![Linus Torvalds](/assets/img/avatar_default.png)
Merge page ref overflow branch. Jann Horn reported that he can overflow the page ref count with sufficient memory (and a filesystem that is intentionally extremely slow). Admittedly it's not exactly easy. To have more than four billion references to a page requires a minimum of 32GB of kernel memory just for the pointers to the pages, much less any metadata to keep track of those pointers. Jann needed a total of 140GB of memory and a specially crafted filesystem that leaves all reads pending (in order to not ever free the page references and just keep adding more). Still, we have a fairly straightforward way to limit the two obvious user-controllable sources of page references: direct-IO like page references gotten through get_user_pages(), and the splice pipe page duplication. So let's just do that. * branch page-refs: fs: prevent page refcount overflow in pipe_buf_get mm: prevent get_user_pages() from overflowing page refcount mm: add 'try_get_page()' helper function mm: make page ref count overflow check tighter and more explicit
1213 lines
28 KiB
C
1213 lines
28 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/fs/pipe.c
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*
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* Copyright (C) 1991, 1992, 1999 Linus Torvalds
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*/
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#include <linux/mm.h>
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#include <linux/file.h>
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#include <linux/poll.h>
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#include <linux/slab.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/log2.h>
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#include <linux/mount.h>
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#include <linux/magic.h>
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#include <linux/pipe_fs_i.h>
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#include <linux/uio.h>
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#include <linux/highmem.h>
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#include <linux/pagemap.h>
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#include <linux/audit.h>
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#include <linux/syscalls.h>
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#include <linux/fcntl.h>
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#include <linux/memcontrol.h>
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#include <linux/uaccess.h>
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#include <asm/ioctls.h>
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#include "internal.h"
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/*
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* The max size that a non-root user is allowed to grow the pipe. Can
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* be set by root in /proc/sys/fs/pipe-max-size
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*/
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unsigned int pipe_max_size = 1048576;
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/* Maximum allocatable pages per user. Hard limit is unset by default, soft
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* matches default values.
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*/
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unsigned long pipe_user_pages_hard;
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unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
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/*
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* We use a start+len construction, which provides full use of the
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* allocated memory.
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* -- Florian Coosmann (FGC)
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*
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* Reads with count = 0 should always return 0.
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* -- Julian Bradfield 1999-06-07.
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*
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* FIFOs and Pipes now generate SIGIO for both readers and writers.
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* -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
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*
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* pipe_read & write cleanup
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* -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
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*/
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static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
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{
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if (pipe->files)
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mutex_lock_nested(&pipe->mutex, subclass);
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}
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void pipe_lock(struct pipe_inode_info *pipe)
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{
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/*
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* pipe_lock() nests non-pipe inode locks (for writing to a file)
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*/
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pipe_lock_nested(pipe, I_MUTEX_PARENT);
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}
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EXPORT_SYMBOL(pipe_lock);
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void pipe_unlock(struct pipe_inode_info *pipe)
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{
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if (pipe->files)
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mutex_unlock(&pipe->mutex);
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}
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EXPORT_SYMBOL(pipe_unlock);
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static inline void __pipe_lock(struct pipe_inode_info *pipe)
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{
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mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
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}
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static inline void __pipe_unlock(struct pipe_inode_info *pipe)
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{
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mutex_unlock(&pipe->mutex);
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}
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void pipe_double_lock(struct pipe_inode_info *pipe1,
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struct pipe_inode_info *pipe2)
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{
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BUG_ON(pipe1 == pipe2);
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if (pipe1 < pipe2) {
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pipe_lock_nested(pipe1, I_MUTEX_PARENT);
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pipe_lock_nested(pipe2, I_MUTEX_CHILD);
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} else {
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pipe_lock_nested(pipe2, I_MUTEX_PARENT);
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pipe_lock_nested(pipe1, I_MUTEX_CHILD);
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}
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}
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/* Drop the inode semaphore and wait for a pipe event, atomically */
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void pipe_wait(struct pipe_inode_info *pipe)
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{
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DEFINE_WAIT(wait);
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/*
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* Pipes are system-local resources, so sleeping on them
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* is considered a noninteractive wait:
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*/
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prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
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pipe_unlock(pipe);
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schedule();
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finish_wait(&pipe->wait, &wait);
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pipe_lock(pipe);
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}
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static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
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struct pipe_buffer *buf)
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{
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struct page *page = buf->page;
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/*
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* If nobody else uses this page, and we don't already have a
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* temporary page, let's keep track of it as a one-deep
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* allocation cache. (Otherwise just release our reference to it)
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*/
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if (page_count(page) == 1 && !pipe->tmp_page)
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pipe->tmp_page = page;
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else
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put_page(page);
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}
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static int anon_pipe_buf_steal(struct pipe_inode_info *pipe,
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struct pipe_buffer *buf)
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{
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struct page *page = buf->page;
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if (page_count(page) == 1) {
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memcg_kmem_uncharge(page, 0);
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__SetPageLocked(page);
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return 0;
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}
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return 1;
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}
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/**
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* generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
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* @pipe: the pipe that the buffer belongs to
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* @buf: the buffer to attempt to steal
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*
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* Description:
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* This function attempts to steal the &struct page attached to
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* @buf. If successful, this function returns 0 and returns with
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* the page locked. The caller may then reuse the page for whatever
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* he wishes; the typical use is insertion into a different file
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* page cache.
