Linux Audio

Check our new training course

Loading...
v6.2
   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/pseudo_fs.h>
  18#include <linux/magic.h>
  19#include <linux/pipe_fs_i.h>
  20#include <linux/uio.h>
  21#include <linux/highmem.h>
  22#include <linux/pagemap.h>
  23#include <linux/audit.h>
  24#include <linux/syscalls.h>
  25#include <linux/fcntl.h>
  26#include <linux/memcontrol.h>
  27#include <linux/watch_queue.h>
  28#include <linux/sysctl.h>
  29
  30#include <linux/uaccess.h>
  31#include <asm/ioctls.h>
  32
  33#include "internal.h"
  34
  35/*
  36 * New pipe buffers will be restricted to this size while the user is exceeding
  37 * their pipe buffer quota. The general pipe use case needs at least two
  38 * buffers: one for data yet to be read, and one for new data. If this is less
  39 * than two, then a write to a non-empty pipe may block even if the pipe is not
  40 * full. This can occur with GNU make jobserver or similar uses of pipes as
  41 * semaphores: multiple processes may be waiting to write tokens back to the
  42 * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.
  43 *
  44 * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their
  45 * own risk, namely: pipe writes to non-full pipes may block until the pipe is
  46 * emptied.
  47 */
  48#define PIPE_MIN_DEF_BUFFERS 2
  49
  50/*
  51 * The max size that a non-root user is allowed to grow the pipe. Can
  52 * be set by root in /proc/sys/fs/pipe-max-size
  53 */
  54static unsigned int pipe_max_size = 1048576;
  55
  56/* Maximum allocatable pages per user. Hard limit is unset by default, soft
  57 * matches default values.
  58 */
  59static unsigned long pipe_user_pages_hard;
  60static unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
  61
  62/*
  63 * We use head and tail indices that aren't masked off, except at the point of
  64 * dereference, but rather they're allowed to wrap naturally.  This means there
  65 * isn't a dead spot in the buffer, but the ring has to be a power of two and
  66 * <= 2^31.
  67 * -- David Howells 2019-09-23.
  68 *
  69 * Reads with count = 0 should always return 0.
  70 * -- Julian Bradfield 1999-06-07.
  71 *
  72 * FIFOs and Pipes now generate SIGIO for both readers and writers.
  73 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  74 *
  75 * pipe_read & write cleanup
  76 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  77 */
  78
  79static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  80{
  81	if (pipe->files)
  82		mutex_lock_nested(&pipe->mutex, subclass);
  83}
  84
  85void pipe_lock(struct pipe_inode_info *pipe)
  86{
  87	/*
  88	 * pipe_lock() nests non-pipe inode locks (for writing to a file)
  89	 */
  90	pipe_lock_nested(pipe, I_MUTEX_PARENT);
  91}
  92EXPORT_SYMBOL(pipe_lock);
  93
  94void pipe_unlock(struct pipe_inode_info *pipe)
  95{
  96	if (pipe->files)
  97		mutex_unlock(&pipe->mutex);
  98}
  99EXPORT_SYMBOL(pipe_unlock);
 100
 101static inline void __pipe_lock(struct pipe_inode_info *pipe)
 102{
 103	mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
 104}
 105
 106static inline void __pipe_unlock(struct pipe_inode_info *pipe)
 107{
 108	mutex_unlock(&pipe->mutex);
 109}
 110
 111void pipe_double_lock(struct pipe_inode_info *pipe1,
 112		      struct pipe_inode_info *pipe2)
 113{
 114	BUG_ON(pipe1 == pipe2);
 115
 116	if (pipe1 < pipe2) {
 117		pipe_lock_nested(pipe1, I_MUTEX_PARENT);
 118		pipe_lock_nested(pipe2, I_MUTEX_CHILD);
 119	} else {
 120		pipe_lock_nested(pipe2, I_MUTEX_PARENT);
 121		pipe_lock_nested(pipe1, I_MUTEX_CHILD);
 122	}
 123}
 124
 125static 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
 141static bool anon_pipe_buf_try_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		return false;
 148	memcg_kmem_uncharge_page(page, 0);
 149	__SetPageLocked(page);
 150	return true;
 151}
 152
 153/**
 154 * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
 155 * @pipe:	the pipe that the buffer belongs to
 156 * @buf:	the buffer to attempt to steal
 157 *
 158 * Description:
 159 *	This function attempts to steal the &struct page attached to
 160 *	@buf. If successful, this function returns 0 and returns with
 161 *	the page locked. The caller may then reuse the page for whatever
 162 *	he wishes; the typical use is insertion into a different file
 163 *	page cache.
 164 */
 165bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe,
 166		struct pipe_buffer *buf)
 167{
 168	struct page *page = buf->page;
 169
 170	/*
 171	 * A reference of one is golden, that means that the owner of this
 172	 * page is the only one holding a reference to it. lock the page
 173	 * and return OK.
 174	 */
 175	if (page_count(page) == 1) {
 176		lock_page(page);
 177		return true;
 178	}
 179	return false;
 180}
 181EXPORT_SYMBOL(generic_pipe_buf_try_steal);
 182
 183/**
 184 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 185 * @pipe:	the pipe that the buffer belongs to
 186 * @buf:	the buffer to get a reference to
 187 *
 188 * Description:
 189 *	This function grabs an extra reference to @buf. It's used in
 190 *	the tee() system call, when we duplicate the buffers in one
 191 *	pipe into another.
 192 */
 193bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 194{
 195	return try_get_page(buf->page);
 196}
 197EXPORT_SYMBOL(generic_pipe_buf_get);
 198
 199/**
 200 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 201 * @pipe:	the pipe that the buffer belongs to
 202 * @buf:	the buffer to put a reference to
 203 *
 204 * Description:
 205 *	This function releases a reference to @buf.
 206 */
 207void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 208			      struct pipe_buffer *buf)
 209{
 210	put_page(buf->page);
 211}
 212EXPORT_SYMBOL(generic_pipe_buf_release);
 213
 214static const struct pipe_buf_operations anon_pipe_buf_ops = {
 215	.release	= anon_pipe_buf_release,
 216	.try_steal	= anon_pipe_buf_try_steal,
 217	.get		= generic_pipe_buf_get,
 218};
 219
 220/* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
 221static inline bool pipe_readable(const struct pipe_inode_info *pipe)
 222{
 223	unsigned int head = READ_ONCE(pipe->head);
 224	unsigned int tail = READ_ONCE(pipe->tail);
 225	unsigned int writers = READ_ONCE(pipe->writers);
 226
 227	return !pipe_empty(head, tail) || !writers;
 228}
 229
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 230static ssize_t
 231pipe_read(struct kiocb *iocb, struct iov_iter *to)
 232{
 233	size_t total_len = iov_iter_count(to);
 234	struct file *filp = iocb->ki_filp;
 235	struct pipe_inode_info *pipe = filp->private_data;
 236	bool was_full, wake_next_reader = false;
 237	ssize_t ret;
 238
 239	/* Null read succeeds. */
 240	if (unlikely(total_len == 0))
 241		return 0;
 242
 243	ret = 0;
 244	__pipe_lock(pipe);
 245
 246	/*
 247	 * We only wake up writers if the pipe was full when we started
 248	 * reading in order to avoid unnecessary wakeups.
 249	 *
 250	 * But when we do wake up writers, we do so using a sync wakeup
 251	 * (WF_SYNC), because we want them to get going and generate more
 252	 * data for us.
 253	 */
 254	was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
 255	for (;;) {
 256		/* Read ->head with a barrier vs post_one_notification() */
 257		unsigned int head = smp_load_acquire(&pipe->head);
 258		unsigned int tail = pipe->tail;
 259		unsigned int mask = pipe->ring_size - 1;
 260
 261#ifdef CONFIG_WATCH_QUEUE
 262		if (pipe->note_loss) {
 263			struct watch_notification n;
 264
 265			if (total_len < 8) {
 266				if (ret == 0)
 267					ret = -ENOBUFS;
 268				break;
 269			}
 270
 271			n.type = WATCH_TYPE_META;
 272			n.subtype = WATCH_META_LOSS_NOTIFICATION;
 273			n.info = watch_sizeof(n);
 274			if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
 275				if (ret == 0)
 276					ret = -EFAULT;
 277				break;
 278			}
 279			ret += sizeof(n);
 280			total_len -= sizeof(n);
 281			pipe->note_loss = false;
 282		}
 283#endif
 284
 285		if (!pipe_empty(head, tail)) {
 286			struct pipe_buffer *buf = &pipe->bufs[tail & mask];
 287			size_t chars = buf->len;
 288			size_t written;
 289			int error;
 290
 291			if (chars > total_len) {
 292				if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
 293					if (ret == 0)
 294						ret = -ENOBUFS;
 295					break;
 296				}
 297				chars = total_len;
 298			}
 299
 300			error = pipe_buf_confirm(pipe, buf);
 301			if (error) {
 302				if (!ret)
 303					ret = error;
 304				break;
 305			}
 306
 307			written = copy_page_to_iter(buf->page, buf->offset, chars, to);
 308			if (unlikely(written < chars)) {
 309				if (!ret)
 310					ret = -EFAULT;
 311				break;
 312			}
 313			ret += chars;
 314			buf->offset += chars;
 315			buf->len -= chars;
 316
 317			/* Was it a packet buffer? Clean up and exit */
 318			if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 319				total_len = chars;
 320				buf->len = 0;
 321			}
 322
 323			if (!buf->len) {
 324				pipe_buf_release(pipe, buf);
 325				spin_lock_irq(&pipe->rd_wait.lock);
 326#ifdef CONFIG_WATCH_QUEUE
 327				if (buf->flags & PIPE_BUF_FLAG_LOSS)
 328					pipe->note_loss = true;
 329#endif
 330				tail++;
 331				pipe->tail = tail;
 332				spin_unlock_irq(&pipe->rd_wait.lock);
 333			}
 334			total_len -= chars;
 335			if (!total_len)
 336				break;	/* common path: read succeeded */
 337			if (!pipe_empty(head, tail))	/* More to do? */
 338				continue;
 339		}
 340
 341		if (!pipe->writers)
 342			break;
 343		if (ret)
 344			break;
 345		if (filp->f_flags & O_NONBLOCK) {
 
 346			ret = -EAGAIN;
 347			break;
 348		}
 349		__pipe_unlock(pipe);
 350
 351		/*
 352		 * We only get here if we didn't actually read anything.
 353		 *
 354		 * However, we could have seen (and removed) a zero-sized
 355		 * pipe buffer, and might have made space in the buffers
 356		 * that way.
 357		 *
 358		 * You can't make zero-sized pipe buffers by doing an empty
 359		 * write (not even in packet mode), but they can happen if
 360		 * the writer gets an EFAULT when trying to fill a buffer
 361		 * that already got allocated and inserted in the buffer
 362		 * array.
 363		 *
 364		 * So we still need to wake up any pending writers in the
 365		 * _very_ unlikely case that the pipe was full, but we got
 366		 * no data.
 367		 */
 368		if (unlikely(was_full))
 369			wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 370		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 371
 372		/*
 373		 * But because we didn't read anything, at this point we can
 374		 * just return directly with -ERESTARTSYS if we're interrupted,
 375		 * since we've done any required wakeups and there's no need
 376		 * to mark anything accessed. And we've dropped the lock.
 377		 */
 378		if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0)
 379			return -ERESTARTSYS;
 380
 381		__pipe_lock(pipe);
 382		was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
 383		wake_next_reader = true;
 384	}
 385	if (pipe_empty(pipe->head, pipe->tail))
 386		wake_next_reader = false;
 387	__pipe_unlock(pipe);
 388
 389	if (was_full)
 390		wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 391	if (wake_next_reader)
 392		wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 393	kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 394	if (ret > 0)
 395		file_accessed(filp);
 396	return ret;
 397}
 398
 399static inline int is_packetized(struct file *file)
 400{
 401	return (file->f_flags & O_DIRECT) != 0;
 402}
 403
 404/* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
 405static inline bool pipe_writable(const struct pipe_inode_info *pipe)
 406{
 407	unsigned int head = READ_ONCE(pipe->head);
 408	unsigned int tail = READ_ONCE(pipe->tail);
 409	unsigned int max_usage = READ_ONCE(pipe->max_usage);
 410
 411	return !pipe_full(head, tail, max_usage) ||
 412		!READ_ONCE(pipe->readers);
 413}
 414
 415static ssize_t
 416pipe_write(struct kiocb *iocb, struct iov_iter *from)
 417{
 418	struct file *filp = iocb->ki_filp;
 419	struct pipe_inode_info *pipe = filp->private_data;
 420	unsigned int head;
 421	ssize_t ret = 0;
 422	size_t total_len = iov_iter_count(from);
 423	ssize_t chars;
 424	bool was_empty = false;
 425	bool wake_next_writer = false;
 426
 
