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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);
v5.9
   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
  29#include <linux/uaccess.h>
  30#include <asm/ioctls.h>
  31
  32#include "internal.h"
  33
  34/*
  35 * The max size that a non-root user is allowed to grow the pipe. Can
  36 * be set by root in /proc/sys/fs/pipe-max-size
  37 */
  38unsigned int pipe_max_size = 1048576;
  39
 
 
 
 
 
  40/* Maximum allocatable pages per user. Hard limit is unset by default, soft
  41 * matches default values.
  42 */
  43unsigned long pipe_user_pages_hard;
  44unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
  45
  46/*
  47 * We use head and tail indices that aren't masked off, except at the point of
  48 * dereference, but rather they're allowed to wrap naturally.  This means there
  49 * isn't a dead spot in the buffer, but the ring has to be a power of two and
  50 * <= 2^31.
  51 * -- David Howells 2019-09-23.
  52 *
  53 * Reads with count = 0 should always return 0.
  54 * -- Julian Bradfield 1999-06-07.
  55 *
  56 * FIFOs and Pipes now generate SIGIO for both readers and writers.
  57 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  58 *
  59 * pipe_read & write cleanup
  60 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  61 */
  62
  63static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  64{
  65	if (pipe->files)
  66		mutex_lock_nested(&pipe->mutex, subclass);
  67}
  68
  69void pipe_lock(struct pipe_inode_info *pipe)
  70{
  71	/*
  72	 * pipe_lock() nests non-pipe inode locks (for writing to a file)
  73	 */
  74	pipe_lock_nested(pipe, I_MUTEX_PARENT);
  75}
  76EXPORT_SYMBOL(pipe_lock);
  77
  78void pipe_unlock(struct pipe_inode_info *pipe)
  79{
  80	if (pipe->files)
  81		mutex_unlock(&pipe->mutex);
  82}
  83EXPORT_SYMBOL(pipe_unlock);
  84
  85static inline void __pipe_lock(struct pipe_inode_info *pipe)
  86{
  87	mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
  88}
  89
  90static inline void __pipe_unlock(struct pipe_inode_info *pipe)
  91{
  92	mutex_unlock(&pipe->mutex);
  93}
  94
  95void pipe_double_lock(struct pipe_inode_info *pipe1,
  96		      struct pipe_inode_info *pipe2)
  97{
  98	BUG_ON(pipe1 == pipe2);
  99
 100	if (pipe1 < pipe2) {
 101		pipe_lock_nested(pipe1, I_MUTEX_PARENT);
 102		pipe_lock_nested(pipe2, I_MUTEX_CHILD);
 103	} else {
 104		pipe_lock_nested(pipe2, I_MUTEX_PARENT);
 105		pipe_lock_nested(pipe1, I_MUTEX_CHILD);
 106	}
 107}
 108
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 109static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 110				  struct pipe_buffer *buf)
 111{
 112	struct page *page = buf->page;
 113
 114	/*
 115	 * If nobody else uses this page, and we don't already have a
 116	 * temporary page, let's keep track of it as a one-deep
 117	 * allocation cache. (Otherwise just release our reference to it)
 118	 */
 119	if (page_count(page) == 1 && !pipe->tmp_page)
 120		pipe->tmp_page = page;
 121	else
 122		put_page(page);
 123}
 124
 125static bool anon_pipe_buf_try_steal(struct pipe_inode_info *pipe,
 126		struct pipe_buffer *buf)
 127{
 128	struct page *page = buf->page;
 129
 130	if (page_count(page) != 1)
 131		return false;
 132	memcg_kmem_uncharge_page(page, 0);
 133	__SetPageLocked(page);
 134	return true;
 135}
 136
 137/**
 138 * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
 139 * @pipe:	the pipe that the buffer belongs to
 140 * @buf:	the buffer to attempt to steal
 141 *
 142 * Description:
 143 *	This function attempts to steal the &struct page attached to
 144 *	@buf. If successful, this function returns 0 and returns with
 145 *	the page locked. The caller may then reuse the page for whatever
 146 *	he wishes; the typical use is insertion into a different file
 147 *	page cache.
 148 */
 149bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe,
 150		struct pipe_buffer *buf)
 151{
 152	struct page *page = buf->page;
 153
 154	/*
 155	 * A reference of one is golden, that means that the owner of this
 156	 * page is the only one holding a reference to it. lock the page
 157	 * and return OK.
 158	 */
 159	if (page_count(page) == 1) {
 160		lock_page(page);
 161		return true;
 162	}
 163	return false;
 
 164}
 165EXPORT_SYMBOL(generic_pipe_buf_try_steal);
 166
 167/**
 168 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 169 * @pipe:	the pipe that the buffer belongs to
 170 * @buf:	the buffer to get a reference to
 171 *
 172 * Description:
 173 *	This function grabs an extra reference to @buf. It's used in
 174 *	in the tee() system call, when we duplicate the buffers in one
 175 *	pipe into another.
 176 */
 177bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 178{
 179	return try_get_page(buf->page);
 180}
 181EXPORT_SYMBOL(generic_pipe_buf_get);
 182
 183/**
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 184 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 185 * @pipe:	the pipe that the buffer belongs to
 186 * @buf:	the buffer to put a reference to
 187 *
 188 * Description:
 189 *	This function releases a reference to @buf.
 190 */
 191void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 192			      struct pipe_buffer *buf)
 193{
 194	put_page(buf->page);
 195}
 196EXPORT_SYMBOL(generic_pipe_buf_release);
 197
 198static const struct pipe_buf_operations anon_pipe_buf_ops = {
 199	.release	= anon_pipe_buf_release,
 200	.try_steal	= anon_pipe_buf_try_steal,
 201	.get		= generic_pipe_buf_get,
 
