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v4.6
 
   1/*
   2 *  linux/fs/pipe.c
   3 *
   4 *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
   5 */
   6
   7#include <linux/mm.h>
   8#include <linux/file.h>
   9#include <linux/poll.h>
  10#include <linux/slab.h>
  11#include <linux/module.h>
  12#include <linux/init.h>
  13#include <linux/fs.h>
  14#include <linux/log2.h>
  15#include <linux/mount.h>
 
  16#include <linux/magic.h>
  17#include <linux/pipe_fs_i.h>
  18#include <linux/uio.h>
  19#include <linux/highmem.h>
  20#include <linux/pagemap.h>
  21#include <linux/audit.h>
  22#include <linux/syscalls.h>
  23#include <linux/fcntl.h>
 
 
 
  24
  25#include <asm/uaccess.h>
  26#include <asm/ioctls.h>
  27
  28#include "internal.h"
  29
  30/*
  31 * The max size that a non-root user is allowed to grow the pipe. Can
  32 * be set by root in /proc/sys/fs/pipe-max-size
 
 
 
 
 
 
 
 
 
  33 */
  34unsigned int pipe_max_size = 1048576;
  35
  36/*
  37 * Minimum pipe size, as required by POSIX
 
  38 */
  39unsigned int pipe_min_size = PAGE_SIZE;
  40
  41/* Maximum allocatable pages per user. Hard limit is unset by default, soft
  42 * matches default values.
  43 */
  44unsigned long pipe_user_pages_hard;
  45unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
  46
  47/*
  48 * We use a start+len construction, which provides full use of the 
  49 * allocated memory.
  50 * -- Florian Coosmann (FGC)
  51 * 
 
 
  52 * Reads with count = 0 should always return 0.
  53 * -- Julian Bradfield 1999-06-07.
  54 *
  55 * FIFOs and Pipes now generate SIGIO for both readers and writers.
  56 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  57 *
  58 * pipe_read & write cleanup
  59 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  60 */
  61
  62static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  63{
  64	if (pipe->files)
  65		mutex_lock_nested(&pipe->mutex, subclass);
  66}
  67
  68void pipe_lock(struct pipe_inode_info *pipe)
  69{
  70	/*
  71	 * pipe_lock() nests non-pipe inode locks (for writing to a file)
  72	 */
  73	pipe_lock_nested(pipe, I_MUTEX_PARENT);
  74}
  75EXPORT_SYMBOL(pipe_lock);
  76
  77void pipe_unlock(struct pipe_inode_info *pipe)
  78{
  79	if (pipe->files)
  80		mutex_unlock(&pipe->mutex);
  81}
  82EXPORT_SYMBOL(pipe_unlock);
  83
  84static inline void __pipe_lock(struct pipe_inode_info *pipe)
  85{
  86	mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
  87}
  88
  89static inline void __pipe_unlock(struct pipe_inode_info *pipe)
  90{
  91	mutex_unlock(&pipe->mutex);
  92}
  93
  94void pipe_double_lock(struct pipe_inode_info *pipe1,
  95		      struct pipe_inode_info *pipe2)
  96{
  97	BUG_ON(pipe1 == pipe2);
  98
  99	if (pipe1 < pipe2) {
 100		pipe_lock_nested(pipe1, I_MUTEX_PARENT);
 101		pipe_lock_nested(pipe2, I_MUTEX_CHILD);
 102	} else {
 103		pipe_lock_nested(pipe2, I_MUTEX_PARENT);
 104		pipe_lock_nested(pipe1, I_MUTEX_CHILD);
 105	}
 106}
 107
 108/* Drop the inode semaphore and wait for a pipe event, atomically */
 109void pipe_wait(struct pipe_inode_info *pipe)
 110{
 111	DEFINE_WAIT(wait);
 112
 113	/*
 114	 * Pipes are system-local resources, so sleeping on them
 115	 * is considered a noninteractive wait:
 116	 */
 117	prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
 118	pipe_unlock(pipe);
 119	schedule();
 120	finish_wait(&pipe->wait, &wait);
 121	pipe_lock(pipe);
 122}
 123
 124static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 125				  struct pipe_buffer *buf)
 126{
 127	struct page *page = buf->page;
 128
 129	/*
 130	 * If nobody else uses this page, and we don't already have a
 131	 * temporary page, let's keep track of it as a one-deep
 132	 * allocation cache. (Otherwise just release our reference to it)
 133	 */
 134	if (page_count(page) == 1 && !pipe->tmp_page)
 135		pipe->tmp_page = page;
 136	else
 137		put_page(page);
 138}
 139
 