 
 
 
 
 
 
 
 
 
 
 
 427	/* Null write succeeds. */
 428	if (unlikely(total_len == 0))
 429		return 0;
 430
 431	__pipe_lock(pipe);
 432
 433	if (!pipe->readers) {
 434		send_sig(SIGPIPE, current, 0);
 435		ret = -EPIPE;
 436		goto out;
 437	}
 438
 439#ifdef CONFIG_WATCH_QUEUE
 440	if (pipe->watch_queue) {
 441		ret = -EXDEV;
 442		goto out;
 443	}
 444#endif
 445
 446	/*
 447	 * If it wasn't empty we try to merge new data into
 448	 * the last buffer.
 449	 *
 450	 * That naturally merges small writes, but it also
 451	 * page-aligns the rest of the writes for large writes
 452	 * spanning multiple pages.
 453	 */
 454	head = pipe->head;
 455	was_empty = pipe_empty(head, pipe->tail);
 456	chars = total_len & (PAGE_SIZE-1);
 457	if (chars && !was_empty) {
 458		unsigned int mask = pipe->ring_size - 1;
 459		struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
 460		int offset = buf->offset + buf->len;
 461
 462		if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
 463		    offset + chars <= PAGE_SIZE) {
 464			ret = pipe_buf_confirm(pipe, buf);
 465			if (ret)
 466				goto out;
 467
 468			ret = copy_page_from_iter(buf->page, offset, chars, from);
 469			if (unlikely(ret < chars)) {
 470				ret = -EFAULT;
 471				goto out;
 472			}
 473
 474			buf->len += ret;
 475			if (!iov_iter_count(from))
 476				goto out;
 477		}
 478	}
 479
 480	for (;;) {
 481		if (!pipe->readers) {
 482			send_sig(SIGPIPE, current, 0);
 483			if (!ret)
 484				ret = -EPIPE;
 485			break;
 486		}
 487
 488		head = pipe->head;
 489		if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
 490			unsigned int mask = pipe->ring_size - 1;
 491			struct pipe_buffer *buf = &pipe->bufs[head & mask];
 492			struct page *page = pipe->tmp_page;
 493			int copied;
 494
 495			if (!page) {
 496				page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
 497				if (unlikely(!page)) {
 498					ret = ret ? : -ENOMEM;
 499					break;
 500				}
 501				pipe->tmp_page = page;
 502			}
 503
 504			/* Allocate a slot in the ring in advance and attach an
 505			 * empty buffer.  If we fault or otherwise fail to use
 506			 * it, either the reader will consume it or it'll still
 507			 * be there for the next write.
 508			 */
 509			spin_lock_irq(&pipe->rd_wait.lock);
 510
 511			head = pipe->head;
 512			if (pipe_full(head, pipe->tail, pipe->max_usage)) {
 513				spin_unlock_irq(&pipe->rd_wait.lock);
 514				continue;
 515			}
 516
 517			pipe->head = head + 1;
 518			spin_unlock_irq(&pipe->rd_wait.lock);
 519
 520			/* Insert it into the buffer array */
 521			buf = &pipe->bufs[head & mask];
 522			buf->page = page;
 523			buf->ops = &anon_pipe_buf_ops;
 524			buf->offset = 0;
 525			buf->len = 0;
 526			if (is_packetized(filp))
 527				buf->flags = PIPE_BUF_FLAG_PACKET;
 528			else
 529				buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
 530			pipe->tmp_page = NULL;
 531
 532			copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
 533			if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
 534				if (!ret)
 535					ret = -EFAULT;
 536				break;
 537			}
 538			ret += copied;
 539			buf->offset = 0;
 540			buf->len = copied;
 541
 542			if (!iov_iter_count(from))
 543				break;
 544		}
 545
 546		if (!pipe_full(head, pipe->tail, pipe->max_usage))
 547			continue;
 548
 549		/* Wait for buffer space to become available. */
 550		if (filp->f_flags & O_NONBLOCK) {
 
 551			if (!ret)
 552				ret = -EAGAIN;
 553			break;
 554		}
 555		if (signal_pending(current)) {
 556			if (!ret)
 557				ret = -ERESTARTSYS;
 558			break;
 559		}
 560
 561		/*
 562		 * We're going to release the pipe lock and wait for more
 563		 * space. We wake up any readers if necessary, and then
 564		 * after waiting we need to re-check whether the pipe
 565		 * become empty while we dropped the lock.
 566		 */
 567		__pipe_unlock(pipe);
 568		if (was_empty)
 569			wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 570		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 571		wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
 572		__pipe_lock(pipe);
 573		was_empty = pipe_empty(pipe->head, pipe->tail);
 574		wake_next_writer = true;
 575	}
 576out:
 577	if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
 578		wake_next_writer = false;
 579	__pipe_unlock(pipe);
 580
 581	/*
 582	 * If we do do a wakeup event, we do a 'sync' wakeup, because we
 583	 * want the reader to start processing things asap, rather than
 584	 * leave the data pending.
 585	 *
 586	 * This is particularly important for small writes, because of
 587	 * how (for example) the GNU make jobserver uses small writes to
 588	 * wake up pending jobs
 589	 *
 590	 * Epoll nonsensically wants a wakeup whether the pipe
 591	 * was already empty or not.
 592	 */
 593	if (was_empty || pipe->poll_usage)
 594		wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 595	kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 596	if (wake_next_writer)
 597		wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 598	if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
 599		int err = file_update_time(filp);
 600		if (err)
 601			ret = err;
 602		sb_end_write(file_inode(filp)->i_sb);
 603	}
 604	return ret;
 605}
 606
 607static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 608{
 609	struct pipe_inode_info *pipe = filp->private_data;
 610	unsigned int count, head, tail, mask;
 611
 612	switch (cmd) {
 613	case FIONREAD:
 614		__pipe_lock(pipe);
 615		count = 0;
 616		head = pipe->head;
 617		tail = pipe->tail;
 618		mask = pipe->ring_size - 1;
 619
 620		while (tail != head) {
 621			count += pipe->bufs[tail & mask].len;
 622			tail++;
 623		}
 624		__pipe_unlock(pipe);
 625
 626		return put_user(count, (int __user *)arg);
 627
 628#ifdef CONFIG_WATCH_QUEUE
 629	case IOC_WATCH_QUEUE_SET_SIZE: {
 630		int ret;
 631		__pipe_lock(pipe);
 632		ret = watch_queue_set_size(pipe, arg);
 633		__pipe_unlock(pipe);
 634		return ret;
 635	}
 636
 637	case IOC_WATCH_QUEUE_SET_FILTER:
 638		return watch_queue_set_filter(
 639			pipe, (struct watch_notification_filter __user *)arg);
 640#endif
 641
 642	default:
 643		return -ENOIOCTLCMD;
 644	}
 645}
 646
 647/* No kernel lock held - fine */
 648static __poll_t
 649pipe_poll(struct file *filp, poll_table *wait)
 650{
 651	__poll_t mask;
 652	struct pipe_inode_info *pipe = filp->private_data;
 653	unsigned int head, tail;
 654
 655	/* Epoll has some historical nasty semantics, this enables them */
 656	WRITE_ONCE(pipe->poll_usage, true);
 657
 658	/*
 659	 * Reading pipe state only -- no need for acquiring the semaphore.
 660	 *
 661	 * But because this is racy, the code has to add the
 662	 * entry to the poll table _first_ ..
 663	 */
 664	if (filp->f_mode & FMODE_READ)
 665		poll_wait(filp, &pipe->rd_wait, wait);
 666	if (filp->f_mode & FMODE_WRITE)
 667		poll_wait(filp, &pipe->wr_wait, wait);
 668
 669	/*
 670	 * .. and only then can you do the racy tests. That way,
 671	 * if something changes and you got it wrong, the poll
 672	 * table entry will wake you up and fix it.
 673	 */
 674	head = READ_ONCE(pipe->head);
 675	tail = READ_ONCE(pipe->tail);
 676
 677	mask = 0;
 678	if (filp->f_mode & FMODE_READ) {
 679		if (!pipe_empty(head, tail))
 680			mask |= EPOLLIN | EPOLLRDNORM;
 681		if (!pipe->writers && filp->f_version != pipe->w_counter)
 682			mask |= EPOLLHUP;
 683	}
 684
 685	if (filp->f_mode & FMODE_WRITE) {
 686		if (!pipe_full(head, tail, pipe->max_usage))
 687			mask |= EPOLLOUT | EPOLLWRNORM;
 688		/*
 689		 * Most Unices do not set EPOLLERR for FIFOs but on Linux they
 690		 * behave exactly like pipes for poll().
 691		 */
 692		if (!pipe->readers)
 693			mask |= EPOLLERR;
 694	}
 695
 696	return mask;
 697}
 698
 699static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
 700{
 701	int kill = 0;
 702
 703	spin_lock(&inode->i_lock);
 704	if (!--pipe->files) {
 705		inode->i_pipe = NULL;
 706		kill = 1;
 707	}
 708	spin_unlock(&inode->i_lock);
 709
 710	if (kill)
 711		free_pipe_info(pipe);
 712}
 713
 714static int
 715pipe_release(struct inode *inode, struct file *file)
 716{
 717	struct pipe_inode_info *pipe = file->private_data;
 718
 719	__pipe_lock(pipe);
 720	if (file->f_mode & FMODE_READ)
 721		pipe->readers--;
 722	if (file->f_mode & FMODE_WRITE)
 723		pipe->writers--;
 724
 725	/* Was that the last reader or writer, but not the other side? */
 726	if (!pipe->readers != !pipe->writers) {
 727		wake_up_interruptible_all(&pipe->rd_wait);
 728		wake_up_interruptible_all(&pipe->wr_wait);
 729		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 730		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 731	}
 732	__pipe_unlock(pipe);
 733
 734	put_pipe_info(inode, pipe);
 735	return 0;
 736}
 737
 738static int
 739pipe_fasync(int fd, struct file *filp, int on)
 740{
 741	struct pipe_inode_info *pipe = filp->private_data;
 742	int retval = 0;
 743
 744	__pipe_lock(pipe);
 745	if (filp->f_mode & FMODE_READ)
 746		retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 747	if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 748		retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 749		if (retval < 0 && (filp->f_mode & FMODE_READ))
 750			/* this can happen only if on == T */
 751			fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 752	}
 753	__pipe_unlock(pipe);
 754	return retval;
 755}
 756
 757unsigned long account_pipe_buffers(struct user_struct *user,
 758				   unsigned long old, unsigned long new)
 759{
 760	return atomic_long_add_return(new - old, &user->pipe_bufs);
 761}
 762
 763bool too_many_pipe_buffers_soft(unsigned long user_bufs)
 764{
 765	unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
 766
 767	return soft_limit && user_bufs > soft_limit;
 768}
 769
 770bool too_many_pipe_buffers_hard(unsigned long user_bufs)
 771{
 772	unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
 773
 774	return hard_limit && user_bufs > hard_limit;
 775}
 776
 777bool pipe_is_unprivileged_user(void)
 778{
 779	return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
 780}
 781
 782struct pipe_inode_info *alloc_pipe_info(void)
 783{
 784	struct pipe_inode_info *pipe;
 785	unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
 786	struct user_struct *user = get_current_user();
 787	unsigned long user_bufs;
 788	unsigned int max_size = READ_ONCE(pipe_max_size);
 789
 790	pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
 791	if (pipe == NULL)
 792		goto out_free_uid;
 793
 794	if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
 795		pipe_bufs = max_size >> PAGE_SHIFT;
 796
 797	user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
 798
 799	if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
 800		user_bufs = account_pipe_buffers(user, pipe_bufs, PIPE_MIN_DEF_BUFFERS);
 801		pipe_bufs = PIPE_MIN_DEF_BUFFERS;
 802	}
 803
 804	if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
 805		goto out_revert_acct;
 806
 807	pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
 808			     GFP_KERNEL_ACCOUNT);
 809
 810	if (pipe->bufs) {
 811		init_waitqueue_head(&pipe->rd_wait);
 812		init_waitqueue_head(&pipe->wr_wait);
 813		pipe->r_counter = pipe->w_counter = 1;
 814		pipe->max_usage = pipe_bufs;
 815		pipe->ring_size = pipe_bufs;
 816		pipe->nr_accounted = pipe_bufs;
 817		pipe->user = user;
 818		mutex_init(&pipe->mutex);
 819		return pipe;
 820	}
 821
 822out_revert_acct:
 823	(void) account_pipe_buffers(user, pipe_bufs, 0);
 824	kfree(pipe);
 825out_free_uid:
 826	free_uid(user);
 827	return NULL;
 828}
 829
 830void free_pipe_info(struct pipe_inode_info *pipe)
 831{
 832	unsigned int i;
 833
 834#ifdef CONFIG_WATCH_QUEUE
 835	if (pipe->watch_queue)
 836		watch_queue_clear(pipe->watch_queue);
 837#endif
 838
 839	(void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
 840	free_uid(pipe->user);
 841	for (i = 0; i < pipe->ring_size; i++) {
 842		struct pipe_buffer *buf = pipe->bufs + i;
 843		if (buf->ops)
 844			pipe_buf_release(pipe, buf);
 845	}
 846#ifdef CONFIG_WATCH_QUEUE
 847	if (pipe->watch_queue)
 848		put_watch_queue(pipe->watch_queue);
 849#endif
 850	if (pipe->tmp_page)
 851		__free_page(pipe->tmp_page);
 852	kfree(pipe->bufs);
 853	kfree(pipe);
 854}
 855
 856static struct vfsmount *pipe_mnt __read_mostly;
 857
 858/*
 859 * pipefs_dname() is called from d_path().
 860 */
 861static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 862{
 863	return dynamic_dname(buffer, buflen, "pipe:[%lu]",
 864				d_inode(dentry)->i_ino);
 865}
 866
 867static const struct dentry_operations pipefs_dentry_operations = {
 868	.d_dname	= pipefs_dname,
 869};
 870
 871static struct inode * get_pipe_inode(void)
 872{
 873	struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 874	struct pipe_inode_info *pipe;
 875
 876	if (!inode)
 877		goto fail_inode;
 878
 879	inode->i_ino = get_next_ino();
 880
 881	pipe = alloc_pipe_info();
 882	if (!pipe)
 883		goto fail_iput;
 884
 885	inode->i_pipe = pipe;
 886	pipe->files = 2;
 887	pipe->readers = pipe->writers = 1;
 888	inode->i_fop = &pipefifo_fops;
 889
 890	/*
 891	 * Mark the inode dirty from the very beginning,
 892	 * that way it will never be moved to the dirty
 893	 * list because "mark_inode_dirty()" will think
 894	 * that it already _is_ on the dirty list.
 895	 */
 896	inode->i_state = I_DIRTY;
 897	inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 898	inode->i_uid = current_fsuid();
 899	inode->i_gid = current_fsgid();
 900	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 901
 902	return inode;
 903
 904fail_iput:
 905	iput(inode);
 906
 907fail_inode:
 908	return NULL;
 909}
 910
 911int create_pipe_files(struct file **res, int flags)
 912{
 913	struct inode *inode = get_pipe_inode();
 914	struct file *f;
 915	int error;
 916
 917	if (!inode)
 918		return -ENFILE;
 919
 920	if (flags & O_NOTIFICATION_PIPE) {
 921		error = watch_queue_init(inode->i_pipe);
 922		if (error) {
 923			free_pipe_info(inode->i_pipe);
 924			iput(inode);
 925			return error;
 926		}
 927	}
 928
 929	f = alloc_file_pseudo(inode, pipe_mnt, "",
 930				O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
 931				&pipefifo_fops);
 932	if (IS_ERR(f)) {
 933		free_pipe_info(inode->i_pipe);
 934		iput(inode);
 935		return PTR_ERR(f);
 936	}
 937
 938	f->private_data = inode->i_pipe;
 939
 940	res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
 941				  &pipefifo_fops);
 942	if (IS_ERR(res[0])) {
 943		put_pipe_info(inode, inode->i_pipe);
 944		fput(f);
 945		return PTR_ERR(res[0]);
 946	}
 947	res[0]->private_data = inode->i_pipe;
 948	res[1] = f;
 949	stream_open(inode, res[0]);
 950	stream_open(inode, res[1]);
 951	return 0;
 952}
 953
 954static int __do_pipe_flags(int *fd, struct file **files, int flags)
 955{
 956	int error;
 957	int fdw, fdr;
 958
 959	if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
 960		return -EINVAL;
 961
 962	error = create_pipe_files(files, flags);
 963	if (error)
 964		return error;
 965
 966	error = get_unused_fd_flags(flags);
 967	if (error < 0)
 968		goto err_read_pipe;
 969	fdr = error;
 970
 971	error = get_unused_fd_flags(flags);
 972	if (error < 0)
 973		goto err_fdr;
 974	fdw = error;
 975
 976	audit_fd_pair(fdr, fdw);
 977	fd[0] = fdr;
 978	fd[1] = fdw;
 