 
 202};
 203
 204/* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
 205static inline bool pipe_readable(const struct pipe_inode_info *pipe)
 206{
 207	unsigned int head = READ_ONCE(pipe->head);
 208	unsigned int tail = READ_ONCE(pipe->tail);
 209	unsigned int writers = READ_ONCE(pipe->writers);
 210
 211	return !pipe_empty(head, tail) || !writers;
 212}
 213
 214static ssize_t
 215pipe_read(struct kiocb *iocb, struct iov_iter *to)
 216{
 217	size_t total_len = iov_iter_count(to);
 218	struct file *filp = iocb->ki_filp;
 219	struct pipe_inode_info *pipe = filp->private_data;
 220	bool was_full, wake_next_reader = false;
 221	ssize_t ret;
 222
 223	/* Null read succeeds. */
 224	if (unlikely(total_len == 0))
 225		return 0;
 226
 
 227	ret = 0;
 228	__pipe_lock(pipe);
 229
 230	/*
 231	 * We only wake up writers if the pipe was full when we started
 232	 * reading in order to avoid unnecessary wakeups.
 233	 *
 234	 * But when we do wake up writers, we do so using a sync wakeup
 235	 * (WF_SYNC), because we want them to get going and generate more
 236	 * data for us.
 237	 */
 238	was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
 239	for (;;) {
 240		unsigned int head = pipe->head;
 241		unsigned int tail = pipe->tail;
 242		unsigned int mask = pipe->ring_size - 1;
 243
 244#ifdef CONFIG_WATCH_QUEUE
 245		if (pipe->note_loss) {
 246			struct watch_notification n;
 247
 248			if (total_len < 8) {
 249				if (ret == 0)
 250					ret = -ENOBUFS;
 251				break;
 252			}
 253
 254			n.type = WATCH_TYPE_META;
 255			n.subtype = WATCH_META_LOSS_NOTIFICATION;
 256			n.info = watch_sizeof(n);
 257			if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
 258				if (ret == 0)
 259					ret = -EFAULT;
 260				break;
 261			}
 262			ret += sizeof(n);
 263			total_len -= sizeof(n);
 264			pipe->note_loss = false;
 265		}
 266#endif
 267
 268		if (!pipe_empty(head, tail)) {
 269			struct pipe_buffer *buf = &pipe->bufs[tail & mask];
 270			size_t chars = buf->len;
 271			size_t written;
 272			int error;
 273
 274			if (chars > total_len) {
 275				if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
 276					if (ret == 0)
 277						ret = -ENOBUFS;
 278					break;
 279				}
 280				chars = total_len;
 281			}
 282
 283			error = pipe_buf_confirm(pipe, buf);
 284			if (error) {
 285				if (!ret)
 286					ret = error;
 287				break;
 288			}
 289
 290			written = copy_page_to_iter(buf->page, buf->offset, chars, to);
 291			if (unlikely(written < chars)) {
 292				if (!ret)
 293					ret = -EFAULT;
 294				break;
 295			}
 296			ret += chars;
 297			buf->offset += chars;
 298			buf->len -= chars;
 299
 300			/* Was it a packet buffer? Clean up and exit */
 301			if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 302				total_len = chars;
 303				buf->len = 0;
 304			}
 305
 306			if (!buf->len) {
 307				pipe_buf_release(pipe, buf);
 308				spin_lock_irq(&pipe->rd_wait.lock);
 309#ifdef CONFIG_WATCH_QUEUE
 310				if (buf->flags & PIPE_BUF_FLAG_LOSS)
 311					pipe->note_loss = true;
 312#endif
 313				tail++;
 314				pipe->tail = tail;
 315				spin_unlock_irq(&pipe->rd_wait.lock);
 316			}
 317			total_len -= chars;
 318			if (!total_len)
 319				break;	/* common path: read succeeded */
 320			if (!pipe_empty(head, tail))	/* More to do? */
 321				continue;
 322		}
 323
 
 324		if (!pipe->writers)
 325			break;
 326		if (ret)
 327			break;
 328		if (filp->f_flags & O_NONBLOCK) {
 329			ret = -EAGAIN;
 
 
 
 
 
 
 
 
 
 
 