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*/
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int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
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struct pipe_buffer *buf)
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{
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struct page *page = buf->page;
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/*
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* A reference of one is golden, that means that the owner of this
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* page is the only one holding a reference to it. lock the page
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* and return OK.
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*/
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if (page_count(page) == 1) {
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lock_page(page);
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return 0;
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}
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return 1;
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}
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EXPORT_SYMBOL(generic_pipe_buf_steal);
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/**
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* generic_pipe_buf_get - get a reference to a &struct pipe_buffer
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* @pipe: the pipe that the buffer belongs to
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* @buf: the buffer to get a reference to
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*
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* Description:
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* This function grabs an extra reference to @buf. It's used in
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* in the tee() system call, when we duplicate the buffers in one
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* pipe into another.
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*/
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bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
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{
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return try_get_page(buf->page);
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}
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EXPORT_SYMBOL(generic_pipe_buf_get);
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/**
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* generic_pipe_buf_confirm - verify contents of the pipe buffer
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* @info: the pipe that the buffer belongs to
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* @buf: the buffer to confirm
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*
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* Description:
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* This function does nothing, because the generic pipe code uses
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* pages that are always good when inserted into the pipe.
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*/
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int generic_pipe_buf_confirm(struct pipe_inode_info *info,
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struct pipe_buffer *buf)
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{
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return 0;
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}
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EXPORT_SYMBOL(generic_pipe_buf_confirm);
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/**
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* generic_pipe_buf_release - put a reference to a &struct pipe_buffer
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* @pipe: the pipe that the buffer belongs to
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* @buf: the buffer to put a reference to
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*
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* Description:
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* This function releases a reference to @buf.
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*/
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void generic_pipe_buf_release(struct pipe_inode_info *pipe,
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struct pipe_buffer *buf)
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{
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put_page(buf->page);
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}
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EXPORT_SYMBOL(generic_pipe_buf_release);
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/* New data written to a pipe may be appended to a buffer with this type. */
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static const struct pipe_buf_operations anon_pipe_buf_ops = {
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.confirm = generic_pipe_buf_confirm,
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.release = anon_pipe_buf_release,
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.steal = anon_pipe_buf_steal,
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.get = generic_pipe_buf_get,
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};
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static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = {
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.confirm = generic_pipe_buf_confirm,
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.release = anon_pipe_buf_release,
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.steal = anon_pipe_buf_steal,
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.get = generic_pipe_buf_get,
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};
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static const struct pipe_buf_operations packet_pipe_buf_ops = {
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.confirm = generic_pipe_buf_confirm,
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.release = anon_pipe_buf_release,
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.steal = anon_pipe_buf_steal,
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.get = generic_pipe_buf_get,
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};
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/**
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* pipe_buf_mark_unmergeable - mark a &struct pipe_buffer as unmergeable
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* @buf: the buffer to mark
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*
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* Description:
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* This function ensures that no future writes will be merged into the
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* given &struct pipe_buffer. This is necessary when multiple pipe buffers
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* share the same backing page.
