file **res, int flags)
 729 {
 730         int err;
 731         struct inode *inode = get_pipe_inode();
 732         struct file *f;
 733         struct path path;
 734         static struct qstr name = { .name = "" };
 735
 736         if (!inode)
 737                 return -ENFILE;
 738
 739         err = -ENOMEM;
 740         path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
 741         if (!path.dentry)
 742                 goto err_inode;
 743         path.mnt = mntget(pipe_mnt);
 744
 745         d_instantiate(path.dentry, inode);
 746
 747         f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops);
 748         if (IS_ERR(f)) {
 749                 err = PTR_ERR(f);
 750                 goto err_dentry;
 751         }
 752
 753         f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
 754         f->private_data = inode->i_pipe;
 755
 756         res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
 757         if (IS_ERR(res[0])) {
 758                 err = PTR_ERR(res[0]);
 759                 goto err_file;
 760         }
 761
 762         path_get(&path);
 763         res[0]->private_data = inode->i_pipe;
 764         res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
 765         res[1] = f;
 766         return 0;
 767
 768 err_file:
 769         put_filp(f);
 770 err_dentry:
 771         free_pipe_info(inode->i_pipe);
 772         path_put(&path);
 773         return err;
 774
 775 err_inode:
 776         free_pipe_info(inode->i_pipe);
 777         iput(inode);
 778         return err;
 779 }
 780
 781 static int __do_pipe_flags(int *fd, struct file **files, int flags)
 782 {
 783         int error;
 784         int fdw, fdr;
 785
 786         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
 787                 return -EINVAL;
 788
 789         error = create_pipe_files(files, flags);
 790         if (error)
 791                 return error;
 792
 793         error = get_unused_fd_flags(flags);
 794         if (error < 0)
 795                 goto err_read_pipe;
 796         fdr = error;
 797
 798         error = get_unused_fd_flags(flags);
 799         if (error < 0)
 800                 goto err_fdr;
 801         fdw = error;
 802
 803         audit_fd_pair(fdr, fdw);
 804         fd[0] = fdr;
 805         fd[1] = fdw;
 806         return 0;
 807
 808  err_fdr:
 809         put_unused_fd(fdr);
 810  err_read_pipe:
 811         fput(files[0]);
 812         fput(files[1]);
 813         return error;
 814 }
 815
 816 int do_pipe_flags(int *fd, int flags)
 817 {
 818         struct file *files[2];
 819         int error = __do_pipe_flags(fd, files, flags);
 820         if (!error) {
 821                 fd_install(fd[0], files[0]);
 822                 fd_install(fd[1], files[1]);
 823         }
 824         return error;
 825 }
 826
 827 /*
 828  * sys_pipe() is the normal C calling standard for creating
 829  * a pipe. It's not the way Unix traditionally does this, though.
 830  */
 831 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
 832 {
 833         struct file *files[2];
 834         int fd[2];
 835         int error;
 836
 837         error = __do_pipe_flags(fd, files, flags);
 838         if (!error) {
 839                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
 840                         fput(files[0]);
 841                         fput(files[1]);
 842                         put_unused_fd(fd[0]);
 843                         put_unused_fd(fd[1]);
 844                         error = -EFAULT;
 845                 } else {
 846                         fd_install(fd[0], files[0]);
 847                         fd_install(fd[1], files[1]);
 848                 }
 849         }
 850         return error;
 851 }
 852
 853 SYSCALL_DEFINE1(pipe, int __user *, fildes)
 854 {
 855         return sys_pipe2(fildes, 0);
 856 }
 857
 858 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
 859 {
 860         int cur = *cnt;
 861
 862         while (cur == *cnt) {
 863                 pipe_wait(pipe);
 864                 if (signal_pending(current))
 865                         break;
 866         }
 867         return cur == *cnt ? -ERESTARTSYS : 0;
 868 }
 869
 870 static void wake_up_partner(struct pipe_inode_info *pipe)
 871 {
 872         wake_up_interruptible(&pipe->wait);
 873 }
 874
 875 static int fifo_open(struct inode *inode, struct file *filp)
 876 {
 877         struct pipe_inode_info *pipe;
 878         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
 879         int ret;
 880
 881         filp->f_version = 0;
 882
 883         spin_lock(&inode->i_lock);
 884         if (inode->i_pipe) {
 885                 pipe = inode->i_pipe;
 886                 pipe->files++;
 887                 spin_unlock(&inode->i_lock);
 888         } else {
 889                 spin_unlock(&inode->i_lock);
 890                 pipe = alloc_pipe_info();
 891                 if (!pipe)
 892                         return -ENOMEM;
 893                 pipe->files = 1;
 894                 spin_lock(&inode->i_lock);
 895                 if (unlikely(inode->i_pipe)) {
 896                         inode->i_pipe->files++;
 897                         spin_unlock(&inode->i_lock);
 898                         free_pipe_info(pipe);
 899                         pipe = inode->i_pipe;
 900                 } else {
 901                         inode->i_pipe = pipe;
 902                         spin_unlock(&inode->i_lock);
 903                 }
 904         }
 905         filp->private_data = pipe;
 906         /* OK, we have a pipe and it's pinned down */
 907
 908         __pipe_lock(pipe);
 909
 910         /* We can only do regular read/write on fifos */
 911         filp->f_mode &= (FMODE_READ | FMODE_WRITE);
 912
 913         switch (filp->f_mode) {
 914         case FMODE_READ:
 915         /*
 916          *  O_RDONLY
 917          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
 918          *  opened, even when there is no process writing the FIFO.