 
 
 979	return 0;
 980
 981 err_fdr:
 982	put_unused_fd(fdr);
 983 err_read_pipe:
 984	fput(files[0]);
 985	fput(files[1]);
 986	return error;
 987}
 988
 989int do_pipe_flags(int *fd, int flags)
 990{
 991	struct file *files[2];
 992	int error = __do_pipe_flags(fd, files, flags);
 993	if (!error) {
 994		fd_install(fd[0], files[0]);
 995		fd_install(fd[1], files[1]);
 996	}
 997	return error;
 998}
 999
1000/*
1001 * sys_pipe() is the normal C calling standard for creating
1002 * a pipe. It's not the way Unix traditionally does this, though.
1003 */
1004static int do_pipe2(int __user *fildes, int flags)
1005{
1006	struct file *files[2];
1007	int fd[2];
1008	int error;
1009
1010	error = __do_pipe_flags(fd, files, flags);
1011	if (!error) {
1012		if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
1013			fput(files[0]);
1014			fput(files[1]);
1015			put_unused_fd(fd[0]);
1016			put_unused_fd(fd[1]);
1017			error = -EFAULT;
1018		} else {
1019			fd_install(fd[0], files[0]);
1020			fd_install(fd[1], files[1]);
1021		}
1022	}
1023	return error;
1024}
1025
1026SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1027{
1028	return do_pipe2(fildes, flags);
1029}
1030
1031SYSCALL_DEFINE1(pipe, int __user *, fildes)
1032{
1033	return do_pipe2(fildes, 0);
1034}
1035
1036/*
1037 * This is the stupid "wait for pipe to be readable or writable"
1038 * model.
1039 *
1040 * See pipe_read/write() for the proper kind of exclusive wait,
1041 * but that requires that we wake up any other readers/writers
1042 * if we then do not end up reading everything (ie the whole
1043 * "wake_next_reader/writer" logic in pipe_read/write()).
1044 */
1045void pipe_wait_readable(struct pipe_inode_info *pipe)
1046{
1047	pipe_unlock(pipe);
1048	wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
1049	pipe_lock(pipe);
1050}
1051
1052void pipe_wait_writable(struct pipe_inode_info *pipe)
1053{
1054	pipe_unlock(pipe);
1055	wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
1056	pipe_lock(pipe);
1057}
1058
1059/*
1060 * This depends on both the wait (here) and the wakeup (wake_up_partner)
1061 * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
1062 * race with the count check and waitqueue prep.
1063 *
1064 * Normally in order to avoid races, you'd do the prepare_to_wait() first,
1065 * then check the condition you're waiting for, and only then sleep. But
1066 * because of the pipe lock, we can check the condition before being on
1067 * the wait queue.
1068 *
1069 * We use the 'rd_wait' waitqueue for pipe partner waiting.
1070 */
1071static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1072{
1073	DEFINE_WAIT(rdwait);
1074	int cur = *cnt;
1075
1076	while (cur == *cnt) {
1077		prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
1078		pipe_unlock(pipe);
1079		schedule();
1080		finish_wait(&pipe->rd_wait, &rdwait);
1081		pipe_lock(pipe);
1082		if (signal_pending(current))
1083			break;
1084	}
1085	return cur == *cnt ? -ERESTARTSYS : 0;
1086}
1087
1088static void wake_up_partner(struct pipe_inode_info *pipe)
1089{
1090	wake_up_interruptible_all(&pipe->rd_wait);
1091}
1092
1093static int fifo_open(struct inode *inode, struct file *filp)
1094{
1095	struct pipe_inode_info *pipe;
1096	bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1097	int ret;
1098
1099	filp->f_version = 0;
1100
1101	spin_lock(&inode->i_lock);
1102	if (inode->i_pipe) {
1103		pipe = inode->i_pipe;
1104		pipe->files++;
1105		spin_unlock(&inode->i_lock);
1106	} else {
1107		spin_unlock(&inode->i_lock);
1108		pipe = alloc_pipe_info();
1109		if (!pipe)
1110			return -ENOMEM;
1111		pipe->files = 1;
1112		spin_lock(&inode->i_lock);
1113		if (unlikely(inode->i_pipe)) {
1114			inode->i_pipe->files++;
1115			spin_unlock(&inode->i_lock);
1116			free_pipe_info(pipe);
1117			pipe = inode->i_pipe;
1118		} else {
1119			inode->i_pipe = pipe;
1120			spin_unlock(&inode->i_lock);
1121		}
1122	}
1123	filp->private_data = pipe;
1124	/* OK, we have a pipe and it's pinned down */
1125
1126	__pipe_lock(pipe);
1127
1128	/* We can only do regular read/write on fifos */
1129	stream_open(inode, filp);
1130
1131	switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
1132	case FMODE_READ:
1133	/*
1134	 *  O_RDONLY
1135	 *  POSIX.1 says that O_NONBLOCK means return with the FIFO
1136	 *  opened, even when there is no process writing the FIFO.
1137	 */
1138		pipe->r_counter++;
1139		if (pipe->readers++ == 0)
1140			wake_up_partner(pipe);
1141
1142		if (!is_pipe && !pipe->writers) {
1143			if ((filp->f_flags & O_NONBLOCK)) {
1144				/* suppress EPOLLHUP until we have
1145				 * seen a writer */
1146				filp->f_version = pipe->w_counter;
1147			} else {
1148				if (wait_for_partner(pipe, &pipe->w_counter))
1149					goto err_rd;
1150			}
1151		}
1152		break;
1153
1154	case FMODE_WRITE:
1155	/*
1156	 *  O_WRONLY
1157	 *  POSIX.1 says that O_NONBLOCK means return -1 with
1158	 *  errno=ENXIO when there is no process reading the FIFO.
1159	 */
1160		ret = -ENXIO;
1161		if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1162			goto err;
1163
1164		pipe->w_counter++;
1165		if (!pipe->writers++)
1166			wake_up_partner(pipe);
1167
1168		if (!is_pipe && !pipe->readers) {
1169			if (wait_for_partner(pipe, &pipe->r_counter))
1170				goto err_wr;
1171		}
1172		break;
1173
1174	case FMODE_READ | FMODE_WRITE:
1175	/*
1176	 *  O_RDWR
1177	 *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1178	 *  This implementation will NEVER block on a O_RDWR open, since
1179	 *  the process can at least talk to itself.
1180	 */
1181
1182		pipe->readers++;
1183		pipe->writers++;
1184		pipe->r_counter++;
1185		pipe->w_counter++;
1186		if (pipe->readers == 1 || pipe->writers == 1)
1187			wake_up_partner(pipe);
1188		break;
1189
1190	default:
1191		ret = -EINVAL;
1192		goto err;
1193	}
1194
1195	/* Ok! */
1196	__pipe_unlock(pipe);
1197	return 0;
1198
1199err_rd:
1200	if (!--pipe->readers)
1201		wake_up_interruptible(&pipe->wr_wait);
1202	ret = -ERESTARTSYS;
1203	goto err;
1204
1205err_wr:
1206	if (!--pipe->writers)
1207		wake_up_interruptible_all(&pipe->rd_wait);
1208	ret = -ERESTARTSYS;
1209	goto err;
1210
1211err:
1212	__pipe_unlock(pipe);
1213
1214	put_pipe_info(inode, pipe);
1215	return ret;
1216}
1217
1218const struct file_operations pipefifo_fops = {
1219	.open		= fifo_open,
1220	.llseek		= no_llseek,
1221	.read_iter	= pipe_read,
1222	.write_iter	= pipe_write,
1223	.poll		= pipe_poll,
1224	.unlocked_ioctl	= pipe_ioctl,
1225	.release	= pipe_release,
1226	.fasync		= pipe_fasync,
1227	.splice_write	= iter_file_splice_write,
1228};
1229
1230/*
1231 * Currently we rely on the pipe array holding a power-of-2 number
1232 * of pages. Returns 0 on error.
1233 */
1234unsigned int round_pipe_size(unsigned long size)
1235{
1236	if (size > (1U << 31))
1237		return 0;
1238
1239	/* Minimum pipe size, as required by POSIX */
1240	if (size < PAGE_SIZE)
1241		return PAGE_SIZE;
1242
1243	return roundup_pow_of_two(size);
1244}
1245
1246/*
1247 * Resize the pipe ring to a number of slots.
1248 *
1249 * Note the pipe can be reduced in capacity, but only if the current
1250 * occupancy doesn't exceed nr_slots; if it does, EBUSY will be
1251 * returned instead.
1252 */
1253int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
1254{
1255	struct pipe_buffer *bufs;
1256	unsigned int head, tail, mask, n;
1257
1258	bufs = kcalloc(nr_slots, sizeof(*bufs),
1259		       GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1260	if (unlikely(!bufs))
1261		return -ENOMEM;
1262
1263	spin_lock_irq(&pipe->rd_wait.lock);
1264	mask = pipe->ring_size - 1;
1265	head = pipe->head;
1266	tail = pipe->tail;
1267
1268	n = pipe_occupancy(head, tail);
1269	if (nr_slots < n) {
1270		spin_unlock_irq(&pipe->rd_wait.lock);
1271		kfree(bufs);
1272		return -EBUSY;
1273	}
1274
1275	/*
1276	 * The pipe array wraps around, so just start the new one at zero
1277	 * and adjust the indices.
1278	 */
1279	if (n > 0) {
1280		unsigned int h = head & mask;
1281		unsigned int t = tail & mask;
1282		if (h > t) {
1283			memcpy(bufs, pipe->bufs + t,
1284			       n * sizeof(struct pipe_buffer));
1285		} else {
1286			unsigned int tsize = pipe->ring_size - t;
1287			if (h > 0)
1288				memcpy(bufs + tsize, pipe->bufs,
1289				       h * sizeof(struct pipe_buffer));
1290			memcpy(bufs, pipe->bufs + t,
1291			       tsize * sizeof(struct pipe_buffer));
1292		}
1293	}
1294
1295	head = n;
1296	tail = 0;
1297
1298	kfree(pipe->bufs);
1299	pipe->bufs = bufs;
1300	pipe->ring_size = nr_slots;
1301	if (pipe->max_usage > nr_slots)
1302		pipe->max_usage = nr_slots;
1303	pipe->tail = tail;
1304	pipe->head = head;
1305
 