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*/
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void pipe_buf_mark_unmergeable(struct pipe_buffer *buf)
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{
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if (buf->ops == &anon_pipe_buf_ops)
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buf->ops = &anon_pipe_buf_nomerge_ops;
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}
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static bool pipe_buf_can_merge(struct pipe_buffer *buf)
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{
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return buf->ops == &anon_pipe_buf_ops;
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}
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static ssize_t
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pipe_read(struct kiocb *iocb, struct iov_iter *to)
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{
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size_t total_len = iov_iter_count(to);
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struct file *filp = iocb->ki_filp;
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struct pipe_inode_info *pipe = filp->private_data;
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int do_wakeup;
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ssize_t ret;
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/* Null read succeeds. */
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if (unlikely(total_len == 0))
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return 0;
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do_wakeup = 0;
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ret = 0;
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__pipe_lock(pipe);
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for (;;) {
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int bufs = pipe->nrbufs;
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if (bufs) {
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int curbuf = pipe->curbuf;
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struct pipe_buffer *buf = pipe->bufs + curbuf;
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size_t chars = buf->len;
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size_t written;
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int error;
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if (chars > total_len)
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chars = total_len;
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error = pipe_buf_confirm(pipe, buf);
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if (error) {
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if (!ret)
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ret = error;
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break;
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}
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written = copy_page_to_iter(buf->page, buf->offset, chars, to);
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if (unlikely(written < chars)) {
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if (!ret)
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ret = -EFAULT;
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break;
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}
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ret += chars;
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buf->offset += chars;
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buf->len -= chars;
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/* Was it a packet buffer? Clean up and exit */
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if (buf->flags & PIPE_BUF_FLAG_PACKET) {
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total_len = chars;
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buf->len = 0;
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}
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if (!buf->len) {
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pipe_buf_release(pipe, buf);
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curbuf = (curbuf + 1) & (pipe->buffers - 1);
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pipe->curbuf = curbuf;
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pipe->nrbufs = --bufs;
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do_wakeup = 1;
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}
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total_len -= chars;
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if (!total_len)
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break; /* common path: read succeeded */
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}
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if (bufs) /* More to do? */
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continue;
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if (!pipe->writers)
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break;
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if (!pipe->waiting_writers) {
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/* syscall merging: Usually we must not sleep
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* if O_NONBLOCK is set, or if we got some data.
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* But if a writer sleeps in kernel space, then
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* we can wait for that data without violating POSIX.
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*/
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if (ret)
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break;
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if (filp->f_flags & O_NONBLOCK) {
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ret = -EAGAIN;
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break;
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}
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}
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if (signal_pending(current)) {
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if (!ret)
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ret = -ERESTARTSYS;
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break;
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}
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if (do_wakeup) {
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wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
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kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
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}
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pipe_wait(pipe);
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}
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__pipe_unlock(pipe);
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/* Signal writers asynchronously that there is more room. */
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if (do_wakeup) {
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wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
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kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
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}
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if (ret > 0)
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file_accessed(filp);
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return ret;
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}
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static inline int is_packetized(struct file *file)
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{
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return (file->f_flags & O_DIRECT) != 0;
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}
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static ssize_t
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pipe_write(struct kiocb *iocb, struct iov_iter *from)
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{
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struct file *filp = iocb->ki_filp;
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struct pipe_inode_info *pipe = filp->private_data;
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ssize_t ret = 0;
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int do_wakeup = 0;
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size_t total_len = iov_iter_count(from);
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ssize_t chars;
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/* Null write succeeds. */
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if (unlikely(total_len == 0))
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return 0;
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__pipe_lock(pipe);
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if (!pipe->readers) {
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send_sig(SIGPIPE, current, 0);
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ret = -EPIPE;
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goto out;
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}
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/* We try to merge small writes */
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chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
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if (pipe->nrbufs && chars != 0) {
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int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
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(pipe->buffers - 1);
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struct pipe_buffer *buf = pipe->bufs + lastbuf;
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int offset = buf->offset + buf->len;
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if (pipe_buf_can_merge(buf) && offset + chars <= PAGE_SIZE) {
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ret = pipe_buf_confirm(pipe, buf);
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if (ret)
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goto out;
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ret = copy_page_from_iter(buf->page, offset, chars, from);
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if (unlikely(ret < chars)) {
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ret = -EFAULT;
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goto out;
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}
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do_wakeup = 1;
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buf->len += ret;
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if (!iov_iter_count(from))
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goto out;
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}
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}
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for (;;) {
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int bufs;
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if (!pipe->readers) {
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send_sig(SIGPIPE, current, 0);
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if (!ret)
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ret = -EPIPE;
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break;
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}
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bufs = pipe->nrbufs;
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if (bufs < pipe->buffers) {
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int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
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struct pipe_buffer *buf = pipe->bufs + newbuf;
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struct page *page = pipe->tmp_page;
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int copied;
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if (!page) {
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page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
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if (unlikely(!page)) {
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ret = ret ? : -ENOMEM;
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break;
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}
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pipe->tmp_page = page;
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}
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/* Always wake up, even if the copy fails. Otherwise
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* we lock up (O_NONBLOCK-)readers that sleep due to
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* syscall merging.