 919          */
 920                 pipe->r_counter++;
 921                 if (pipe->readers++ == 0)
 922                         wake_up_partner(pipe);
 923
 924                 if (!is_pipe && !pipe->writers) {
 925                         if ((filp->f_flags & O_NONBLOCK)) {
 926                                 /* suppress POLLHUP until we have
 927                                  * seen a writer */
 928                                 filp->f_version = pipe->w_counter;
 929                         } else {
 930                                 if (wait_for_partner(pipe, &pipe->w_counter))
 931                                         goto err_rd;
 932                         }
 933                 }
 934                 break;
 935
 936         case FMODE_WRITE:
 937         /*
 938          *  O_WRONLY
 939          *  POSIX.1 says that O_NONBLOCK means return -1 with
 940          *  errno=ENXIO when there is no process reading the FIFO.
 941          */
 942                 ret = -ENXIO;
 943                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
 944                         goto err;
 945
 946                 pipe->w_counter++;
 947                 if (!pipe->writers++)
 948                         wake_up_partner(pipe);
 949
 950                 if (!is_pipe && !pipe->readers) {
 951                         if (wait_for_partner(pipe, &pipe->r_counter))
 952                                 goto err_wr;
 953                 }
 954                 break;
 955
 956         case FMODE_READ | FMODE_WRITE:
 957         /*
 958          *  O_RDWR
 959          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
 960          *  This implementation will NEVER block on a O_RDWR open, since
 961          *  the process can at least talk to itself.
 962          */
 963
 964                 pipe->readers++;
 965                 pipe->writers++;
 966                 pipe->r_counter++;
 967                 pipe->w_counter++;
 968                 if (pipe->readers == 1 || pipe->writers == 1)
 969                         wake_up_partner(pipe);
 970                 break;
 971
 972         default:
 973                 ret = -EINVAL;
 974                 goto err;
 975         }
 976
 977         /* Ok! */
 978         __pipe_unlock(pipe);
 979         return 0;
 980
 981 err_rd:
 982         if (!--pipe->readers)
 983                 wake_up_interruptible(&pipe->wait);
 984         ret = -ERESTARTSYS;
 985         goto err;
 986
 987 err_wr:
 988         if (!--pipe->writers)
 989                 wake_up_interruptible(&pipe->wait);
 990         ret = -ERESTARTSYS;
 991         goto err;
 992
 993 err:
 994         __pipe_unlock(pipe);
 995
 996         put_pipe_info(inode, pipe);
 997         return ret;
 998 }
 999
1000 const struct file_operations pipefifo_fops = {
1001         .open           = fifo_open,
1002         .llseek         = no_llseek,
1003         .read_iter      = pipe_read,
1004         .write_iter     = pipe_write,
1005         .poll           = pipe_poll,
1006         .unlocked_ioctl = pipe_ioctl,
1007         .release        = pipe_release,
1008         .fasync         = pipe_fasync,
1009 };
1010
1011 /*
1012  * Currently we rely on the pipe array holding a power-of-2 number
1013  * of pages.
1014  */
1015 static inline unsigned int round_pipe_size(unsigned int size)
1016 {
1017         unsigned long nr_pages;
1018
1019         nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1020         return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1021 }
1022
1023 /*
1024  * Allocate a new array of pipe buffers and copy the info over. Returns the
1025  * pipe size if successful, or return -ERROR on error.
1026  */
1027 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1028 {
1029         struct pipe_buffer *bufs;
1030         unsigned int size, nr_pages;
1031         long ret = 0;
1032
1033         size = round_pipe_size(arg);
1034         nr_pages = size >> PAGE_SHIFT;
1035
1036         if (!nr_pages)
1037                 return -EINVAL;
1038
1039         /*
1040          * If trying to increase the pipe capacity, check that an
1041          * unprivileged user is not trying to exceed various limits
1042          * (soft limit check here, hard limit check just below).