 
 330			break;
 331		}
 332		__pipe_unlock(pipe);
 333
 334		/*
 335		 * We only get here if we didn't actually read anything.
 336		 *
 337		 * However, we could have seen (and removed) a zero-sized
 338		 * pipe buffer, and might have made space in the buffers
 339		 * that way.
 340		 *
 341		 * You can't make zero-sized pipe buffers by doing an empty
 342		 * write (not even in packet mode), but they can happen if
 343		 * the writer gets an EFAULT when trying to fill a buffer
 344		 * that already got allocated and inserted in the buffer
 345		 * array.
 346		 *
 347		 * So we still need to wake up any pending writers in the
 348		 * _very_ unlikely case that the pipe was full, but we got
 349		 * no data.
 350		 */
 351		if (unlikely(was_full)) {
 352			wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 353			kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 354		}
 355
 356		/*
 357		 * But because we didn't read anything, at this point we can
 358		 * just return directly with -ERESTARTSYS if we're interrupted,
 359		 * since we've done any required wakeups and there's no need
 360		 * to mark anything accessed. And we've dropped the lock.
 361		 */
 362		if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0)
 363			return -ERESTARTSYS;
 364
 365		__pipe_lock(pipe);
 366		was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
 367		wake_next_reader = true;
 368	}
 369	if (pipe_empty(pipe->head, pipe->tail))
 370		wake_next_reader = false;
 371	__pipe_unlock(pipe);
 372
 373	if (was_full) {
 374		wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 
 375		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 376	}
 377	if (wake_next_reader)
 378		wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 379	if (ret > 0)
 380		file_accessed(filp);
 381	return ret;
 382}
 383
 384static inline int is_packetized(struct file *file)
 385{
 386	return (file->f_flags & O_DIRECT) != 0;
 387}
 388
 389/* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
 390static inline bool pipe_writable(const struct pipe_inode_info *pipe)
 391{
 392	unsigned int head = READ_ONCE(pipe->head);
 393	unsigned int tail = READ_ONCE(pipe->tail);
 394	unsigned int max_usage = READ_ONCE(pipe->max_usage);
 395
 396	return !pipe_full(head, tail, max_usage) ||
 397		!READ_ONCE(pipe->readers);
 398}
 399
 400static ssize_t
 401pipe_write(struct kiocb *iocb, struct iov_iter *from)
 402{
 403	struct file *filp = iocb->ki_filp;
 404	struct pipe_inode_info *pipe = filp->private_data;
 405	unsigned int head;
 406	ssize_t ret = 0;
 
 407	size_t total_len = iov_iter_count(from);
 408	ssize_t chars;
 409	bool was_empty = false;
 410	bool wake_next_writer = false;
 411
 412	/* Null write succeeds. */
 413	if (unlikely(total_len == 0))
 414		return 0;
 415
 416	__pipe_lock(pipe);
 417
 418	if (!pipe->readers) {
 419		send_sig(SIGPIPE, current, 0);
 420		ret = -EPIPE;
 421		goto out;
 422	}
 423
 424#ifdef CONFIG_WATCH_QUEUE
 425	if (pipe->watch_queue) {
 426		ret = -EXDEV;
 427		goto out;
 428	}
 429#endif
 430
 431	/*
 432	 * Only wake up if the pipe started out empty, since
 433	 * otherwise there should be no readers waiting.
 434	 *
 435	 * If it wasn't empty we try to merge new data into
 436	 * the last buffer.
 437	 *
 438	 * That naturally merges small writes, but it also
 439	 * page-aligs the rest of the writes for large writes
 440	 * spanning multiple pages.
 441	 */
 442	head = pipe->head;
 443	was_empty = pipe_empty(head, pipe->tail);
 444	chars = total_len & (PAGE_SIZE-1);
 445	if (chars && !was_empty) {
 446		unsigned int mask = pipe->ring_size - 1;
 447		struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
 448		int offset = buf->offset + buf->len;
 449
 450		if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
 451		    offset + chars <= PAGE_SIZE) {
 452			ret = pipe_buf_confirm(pipe, buf);
 453			if (ret)
 454				goto out;
 455
 456			ret = copy_page_from_iter(buf->page, offset, chars, from);
 457			if (unlikely(ret < chars)) {
 458				ret = -EFAULT;
 459				goto out;
 460			}
 461
 462			buf->len += ret;
 463			if (!iov_iter_count(from))
 464				goto out;
 465		}
 466	}
 467
 468	for (;;) {
 
 
 469		if (!pipe->readers) {
 470			send_sig(SIGPIPE, current, 0);
 471			if (!ret)
 472				ret = -EPIPE;
 473			break;
 474		}
 475
 476		head = pipe->head;
 477		if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
 478			unsigned int mask = pipe->ring_size - 1;
 479			struct pipe_buffer *buf = &pipe->bufs[head & mask];
 480			struct page *page = pipe->tmp_page;
 481			int copied;
 482
 483			if (!page) {
 484				page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
 485				if (unlikely(!page)) {
 486					ret = ret ? : -ENOMEM;
 487					break;
 488				}
 489				pipe->tmp_page = page;
 490			}
 491
 492			/* Allocate a slot in the ring in advance and attach an
 493			 * empty buffer.  If we fault or otherwise fail to use
 494			 * it, either the reader will consume it or it'll still
 495			 * be there for the next write.
 496			 */
 497			spin_lock_irq(&pipe->rd_wait.lock);
 498
 499			head = pipe->head;
 500			if (pipe_full(head, pipe->tail, pipe->max_usage)) {
 501				spin_unlock_irq(&pipe->rd_wait.lock);
 502				continue;
 503			}
 504
 505			pipe->head = head + 1;
 506			spin_unlock_irq(&pipe->rd_wait.lock);
 507
 508			/* Insert it into the buffer array */
 509			buf = &pipe->bufs[head & mask];
 510			buf->page = page;
 511			buf->ops = &anon_pipe_buf_ops;
 512			buf->offset = 0;
 513			buf->len = 0;
 514			if (is_packetized(filp))
 515				buf->flags = PIPE_BUF_FLAG_PACKET;
 516			else
 517				buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
 518			pipe->tmp_page = NULL;
 519
 520			copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
 521			if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
 522				if (!ret)
 523					ret = -EFAULT;
 524				break;
 525			}
 526			ret += copied;
 
 
 
 
 527			buf->offset = 0;
 528			buf->len = copied;
 
 
 
 
 
 
 