 
 
 
 
1306	spin_unlock_irq(&pipe->rd_wait.lock);
1307
1308	/* This might have made more room for writers */
1309	wake_up_interruptible(&pipe->wr_wait);
1310	return 0;
1311}
1312
1313/*
1314 * Allocate a new array of pipe buffers and copy the info over. Returns the
1315 * pipe size if successful, or return -ERROR on error.
1316 */
1317static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1318{
1319	unsigned long user_bufs;
1320	unsigned int nr_slots, size;
1321	long ret = 0;
1322
1323#ifdef CONFIG_WATCH_QUEUE
1324	if (pipe->watch_queue)
1325		return -EBUSY;
1326#endif
1327
1328	size = round_pipe_size(arg);
1329	nr_slots = size >> PAGE_SHIFT;
1330
1331	if (!nr_slots)
1332		return -EINVAL;
1333
1334	/*
1335	 * If trying to increase the pipe capacity, check that an
1336	 * unprivileged user is not trying to exceed various limits
1337	 * (soft limit check here, hard limit check just below).
1338	 * Decreasing the pipe capacity is always permitted, even
1339	 * if the user is currently over a limit.
1340	 */
1341	if (nr_slots > pipe->max_usage &&
1342			size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1343		return -EPERM;
1344
1345	user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
1346
1347	if (nr_slots > pipe->max_usage &&
1348			(too_many_pipe_buffers_hard(user_bufs) ||
1349			 too_many_pipe_buffers_soft(user_bufs)) &&
1350			pipe_is_unprivileged_user()) {
1351		ret = -EPERM;
1352		goto out_revert_acct;
1353	}
1354
1355	ret = pipe_resize_ring(pipe, nr_slots);
1356	if (ret < 0)
1357		goto out_revert_acct;
1358
1359	pipe->max_usage = nr_slots;
1360	pipe->nr_accounted = nr_slots;
1361	return pipe->max_usage * PAGE_SIZE;
1362
1363out_revert_acct:
1364	(void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
1365	return ret;
1366}
1367
1368/*
1369 * Note that i_pipe and i_cdev share the same location, so checking ->i_pipe is
1370 * not enough to verify that this is a pipe.
1371 */
1372struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
1373{
1374	struct pipe_inode_info *pipe = file->private_data;
1375
1376	if (file->f_op != &pipefifo_fops || !pipe)
1377		return NULL;
1378#ifdef CONFIG_WATCH_QUEUE
1379	if (for_splice && pipe->watch_queue)
1380		return NULL;
1381#endif
1382	return pipe;
1383}
1384
1385long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1386{
1387	struct pipe_inode_info *pipe;
1388	long ret;
1389
1390	pipe = get_pipe_info(file, false);
1391	if (!pipe)
1392		return -EBADF;
1393
1394	__pipe_lock(pipe);
1395
1396	switch (cmd) {
1397	case F_SETPIPE_SZ:
1398		ret = pipe_set_size(pipe, arg);
1399		break;
1400	case F_GETPIPE_SZ:
1401		ret = pipe->max_usage * PAGE_SIZE;
1402		break;
1403	default:
1404		ret = -EINVAL;
1405		break;
1406	}
1407
1408	__pipe_unlock(pipe);
1409	return ret;
1410}
1411
1412static const struct super_operations pipefs_ops = {
1413	.destroy_inode = free_inode_nonrcu,
1414	.statfs = simple_statfs,
1415};
1416
1417/*
1418 * pipefs should _never_ be mounted by userland - too much of security hassle,
1419 * no real gain from having the whole whorehouse mounted. So we don't need
1420 * any operations on the root directory. However, we need a non-trivial
1421 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1422 */
1423
1424static int pipefs_init_fs_context(struct fs_context *fc)
1425{
1426	struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
1427	if (!ctx)
1428		return -ENOMEM;
1429	ctx->ops = &pipefs_ops;
1430	ctx->dops = &pipefs_dentry_operations;
1431	return 0;
1432}
1433
1434static struct file_system_type pipe_fs_type = {
1435	.name		= "pipefs",
1436	.init_fs_context = pipefs_init_fs_context,
1437	.kill_sb	= kill_anon_super,
1438};
1439
1440#ifdef CONFIG_SYSCTL
1441static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
1442					unsigned int *valp,
1443					int write, void *data)
1444{
1445	if (write) {
1446		unsigned int val;
1447
1448		val = round_pipe_size(*lvalp);
1449		if (val == 0)
1450			return -EINVAL;
1451
1452		*valp = val;
1453	} else {
1454		unsigned int val = *valp;
1455		*lvalp = (unsigned long) val;
1456	}
1457
1458	return 0;
1459}
1460
1461static int proc_dopipe_max_size(struct ctl_table *table, int write,
1462				void *buffer, size_t *lenp, loff_t *ppos)
1463{
1464	return do_proc_douintvec(table, write, buffer, lenp, ppos,
1465				 do_proc_dopipe_max_size_conv, NULL);
1466}
1467
1468static struct ctl_table fs_pipe_sysctls[] = {
1469	{
1470		.procname	= "pipe-max-size",
1471		.data		= &pipe_max_size,
1472		.maxlen		= sizeof(pipe_max_size),
1473		.mode		= 0644,
1474		.proc_handler	= proc_dopipe_max_size,
1475	},
1476	{
1477		.procname	= "pipe-user-pages-hard",
1478		.data		= &pipe_user_pages_hard,
1479		.maxlen		= sizeof(pipe_user_pages_hard),
1480		.mode		= 0644,
1481		.proc_handler	= proc_doulongvec_minmax,
1482	},
1483	{
1484		.procname	= "pipe-user-pages-soft",
1485		.data		= &pipe_user_pages_soft,
1486		.maxlen		= sizeof(pipe_user_pages_soft),
1487		.mode		= 0644,
1488		.proc_handler	= proc_doulongvec_minmax,
1489	},
1490	{ }
1491};
1492#endif
1493
1494static int __init init_pipe_fs(void)
1495{
1496	int err = register_filesystem(&pipe_fs_type);
1497
1498	if (!err) {
1499		pipe_mnt = kern_mount(&pipe_fs_type);
1500		if (IS_ERR(pipe_mnt)) {
1501			err = PTR_ERR(pipe_mnt);
1502			unregister_filesystem(&pipe_fs_type);
1503		}
1504	}
1505#ifdef CONFIG_SYSCTL
1506	register_sysctl_init("fs", fs_pipe_sysctls);
1507#endif
1508	return err;
1509}
1510
1511fs_initcall(init_pipe_fs);
v6.8
   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/pseudo_fs.h>
  18#include <linux/magic.h>
  19#include <linux/pipe_fs_i.h>
  20#include <linux/uio.h>
  21#include <linux/highmem.h>
  22#include <linux/pagemap.h>
  23#include <linux/audit.h>
  24#include <linux/syscalls.h>
  25#include <linux/fcntl.h>
  26#include <linux/memcontrol.h>
  27#include <linux/watch_queue.h>
  28#include <linux/sysctl.h>
  29
  30#include <linux/uaccess.h>
  31#include <asm/ioctls.h>
  32
  33#include "internal.h"
  34
  35/*
  36 * New pipe buffers will be restricted to this size while the user is exceeding
  37 * their pipe buffer quota. The general pipe use case needs at least two
  38 * buffers: one for data yet to be read, and one for new data. If this is less
  39 * than two, then a write to a non-empty pipe may block even if the pipe is not
  40 * full. This can occur with GNU make jobserver or similar uses of pipes as
  41 * semaphores: multiple processes may be waiting to write tokens back to the
  42 * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.
  43 *
  44 * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their
  45 * own risk, namely: pipe writes to non-full pipes may block until the pipe is
  46 * emptied.
  47 */
  48#define PIPE_MIN_DEF_BUFFERS 2
  49
  50/*
  51 * The max size that a non-root user is allowed to grow the pipe. Can
  52 * be set by root in /proc/sys/fs/pipe-max-size
  53 */
  54static unsigned int pipe_max_size = 1048576;
  55
  56/* Maximum allocatable pages per user. Hard limit is unset by default, soft
  57 * matches default values.
  58 */
  59static unsigned long pipe_user_pages_hard;
  60static unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
  61
  62/*
  63 * We use head and tail indices that aren't masked off, except at the point of
  64 * dereference, but rather they're allowed to wrap naturally.  This means there
  65 * isn't a dead spot in the buffer, but the ring has to be a power of two and
  66 * <= 2^31.
  67 * -- David Howells 2019-09-23.
  68 *
  69 * Reads with count = 0 should always return 0.
  70 * -- Julian Bradfield 1999-06-07.
  71 *
  72 * FIFOs and Pipes now generate SIGIO for both readers and writers.
  73 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  74 *
  75 * pipe_read & write cleanup
  76 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  77 */
  78
  79static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  80{
  81	if (pipe->files)
  82		mutex_lock_nested(&pipe->mutex, subclass);
  83}
  84
  85void pipe_lock(struct pipe_inode_info *pipe)
  86{
  87	/*
  88	 * pipe_lock() nests non-pipe inode locks (for writing to a file)
  89	 */
  90	pipe_lock_nested(pipe, I_MUTEX_PARENT);
  91}
  92EXPORT_SYMBOL(pipe_lock);
  93
  94void pipe_unlock(struct pipe_inode_info *pipe)
  95{
  96	if (pipe->files)
  97		mutex_unlock(&pipe->mutex);
  98}
  99EXPORT_SYMBOL(pipe_unlock);
 100
 101static inline void __pipe_lock(struct pipe_inode_info *pipe)
 102{
 103	mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
 104}
 105
 106static inline void __pipe_unlock(struct pipe_inode_info *pipe)
 107{
 108	mutex_unlock(&pipe->mutex);
 109}
 110
 111void pipe_double_lock(struct pipe_inode_info *pipe1,
 112		      struct pipe_inode_info *pipe2)
 113{
 114	BUG_ON(pipe1 == pipe2);
 115
 116	if (pipe1 < pipe2) {
 117		pipe_lock_nested(pipe1, I_MUTEX_PARENT);
 118		pipe_lock_nested(pipe2, I_MUTEX_CHILD);
 119	} else {
 120		pipe_lock_nested(pipe2, I_MUTEX_PARENT);
 121		pipe_lock_nested(pipe1, I_MUTEX_CHILD);
 122	}
 123}
 124
 125static 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
 141static bool anon_pipe_buf_try_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		return false;
 148	memcg_kmem_uncharge_page(page, 0);
 149	__SetPageLocked(page);
 150	return true;
 151}
 152
 153/**
 154 * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
 155 * @pipe:	the pipe that the buffer belongs to
 156 * @buf:	the buffer to attempt to steal
 157 *
 158 * Description:
 159 *	This function attempts to steal the &struct page attached to
 160 *	@buf. If successful, this function returns 0 and returns with
 161 *	the page locked. The caller may then reuse the page for whatever
 162 *	he wishes; the typical use is insertion into a different file
 163 *	page cache.
 164 */
 165bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe,
 166		struct pipe_buffer *buf)
 167{
 168	struct page *page = buf->page;
 169
 170	/*
 171	 * A reference of one is golden, that means that the owner of this
 172	 * page is the only one holding a reference to it. lock the page
 173	 * and return OK.
 174	 */
 175	if (page_count(page) == 1) {
 176		lock_page(page);
 177		return true;
 178	}
 179	return false;
 180}
 181EXPORT_SYMBOL(generic_pipe_buf_try_steal);
 182
 183/**
 184 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 185 * @pipe:	the pipe that the buffer belongs to
 186 * @buf:	the buffer to get a reference to
 187 *
 188 * Description:
 189 *	This function grabs an extra reference to @buf. It's used in
 190 *	the tee() system call, when we duplicate the buffers in one
 191 *	pipe into another.
 192 */
 193bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 194{
 195	return try_get_page(buf->page);
 196}
 197EXPORT_SYMBOL(generic_pipe_buf_get);
 198
 199/**
 200 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 201 * @pipe:	the pipe that the buffer belongs to
 202 * @buf:	the buffer to put a reference to
 203 *
 204 * Description:
 205 *	This function releases a reference to @buf.
 206 */
 207void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 208			      struct pipe_buffer *buf)
 209{
 210	put_page(buf->page);
 211}
 212EXPORT_SYMBOL(generic_pipe_buf_release);
 213
 214static const struct pipe_buf_operations anon_pipe_buf_ops = {
 215	.release	= anon_pipe_buf_release,
 216	.try_steal	= anon_pipe_buf_try_steal,
 217	.get		= generic_pipe_buf_get,
 218};
 219
 220/* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
 221static inline bool pipe_readable(const struct pipe_inode_info *pipe)
 222{
 223	unsigned int head = READ_ONCE(pipe->head);
 224	unsigned int tail = READ_ONCE(pipe->tail);
 225	unsigned int writers = READ_ONCE(pipe->writers);
 226
 227	return !pipe_empty(head, tail) || !writers;
 228}
 229
 230static inline unsigned int pipe_update_tail(struct pipe_inode_info *pipe,
 231					    struct pipe_buffer *buf,
 232					    unsigned int tail)
 233{
 234	pipe_buf_release(pipe, buf);
 235
 236	/*
 237	 * If the pipe has a watch_queue, we need additional protection
 238	 * by the spinlock because notifications get posted with only
 239	 * this spinlock, no mutex
 240	 */
 241	if (pipe_has_watch_queue(pipe)) {
 242		spin_lock_irq(&pipe->rd_wait.lock);
 243#ifdef CONFIG_WATCH_QUEUE
 244		if (buf->flags & PIPE_BUF_FLAG_LOSS)
 245			pipe->note_loss = true;
 246#endif
 247		pipe->tail = ++tail;
 248		spin_unlock_irq(&pipe->rd_wait.lock);
 249		return tail;
 250	}
 251
 252	/*
 253	 * Without a watch_queue, we can simply increment the tail
 254	 * without the spinlock - the mutex is enough.
 255	 */
 256	pipe->tail = ++tail;
 257	return tail;
 258}
 259
 260static ssize_t
 261pipe_read(struct kiocb *iocb, struct iov_iter *to)
 262{
 263	size_t total_len = iov_iter_count(to);
 264	struct file *filp = iocb->ki_filp;
 265	struct pipe_inode_info *pipe = filp->private_data;
 266	bool was_full, wake_next_reader = false;
 267	ssize_t ret;
 268
 269	/* Null read succeeds. */
 270	if (unlikely(total_len == 0))
 271		return 0;
 272
 273	ret = 0;
 274	__pipe_lock(pipe);
 275
 276	/*
 277	 * We only wake up writers if the pipe was full when we started
 278	 * reading in order to avoid unnecessary wakeups.
 279	 *
 280	 * But when we do wake up writers, we do so using a sync wakeup
 281	 * (WF_SYNC), because we want them to get going and generate more
 282	 * data for us.
 283	 */
 284	was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
 285	for (;;) {
 286		/* Read ->head with a barrier vs post_one_notification() */
 287		unsigned int head = smp_load_acquire(&pipe->head);
 288		unsigned int tail = pipe->tail;
 289		unsigned int mask = pipe->ring_size - 1;
 290
 291#ifdef CONFIG_WATCH_QUEUE
 292		if (pipe->note_loss) {
 293			struct watch_notification n;
 294
 295			if (total_len < 8) {
 296				if (ret == 0)
 297					ret = -ENOBUFS;
 298				break;
 299			}
 300
 301			n.type = WATCH_TYPE_META;
 302			n.subtype = WATCH_META_LOSS_NOTIFICATION;
 303			n.info = watch_sizeof(n);
 304			if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
 305				if (ret == 0)
 306					ret = -EFAULT;
 307				break;
 308			}
 309			ret += sizeof(n);
 310			total_len -= sizeof(n);
 311			pipe->note_loss = false;
 312		}
 313#endif
 314
 315		if (!pipe_empty(head, tail)) {
 316			struct pipe_buffer *buf = &pipe->bufs[tail & mask];
 317			size_t chars = buf->len;
 318			size_t written;
 319			int error;
 320
 321			if (chars > total_len) {
 322				if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
 323					if (ret == 0)
 324						ret = -ENOBUFS;
 325					break;
 326				}
 327				chars = total_len;
 328			}
 329
 330			error = pipe_buf_confirm(pipe, buf);
 331			if (error) {
 332				if (!ret)
 333					ret = error;
 334				break;
 335			}
 336
 337			written = copy_page_to_iter(buf->page, buf->offset, chars, to);
 338			if (unlikely(written < chars)) {
 339				if (!ret)
 340					ret = -EFAULT;
 341				break;
 342			}
 343			ret += chars;
 344			buf->offset += chars;
 345			buf->len -= chars;
 346
 347			/* Was it a packet buffer? Clean up and exit */
 348			if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 349				total_len = chars;
 350				buf->len = 0;
 351			}
 352
 353			if (!buf->len)
 354				tail = pipe_update_tail(pipe, buf, tail);
 
 
 
 
 
 
 
 
 