1043          * Decreasing the pipe capacity is always permitted, even
1044          * if the user is currently over a limit.
1045          */
1046         if (nr_pages > pipe->buffers &&
1047                         size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1048                 return -EPERM;
1049
1050         account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
1051
1052         if (nr_pages > pipe->buffers &&
1053                         (too_many_pipe_buffers_hard(pipe->user) ||
1054                          too_many_pipe_buffers_soft(pipe->user)) &&
1055                         !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) {
1056                 ret = -EPERM;
1057                 goto out_revert_acct;
1058         }
1059
1060         /*
1061          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1062          * expect a lot of shrink+grow operations, just free and allocate
1063          * again like we would do for growing. If the pipe currently
1064          * contains more buffers than arg, then return busy.
1065          */
1066         if (nr_pages < pipe->nrbufs) {
1067                 ret = -EBUSY;
1068                 goto out_revert_acct;
1069         }
1070
1071         bufs = kcalloc(nr_pages, sizeof(*bufs),
1072                        GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1073         if (unlikely(!bufs)) {
1074                 ret = -ENOMEM;
1075                 goto out_revert_acct;
1076         }
1077
1078         /*
1079          * The pipe array wraps around, so just start the new one at zero
1080          * and adjust the indexes.
1081          */
1082         if (pipe->nrbufs) {
1083                 unsigned int tail;
1084                 unsigned int head;
1085
1086                 tail = pipe->curbuf + pipe->nrbufs;
1087                 if (tail < pipe->buffers)
1088                         tail = 0;
1089                 else
1090                         tail &= (pipe->buffers - 1);
1091
1092                 head = pipe->nrbufs - tail;
1093                 if (head)
1094                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1095                 if (tail)
1096                         memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1097         }
1098
1099         pipe->curbuf = 0;
1100         kfree(pipe->bufs);
1101         pipe->bufs = bufs;
1102         pipe->buffers = nr_pages;
1103         return nr_pages * PAGE_SIZE;
1104
1105 out_revert_acct:
1106         account_pipe_buffers(pipe->user, nr_pages, pipe->buffers);
1107         return ret;
1108 }
1109
1110 /*
1111  * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1112  * will return an error.
1113  */
1114 int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1115                  size_t *lenp, loff_t *ppos)
1116 {
1117         int ret;
1118
1119         ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1120         if (ret < 0 || !write)
1121                 return ret;
1122
1123         pipe_max_size = round_pipe_size(pipe_max_size);
1124         return ret;
1125 }
1126
1127 /*
1128  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1129  * location, so checking ->i_pipe is not enough to verify that this is a
1130  * pipe.
1131  */
1132 struct pipe_inode_info *get_pipe_info(struct file *file)
1133 {
1134         return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1135 }
1136
1137 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1138 {
1139         struct pipe_inode_info *pipe;
1140         long ret;
1141
1142         pipe = get_pipe_info(file);
1143         if (!pipe)
1144                 return -EBADF;
1145
1146         __pipe_lock(pipe);
1147
1148         switch (cmd) {
1149         case F_SETPIPE_SZ:
1150                 ret = pipe_set_size(pipe, arg);
1151                 break;
1152         case F_GETPIPE_SZ:
1153                 ret = pipe->buffers * PAGE_SIZE;
1154                 break;
1155         default:
1156                 ret = -EINVAL;
1157                 break;
1158         }
1159
1160         __pipe_unlock(pipe);
1161         return ret;
1162 }
1163
1164 static const struct super_operations pipefs_ops = {
1165         .destroy_inode = free_inode_nonrcu,
1166         .statfs = simple_statfs,
1167 };
1168
1169 /*
1170  * pipefs should _never_ be mounted by userland - too much of security hassle,
1171  * no real gain from having the whole whorehouse mounted. So we don't need
1172  * any operations on the root directory. However, we need a non-trivial
1173  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1174  */
1175 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1176                          int flags, const char *dev_name, void *data)
1177 {
1178         return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1179                         &pipefs_dentry_operations, PIPEFS_MAGIC);
1180 }
1181
1182 static struct file_system_type pipe_fs_type = {
1183         .name           = "pipefs",
1184         .mount          = pipefs_mount,
1185         .kill_sb        = kill_anon_super,
1186 };
1187
1188 static int __init init_pipe_fs(void)
1189 {
1190         int err = register_filesystem(&pipe_fs_type);
1191
1192         if (!err) {
1193                 pipe_mnt = kern_mount(&pipe_fs_type);
1194                 if (IS_ERR(pipe_mnt)) {
1195                         err = PTR_ERR(pipe_mnt);
1196                         unregister_filesystem(&pipe_fs_type);
1197                 }
1198         }
1199         return err;
1200 }
1201
1202 fs_initcall(init_pipe_fs);