 
 
 
 
 
 
 
 
 
 
 
 140/**
 141 * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
 142 * @pipe:	the pipe that the buffer belongs to
 143 * @buf:	the buffer to attempt to steal
 144 *
 145 * Description:
 146 *	This function attempts to steal the &struct page attached to
 147 *	@buf. If successful, this function returns 0 and returns with
 148 *	the page locked. The caller may then reuse the page for whatever
 149 *	he wishes; the typical use is insertion into a different file
 150 *	page cache.
 151 */
 152int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 153			   struct pipe_buffer *buf)
 154{
 155	struct page *page = buf->page;
 156
 157	/*
 158	 * A reference of one is golden, that means that the owner of this
 159	 * page is the only one holding a reference to it. lock the page
 160	 * and return OK.
 161	 */
 162	if (page_count(page) == 1) {
 163		lock_page(page);
 164		return 0;
 165	}
 166
 167	return 1;
 168}
 169EXPORT_SYMBOL(generic_pipe_buf_steal);
 170
 171/**
 172 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 173 * @pipe:	the pipe that the buffer belongs to
 174 * @buf:	the buffer to get a reference to
 175 *
 176 * Description:
 177 *	This function grabs an extra reference to @buf. It's used in
 178 *	in the tee() system call, when we duplicate the buffers in one
 179 *	pipe into another.
 180 */
 181void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 182{
 183	get_page(buf->page);
 184}
 185EXPORT_SYMBOL(generic_pipe_buf_get);
 186
 187/**
 188 * generic_pipe_buf_confirm - verify contents of the pipe buffer
 189 * @info:	the pipe that the buffer belongs to
 190 * @buf:	the buffer to confirm
 191 *
 192 * Description:
 193 *	This function does nothing, because the generic pipe code uses
 194 *	pages that are always good when inserted into the pipe.
 195 */
 196int generic_pipe_buf_confirm(struct pipe_inode_info *info,
 197			     struct pipe_buffer *buf)
 198{
 199	return 0;
 200}
 201EXPORT_SYMBOL(generic_pipe_buf_confirm);
 202
 203/**
 204 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 205 * @pipe:	the pipe that the buffer belongs to
 206 * @buf:	the buffer to put a reference to
 207 *
 208 * Description:
 209 *	This function releases a reference to @buf.
 210 */
 211void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 212			      struct pipe_buffer *buf)
 213{
 214	put_page(buf->page);
 215}
 216EXPORT_SYMBOL(generic_pipe_buf_release);
 217
 218static const struct pipe_buf_operations anon_pipe_buf_ops = {
 219	.can_merge = 1,
 220	.confirm = generic_pipe_buf_confirm,
 221	.release = anon_pipe_buf_release,
 222	.steal = generic_pipe_buf_steal,
 223	.get = generic_pipe_buf_get,
 224};
 225
 226static const struct pipe_buf_operations packet_pipe_buf_ops = {
 227	.can_merge = 0,
 228	.confirm = generic_pipe_buf_confirm,
 229	.release = anon_pipe_buf_release,
 230	.steal = generic_pipe_buf_steal,
 231	.get = generic_pipe_buf_get,
 232};
 
 
 233
 234static ssize_t
 235pipe_read(struct kiocb *iocb, struct iov_iter *to)
 236{
 237	size_t total_len = iov_iter_count(to);
 238	struct file *filp = iocb->ki_filp;
 239	struct pipe_inode_info *pipe = filp->private_data;
 240	int do_wakeup;
 241	ssize_t ret;
 242
 243	/* Null read succeeds. */
 244	if (unlikely(total_len == 0))
 245		return 0;
 246
 247	do_wakeup = 0;
 248	ret = 0;
 249	__pipe_lock(pipe);
 
 
 
 
 
 
 
 
 
 
 250	for (;;) {
 251		int bufs = pipe->nrbufs;
 252		if (bufs) {
 253			int curbuf = pipe->curbuf;
 254			struct pipe_buffer *buf = pipe->bufs + curbuf;
 255			const struct pipe_buf_operations *ops = buf->ops;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 256			size_t chars = buf->len;
 257			size_t written;
 258			int error;
 259
 260			if (chars > total_len)
 
 
 
 
 
 261				chars = total_len;
 