 355			total_len -= chars;
 356			if (!total_len)
 357				break;	/* common path: read succeeded */
 358			if (!pipe_empty(head, tail))	/* More to do? */
 359				continue;
 360		}
 361
 362		if (!pipe->writers)
 363			break;
 364		if (ret)
 365			break;
 366		if ((filp->f_flags & O_NONBLOCK) ||
 367		    (iocb->ki_flags & IOCB_NOWAIT)) {
 368			ret = -EAGAIN;
 369			break;
 370		}
 371		__pipe_unlock(pipe);
 372
 373		/*
 374		 * We only get here if we didn't actually read anything.
 375		 *
 376		 * However, we could have seen (and removed) a zero-sized
 377		 * pipe buffer, and might have made space in the buffers
 378		 * that way.
 379		 *
 380		 * You can't make zero-sized pipe buffers by doing an empty
 381		 * write (not even in packet mode), but they can happen if
 382		 * the writer gets an EFAULT when trying to fill a buffer
 383		 * that already got allocated and inserted in the buffer
 384		 * array.
 385		 *
 386		 * So we still need to wake up any pending writers in the
 387		 * _very_ unlikely case that the pipe was full, but we got
 388		 * no data.
 389		 */
 390		if (unlikely(was_full))
 391			wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 392		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 393
 394		/*
 395		 * But because we didn't read anything, at this point we can
 396		 * just return directly with -ERESTARTSYS if we're interrupted,
 397		 * since we've done any required wakeups and there's no need
 398		 * to mark anything accessed. And we've dropped the lock.
 399		 */
 400		if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0)
 401			return -ERESTARTSYS;
 402
 403		__pipe_lock(pipe);
 404		was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
 405		wake_next_reader = true;
 406	}
 407	if (pipe_empty(pipe->head, pipe->tail))
 408		wake_next_reader = false;
 409	__pipe_unlock(pipe);
 410
 411	if (was_full)
 412		wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 413	if (wake_next_reader)
 414		wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 415	kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 416	if (ret > 0)
 417		file_accessed(filp);
 418	return ret;
 419}
 420
 421static inline int is_packetized(struct file *file)
 422{
 423	return (file->f_flags & O_DIRECT) != 0;
 424}
 425
 426/* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
 427static inline bool pipe_writable(const struct pipe_inode_info *pipe)
 428{
 429	unsigned int head = READ_ONCE(pipe->head);
 430	unsigned int tail = READ_ONCE(pipe->tail);
 431	unsigned int max_usage = READ_ONCE(pipe->max_usage);
 432
 433	return !pipe_full(head, tail, max_usage) ||
 434		!READ_ONCE(pipe->readers);
 435}
 436
 437static ssize_t
 438pipe_write(struct kiocb *iocb, struct iov_iter *from)
 439{
 440	struct file *filp = iocb->ki_filp;
 441	struct pipe_inode_info *pipe = filp->private_data;
 442	unsigned int head;
 443	ssize_t ret = 0;
 444	size_t total_len = iov_iter_count(from);
 445	ssize_t chars;
 446	bool was_empty = false;
 447	bool wake_next_writer = false;
 448
 449	/*
 450	 * Reject writing to watch queue pipes before the point where we lock
 451	 * the pipe.
 452	 * Otherwise, lockdep would be unhappy if the caller already has another
 453	 * pipe locked.
 454	 * If we had to support locking a normal pipe and a notification pipe at
 455	 * the same time, we could set up lockdep annotations for that, but
 456	 * since we don't actually need that, it's simpler to just bail here.
 457	 */
 458	if (pipe_has_watch_queue(pipe))
 459		return -EXDEV;
 460
 461	/* Null write succeeds. */
 462	if (unlikely(total_len == 0))
 463		return 0;
 464
 465	__pipe_lock(pipe);
 466
 467	if (!pipe->readers) {
 468		send_sig(SIGPIPE, current, 0);
 469		ret = -EPIPE;
 470		goto out;
 471	}
 472
 
 
 
 
 
 
 
 473	/*
 474	 * If it wasn't empty we try to merge new data into
 475	 * the last buffer.
 476	 *
 477	 * That naturally merges small writes, but it also
 478	 * page-aligns the rest of the writes for large writes
 479	 * spanning multiple pages.
 480	 */
 481	head = pipe->head;
 482	was_empty = pipe_empty(head, pipe->tail);
 483	chars = total_len & (PAGE_SIZE-1);
 484	if (chars && !was_empty) {
 485		unsigned int mask = pipe->ring_size - 1;
 486		struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
 487		int offset = buf->offset + buf->len;
 488
 489		if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
 490		    offset + chars <= PAGE_SIZE) {
 491			ret = pipe_buf_confirm(pipe, buf);
 492			if (ret)
 493				goto out;
 494
 495			ret = copy_page_from_iter(buf->page, offset, chars, from);
 496			if (unlikely(ret < chars)) {
 497				ret = -EFAULT;
 498				goto out;
 499			}
 500
 501			buf->len += ret;
 502			if (!iov_iter_count(from))
 503				goto out;
 504		}
 505	}
 506
 507	for (;;) {
 508		if (!pipe->readers) {
 509			send_sig(SIGPIPE, current, 0);
 510			if (!ret)
 511				ret = -EPIPE;
 512			break;
 513		}
 514
 515		head = pipe->head;
 516		if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
 517			unsigned int mask = pipe->ring_size - 1;
 518			struct pipe_buffer *buf;
 519			struct page *page = pipe->tmp_page;
 520			int copied;
 521
 522			if (!page) {
 523				page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
 524				if (unlikely(!page)) {
 525					ret = ret ? : -ENOMEM;
 526					break;
 527				}
 528				pipe->tmp_page = page;
 529			}
 530
 531			/* Allocate a slot in the ring in advance and attach an
 532			 * empty buffer.  If we fault or otherwise fail to use
 533			 * it, either the reader will consume it or it'll still
 534			 * be there for the next write.
 535			 */
 
 
 
 
 
 
 
 
 536			pipe->head = head + 1;
 
 537
 538			/* Insert it into the buffer array */
 539			buf = &pipe->bufs[head & mask];
 540			buf->page = page;
 541			buf->ops = &anon_pipe_buf_ops;
 542			buf->offset = 0;
 543			buf->len = 0;
 544			if (is_packetized(filp))
 545				buf->flags = PIPE_BUF_FLAG_PACKET;
 546			else
 547				buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
 548			pipe->tmp_page = NULL;
 549
 550			copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
 551			if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
 552				if (!ret)
 553					ret = -EFAULT;
 554				break;
 555			}
 556			ret += copied;
 