 529
 530			if (!iov_iter_count(from))
 531				break;
 532		}
 533
 534		if (!pipe_full(head, pipe->tail, pipe->max_usage))
 535			continue;
 536
 537		/* Wait for buffer space to become available. */
 538		if (filp->f_flags & O_NONBLOCK) {
 539			if (!ret)
 540				ret = -EAGAIN;
 541			break;
 542		}
 543		if (signal_pending(current)) {
 544			if (!ret)
 545				ret = -ERESTARTSYS;
 546			break;
 547		}
 548
 549		/*
 550		 * We're going to release the pipe lock and wait for more
 551		 * space. We wake up any readers if necessary, and then
 552		 * after waiting we need to re-check whether the pipe
 553		 * become empty while we dropped the lock.
 554		 */
 555		__pipe_unlock(pipe);
 556		if (was_empty) {
 557			wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 558			kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 
 559		}
 560		wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
 561		__pipe_lock(pipe);
 562		was_empty = pipe_empty(pipe->head, pipe->tail);
 563		wake_next_writer = true;
 564	}
 565out:
 566	if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
 567		wake_next_writer = false;
 568	__pipe_unlock(pipe);
 569
 570	/*
 571	 * If we do do a wakeup event, we do a 'sync' wakeup, because we
 572	 * want the reader to start processing things asap, rather than
 573	 * leave the data pending.
 574	 *
 575	 * This is particularly important for small writes, because of
 576	 * how (for example) the GNU make jobserver uses small writes to
 577	 * wake up pending jobs
 578	 */
 579	if (was_empty) {
 580		wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
 581		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 582	}
 583	if (wake_next_writer)
 584		wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
 585	if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
 586		int err = file_update_time(filp);
 587		if (err)
 588			ret = err;
 589		sb_end_write(file_inode(filp)->i_sb);
 590	}
 591	return ret;
 592}
 593
 594static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 595{
 596	struct pipe_inode_info *pipe = filp->private_data;
 597	int count, head, tail, mask;
 598
 599	switch (cmd) {
 600	case FIONREAD:
 601		__pipe_lock(pipe);
 602		count = 0;
 603		head = pipe->head;
 604		tail = pipe->tail;
 605		mask = pipe->ring_size - 1;
 606
 607		while (tail != head) {
 608			count += pipe->bufs[tail & mask].len;
 609			tail++;
 610		}
 611		__pipe_unlock(pipe);
 612
 613		return put_user(count, (int __user *)arg);
 614
 615#ifdef CONFIG_WATCH_QUEUE
 616	case IOC_WATCH_QUEUE_SET_SIZE: {
 617		int ret;
 618		__pipe_lock(pipe);
 619		ret = watch_queue_set_size(pipe, arg);
 620		__pipe_unlock(pipe);
 621		return ret;
 622	}
 623
 624	case IOC_WATCH_QUEUE_SET_FILTER:
 625		return watch_queue_set_filter(
 626			pipe, (struct watch_notification_filter __user *)arg);
 627#endif
 628
 629	default:
 630		return -ENOIOCTLCMD;
 631	}
 632}
 633
 634/* No kernel lock held - fine */
 635static __poll_t
 636pipe_poll(struct file *filp, poll_table *wait)
 637{
 638	__poll_t mask;
 639	struct pipe_inode_info *pipe = filp->private_data;
 640	unsigned int head, tail;
 641
 642	/*
 643	 * Reading pipe state only -- no need for acquiring the semaphore.
 644	 *
 645	 * But because this is racy, the code has to add the
 646	 * entry to the poll table _first_ ..
 647	 */
 648	if (filp->f_mode & FMODE_READ)
 649		poll_wait(filp, &pipe->rd_wait, wait);
 650	if (filp->f_mode & FMODE_WRITE)
 651		poll_wait(filp, &pipe->wr_wait, wait);
 652
 653	/*
 654	 * .. and only then can you do the racy tests. That way,
 655	 * if something changes and you got it wrong, the poll
 656	 * table entry will wake you up and fix it.
 657	 */
 658	head = READ_ONCE(pipe->head);
 659	tail = READ_ONCE(pipe->tail);
 660
 