 262
 263			error = ops->confirm(pipe, buf);
 264			if (error) {
 265				if (!ret)
 266					ret = error;
 267				break;
 268			}
 269
 270			written = copy_page_to_iter(buf->page, buf->offset, chars, to);
 271			if (unlikely(written < chars)) {
 272				if (!ret)
 273					ret = -EFAULT;
 274				break;
 275			}
 276			ret += chars;
 277			buf->offset += chars;
 278			buf->len -= chars;
 279
 280			/* Was it a packet buffer? Clean up and exit */
 281			if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 282				total_len = chars;
 283				buf->len = 0;
 284			}
 285
 286			if (!buf->len) {
 287				buf->ops = NULL;
 288				ops->release(pipe, buf);
 289				curbuf = (curbuf + 1) & (pipe->buffers - 1);
 290				pipe->curbuf = curbuf;
 291				pipe->nrbufs = --bufs;
 292				do_wakeup = 1;
 
 
 
 293			}
 294			total_len -= chars;
 295			if (!total_len)
 296				break;	/* common path: read succeeded */
 
 
 297		}
 298		if (bufs)	/* More to do? */
 299			continue;
 300		if (!pipe->writers)
 301			break;
 302		if (!pipe->waiting_writers) {
 303			/* syscall merging: Usually we must not sleep
 304			 * if O_NONBLOCK is set, or if we got some data.
 305			 * But if a writer sleeps in kernel space, then
 306			 * we can wait for that data without violating POSIX.
 307			 */
 308			if (ret)
 309				break;
 310			if (filp->f_flags & O_NONBLOCK) {
 311				ret = -EAGAIN;
 312				break;
 313			}
 314		}
 315		if (signal_pending(current)) {
 316			if (!ret)
 317				ret = -ERESTARTSYS;
 318			break;
 319		}
 320		if (do_wakeup) {
 321			wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 322 			kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 323		}
 324		pipe_wait(pipe);
 325	}
 326	__pipe_unlock(pipe);
 327
 328	/* Signal writers asynchronously that there is more room. */
 329	if (do_wakeup) {
 330		wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 331		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 
 
 
 
 
 
 
 
 
 
 
 
 
 332	}
 
 
 
 
 
 
 
 
 
 333	if (ret > 0)
 334		file_accessed(filp);
 335	return ret;
 336}
 337
 338static inline int is_packetized(struct file *file)
 339{
 340	return (file->f_flags & O_DIRECT) != 0;
 341}
 342
 
 
 
 
 
 
 
 
 
 
 
 343static ssize_t
 344pipe_write(struct kiocb *iocb, struct iov_iter *from)
 345{
 346	struct file *filp = iocb->ki_filp;
 347	struct pipe_inode_info *pipe = filp->private_data;
 
 348	ssize_t ret = 0;
 349	int do_wakeup = 0;
 350	size_t total_len = iov_iter_count(from);
 351	ssize_t chars;
 
 
 352
 353	/* Null write succeeds. */
 354	if (unlikely(total_len == 0))
 355		return 0;
 356
 357	__pipe_lock(pipe);
 358
 359	if (!pipe->readers) {
 360		send_sig(SIGPIPE, current, 0);
 361		ret = -EPIPE;
 362		goto out;
 363	}
 364
 365	/* We try to merge small writes */
 366	chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 367	if (pipe->nrbufs && chars != 0) {
 368		int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 369							(pipe->buffers - 1);
 370		struct pipe_buffer *buf = pipe->bufs + lastbuf;
 371		const struct pipe_buf_operations *ops = buf->ops;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 372		int offset = buf->offset + buf->len;
 373
 374		if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 375			ret = ops->confirm(pipe, buf);
 
 376			if (ret)
 377				goto out;
 378
 379			ret = copy_page_from_iter(buf->page, offset, chars, from);
 380			if (unlikely(ret < chars)) {
 381				ret = -EFAULT;
 382				goto out;
 383			}
 384			do_wakeup = 1;
 385			buf->len += ret;
 386			if (!iov_iter_count(from))
 387				goto out;
 388		}
 389	}
 390
 391	for (;;) {
 392		int bufs;
 393
 394		if (!pipe->readers) {
 395			send_sig(SIGPIPE, current, 0);
 396			if (!ret)
 397				ret = -EPIPE;
 398			break;
 399		}
 400		bufs = pipe->nrbufs;
 401		if (bufs < pipe->buffers) {
 402			int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
 403			struct pipe_buffer *buf = pipe->bufs + newbuf;
 
 404			struct page *page = pipe->tmp_page;
 405			int copied;
 406
 407			if (!page) {
 408				page = alloc_page(GFP_HIGHUSER);
 409				if (unlikely(!page)) {
 410					ret = ret ? : -ENOMEM;
 411					break;
 412				}
 413				pipe->tmp_page = page;
 414			}
 415			/* Always wake up, even if the copy fails. Otherwise
 416			 * we lock up (O_NONBLOCK-)readers that sleep due to
 417			 * syscall merging.
 418			 * FIXME! Is this really true?
 