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* FIXME! Is this really true?
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*/
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do_wakeup = 1;
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copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
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if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
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if (!ret)
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ret = -EFAULT;
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break;
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}
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ret += copied;
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|
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/* Insert it into the buffer array */
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buf->page = page;
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buf->ops = &anon_pipe_buf_ops;
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buf->offset = 0;
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buf->len = copied;
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buf->flags = 0;
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if (is_packetized(filp)) {
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buf->ops = &packet_pipe_buf_ops;
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buf->flags = PIPE_BUF_FLAG_PACKET;
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}
|
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pipe->nrbufs = ++bufs;
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pipe->tmp_page = NULL;
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|
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if (!iov_iter_count(from))
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break;
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}
|
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if (bufs < pipe->buffers)
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continue;
|
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if (filp->f_flags & O_NONBLOCK) {
|
|
if (!ret)
|
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ret = -EAGAIN;
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break;
|
|
}
|
|
if (signal_pending(current)) {
|
|
if (!ret)
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ret = -ERESTARTSYS;
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|
break;
|
|
}
|
|
if (do_wakeup) {
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|
wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLRDNORM);
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|
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
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|
do_wakeup = 0;
|
|
}
|
|
pipe->waiting_writers++;
|
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pipe_wait(pipe);
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pipe->waiting_writers--;
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}
|
|
out:
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|
__pipe_unlock(pipe);
|
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if (do_wakeup) {
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wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLRDNORM);
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|
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
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}
|
|
if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
|
|
int err = file_update_time(filp);
|
|
if (err)
|
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ret = err;
|
|
sb_end_write(file_inode(filp)->i_sb);
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
|
|
{
|
|
struct pipe_inode_info *pipe = filp->private_data;
|
|
int count, buf, nrbufs;
|
|
|
|
switch (cmd) {
|
|
case FIONREAD:
|
|
__pipe_lock(pipe);
|
|
count = 0;
|
|
buf = pipe->curbuf;
|
|
nrbufs = pipe->nrbufs;
|
|
while (--nrbufs >= 0) {
|
|
count += pipe->bufs[buf].len;
|
|
buf = (buf+1) & (pipe->buffers - 1);
|
|
}
|
|
__pipe_unlock(pipe);
|
|
|
|
return put_user(count, (int __user *)arg);
|
|
default:
|
|
return -ENOIOCTLCMD;
|
|
}
|
|
}
|
|
|
|
/* No kernel lock held - fine */
|
|
static __poll_t
|
|
pipe_poll(struct file *filp, poll_table *wait)
|
|
{
|
|
__poll_t mask;
|
|
struct pipe_inode_info *pipe = filp->private_data;
|
|
int nrbufs;
|
|
|
|
poll_wait(filp, &pipe->wait, wait);
|
|
|
|
/* Reading only -- no need for acquiring the semaphore. */
|
|
nrbufs = pipe->nrbufs;
|
|
mask = 0;
|
|
if (filp->f_mode & FMODE_READ) {
|
|
mask = (nrbufs > 0) ? EPOLLIN | EPOLLRDNORM : 0;
|
|
if (!pipe->writers && filp->f_version != pipe->w_counter)
|
|
mask |= EPOLLHUP;
|
|
}
|
|
|
|
if (filp->f_mode & FMODE_WRITE) {
|
|
mask |= (nrbufs < pipe->buffers) ? EPOLLOUT | EPOLLWRNORM : 0;
|
|
/*
|
|
* Most Unices do not set EPOLLERR for FIFOs but on Linux they
|
|
* behave exactly like pipes for poll().