 557			buf->len = copied;
 558
 559			if (!iov_iter_count(from))
 560				break;
 561		}
 562
 563		if (!pipe_full(head, pipe->tail, pipe->max_usage))
 564			continue;
 565
 566		/* Wait for buffer space to become available. */
 567		if ((filp->f_flags & O_NONBLOCK) ||
 568		    (iocb->ki_flags & IOCB_NOWAIT)) {
 569			if (!ret)
 570				ret = -EAGAIN;
 571			break;
 572		}
 573		if (signal_pending(current)) {
 574			if (!ret)
 575				ret = -ERESTARTSYS;
 576			break;
 577		}
 578
 579		/*
 580		 * We're going to release the pipe lock and wait for more
 581		 * space. We wake up any readers if necessary, and then
 582		 * after waiting we need to re-check whether the pipe
 583		 * become empty while we dropped the lock.
 584		 */
 585		__pipe_unlock(pipe);
 586		if (was_empty)
 587			wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 588		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 589		wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
 590		__pipe_lock(pipe);
 591		was_empty = pipe_empty(pipe->head, pipe->tail);
 592		wake_next_writer = true;
 593	}
 594out:
 595	if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
 596		wake_next_writer = false;
 597	__pipe_unlock(pipe);
 598
 599	/*
 600	 * If we do do a wakeup event, we do a 'sync' wakeup, because we
 601	 * want the reader to start processing things asap, rather than
 602	 * leave the data pending.
 603	 *
 604	 * This is particularly important for small writes, because of
 605	 * how (for example) the GNU make jobserver uses small writes to
 606	 * wake up pending jobs
 607	 *
 608	 * Epoll nonsensically wants a wakeup whether the pipe
 609	 * was already empty or not.
 610	 */
 611	if (was_empty || pipe->poll_usage)
 612		wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 613	kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 614	if (wake_next_writer)
 615		wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 616	if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
 617		int err = file_update_time(filp);
 618		if (err)
 619			ret = err;
 620		sb_end_write(file_inode(filp)->i_sb);
 621	}
 622	return ret;
 623}
 624
 625static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 626{
 627	struct pipe_inode_info *pipe = filp->private_data;
 628	unsigned int count, head, tail, mask;
 629
 630	switch (cmd) {
 631	case FIONREAD:
 632		__pipe_lock(pipe);
 633		count = 0;
 634		head = pipe->head;
 635		tail = pipe->tail;
 636		mask = pipe->ring_size - 1;
 637
 638		while (tail != head) {
 639			count += pipe->bufs[tail & mask].len;
 640			tail++;
 641		}
 642		__pipe_unlock(pipe);
 643
 644		return put_user(count, (int __user *)arg);
 645
 646#ifdef CONFIG_WATCH_QUEUE
 647	case IOC_WATCH_QUEUE_SET_SIZE: {
 648		int ret;
 649		__pipe_lock(pipe);
 650		ret = watch_queue_set_size(pipe, arg);
 651		__pipe_unlock(pipe);
 652		return ret;
 653	}
 654
 655	case IOC_WATCH_QUEUE_SET_FILTER:
 656		return watch_queue_set_filter(
 657			pipe, (struct watch_notification_filter __user *)arg);
 658#endif
 659
 660	default:
 661		return -ENOIOCTLCMD;
 662	}
 663}
 664
 665/* No kernel lock held - fine */
 666static __poll_t
 667pipe_poll(struct file *filp, poll_table *wait)
 668{
 669	__poll_t mask;
 670	struct pipe_inode_info *pipe = filp->private_data;
 671	unsigned int head, tail;
 672
 673	/* Epoll has some historical nasty semantics, this enables them */
 674	WRITE_ONCE(pipe->poll_usage, true);
 675
 676	/*
 677	 * Reading pipe state only -- no need for acquiring the semaphore.
 678	 *
 679	 * But because this is racy, the code has to add the
 680	 * entry to the poll table _first_ ..
 681	 */
 682	if (filp->f_mode & FMODE_READ)
 683		poll_wait(filp, &pipe->rd_wait, wait);
 684	if (filp->f_mode & FMODE_WRITE)
 685		poll_wait(filp, &pipe->wr_wait, wait);
 686
 687	/*
 688	 * .. and only then can you do the racy tests. That way,
 689	 * if something changes and you got it wrong, the poll
 690	 * table entry will wake you up and fix it.
 691	 */
 692	head = READ_ONCE(pipe->head);
 693	tail = READ_ONCE(pipe->tail);
 694
 695	mask = 0;
 696	if (filp->f_mode & FMODE_READ) {
 697		if (!pipe_empty(head, tail))
 698			mask |= EPOLLIN | EPOLLRDNORM;
 699		if (!pipe->writers && filp->f_version != pipe->w_counter)
 700			mask |= EPOLLHUP;
 701	}
 702
 703	if (filp->f_mode & FMODE_WRITE) {
 704		if (!pipe_full(head, tail, pipe->max_usage))
 705			mask |= EPOLLOUT | EPOLLWRNORM;
 706		/*
 707		 * Most Unices do not set EPOLLERR for FIFOs but on Linux they
 708		 * behave exactly like pipes for poll().
 709		 */
 710		if (!pipe->readers)
 711			mask |= EPOLLERR;
 712	}
 713
 714	return mask;
 715}
 716
 717static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
 718{
 719	int kill = 0;
 720
 721	spin_lock(&inode->i_lock);
 722	if (!--pipe->files) {
 723		inode->i_pipe = NULL;
 724		kill = 1;
 725	}
 726	spin_unlock(&inode->i_lock);
 727
 728	if (kill)
 729		free_pipe_info(pipe);
 730}
 731
 732static int
 733pipe_release(struct inode *inode, struct file *file)
 734{
 735	struct pipe_inode_info *pipe = file->private_data;
 736
 737	__pipe_lock(pipe);
 738	if (file->f_mode & FMODE_READ)
 739		pipe->readers--;
 740	if (file->f_mode & FMODE_WRITE)
 741		pipe->writers--;
 742
 743	/* Was that the last reader or writer, but not the other side? */
 744	if (!pipe->readers != !pipe->writers) {
 745		wake_up_interruptible_all(&pipe->rd_wait);
 746		wake_up_interruptible_all(&pipe->wr_wait);
 747		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 748		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 749	}
 750	__pipe_unlock(pipe);
 751
 752	put_pipe_info(inode, pipe);
 753	return 0;
 754}
 755
 756static int
 757pipe_fasync(int fd, struct file *filp, int on)
 758{
 759	struct pipe_inode_info *pipe = filp->private_data;
 760	int retval = 0;
 761
 762	__pipe_lock(pipe);
 763	if (filp->f_mode & FMODE_READ)
 764		retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 765	if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 766		retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 767		if (retval < 0 && (filp->f_mode & FMODE_READ))
 768			/* this can happen only if on == T */
 769			fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 770	}
 771	__pipe_unlock(pipe);
 772	return retval;
 773}
 774
 775unsigned long account_pipe_buffers(struct user_struct *user,
 776				   unsigned long old, unsigned long new)
 777{
 778	return atomic_long_add_return(new - old, &user->pipe_bufs);
 779}
 780
 781bool too_many_pipe_buffers_soft(unsigned long user_bufs)
 782{
 783	unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
 784
 785	return soft_limit && user_bufs > soft_limit;
 786}
 787
 788bool too_many_pipe_buffers_hard(unsigned long user_bufs)
 789{
 790	unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
 791
 792	return hard_limit && user_bufs > hard_limit;
 793}
 794
 795bool pipe_is_unprivileged_user(void)
 796{
 797	return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
 798}
 799
 800struct pipe_inode_info *alloc_pipe_info(void)
 801{
 802	struct pipe_inode_info *pipe;
 803	unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
 804	struct user_struct *user = get_current_user();
 805	unsigned long user_bufs;
 806	unsigned int max_size = READ_ONCE(pipe_max_size);
 807
 808	pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
 809	if (pipe == NULL)
 810		goto out_free_uid;
 811
 812	if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
 813		pipe_bufs = max_size >> PAGE_SHIFT;
 814
 815	user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
 816
 817	if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
 818		user_bufs = account_pipe_buffers(user, pipe_bufs, PIPE_MIN_DEF_BUFFERS);
 819		pipe_bufs = PIPE_MIN_DEF_BUFFERS;
 820	}
 821
 822	if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
 823		goto out_revert_acct;
 824
 825	pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
 826			     GFP_KERNEL_ACCOUNT);
 827
 828	if (pipe->bufs) {
 829		init_waitqueue_head(&pipe->rd_wait);
 830		init_waitqueue_head(&pipe->wr_wait);
 831		pipe->r_counter = pipe->w_counter = 1;
 832		pipe->max_usage = pipe_bufs;
 833		pipe->ring_size = pipe_bufs;
 834		pipe->nr_accounted = pipe_bufs;
 835		pipe->user = user;
 836		mutex_init(&pipe->mutex);
 837		return pipe;
 838	}
 839
 840out_revert_acct:
 841	(void) account_pipe_buffers(user, pipe_bufs, 0);
 842	kfree(pipe);
 843out_free_uid:
 844	free_uid(user);
 845	return NULL;
 846}
 847
 848void free_pipe_info(struct pipe_inode_info *pipe)
 849{
 850	unsigned int i;
 851
 852#ifdef CONFIG_WATCH_QUEUE
 853	if (pipe->watch_queue)
 854		watch_queue_clear(pipe->watch_queue);
 855#endif
 856
 857	(void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
 858	free_uid(pipe->user);
 859	for (i = 0; i < pipe->ring_size; i++) {
 860		struct pipe_buffer *buf = pipe->bufs + i;
 861		if (buf->ops)
 862			pipe_buf_release(pipe, buf);
 863	}
 864#ifdef CONFIG_WATCH_QUEUE
 865	if (pipe->watch_queue)
 866		put_watch_queue(pipe->watch_queue);
 867#endif
 868	if (pipe->tmp_page)
 869		__free_page(pipe->tmp_page);
 870	kfree(pipe->bufs);
 871	kfree(pipe);
 872}
 873
 874static struct vfsmount *pipe_mnt __ro_after_init;
 875
 876/*
 877 * pipefs_dname() is called from d_path().
 878 */
 879static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 880{
 881	return dynamic_dname(buffer, buflen, "pipe:[%lu]",
 882				d_inode(dentry)->i_ino);
 883}
 884
 885static const struct dentry_operations pipefs_dentry_operations = {
 886	.d_dname	= pipefs_dname,
 887};
 888
 889static struct inode * get_pipe_inode(void)
 890{
 891	struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 892	struct pipe_inode_info *pipe;
 893
 894	if (!inode)
 895		goto fail_inode;
 896
 897	inode->i_ino = get_next_ino();
 898
 899	pipe = alloc_pipe_info();
 900	if (!pipe)
 901		goto fail_iput;
 902
 903	inode->i_pipe = pipe;
 904	pipe->files = 2;
 905	pipe->readers = pipe->writers = 1;
 906	inode->i_fop = &pipefifo_fops;
 907
 908	/*
 909	 * Mark the inode dirty from the very beginning,
 910	 * that way it will never be moved to the dirty
 911	 * list because "mark_inode_dirty()" will think
 912	 * that it already _is_ on the dirty list.
 913	 */
 914	inode->i_state = I_DIRTY;
 915	inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 916	inode->i_uid = current_fsuid();
 917	inode->i_gid = current_fsgid();
 918	simple_inode_init_ts(inode);
 919
 920	return inode;
 921
 922fail_iput:
 923	iput(inode);
 924
 925fail_inode:
 926	return NULL;
 927}
 928
 929int create_pipe_files(struct file **res, int flags)
 930{
 931	struct inode *inode = get_pipe_inode();
 932	struct file *f;
 933	int error;
 934
 935	if (!inode)
 936		return -ENFILE;
 937
 938	if (flags & O_NOTIFICATION_PIPE) {