 
 661	mask = 0;
 662	if (filp->f_mode & FMODE_READ) {
 663		if (!pipe_empty(head, tail))
 664			mask |= EPOLLIN | EPOLLRDNORM;
 665		if (!pipe->writers && filp->f_version != pipe->w_counter)
 666			mask |= EPOLLHUP;
 667	}
 668
 669	if (filp->f_mode & FMODE_WRITE) {
 670		if (!pipe_full(head, tail, pipe->max_usage))
 671			mask |= EPOLLOUT | EPOLLWRNORM;
 672		/*
 673		 * Most Unices do not set EPOLLERR for FIFOs but on Linux they
 674		 * behave exactly like pipes for poll().
 675		 */
 676		if (!pipe->readers)
 677			mask |= EPOLLERR;
 678	}
 679
 680	return mask;
 681}
 682
 683static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
 684{
 685	int kill = 0;
 686
 687	spin_lock(&inode->i_lock);
 688	if (!--pipe->files) {
 689		inode->i_pipe = NULL;
 690		kill = 1;
 691	}
 692	spin_unlock(&inode->i_lock);
 693
 694	if (kill)
 695		free_pipe_info(pipe);
 696}
 697
 698static int
 699pipe_release(struct inode *inode, struct file *file)
 700{
 701	struct pipe_inode_info *pipe = file->private_data;
 702
 703	__pipe_lock(pipe);
 704	if (file->f_mode & FMODE_READ)
 705		pipe->readers--;
 706	if (file->f_mode & FMODE_WRITE)
 707		pipe->writers--;
 708
 709	/* Was that the last reader or writer, but not the other side? */
 710	if (!pipe->readers != !pipe->writers) {
 711		wake_up_interruptible_all(&pipe->rd_wait);
 712		wake_up_interruptible_all(&pipe->wr_wait);
 713		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 714		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 715	}
 716	__pipe_unlock(pipe);
 717
 718	put_pipe_info(inode, pipe);
 719	return 0;
 720}
 721
 722static int
 723pipe_fasync(int fd, struct file *filp, int on)
 724{
 725	struct pipe_inode_info *pipe = filp->private_data;
 726	int retval = 0;
 727
 728	__pipe_lock(pipe);
 729	if (filp->f_mode & FMODE_READ)
 730		retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 731	if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 732		retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 733		if (retval < 0 && (filp->f_mode & FMODE_READ))
 734			/* this can happen only if on == T */
 735			fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 736	}
 737	__pipe_unlock(pipe);
 738	return retval;
 739}
 740
 741unsigned long account_pipe_buffers(struct user_struct *user,
 742				   unsigned long old, unsigned long new)
 743{
 744	return atomic_long_add_return(new - old, &user->pipe_bufs);
 745}
 746
 747bool too_many_pipe_buffers_soft(unsigned long user_bufs)
 748{
 749	unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
 750
 751	return soft_limit && user_bufs > soft_limit;
 752}
 753
 754bool too_many_pipe_buffers_hard(unsigned long user_bufs)
 755{
 756	unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
 757
 758	return hard_limit && user_bufs > hard_limit;
 759}
 760
 761bool pipe_is_unprivileged_user(void)
 762{
 763	return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
 764}
 765
 766struct pipe_inode_info *alloc_pipe_info(void)
 767{
 768	struct pipe_inode_info *pipe;
 769	unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
 770	struct user_struct *user = get_current_user();
 771	unsigned long user_bufs;
 772	unsigned int max_size = READ_ONCE(pipe_max_size);
 773
 774	pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
 775	if (pipe == NULL)
 776		goto out_free_uid;
 
 
 
 
 
 
 
 777
 778	if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
 779		pipe_bufs = max_size >> PAGE_SHIFT;
 780
 781	user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
 782
 783	if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
 784		user_bufs = account_pipe_buffers(user, pipe_bufs, 1);
 785		pipe_bufs = 1;
 786	}
 787
 788	if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
 789		goto out_revert_acct;
 790
 791	pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
 792			     GFP_KERNEL_ACCOUNT);
 793
 794	if (pipe->bufs) {
 795		init_waitqueue_head(&pipe->rd_wait);
 796		init_waitqueue_head(&pipe->wr_wait);
 797		pipe->r_counter = pipe->w_counter = 1;
 798		pipe->max_usage = pipe_bufs;
 799		pipe->ring_size = pipe_bufs;
 800		pipe->nr_accounted = pipe_bufs;
 801		pipe->user = user;
 802		mutex_init(&pipe->mutex);
 803		return pipe;
 804	}
 805
 806out_revert_acct:
 807	(void) account_pipe_buffers(user, pipe_bufs, 0);
 808	kfree(pipe);
 809out_free_uid:
 810	free_uid(user);
 811	return NULL;
 812}
 813
 814void free_pipe_info(struct pipe_inode_info *pipe)
 815{
 816	int i;
 817
 818#ifdef CONFIG_WATCH_QUEUE
 819	if (pipe->watch_queue) {
 820		watch_queue_clear(pipe->watch_queue);
 821		put_watch_queue(pipe->watch_queue);
 822	}
 823#endif
 824
 825	(void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
 826	free_uid(pipe->user);
 827	for (i = 0; i < pipe->ring_size; i++) {
 828		struct pipe_buffer *buf = pipe->bufs + i;
 829		if (buf->ops)
 830			pipe_buf_release(pipe, buf);
 831	}
 832	if (pipe->tmp_page)
 833		__free_page(pipe->tmp_page);
 834	kfree(pipe->bufs);
 835	kfree(pipe);
 836}
 837
 838static struct vfsmount *pipe_mnt __read_mostly;
 839
 840/*
 841 * pipefs_dname() is called from d_path().
 842 */
 843static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 844{
 845	return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 846				d_inode(dentry)->i_ino);
 847}
 848
 849static const struct dentry_operations pipefs_dentry_operations = {
 850	.d_dname	= pipefs_dname,
 851};
 852
 853static struct inode * get_pipe_inode(void)
 854{
 855	struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 856	struct pipe_inode_info *pipe;
 857
 858	if (!inode)
 859		goto fail_inode;
 860
 861	inode->i_ino = get_next_ino();
 862
 863	pipe = alloc_pipe_info();
 864	if (!pipe)
 865		goto fail_iput;
 866
 867	inode->i_pipe = pipe;
 868	pipe->files = 2;
 869	pipe->readers = pipe->writers = 1;
 870	inode->i_fop = &pipefifo_fops;
 871
 872	/*
 873	 * Mark the inode dirty from the very beginning,
 874	 * that way it will never be moved to the dirty
 875	 * list because "mark_inode_dirty()" will think
 876	 * that it already _is_ on the dirty list.
 877	 */
 878	inode->i_state = I_DIRTY;
 879	inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 880	inode->i_uid = current_fsuid();
 881	inode->i_gid = current_fsgid();
 882	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 883
 884	return inode;
 885
 886fail_iput:
 887	iput(inode);
 888
 889fail_inode:
 890	return NULL;
 891}
 892
 893int create_pipe_files(struct file **res, int flags)
 894{
 
 895	struct inode *inode = get_pipe_inode();
 896	struct file *f;
 897	int error;
 