 419			 */
 420			do_wakeup = 1;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 421			copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
 422			if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
 423				if (!ret)
 424					ret = -EFAULT;
 425				break;
 426			}
 427			ret += copied;
 428
 429			/* Insert it into the buffer array */
 430			buf->page = page;
 431			buf->ops = &anon_pipe_buf_ops;
 432			buf->offset = 0;
 433			buf->len = copied;
 434			buf->flags = 0;
 435			if (is_packetized(filp)) {
 436				buf->ops = &packet_pipe_buf_ops;
 437				buf->flags = PIPE_BUF_FLAG_PACKET;
 438			}
 439			pipe->nrbufs = ++bufs;
 440			pipe->tmp_page = NULL;
 441
 442			if (!iov_iter_count(from))
 443				break;
 444		}
 445		if (bufs < pipe->buffers)
 
 446			continue;
 
 
 447		if (filp->f_flags & O_NONBLOCK) {
 448			if (!ret)
 449				ret = -EAGAIN;
 450			break;
 451		}
 452		if (signal_pending(current)) {
 453			if (!ret)
 454				ret = -ERESTARTSYS;
 455			break;
 456		}
 457		if (do_wakeup) {
 458			wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 459			kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 460			do_wakeup = 0;
 461		}
 462		pipe->waiting_writers++;
 463		pipe_wait(pipe);
 464		pipe->waiting_writers--;
 
 
 
 
 
 
 
 465	}
 466out:
 
 
 467	__pipe_unlock(pipe);
 468	if (do_wakeup) {
 469		wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 470		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 471	}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 472	if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
 473		int err = file_update_time(filp);
 474		if (err)
 475			ret = err;
 476		sb_end_write(file_inode(filp)->i_sb);
 477	}
 478	return ret;
 479}
 480
 481static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 482{
 483	struct pipe_inode_info *pipe = filp->private_data;
 484	int count, buf, nrbufs;
 485
 486	switch (cmd) {
 487		case FIONREAD:
 488			__pipe_lock(pipe);
 489			count = 0;
 490			buf = pipe->curbuf;
 491			nrbufs = pipe->nrbufs;
 492			while (--nrbufs >= 0) {
 493				count += pipe->bufs[buf].len;
 494				buf = (buf+1) & (pipe->buffers - 1);
 495			}
 496			__pipe_unlock(pipe);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 497
 498			return put_user(count, (int __user *)arg);
 499		default:
 500			return -ENOIOCTLCMD;
 501	}
 502}
 503
 504/* No kernel lock held - fine */
 505static unsigned int
 506pipe_poll(struct file *filp, poll_table *wait)
 507{
 508	unsigned int mask;
 509	struct pipe_inode_info *pipe = filp->private_data;
 510	int nrbufs;
 
 
 
 511
 512	poll_wait(filp, &pipe->wait, wait);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 513
 514	/* Reading only -- no need for acquiring the semaphore.  */
 515	nrbufs = pipe->nrbufs;
 516	mask = 0;
 517	if (filp->f_mode & FMODE_READ) {
 518		mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 
 519		if (!pipe->writers && filp->f_version != pipe->w_counter)
 520			mask |= POLLHUP;
 521	}
 522
 523	if (filp->f_mode & FMODE_WRITE) {
 524		mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
 
 525		/*
 526		 * Most Unices do not set POLLERR for FIFOs but on Linux they
 527		 * behave exactly like pipes for poll().
 528		 */
 529		if (!pipe->readers)
 530			mask |= POLLERR;
 531	}
 532
 533	return mask;
 534}
 535
 536static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
 537{
 538	int kill = 0;
 539
 540	spin_lock(&inode->i_lock);
 541	if (!--pipe->files) {
 542		inode->i_pipe = NULL;
 543		kill = 1;
 544	}
 545	spin_unlock(&inode->i_lock);
 546
 547	if (kill)
 548		free_pipe_info(pipe);
 549}
 550
 551static int
 552pipe_release(struct inode *inode, struct file *file)
 553{
 554	struct pipe_inode_info *pipe = file->private_data;
 555
 556	__pipe_lock(pipe);
 557	if (file->f_mode & FMODE_READ)
 558		pipe->readers--;
 559	if (file->f_mode & FMODE_WRITE)
 560		pipe->writers--;
 561
 562	if (pipe->readers || pipe->writers) {
 563		wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
 