 939		error = watch_queue_init(inode->i_pipe);
 940		if (error) {
 941			free_pipe_info(inode->i_pipe);
 942			iput(inode);
 943			return error;
 944		}
 945	}
 946
 947	f = alloc_file_pseudo(inode, pipe_mnt, "",
 948				O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
 949				&pipefifo_fops);
 950	if (IS_ERR(f)) {
 951		free_pipe_info(inode->i_pipe);
 952		iput(inode);
 953		return PTR_ERR(f);
 954	}
 955
 956	f->private_data = inode->i_pipe;
 957
 958	res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
 959				  &pipefifo_fops);
 960	if (IS_ERR(res[0])) {
 961		put_pipe_info(inode, inode->i_pipe);
 962		fput(f);
 963		return PTR_ERR(res[0]);
 964	}
 965	res[0]->private_data = inode->i_pipe;
 966	res[1] = f;
 967	stream_open(inode, res[0]);
 968	stream_open(inode, res[1]);
 969	return 0;
 970}
 971
 972static int __do_pipe_flags(int *fd, struct file **files, int flags)
 973{
 974	int error;
 975	int fdw, fdr;
 976
 977	if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
 978		return -EINVAL;
 979
 980	error = create_pipe_files(files, flags);
 981	if (error)
 982		return error;
 983
 984	error = get_unused_fd_flags(flags);
 985	if (error < 0)
 986		goto err_read_pipe;
 987	fdr = error;
 988
 989	error = get_unused_fd_flags(flags);
 990	if (error < 0)
 991		goto err_fdr;
 992	fdw = error;
 993
 994	audit_fd_pair(fdr, fdw);
 995	fd[0] = fdr;
 996	fd[1] = fdw;
 997	/* pipe groks IOCB_NOWAIT */
 998	files[0]->f_mode |= FMODE_NOWAIT;
 999	files[1]->f_mode |= FMODE_NOWAIT;
1000	return 0;
1001
1002 err_fdr:
1003	put_unused_fd(fdr);
1004 err_read_pipe:
1005	fput(files[0]);
1006	fput(files[1]);
1007	return error;
1008}
1009
1010int do_pipe_flags(int *fd, int flags)
1011{
1012	struct file *files[2];
1013	int error = __do_pipe_flags(fd, files, flags);
1014	if (!error) {
1015		fd_install(fd[0], files[0]);
1016		fd_install(fd[1], files[1]);
1017	}
1018	return error;
1019}
1020
1021/*
1022 * sys_pipe() is the normal C calling standard for creating
1023 * a pipe. It's not the way Unix traditionally does this, though.
1024 */
1025static int do_pipe2(int __user *fildes, int flags)
1026{
1027	struct file *files[2];
1028	int fd[2];
1029	int error;
1030
1031	error = __do_pipe_flags(fd, files, flags);
1032	if (!error) {
1033		if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
1034			fput(files[0]);
1035			fput(files[1]);
1036			put_unused_fd(fd[0]);
1037			put_unused_fd(fd[1]);
1038			error = -EFAULT;
1039		} else {
1040			fd_install(fd[0], files[0]);
1041			fd_install(fd[1], files[1]);
1042		}
1043	}
1044	return error;
1045}
1046
1047SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1048{
1049	return do_pipe2(fildes, flags);
1050}
1051
1052SYSCALL_DEFINE1(pipe, int __user *, fildes)
1053{
1054	return do_pipe2(fildes, 0);
1055}
1056
1057/*
1058 * This is the stupid "wait for pipe to be readable or writable"
1059 * model.
1060 *
1061 * See pipe_read/write() for the proper kind of exclusive wait,
1062 * but that requires that we wake up any other readers/writers
1063 * if we then do not end up reading everything (ie the whole
1064 * "wake_next_reader/writer" logic in pipe_read/write()).
1065 */
1066void pipe_wait_readable(struct pipe_inode_info *pipe)
1067{
1068	pipe_unlock(pipe);
1069	wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
1070	pipe_lock(pipe);
1071}
1072
1073void pipe_wait_writable(struct pipe_inode_info *pipe)
1074{
1075	pipe_unlock(pipe);
1076	wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
1077	pipe_lock(pipe);
1078}
1079
1080/*
1081 * This depends on both the wait (here) and the wakeup (wake_up_partner)
1082 * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
1083 * race with the count check and waitqueue prep.
1084 *
1085 * Normally in order to avoid races, you'd do the prepare_to_wait() first,
1086 * then check the condition you're waiting for, and only then sleep. But
1087 * because of the pipe lock, we can check the condition before being on
1088 * the wait queue.
1089 *
1090 * We use the 'rd_wait' waitqueue for pipe partner waiting.
1091 */
1092static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1093{
1094	DEFINE_WAIT(rdwait);
1095	int cur = *cnt;
1096
1097	while (cur == *cnt) {
1098		prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
1099		pipe_unlock(pipe);
1100		schedule();
1101		finish_wait(&pipe->rd_wait, &rdwait);
1102		pipe_lock(pipe);
1103		if (signal_pending(current))
1104			break;
1105	}
1106	return cur == *cnt ? -ERESTARTSYS : 0;
1107}
1108
1109static void wake_up_partner(struct pipe_inode_info *pipe)
1110{
1111	wake_up_interruptible_all(&pipe->rd_wait);
1112}
1113
1114static int fifo_open(struct inode *inode, struct file *filp)
1115{
1116	struct pipe_inode_info *pipe;
1117	bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1118	int ret;
1119
1120	filp->f_version = 0;
1121
1122	spin_lock(&inode->i_lock);
1123	if (inode->i_pipe) {
1124		pipe = inode->i_pipe;
1125		pipe->files++;
1126		spin_unlock(&inode->i_lock);
1127	} else {
1128		spin_unlock(&inode->i_lock);
1129		pipe = alloc_pipe_info();
1130		if (!pipe)
1131			return -ENOMEM;
1132		pipe->files = 1;
1133		spin_lock(&inode->i_lock);
1134		if (unlikely(inode->i_pipe)) {
1135			inode->i_pipe->files++;
1136			spin_unlock(&inode->i_lock);
1137			free_pipe_info(pipe);
1138			pipe = inode->i_pipe;
1139		} else {
1140			inode->i_pipe = pipe;
1141			spin_unlock(&inode->i_lock);
1142		}
1143	}
1144	filp->private_data = pipe;
1145	/* OK, we have a pipe and it's pinned down */
1146
1147	__pipe_lock(pipe);
1148
1149	/* We can only do regular read/write on fifos */
1150	stream_open(inode, filp);
1151
1152	switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
1153	case FMODE_READ:
1154	/*
1155	 *  O_RDONLY
1156	 *  POSIX.1 says that O_NONBLOCK means return with the FIFO
1157	 *  opened, even when there is no process writing the FIFO.
1158	 */
1159		pipe->r_counter++;
1160		if (pipe->readers++ == 0)
1161			wake_up_partner(pipe);
1162
1163		if (!is_pipe && !pipe->writers) {
1164			if ((filp->f_flags & O_NONBLOCK)) {
1165				/* suppress EPOLLHUP until we have
1166				 * seen a writer */
1167				filp->f_version = pipe->w_counter;
1168			} else {
1169				if (wait_for_partner(pipe, &pipe->w_counter))
1170					goto err_rd;
1171			}
1172		}
1173		break;
1174
1175	case FMODE_WRITE:
1176	/*
1177	 *  O_WRONLY
1178	 *  POSIX.1 says that O_NONBLOCK means return -1 with
1179	 *  errno=ENXIO when there is no process reading the FIFO.
1180	 */
1181		ret = -ENXIO;
1182		if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1183			goto err;
1184
1185		pipe->w_counter++;
1186		if (!pipe->writers++)
1187			wake_up_partner(pipe);
1188
1189		if (!is_pipe && !pipe->readers) {
1190			if (wait_for_partner(pipe, &pipe->r_counter))
1191				goto err_wr;
1192		}
1193		break;
1194
1195	case FMODE_READ | FMODE_WRITE:
1196	/*
1197	 *  O_RDWR
1198	 *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1199	 *  This implementation will NEVER block on a O_RDWR open, since
1200	 *  the process can at least talk to itself.
1201	 */
1202
1203		pipe->readers++;
1204		pipe->writers++;
1205		pipe->r_counter++;
1206		pipe->w_counter++;
1207		if (pipe->readers == 1 || pipe->writers == 1)
1208			wake_up_partner(pipe);
1209		break;
1210
1211	default:
1212		ret = -EINVAL;
1213		goto err;
1214	}
1215
1216	/* Ok! */
1217	__pipe_unlock(pipe);
1218	return 0;
1219
1220err_rd:
1221	if (!--pipe->readers)
1222		wake_up_interruptible(&pipe->wr_wait);
1223	ret = -ERESTARTSYS;
1224	goto err;
1225
1226err_wr:
1227	if (!--pipe->writers)
1228		wake_up_interruptible_all(&pipe->rd_wait);
1229	ret = -ERESTARTSYS;
1230	goto err;
1231
1232err:
1233	__pipe_unlock(pipe);
1234
1235	put_pipe_info(inode, pipe);
1236	return ret;
1237}
1238
1239const struct file_operations pipefifo_fops = {
1240	.open		= fifo_open,
1241	.llseek		= no_llseek,
1242	.read_iter	= pipe_read,
1243	.write_iter	= pipe_write,
1244	.poll		= pipe_poll,
1245	.unlocked_ioctl	= pipe_ioctl,
1246	.release	= pipe_release,
1247	.fasync		= pipe_fasync,
1248	.splice_write	= iter_file_splice_write,
1249};
1250
1251/*
1252 * Currently we rely on the pipe array holding a power-of-2 number
1253 * of pages. Returns 0 on error.
1254 */
1255unsigned int round_pipe_size(unsigned int size)
1256{
1257	if (size > (1U << 31))
1258		return 0;
1259
1260	/* Minimum pipe size, as required by POSIX */
1261	if (size < PAGE_SIZE)
1262		return PAGE_SIZE;
1263
1264	return roundup_pow_of_two(size);
1265}
1266
1267/*
1268 * Resize the pipe ring to a number of slots.
1269 *
1270 * Note the pipe can be reduced in capacity, but only if the current
1271 * occupancy doesn't exceed nr_slots; if it does, EBUSY will be
1272 * returned instead.
1273 */
1274int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
1275{
1276	struct pipe_buffer *bufs;
1277	unsigned int head, tail, mask, n;
1278
1279	bufs = kcalloc(nr_slots, sizeof(*bufs),
1280		       GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1281	if (unlikely(!bufs))
1282		return -ENOMEM;
1283
1284	spin_lock_irq(&pipe->rd_wait.lock);
1285	mask = pipe->ring_size - 1;
1286	head = pipe->head;
1287	tail = pipe->tail;
1288
1289	n = pipe_occupancy(head, tail);
1290	if (nr_slots < n) {
1291		spin_unlock_irq(&pipe->rd_wait.lock);
1292		kfree(bufs);
1293		return -EBUSY;
1294	}
1295
1296	/*
1297	 * The pipe array wraps around, so just start the new one at zero
1298	 * and adjust the indices.
1299	 */
1300	if (n > 0) {
1301		unsigned int h = head & mask;
1302		unsigned int t = tail & mask;
1303		if (h > t) {
1304			memcpy(bufs, pipe->bufs + t,
1305			       n * sizeof(struct pipe_buffer));
1306		} else {
1307			unsigned int tsize = pipe->ring_size - t;
1308			if (h > 0)
1309				memcpy(bufs + tsize, pipe->bufs,
1310				       h * sizeof(struct pipe_buffer));
1311			memcpy(bufs, pipe->bufs + t,
1312			       tsize * sizeof(struct pipe_buffer));
1313		}
1314	}
1315
1316	head = n;
1317	tail = 0;
1318
1319	kfree(pipe->bufs);
1320	pipe->bufs = bufs;
1321	pipe->ring_size = nr_slots;
1322	if (pipe->max_usage > nr_slots)
1323		pipe->max_usage = nr_slots;
1324	pipe->tail = tail;
1325	pipe->head = head;
1326
1327	if (!pipe_has_watch_queue(pipe)) {
1328		pipe->max_usage = nr_slots;
1329		pipe->nr_accounted = nr_slots;
1330	}
1331
1332	spin_unlock_irq(&pipe->rd_wait.lock);
1333
1334	/* This might have made more room for writers */
1335	wake_up_interruptible(&pipe->wr_wait);
1336	return 0;
1337}
1338
1339/*
1340 * Allocate a new array of pipe buffers and copy the info over. Returns the
1341 * pipe size if successful, or return -ERROR on error.
1342 */
1343static long pipe_set_size(struct pipe_inode_info *pipe, unsigned int arg)
1344{
1345	unsigned long user_bufs;
1346	unsigned int nr_slots, size;
1347	long ret = 0;
1348
1349	if (pipe_has_watch_queue(pipe))
 