 898
 899	if (!inode)
 900		return -ENFILE;
 901
 902	if (flags & O_NOTIFICATION_PIPE) {
 903		error = watch_queue_init(inode->i_pipe);
 904		if (error) {
 905			free_pipe_info(inode->i_pipe);
 906			iput(inode);
 907			return error;
 908		}
 909	}
 910
 911	f = alloc_file_pseudo(inode, pipe_mnt, "",
 912				O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
 913				&pipefifo_fops);
 914	if (IS_ERR(f)) {
 915		free_pipe_info(inode->i_pipe);
 916		iput(inode);
 917		return PTR_ERR(f);
 918	}
 919
 
 920	f->private_data = inode->i_pipe;
 921
 922	res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
 923				  &pipefifo_fops);
 924	if (IS_ERR(res[0])) {
 925		put_pipe_info(inode, inode->i_pipe);
 926		fput(f);
 927		return PTR_ERR(res[0]);
 928	}
 
 
 929	res[0]->private_data = inode->i_pipe;
 
 930	res[1] = f;
 931	stream_open(inode, res[0]);
 932	stream_open(inode, res[1]);
 933	return 0;
 
 
 
 
 
 
 
 
 
 
 
 
 934}
 935
 936static int __do_pipe_flags(int *fd, struct file **files, int flags)
 937{
 938	int error;
 939	int fdw, fdr;
 940
 941	if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
 942		return -EINVAL;
 943
 944	error = create_pipe_files(files, flags);
 945	if (error)
 946		return error;
 947
 948	error = get_unused_fd_flags(flags);
 949	if (error < 0)
 950		goto err_read_pipe;
 951	fdr = error;
 952
 953	error = get_unused_fd_flags(flags);
 954	if (error < 0)
 955		goto err_fdr;
 956	fdw = error;
 957
 958	audit_fd_pair(fdr, fdw);
 959	fd[0] = fdr;
 960	fd[1] = fdw;
 961	return 0;
 962
 963 err_fdr:
 964	put_unused_fd(fdr);
 965 err_read_pipe:
 966	fput(files[0]);
 967	fput(files[1]);
 968	return error;
 969}
 970
 971int do_pipe_flags(int *fd, int flags)
 972{
 973	struct file *files[2];
 974	int error = __do_pipe_flags(fd, files, flags);
 975	if (!error) {
 976		fd_install(fd[0], files[0]);
 977		fd_install(fd[1], files[1]);
 978	}
 979	return error;
 980}
 981
 982/*
 983 * sys_pipe() is the normal C calling standard for creating
 984 * a pipe. It's not the way Unix traditionally does this, though.
 985 */
 986static int do_pipe2(int __user *fildes, int flags)
 987{
 988	struct file *files[2];
 989	int fd[2];
 990	int error;
 991
 992	error = __do_pipe_flags(fd, files, flags);
 993	if (!error) {
 994		if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
 995			fput(files[0]);
 996			fput(files[1]);
 997			put_unused_fd(fd[0]);
 998			put_unused_fd(fd[1]);
 999			error = -EFAULT;
1000		} else {
1001			fd_install(fd[0], files[0]);
1002			fd_install(fd[1], files[1]);
1003		}
1004	}
1005	return error;
1006}
1007
1008SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1009{
1010	return do_pipe2(fildes, flags);
1011}
1012
1013SYSCALL_DEFINE1(pipe, int __user *, fildes)
1014{
1015	return do_pipe2(fildes, 0);
1016}
1017
1018/*
1019 * This is the stupid "wait for pipe to be readable or writable"
1020 * model.
1021 *
1022 * See pipe_read/write() for the proper kind of exclusive wait,
1023 * but that requires that we wake up any other readers/writers
1024 * if we then do not end up reading everything (ie the whole
1025 * "wake_next_reader/writer" logic in pipe_read/write()).
1026 */
1027void pipe_wait_readable(struct pipe_inode_info *pipe)
1028{
1029	pipe_unlock(pipe);
1030	wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
1031	pipe_lock(pipe);
1032}
1033
1034void pipe_wait_writable(struct pipe_inode_info *pipe)
1035{
1036	pipe_unlock(pipe);
1037	wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
1038	pipe_lock(pipe);
1039}
1040
1041/*
1042 * This depends on both the wait (here) and the wakeup (wake_up_partner)
1043 * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
1044 * race with the count check and waitqueue prep.
1045 *
1046 * Normally in order to avoid races, you'd do the prepare_to_wait() first,
1047 * then check the condition you're waiting for, and only then sleep. But
1048 * because of the pipe lock, we can check the condition before being on
1049 * the wait queue.
1050 *
1051 * We use the 'rd_wait' waitqueue for pipe partner waiting.
1052 */
1053static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1054{
1055	DEFINE_WAIT(rdwait);
1056	int cur = *cnt;
1057
1058	while (cur == *cnt) {
1059		prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
1060		pipe_unlock(pipe);
1061		schedule();
1062		finish_wait(&pipe->rd_wait, &rdwait);
1063		pipe_lock(pipe);
1064		if (signal_pending(current))
1065			break;
1066	}
1067	return cur == *cnt ? -ERESTARTSYS : 0;
1068}
1069
1070static void wake_up_partner(struct pipe_inode_info *pipe)
1071{
1072	wake_up_interruptible_all(&pipe->rd_wait);
1073}
1074
1075static int fifo_open(struct inode *inode, struct file *filp)
1076{
1077	struct pipe_inode_info *pipe;
1078	bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1079	int ret;
1080
1081	filp->f_version = 0;
1082
1083	spin_lock(&inode->i_lock);
1084	if (inode->i_pipe) {
1085		pipe = inode->i_pipe;