 
 564		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 565		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 566	}
 567	__pipe_unlock(pipe);
 568
 569	put_pipe_info(inode, pipe);
 570	return 0;
 571}
 572
 573static int
 574pipe_fasync(int fd, struct file *filp, int on)
 575{
 576	struct pipe_inode_info *pipe = filp->private_data;
 577	int retval = 0;
 578
 579	__pipe_lock(pipe);
 580	if (filp->f_mode & FMODE_READ)
 581		retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 582	if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 583		retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 584		if (retval < 0 && (filp->f_mode & FMODE_READ))
 585			/* this can happen only if on == T */
 586			fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 587	}
 588	__pipe_unlock(pipe);
 589	return retval;
 590}
 591
 592static void account_pipe_buffers(struct pipe_inode_info *pipe,
 593                                 unsigned long old, unsigned long new)
 594{
 595	atomic_long_add(new - old, &pipe->user->pipe_bufs);
 596}
 597
 598static bool too_many_pipe_buffers_soft(struct user_struct *user)
 599{
 600	return pipe_user_pages_soft &&
 601	       atomic_long_read(&user->pipe_bufs) >= pipe_user_pages_soft;
 
 
 
 
 
 
 
 
 602}
 603
 604static bool too_many_pipe_buffers_hard(struct user_struct *user)
 605{
 606	return pipe_user_pages_hard &&
 607	       atomic_long_read(&user->pipe_bufs) >= pipe_user_pages_hard;
 608}
 609
 610struct pipe_inode_info *alloc_pipe_info(void)
 611{
 612	struct pipe_inode_info *pipe;
 
 
 
 
 613
 614	pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 615	if (pipe) {
 616		unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
 617		struct user_struct *user = get_current_user();
 618
 619		if (!too_many_pipe_buffers_hard(user)) {
 620			if (too_many_pipe_buffers_soft(user))
 621				pipe_bufs = 1;
 622			pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * pipe_bufs, GFP_KERNEL);
 623		}
 624
 625		if (pipe->bufs) {
 626			init_waitqueue_head(&pipe->wait);
 627			pipe->r_counter = pipe->w_counter = 1;
 628			pipe->buffers = pipe_bufs;
 629			pipe->user = user;
 630			account_pipe_buffers(pipe, 0, pipe_bufs);
 631			mutex_init(&pipe->mutex);
 632			return pipe;
 633		}
 634		free_uid(user);
 635		kfree(pipe);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 636	}
 637
 
 
 
 
 
 638	return NULL;
 639}
 640
 641void free_pipe_info(struct pipe_inode_info *pipe)
 642{
 643	int i;
 
 
 
 
 
 644
 645	account_pipe_buffers(pipe, pipe->buffers, 0);
 646	free_uid(pipe->user);
 647	for (i = 0; i < pipe->buffers; i++) {
 648		struct pipe_buffer *buf = pipe->bufs + i;
 649		if (buf->ops)
 650			buf->ops->release(pipe, buf);
 651	}
 
 
 
 
 652	if (pipe->tmp_page)
 653		__free_page(pipe->tmp_page);
 654	kfree(pipe->bufs);
 655	kfree(pipe);
 656}
 657
 658static struct vfsmount *pipe_mnt __read_mostly;
 659
 660/*
 661 * pipefs_dname() is called from d_path().
 662 */
 663static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 664{
 665	return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 666				d_inode(dentry)->i_ino);
 667}
 668
 669static const struct dentry_operations pipefs_dentry_operations = {
 670	.d_dname	= pipefs_dname,
 671};
 672
 673static struct inode * get_pipe_inode(void)
 674{
 675	struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 676	struct pipe_inode_info *pipe;
 677
 678	if (!inode)
 679		goto fail_inode;
 680
 681	inode->i_ino = get_next_ino();
 682
 683	pipe = alloc_pipe_info();
 684	if (!pipe)
 685		goto fail_iput;
 686
 687	inode->i_pipe = pipe;
 688	pipe->files = 2;
 689	pipe->readers = pipe->writers = 1;
 690	inode->i_fop = &pipefifo_fops;
 691
 692	/*
 693	 * Mark the inode dirty from the very beginning,
 694	 * that way it will never be moved to the dirty
 695	 * list because "mark_inode_dirty()" will think
 696	 * that it already _is_ on the dirty list.
 697	 */
 698	inode->i_state = I_DIRTY;
 699	inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 700	inode->i_uid = current_fsuid();
 701	inode->i_gid = current_fsgid();
 702	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 703
 704	return inode;
 705
 706fail_iput:
 707	iput(inode);
 708
 709fail_inode:
 710	return NULL;
 711}
 712
 713int create_pipe_files(struct file **res, int flags)
 714{
 715	int err;
 716	struct inode *inode = get_pipe_inode();
 717	struct file *f;
 718	struct path path;
 719	static struct qstr name = { .name = "" };
 720
 721	if (!inode)
 722		return -ENFILE;
 723
 724	err = -ENOMEM;
 725	path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
 726	if (!path.dentry)
 727		goto err_inode;
 728	path.mnt = mntget(pipe_mnt);
 729
 730	d_instantiate(path.dentry, inode);
 