|
|
*/
|
|
if (!pipe->readers)
|
|
mask |= EPOLLERR;
|
|
}
|
|
|
|
return mask;
|
|
}
|
|
|
|
static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
|
|
{
|
|
int kill = 0;
|
|
|
|
spin_lock(&inode->i_lock);
|
|
if (!--pipe->files) {
|
|
inode->i_pipe = NULL;
|
|
kill = 1;
|
|
}
|
|
spin_unlock(&inode->i_lock);
|
|
|
|
if (kill)
|
|
free_pipe_info(pipe);
|
|
}
|
|
|
|
static int
|
|
pipe_release(struct inode *inode, struct file *file)
|
|
{
|
|
struct pipe_inode_info *pipe = file->private_data;
|
|
|
|
__pipe_lock(pipe);
|
|
if (file->f_mode & FMODE_READ)
|
|
pipe->readers--;
|
|
if (file->f_mode & FMODE_WRITE)
|
|
pipe->writers--;
|
|
|
|
if (pipe->readers || pipe->writers) {
|
|
wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLOUT | EPOLLRDNORM | EPOLLWRNORM | EPOLLERR | EPOLLHUP);
|
|
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
|
|
kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
|
|
}
|
|
__pipe_unlock(pipe);
|
|
|
|
put_pipe_info(inode, pipe);
|
|
return 0;
|
|
}
|
|
|
|
static int
|
|
pipe_fasync(int fd, struct file *filp, int on)
|
|
{
|
|
struct pipe_inode_info *pipe = filp->private_data;
|
|
int retval = 0;
|
|
|
|
__pipe_lock(pipe);
|
|
if (filp->f_mode & FMODE_READ)
|
|
retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
|
|
if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
|
|
retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
|
|
if (retval < 0 && (filp->f_mode & FMODE_READ))
|
|
/* this can happen only if on == T */
|
|
fasync_helper(-1, filp, 0, &pipe->fasync_readers);
|
|
}
|
|
__pipe_unlock(pipe);
|
|
return retval;
|
|
}
|
|
|
|
static unsigned long account_pipe_buffers(struct user_struct *user,
|
|
unsigned long old, unsigned long new)
|
|
{
|
|
return atomic_long_add_return(new - old, &user->pipe_bufs);
|
|
}
|
|
|
|
static bool too_many_pipe_buffers_soft(unsigned long user_bufs)
|
|
{
|
|
unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
|
|
|
|
return soft_limit && user_bufs > soft_limit;
|
|
}
|
|
|
|
static bool too_many_pipe_buffers_hard(unsigned long user_bufs)
|
|
{
|
|
unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
|
|
|
|
return hard_limit && user_bufs > hard_limit;
|
|
}
|
|
|
|
static bool is_unprivileged_user(void)
|
|
{
|
|
return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
|
|
}
|
|
|
|
struct pipe_inode_info *alloc_pipe_info(void)
|
|
{
|
|
struct pipe_inode_info *pipe;
|
|
unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
|
|
struct user_struct *user = get_current_user();
|
|
unsigned long user_bufs;
|
|
unsigned int max_size = READ_ONCE(pipe_max_size);
|
|
|
|
pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
|
|
if (pipe == NULL)
|
|
goto out_free_uid;
|
|
|
|
if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
|
|
pipe_bufs = max_size >> PAGE_SHIFT;
|
|
|
|
user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
|
|
|
|
if (too_many_pipe_buffers_soft(user_bufs) && is_unprivileged_user()) {
|
|
user_bufs = account_pipe_buffers(user, pipe_bufs, 1);
|
|
pipe_bufs = 1;
|
|
}
|
|
|
|
if (too_many_pipe_buffers_hard(user_bufs) && is_unprivileged_user())
|
|
goto out_revert_acct;
|
|
|
|
pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
|
|
GFP_KERNEL_ACCOUNT);
|
|
|
|
if (pipe->bufs) {
|
|
init_waitqueue_head(&pipe->wait);
|
|
pipe->r_counter = pipe->w_counter = 1;
|
|
pipe->buffers = pipe_bufs;
|
|
pipe->user = user;
|
|
mutex_init(&pipe->mutex);
|
|
return pipe;
|
|
}
|
|
|
|
out_revert_acct:
|
|
(void) account_pipe_buffers(user, pipe_bufs, 0);
|
|
kfree(pipe);
|
|
out_free_uid:
|
|
free_uid(user);
|
|
return NULL;
|
|
}
|
|
|
|
void free_pipe_info(struct pipe_inode_info *pipe)
|
|
{
|
|
int i;
|
|
|
|
(void) account_pipe_buffers(pipe->user, pipe->buffers, 0);
|
|
free_uid(pipe->user);
|
|
for (i = 0; i < pipe->buffers; i++) {
|
|
struct pipe_buffer *buf = pipe->bufs + i;
|
|
if (buf->ops)
|
|
pipe_buf_release(pipe, buf);
|
|
}
|
|
if (pipe->tmp_page)
|
|
__free_page(pipe->tmp_page);
|
|
kfree(pipe->bufs);
|
|
kfree(pipe);
|
|
}
|
|
|
|
static struct vfsmount *pipe_mnt __read_mostly;
|
|
|
|
/*
|
|
* pipefs_dname() is called from d_path().