1086		pipe->files++;
1087		spin_unlock(&inode->i_lock);
1088	} else {
1089		spin_unlock(&inode->i_lock);
1090		pipe = alloc_pipe_info();
1091		if (!pipe)
1092			return -ENOMEM;
1093		pipe->files = 1;
1094		spin_lock(&inode->i_lock);
1095		if (unlikely(inode->i_pipe)) {
1096			inode->i_pipe->files++;
1097			spin_unlock(&inode->i_lock);
1098			free_pipe_info(pipe);
1099			pipe = inode->i_pipe;
1100		} else {
1101			inode->i_pipe = pipe;
1102			spin_unlock(&inode->i_lock);
1103		}
1104	}
1105	filp->private_data = pipe;
1106	/* OK, we have a pipe and it's pinned down */
1107
1108	__pipe_lock(pipe);
1109
1110	/* We can only do regular read/write on fifos */
1111	stream_open(inode, filp);
1112
1113	switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
1114	case FMODE_READ:
1115	/*
1116	 *  O_RDONLY
1117	 *  POSIX.1 says that O_NONBLOCK means return with the FIFO
1118	 *  opened, even when there is no process writing the FIFO.
1119	 */
1120		pipe->r_counter++;
1121		if (pipe->readers++ == 0)
1122			wake_up_partner(pipe);
1123
1124		if (!is_pipe && !pipe->writers) {
1125			if ((filp->f_flags & O_NONBLOCK)) {
1126				/* suppress EPOLLHUP until we have
1127				 * seen a writer */
1128				filp->f_version = pipe->w_counter;
1129			} else {
1130				if (wait_for_partner(pipe, &pipe->w_counter))
1131					goto err_rd;
1132			}
1133		}
1134		break;
1135
1136	case FMODE_WRITE:
1137	/*
1138	 *  O_WRONLY
1139	 *  POSIX.1 says that O_NONBLOCK means return -1 with
1140	 *  errno=ENXIO when there is no process reading the FIFO.
1141	 */
1142		ret = -ENXIO;
1143		if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1144			goto err;
1145
1146		pipe->w_counter++;
1147		if (!pipe->writers++)
1148			wake_up_partner(pipe);
1149
1150		if (!is_pipe && !pipe->readers) {
1151			if (wait_for_partner(pipe, &pipe->r_counter))
1152				goto err_wr;
1153		}
1154		break;
1155
1156	case FMODE_READ | FMODE_WRITE:
1157	/*
1158	 *  O_RDWR
1159	 *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1160	 *  This implementation will NEVER block on a O_RDWR open, since
1161	 *  the process can at least talk to itself.
1162	 */
1163
1164		pipe->readers++;
1165		pipe->writers++;
1166		pipe->r_counter++;
1167		pipe->w_counter++;
1168		if (pipe->readers == 1 || pipe->writers == 1)
1169			wake_up_partner(pipe);
1170		break;
1171
1172	default:
1173		ret = -EINVAL;
1174		goto err;
1175	}
1176
1177	/* Ok! */
1178	__pipe_unlock(pipe);
1179	return 0;
1180
1181err_rd:
1182	if (!--pipe->readers)
1183		wake_up_interruptible(&pipe->wr_wait);
1184	ret = -ERESTARTSYS;
1185	goto err;
1186
1187err_wr:
1188	if (!--pipe->writers)
1189		wake_up_interruptible_all(&pipe->rd_wait);
1190	ret = -ERESTARTSYS;
1191	goto err;
1192
1193err:
1194	__pipe_unlock(pipe);
1195
1196	put_pipe_info(inode, pipe);
1197	return ret;
1198}
1199
1200const struct file_operations pipefifo_fops = {
1201	.open		= fifo_open,
1202	.llseek		= no_llseek,
1203	.read_iter	= pipe_read,
1204	.write_iter	= pipe_write,
1205	.poll		= pipe_poll,
1206	.unlocked_ioctl	= pipe_ioctl,
1207	.release	= pipe_release,
1208	.fasync		= pipe_fasync,
1209};
1210
1211/*
1212 * Currently we rely on the pipe array holding a power-of-2 number
1213 * of pages. Returns 0 on error.
1214 */
1215unsigned int round_pipe_size(unsigned long size)
1216{
1217	if (size > (1U << 31))
1218		return 0;
1219
1220	/* Minimum pipe size, as required by POSIX */
1221	if (size < PAGE_SIZE)
1222		return PAGE_SIZE;
1223
1224	return roundup_pow_of_two(size);
1225}
1226
1227/*
1228 * Resize the pipe ring to a number of slots.
1229 */
1230int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
1231{
1232	struct pipe_buffer *bufs;
1233	unsigned int head, tail, mask, n;
1234
1235	/*
1236	 * We can shrink the pipe, if arg is greater than the ring occupancy.
1237	 * Since we don't expect a lot of shrink+grow operations, just free and
1238	 * allocate again like we would do for growing.  If the pipe currently
1239	 * contains more buffers than arg, then return busy.
1240	 */
1241	mask = pipe->ring_size - 1;
1242	head = pipe->head;
1243	tail = pipe->tail;
1244	n = pipe_occupancy(pipe->head, pipe->tail);
1245	if (nr_slots < n)
1246		return -EBUSY;
1247
1248	bufs = kcalloc(nr_slots, sizeof(*bufs),
1249		       GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1250	if (unlikely(!bufs))
1251		return -ENOMEM;
1252
1253	/*
1254	 * The pipe array wraps around, so just start the new one at zero
1255	 * and adjust the indices.
1256	 */
1257	if (n > 0) {
1258		unsigned int h = head & mask;
1259		unsigned int t = tail & mask;
1260		if (h > t) {
1261			memcpy(bufs, pipe->bufs + t,
1262			       n * sizeof(struct pipe_buffer));
1263		} else {
1264			unsigned int tsize = pipe->ring_size - t;
1265			if (h > 0)
1266				memcpy(bufs + tsize, pipe->bufs,
1267				       h * sizeof(struct pipe_buffer));
1268			memcpy(bufs, pipe->bufs + t,
1269			       tsize * sizeof(struct pipe_buffer));
1270		}
 