 731
 732	f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops);
 
 
 733	if (IS_ERR(f)) {
 734		err = PTR_ERR(f);
 735		goto err_dentry;
 
 736	}
 737
 738	f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
 739	f->private_data = inode->i_pipe;
 740
 741	res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
 
 742	if (IS_ERR(res[0])) {
 743		err = PTR_ERR(res[0]);
 744		goto err_file;
 
 745	}
 746
 747	path_get(&path);
 748	res[0]->private_data = inode->i_pipe;
 749	res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
 750	res[1] = f;
 
 
 751	return 0;
 752
 753err_file:
 754	put_filp(f);
 755err_dentry:
 756	free_pipe_info(inode->i_pipe);
 757	path_put(&path);
 758	return err;
 759
 760err_inode:
 761	free_pipe_info(inode->i_pipe);
 762	iput(inode);
 763	return err;
 764}
 765
 766static int __do_pipe_flags(int *fd, struct file **files, int flags)
 767{
 768	int error;
 769	int fdw, fdr;
 770
 771	if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
 772		return -EINVAL;
 773
 774	error = create_pipe_files(files, flags);
 775	if (error)
 776		return error;
 777
 778	error = get_unused_fd_flags(flags);
 779	if (error < 0)
 780		goto err_read_pipe;
 781	fdr = error;
 782
 783	error = get_unused_fd_flags(flags);
 784	if (error < 0)
 785		goto err_fdr;
 786	fdw = error;
 787
 788	audit_fd_pair(fdr, fdw);
 789	fd[0] = fdr;
 790	fd[1] = fdw;
 791	return 0;
 792
 793 err_fdr:
 794	put_unused_fd(fdr);
 795 err_read_pipe:
 796	fput(files[0]);
 797	fput(files[1]);
 798	return error;
 799}
 800
 801int do_pipe_flags(int *fd, int flags)
 802{
 803	struct file *files[2];
 804	int error = __do_pipe_flags(fd, files, flags);
 805	if (!error) {
 806		fd_install(fd[0], files[0]);
 807		fd_install(fd[1], files[1]);
 808	}
 809	return error;
 810}
 811
 812/*
 813 * sys_pipe() is the normal C calling standard for creating
 814 * a pipe. It's not the way Unix traditionally does this, though.
 815 */
 816SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
 817{
 818	struct file *files[2];
 819	int fd[2];
 820	int error;
 821
 822	error = __do_pipe_flags(fd, files, flags);
 823	if (!error) {
 824		if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
 825			fput(files[0]);
 826			fput(files[1]);
 827			put_unused_fd(fd[0]);
 828			put_unused_fd(fd[1]);
 829			error = -EFAULT;
 830		} else {
 831			fd_install(fd[0], files[0]);
 832			fd_install(fd[1], files[1]);
 833		}
 834	}
 835	return error;
 836}
 837
 
 
 
 
 
 838SYSCALL_DEFINE1(pipe, int __user *, fildes)
 839{
 840	return sys_pipe2(fildes, 0);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 841}
 842
 
 
 
 
 
 
 
 
 
 
 
 
 843static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
 844{
 845	int cur = *cnt;	
 
 846
 847	while (cur == *cnt) {
 848		pipe_wait(pipe);
 
 
 