|
|
*/
|
|
static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
|
|
{
|
|
return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
|
|
d_inode(dentry)->i_ino);
|
|
}
|
|
|
|
static const struct dentry_operations pipefs_dentry_operations = {
|
|
.d_dname = pipefs_dname,
|
|
};
|
|
|
|
static struct inode * get_pipe_inode(void)
|
|
{
|
|
struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
|
|
struct pipe_inode_info *pipe;
|
|
|
|
if (!inode)
|
|
goto fail_inode;
|
|
|
|
inode->i_ino = get_next_ino();
|
|
|
|
pipe = alloc_pipe_info();
|
|
if (!pipe)
|
|
goto fail_iput;
|
|
|
|
inode->i_pipe = pipe;
|
|
pipe->files = 2;
|
|
pipe->readers = pipe->writers = 1;
|
|
inode->i_fop = &pipefifo_fops;
|
|
|
|
/*
|
|
* Mark the inode dirty from the very beginning,
|
|
* that way it will never be moved to the dirty
|
|
* list because "mark_inode_dirty()" will think
|
|
* that it already _is_ on the dirty list.
|
|
*/
|
|
inode->i_state = I_DIRTY;
|
|
inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
|
|
inode->i_uid = current_fsuid();
|
|
inode->i_gid = current_fsgid();
|
|
inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
|
|
|
|
return inode;
|
|
|
|
fail_iput:
|
|
iput(inode);
|
|
|
|
fail_inode:
|
|
return NULL;
|
|
}
|
|
|
|
int create_pipe_files(struct file **res, int flags)
|
|
{
|
|
struct inode *inode = get_pipe_inode();
|
|
struct file *f;
|
|
|
|
if (!inode)
|
|
return -ENFILE;
|
|
|
|
f = alloc_file_pseudo(inode, pipe_mnt, "",
|
|
O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
|
|
&pipefifo_fops);
|
|
if (IS_ERR(f)) {
|
|
free_pipe_info(inode->i_pipe);
|
|
iput(inode);
|
|
return PTR_ERR(f);
|
|
}
|
|
|
|
f->private_data = inode->i_pipe;
|
|
|
|
res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
|
|
&pipefifo_fops);
|
|
if (IS_ERR(res[0])) {
|
|
put_pipe_info(inode, inode->i_pipe);
|
|
fput(f);
|
|
return PTR_ERR(res[0]);
|
|
}
|
|
res[0]->private_data = inode->i_pipe;
|
|
res[1] = f;
|
|
return 0;
|
|
}
|
|
|
|
static int __do_pipe_flags(int *fd, struct file **files, int flags)
|
|
{
|
|
int error;
|
|
int fdw, fdr;
|
|
|
|
if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
|
|
return -EINVAL;
|
|
|
|
error = create_pipe_files(files, flags);
|
|
if (error)
|
|
return error;
|
|
|
|
error = get_unused_fd_flags(flags);
|
|
if (error < 0)
|
|
goto err_read_pipe;
|
|
fdr = error;
|
|
|
|
error = get_unused_fd_flags(flags);
|
|
if (error < 0)
|
|
goto err_fdr;
|
|
fdw = error;
|
|
|
|
audit_fd_pair(fdr, fdw);
|
|
fd[0] = fdr;
|
|
fd[1] = fdw;
|
|
return 0;
|
|
|
|
err_fdr:
|
|
put_unused_fd(fdr);
|
|
err_read_pipe:
|
|
fput(files[0]);
|
|
fput(files[1]);
|
|
return error;
|
|
}
|
|
|
|
int do_pipe_flags(int *fd, int flags)
|
|
{
|
|
struct file *files[2];
|
|
int error = __do_pipe_flags(fd, files, flags);
|
|
if (!error) {
|
|
fd_install(fd[0], files[0]);
|
|
fd_install(fd[1], files[1]);
|
|
}
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* sys_pipe() is the normal C calling standard for creating
|
|
* a pipe. It's not the way Unix traditionally does this, though.