1271	}
1272
1273	head = n;
1274	tail = 0;
1275
1276	kfree(pipe->bufs);
1277	pipe->bufs = bufs;
1278	pipe->ring_size = nr_slots;
1279	if (pipe->max_usage > nr_slots)
1280		pipe->max_usage = nr_slots;
1281	pipe->tail = tail;
1282	pipe->head = head;
1283
1284	/* This might have made more room for writers */
1285	wake_up_interruptible(&pipe->wr_wait);
1286	return 0;
1287}
1288
1289/*
1290 * Allocate a new array of pipe buffers and copy the info over. Returns the
1291 * pipe size if successful, or return -ERROR on error.
1292 */
1293static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1294{
1295	unsigned long user_bufs;
1296	unsigned int nr_slots, size;
1297	long ret = 0;
1298
1299#ifdef CONFIG_WATCH_QUEUE
1300	if (pipe->watch_queue)
1301		return -EBUSY;
1302#endif
1303
1304	size = round_pipe_size(arg);
1305	nr_slots = size >> PAGE_SHIFT;
 
 
 
 
 
 
1306
1307	if (!nr_slots)
1308		return -EINVAL;
1309
1310	/*
1311	 * If trying to increase the pipe capacity, check that an
1312	 * unprivileged user is not trying to exceed various limits
1313	 * (soft limit check here, hard limit check just below).
1314	 * Decreasing the pipe capacity is always permitted, even
1315	 * if the user is currently over a limit.
1316	 */
1317	if (nr_slots > pipe->max_usage &&
1318			size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1319		return -EPERM;
1320
1321	user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
1322
1323	if (nr_slots > pipe->max_usage &&
1324			(too_many_pipe_buffers_hard(user_bufs) ||
1325			 too_many_pipe_buffers_soft(user_bufs)) &&
1326			pipe_is_unprivileged_user()) {
1327		ret = -EPERM;
1328		goto out_revert_acct;
1329	}
1330
1331	ret = pipe_resize_ring(pipe, nr_slots);
1332	if (ret < 0)
1333		goto out_revert_acct;
1334
1335	pipe->max_usage = nr_slots;
1336	pipe->nr_accounted = nr_slots;
1337	return pipe->max_usage * PAGE_SIZE;
1338
1339out_revert_acct:
1340	(void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
1341	return ret;
1342}
1343
1344/*
1345 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1346 * location, so checking ->i_pipe is not enough to verify that this is a
1347 * pipe.
1348 */
1349struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
1350{
1351	struct pipe_inode_info *pipe = file->private_data;
1352
1353	if (file->f_op != &pipefifo_fops || !pipe)
1354		return NULL;
1355#ifdef CONFIG_WATCH_QUEUE
1356	if (for_splice && pipe->watch_queue)
1357		return NULL;
1358#endif
1359	return pipe;
1360}
1361
1362long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1363{
1364	struct pipe_inode_info *pipe;
1365	long ret;
1366
1367	pipe = get_pipe_info(file, false);
1368	if (!pipe)
1369		return -EBADF;
1370
1371	__pipe_lock(pipe);
1372
1373	switch (cmd) {
1374	case F_SETPIPE_SZ:
1375		ret = pipe_set_size(pipe, arg);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1376		break;
 
1377	case F_GETPIPE_SZ:
1378		ret = pipe->max_usage * PAGE_SIZE;
1379		break;
1380	default:
1381		ret = -EINVAL;
1382		break;
1383	}
1384
 
1385	__pipe_unlock(pipe);
1386	return ret;
1387}
1388
1389static const struct super_operations pipefs_ops = {
1390	.destroy_inode = free_inode_nonrcu,
1391	.statfs = simple_statfs,
1392};
1393
1394/*
1395 * pipefs should _never_ be mounted by userland - too much of security hassle,
1396 * no real gain from having the whole whorehouse mounted. So we don't need
1397 * any operations on the root directory. However, we need a non-trivial
1398 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1399 */
1400
1401static int pipefs_init_fs_context(struct fs_context *fc)
1402{
1403	struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
1404	if (!ctx)
1405		return -ENOMEM;
1406	ctx->ops = &pipefs_ops;
1407	ctx->dops = &pipefs_dentry_operations;
1408	return 0;
1409}
1410
1411static struct file_system_type pipe_fs_type = {
1412	.name		= "pipefs",
1413	.init_fs_context = pipefs_init_fs_context,
1414	.kill_sb	= kill_anon_super,
1415};
1416
1417static int __init init_pipe_fs(void)
1418{
1419	int err = register_filesystem(&pipe_fs_type);
1420
1421	if (!err) {
1422		pipe_mnt = kern_mount(&pipe_fs_type);
1423		if (IS_ERR(pipe_mnt)) {
1424			err = PTR_ERR(pipe_mnt);
1425			unregister_filesystem(&pipe_fs_type);
1426		}
1427	}
1428	return err;
1429}
1430
1431fs_initcall(init_pipe_fs);