 
 849		if (signal_pending(current))
 850			break;
 851	}
 852	return cur == *cnt ? -ERESTARTSYS : 0;
 853}
 854
 855static void wake_up_partner(struct pipe_inode_info *pipe)
 856{
 857	wake_up_interruptible(&pipe->wait);
 858}
 859
 860static int fifo_open(struct inode *inode, struct file *filp)
 861{
 862	struct pipe_inode_info *pipe;
 863	bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
 864	int ret;
 865
 866	filp->f_version = 0;
 867
 868	spin_lock(&inode->i_lock);
 869	if (inode->i_pipe) {
 870		pipe = inode->i_pipe;
 871		pipe->files++;
 872		spin_unlock(&inode->i_lock);
 873	} else {
 874		spin_unlock(&inode->i_lock);
 875		pipe = alloc_pipe_info();
 876		if (!pipe)
 877			return -ENOMEM;
 878		pipe->files = 1;
 879		spin_lock(&inode->i_lock);
 880		if (unlikely(inode->i_pipe)) {
 881			inode->i_pipe->files++;
 882			spin_unlock(&inode->i_lock);
 883			free_pipe_info(pipe);
 884			pipe = inode->i_pipe;
 885		} else {
 886			inode->i_pipe = pipe;
 887			spin_unlock(&inode->i_lock);
 888		}
 889	}
 890	filp->private_data = pipe;
 891	/* OK, we have a pipe and it's pinned down */
 892
 893	__pipe_lock(pipe);
 894
 895	/* We can only do regular read/write on fifos */
 896	filp->f_mode &= (FMODE_READ | FMODE_WRITE);
 897
 898	switch (filp->f_mode) {
 899	case FMODE_READ:
 900	/*
 901	 *  O_RDONLY
 902	 *  POSIX.1 says that O_NONBLOCK means return with the FIFO
 903	 *  opened, even when there is no process writing the FIFO.
 904	 */
 905		pipe->r_counter++;
 906		if (pipe->readers++ == 0)
 907			wake_up_partner(pipe);
 908
 909		if (!is_pipe && !pipe->writers) {
 910			if ((filp->f_flags & O_NONBLOCK)) {
 911				/* suppress POLLHUP until we have
 912				 * seen a writer */
 913				filp->f_version = pipe->w_counter;
 914			} else {
 915				if (wait_for_partner(pipe, &pipe->w_counter))
 916					goto err_rd;
 917			}
 918		}
 919		break;
 920	
 921	case FMODE_WRITE:
 922	/*
 923	 *  O_WRONLY
 924	 *  POSIX.1 says that O_NONBLOCK means return -1 with
 925	 *  errno=ENXIO when there is no process reading the FIFO.
 926	 */
 927		ret = -ENXIO;
 928		if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
 929			goto err;
 930
 931		pipe->w_counter++;
 932		if (!pipe->writers++)
 933			wake_up_partner(pipe);
 934
 935		if (!is_pipe && !pipe->readers) {
 936			if (wait_for_partner(pipe, &pipe->r_counter))
 937				goto err_wr;
 938		}
 939		break;
 940	
 941	case FMODE_READ | FMODE_WRITE:
 942	/*
 943	 *  O_RDWR
 944	 *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
 945	 *  This implementation will NEVER block on a O_RDWR open, since
 946	 *  the process can at least talk to itself.
 947	 */
 948
 949		pipe->readers++;
 950		pipe->writers++;
 951		pipe->r_counter++;
 952		pipe->w_counter++;
 953		if (pipe->readers == 1 || pipe->writers == 1)
 954			wake_up_partner(pipe);
 955		break;
 956
 957	default:
 958		ret = -EINVAL;
 959		goto err;
 960	}
 961
 962	/* Ok! */
 963	__pipe_unlock(pipe);
 964	return 0;
 965
 966err_rd:
 967	if (!--pipe->readers)
 968		wake_up_interruptible(&pipe->wait);
 969	ret = -ERESTARTSYS;
 970	goto err;
 971
 972err_wr:
 973	if (!--pipe->writers)
 974		wake_up_interruptible(&pipe->wait);
 975	ret = -ERESTARTSYS;
 976	goto err;
 977
 978err:
 979	__pipe_unlock(pipe);
 980
 981	put_pipe_info(inode, pipe);
 982	return ret;
 983}
 984
 985const struct file_operations pipefifo_fops = {
 986	.open		= fifo_open,
 987	.llseek		= no_llseek,
 988	.read_iter	= pipe_read,
 989	.write_iter	= pipe_write,
 990	.poll		= pipe_poll,
 991	.unlocked_ioctl	= pipe_ioctl,
 992	.release	= pipe_release,
 993	.fasync		= pipe_fasync,
 
 994};
 995
 996/*
 997 * Allocate a new array of pipe buffers and copy the info over. Returns the
 998 * pipe size if successful, or return -ERROR on error.
 999 */
1000static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
1001{
1002	struct pipe_buffer *bufs;
 
1003
1004	/*
1005	 * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1006	 * expect a lot of shrink+grow operations, just free and allocate
1007	 * again like we would do for growing. If the pipe currently
1008	 * contains more buffers than arg, then return busy.
1009	 */
1010	if (nr_pages < pipe->nrbufs)
1011		return -EBUSY;
1012
1013	bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN);
 
 
 
 
 
 
 
 
 
 
 
 
 
1014	if (unlikely(!bufs))
1015		return -ENOMEM;
1016
 
 
 