|
|
*/
|
|
static int do_pipe2(int __user *fildes, int flags)
|
|
{
|
|
struct file *files[2];
|
|
int fd[2];
|
|
int error;
|
|
|
|
error = __do_pipe_flags(fd, files, flags);
|
|
if (!error) {
|
|
if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
|
|
fput(files[0]);
|
|
fput(files[1]);
|
|
put_unused_fd(fd[0]);
|
|
put_unused_fd(fd[1]);
|
|
error = -EFAULT;
|
|
} else {
|
|
fd_install(fd[0], files[0]);
|
|
fd_install(fd[1], files[1]);
|
|
}
|
|
}
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
|
|
{
|
|
return do_pipe2(fildes, flags);
|
|
}
|
|
|
|
SYSCALL_DEFINE1(pipe, int __user *, fildes)
|
|
{
|
|
return do_pipe2(fildes, 0);
|
|
}
|
|
|
|
static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
|
|
{
|
|
int cur = *cnt;
|
|
|
|
while (cur == *cnt) {
|
|
pipe_wait(pipe);
|
|
if (signal_pending(current))
|
|
break;
|
|
}
|
|
return cur == *cnt ? -ERESTARTSYS : 0;
|
|
}
|
|
|
|
static void wake_up_partner(struct pipe_inode_info *pipe)
|
|
{
|
|
wake_up_interruptible(&pipe->wait);
|
|
}
|
|
|
|
static int fifo_open(struct inode *inode, struct file *filp)
|
|
{
|
|
struct pipe_inode_info *pipe;
|
|
bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
|
|
int ret;
|
|
|
|
filp->f_version = 0;
|
|
|
|
spin_lock(&inode->i_lock);
|
|
if (inode->i_pipe) {
|
|
pipe = inode->i_pipe;
|
|
pipe->files++;
|
|
spin_unlock(&inode->i_lock);
|
|
} else {
|
|
spin_unlock(&inode->i_lock);
|
|
pipe = alloc_pipe_info();
|
|
if (!pipe)
|
|
return -ENOMEM;
|
|
pipe->files = 1;
|
|
spin_lock(&inode->i_lock);
|
|
if (unlikely(inode->i_pipe)) {
|
|
inode->i_pipe->files++;
|
|
spin_unlock(&inode->i_lock);
|
|
free_pipe_info(pipe);
|
|
pipe = inode->i_pipe;
|
|
} else {
|
|
inode->i_pipe = pipe;
|
|
spin_unlock(&inode->i_lock);
|
|
}
|
|
}
|
|
filp->private_data = pipe;
|
|
/* OK, we have a pipe and it's pinned down */
|
|
|
|
__pipe_lock(pipe);
|
|
|
|
/* We can only do regular read/write on fifos */
|
|
filp->f_mode &= (FMODE_READ | FMODE_WRITE);
|
|
|
|
switch (filp->f_mode) {
|
|
case FMODE_READ:
|
|
/*
|
|
* O_RDONLY
|
|
* POSIX.1 says that O_NONBLOCK means return with the FIFO
|
|
* opened, even when there is no process writing the FIFO.
|
|
*/
|
|
pipe->r_counter++;
|
|
if (pipe->readers++ == 0)
|
|
wake_up_partner(pipe);
|
|
|
|
if (!is_pipe && !pipe->writers) {
|
|
if ((filp->f_flags & O_NONBLOCK)) {
|
|
/* suppress EPOLLHUP until we have
|
|
* seen a writer */
|
|
filp->f_version = pipe->w_counter;
|
|
} else {
|
|
if (wait_for_partner(pipe, &pipe->w_counter))
|
|
goto err_rd;
|
|
}
|
|
}
|
|
break;
|
|
|
|
case FMODE_WRITE:
|
|
/*
|
|
* O_WRONLY
|
|
* POSIX.1 says that O_NONBLOCK means return -1 with
|
|
* errno=ENXIO when there is no process reading the FIFO.
|
|
*/
|
|
ret = -ENXIO;
|
|
if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
|
|
goto err;
|
|
|
|
pipe->w_counter++;
|
|
if (!pipe->writers++)
|
|
wake_up_partner(pipe);
|
|
|
|
if (!is_pipe && !pipe->readers) {
|
|
if (wait_for_partner(pipe, &pipe->r_counter))
|
|
goto err_wr;
|
|
}
|
|
break;
|
|
|
|
case FMODE_READ | FMODE_WRITE:
|
|
/*
|
|
* O_RDWR
|
|
* POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
|
|
* This implementation will NEVER block on a O_RDWR open, since
|
|
* the process can at least talk to itself.