1350		return -EBUSY;
 
1351
1352	size = round_pipe_size(arg);
1353	nr_slots = size >> PAGE_SHIFT;
1354
1355	if (!nr_slots)
1356		return -EINVAL;
1357
1358	/*
1359	 * If trying to increase the pipe capacity, check that an
1360	 * unprivileged user is not trying to exceed various limits
1361	 * (soft limit check here, hard limit check just below).
1362	 * Decreasing the pipe capacity is always permitted, even
1363	 * if the user is currently over a limit.
1364	 */
1365	if (nr_slots > pipe->max_usage &&
1366			size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1367		return -EPERM;
1368
1369	user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
1370
1371	if (nr_slots > pipe->max_usage &&
1372			(too_many_pipe_buffers_hard(user_bufs) ||
1373			 too_many_pipe_buffers_soft(user_bufs)) &&
1374			pipe_is_unprivileged_user()) {
1375		ret = -EPERM;
1376		goto out_revert_acct;
1377	}
1378
1379	ret = pipe_resize_ring(pipe, nr_slots);
1380	if (ret < 0)
1381		goto out_revert_acct;
1382
 
 
1383	return pipe->max_usage * PAGE_SIZE;
1384
1385out_revert_acct:
1386	(void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
1387	return ret;
1388}
1389
1390/*
1391 * Note that i_pipe and i_cdev share the same location, so checking ->i_pipe is
1392 * not enough to verify that this is a pipe.
1393 */
1394struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
1395{
1396	struct pipe_inode_info *pipe = file->private_data;
1397
1398	if (file->f_op != &pipefifo_fops || !pipe)
1399		return NULL;
1400	if (for_splice && pipe_has_watch_queue(pipe))
 
1401		return NULL;
 
1402	return pipe;
1403}
1404
1405long pipe_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
1406{
1407	struct pipe_inode_info *pipe;
1408	long ret;
1409
1410	pipe = get_pipe_info(file, false);
1411	if (!pipe)
1412		return -EBADF;
1413
1414	__pipe_lock(pipe);
1415
1416	switch (cmd) {
1417	case F_SETPIPE_SZ:
1418		ret = pipe_set_size(pipe, arg);
1419		break;
1420	case F_GETPIPE_SZ:
1421		ret = pipe->max_usage * PAGE_SIZE;
1422		break;
1423	default:
1424		ret = -EINVAL;
1425		break;
1426	}
1427
1428	__pipe_unlock(pipe);
1429	return ret;
1430}
1431
1432static const struct super_operations pipefs_ops = {
1433	.destroy_inode = free_inode_nonrcu,
1434	.statfs = simple_statfs,
1435};
1436
1437/*
1438 * pipefs should _never_ be mounted by userland - too much of security hassle,
1439 * no real gain from having the whole whorehouse mounted. So we don't need
1440 * any operations on the root directory. However, we need a non-trivial
1441 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1442 */
1443
1444static int pipefs_init_fs_context(struct fs_context *fc)
1445{
1446	struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
1447	if (!ctx)
1448		return -ENOMEM;
1449	ctx->ops = &pipefs_ops;
1450	ctx->dops = &pipefs_dentry_operations;
1451	return 0;
1452}
1453
1454static struct file_system_type pipe_fs_type = {
1455	.name		= "pipefs",
1456	.init_fs_context = pipefs_init_fs_context,
1457	.kill_sb	= kill_anon_super,
1458};
1459
1460#ifdef CONFIG_SYSCTL
1461static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
1462					unsigned int *valp,
1463					int write, void *data)
1464{
1465	if (write) {
1466		unsigned int val;
1467
1468		val = round_pipe_size(*lvalp);
1469		if (val == 0)
1470			return -EINVAL;
1471
1472		*valp = val;
1473	} else {
1474		unsigned int val = *valp;
1475		*lvalp = (unsigned long) val;
1476	}
1477
1478	return 0;
1479}
1480
1481static int proc_dopipe_max_size(struct ctl_table *table, int write,
1482				void *buffer, size_t *lenp, loff_t *ppos)
1483{
1484	return do_proc_douintvec(table, write, buffer, lenp, ppos,
1485				 do_proc_dopipe_max_size_conv, NULL);
1486}
1487
1488static struct ctl_table fs_pipe_sysctls[] = {
1489	{
1490		.procname	= "pipe-max-size",
1491		.data		= &pipe_max_size,
1492		.maxlen		= sizeof(pipe_max_size),
1493		.mode		= 0644,
1494		.proc_handler	= proc_dopipe_max_size,
1495	},
1496	{
1497		.procname	= "pipe-user-pages-hard",
1498		.data		= &pipe_user_pages_hard,
1499		.maxlen		= sizeof(pipe_user_pages_hard),
1500		.mode		= 0644,
1501		.proc_handler	= proc_doulongvec_minmax,
1502	},
1503	{
1504		.procname	= "pipe-user-pages-soft",
1505		.data		= &pipe_user_pages_soft,
1506		.maxlen		= sizeof(pipe_user_pages_soft),
1507		.mode		= 0644,
1508		.proc_handler	= proc_doulongvec_minmax,
1509	},
 
1510};
1511#endif
1512
1513static int __init init_pipe_fs(void)
1514{
1515	int err = register_filesystem(&pipe_fs_type);
1516
1517	if (!err) {
1518		pipe_mnt = kern_mount(&pipe_fs_type);
1519		if (IS_ERR(pipe_mnt)) {
1520			err = PTR_ERR(pipe_mnt);
1521			unregister_filesystem(&pipe_fs_type);
1522		}
1523	}
1524#ifdef CONFIG_SYSCTL
1525	register_sysctl_init("fs", fs_pipe_sysctls);
1526#endif
1527	return err;
1528}
1529
1530fs_initcall(init_pipe_fs);