 
 
 
 
 
 
 
 
 
1017	/*
1018	 * The pipe array wraps around, so just start the new one at zero
1019	 * and adjust the indexes.
1020	 */
1021	if (pipe->nrbufs) {
1022		unsigned int tail;
1023		unsigned int head;
1024
1025		tail = pipe->curbuf + pipe->nrbufs;
1026		if (tail < pipe->buffers)
1027			tail = 0;
1028		else
1029			tail &= (pipe->buffers - 1);
1030
1031		head = pipe->nrbufs - tail;
1032		if (head)
1033			memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1034		if (tail)
1035			memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1036	}
1037
1038	account_pipe_buffers(pipe, pipe->buffers, nr_pages);
1039	pipe->curbuf = 0;
 
1040	kfree(pipe->bufs);
1041	pipe->bufs = bufs;
1042	pipe->buffers = nr_pages;
1043	return nr_pages * PAGE_SIZE;
1044}
 
 
1045
1046/*
1047 * Currently we rely on the pipe array holding a power-of-2 number
1048 * of pages.
1049 */
1050static inline unsigned int round_pipe_size(unsigned int size)
1051{
1052	unsigned long nr_pages;
1053
1054	nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1055	return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
 
1056}
1057
1058/*
1059 * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1060 * will return an error.
1061 */
1062int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1063		 size_t *lenp, loff_t *ppos)
1064{
1065	int ret;
 
 
1066
1067	ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1068	if (ret < 0 || !write)
1069		return ret;
 
1070
1071	pipe_max_size = round_pipe_size(pipe_max_size);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1072	return ret;
1073}
1074
1075/*
1076 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1077 * location, so checking ->i_pipe is not enough to verify that this is a
1078 * pipe.
1079 */
1080struct pipe_inode_info *get_pipe_info(struct file *file)
1081{
1082	return file->f_op == &pipefifo_fops ? file->private_data : NULL;
 
 
 
 
 
 
 
 
1083}
1084
1085long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1086{
1087	struct pipe_inode_info *pipe;
1088	long ret;
1089
1090	pipe = get_pipe_info(file);
1091	if (!pipe)
1092		return -EBADF;
1093
1094	__pipe_lock(pipe);
1095
1096	switch (cmd) {
1097	case F_SETPIPE_SZ: {
1098		unsigned int size, nr_pages;
1099
1100		size = round_pipe_size(arg);
1101		nr_pages = size >> PAGE_SHIFT;
1102
1103		ret = -EINVAL;
1104		if (!nr_pages)
1105			goto out;
1106
1107		if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1108			ret = -EPERM;
1109			goto out;
1110		} else if ((too_many_pipe_buffers_hard(pipe->user) ||
1111			    too_many_pipe_buffers_soft(pipe->user)) &&
1112		           !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) {
1113			ret = -EPERM;
1114			goto out;
1115		}
1116		ret = pipe_set_size(pipe, nr_pages);
1117		break;
1118		}
1119	case F_GETPIPE_SZ:
1120		ret = pipe->buffers * PAGE_SIZE;
1121		break;
1122	default:
1123		ret = -EINVAL;
1124		break;
1125	}
1126
1127out:
1128	__pipe_unlock(pipe);
1129	return ret;
1130}
1131
1132static const struct super_operations pipefs_ops = {
1133	.destroy_inode = free_inode_nonrcu,
1134	.statfs = simple_statfs,
1135};
1136
1137/*
1138 * pipefs should _never_ be mounted by userland - too much of security hassle,
1139 * no real gain from having the whole whorehouse mounted. So we don't need
1140 * any operations on the root directory. However, we need a non-trivial
1141 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1142 */
1143static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1144			 int flags, const char *dev_name, void *data)
1145{
1146	return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1147			&pipefs_dentry_operations, PIPEFS_MAGIC);
 
 
 
 
1148}
1149
1150static struct file_system_type pipe_fs_type = {
1151	.name		= "pipefs",
1152	.mount		= pipefs_mount,
1153	.kill_sb	= kill_anon_super,
1154};
1155
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1156static int __init init_pipe_fs(void)
1157{
1158	int err = register_filesystem(&pipe_fs_type);
1159
1160	if (!err) {
1161		pipe_mnt = kern_mount(&pipe_fs_type);
1162		if (IS_ERR(pipe_mnt)) {
1163			err = PTR_ERR(pipe_mnt);
1164			unregister_filesystem(&pipe_fs_type);
1165		}
1166	}
 
 
 
1167	return err;
1168}
1169
1170fs_initcall(init_pipe_fs);
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);