|
|
*/
|
|
|
|
pipe->readers++;
|
|
pipe->writers++;
|
|
pipe->r_counter++;
|
|
pipe->w_counter++;
|
|
if (pipe->readers == 1 || pipe->writers == 1)
|
|
wake_up_partner(pipe);
|
|
break;
|
|
|
|
default:
|
|
ret = -EINVAL;
|
|
goto err;
|
|
}
|
|
|
|
/* Ok! */
|
|
__pipe_unlock(pipe);
|
|
return 0;
|
|
|
|
err_rd:
|
|
if (!--pipe->readers)
|
|
wake_up_interruptible(&pipe->wait);
|
|
ret = -ERESTARTSYS;
|
|
goto err;
|
|
|
|
err_wr:
|
|
if (!--pipe->writers)
|
|
wake_up_interruptible(&pipe->wait);
|
|
ret = -ERESTARTSYS;
|
|
goto err;
|
|
|
|
err:
|
|
__pipe_unlock(pipe);
|
|
|
|
put_pipe_info(inode, pipe);
|
|
return ret;
|
|
}
|
|
|
|
const struct file_operations pipefifo_fops = {
|
|
.open = fifo_open,
|
|
.llseek = no_llseek,
|
|
.read_iter = pipe_read,
|
|
.write_iter = pipe_write,
|
|
.poll = pipe_poll,
|
|
.unlocked_ioctl = pipe_ioctl,
|
|
.release = pipe_release,
|
|
.fasync = pipe_fasync,
|
|
};
|
|
|
|
/*
|
|
* Currently we rely on the pipe array holding a power-of-2 number
|
|
* of pages. Returns 0 on error.
|
|
*/
|
|
unsigned int round_pipe_size(unsigned long size)
|
|
{
|
|
if (size > (1U << 31))
|
|
return 0;
|
|
|
|
/* Minimum pipe size, as required by POSIX */
|
|
if (size < PAGE_SIZE)
|
|
return PAGE_SIZE;
|
|
|
|
return roundup_pow_of_two(size);
|
|
}
|
|
|
|
/*
|
|
* Allocate a new array of pipe buffers and copy the info over. Returns the
|
|
* pipe size if successful, or return -ERROR on error.
|
|
*/
|
|
static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
|
|
{
|
|
struct pipe_buffer *bufs;
|
|
unsigned int size, nr_pages;
|
|
unsigned long user_bufs;
|
|
long ret = 0;
|
|
|
|
size = round_pipe_size(arg);
|
|
nr_pages = size >> PAGE_SHIFT;
|
|
|
|
if (!nr_pages)
|
|
return -EINVAL;
|
|
|
|
/*
|
|
* If trying to increase the pipe capacity, check that an
|
|
* unprivileged user is not trying to exceed various limits
|
|
* (soft limit check here, hard limit check just below).
|
|
* Decreasing the pipe capacity is always permitted, even
|
|
* if the user is currently over a limit.
|
|
*/
|
|
if (nr_pages > pipe->buffers &&
|
|
size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
|
|
return -EPERM;
|
|
|
|
user_bufs = account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
|
|
|
|
if (nr_pages > pipe->buffers &&
|
|
(too_many_pipe_buffers_hard(user_bufs) ||
|
|
too_many_pipe_buffers_soft(user_bufs)) &&
|
|
is_unprivileged_user()) {
|
|
ret = -EPERM;
|
|
goto out_revert_acct;
|
|
}
|
|
|
|
/*
|
|
* We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
|
|
* expect a lot of shrink+grow operations, just free and allocate
|
|
* again like we would do for growing. If the pipe currently
|
|
* contains more buffers than arg, then return busy.
|
|
*/
|
|
if (nr_pages < pipe->nrbufs) {
|
|
ret = -EBUSY;
|
|
goto out_revert_acct;
|
|
}
|
|
|
|
bufs = kcalloc(nr_pages, sizeof(*bufs),
|
|
GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
|
|
if (unlikely(!bufs)) {
|
|
ret = -ENOMEM;
|
|
goto out_revert_acct;
|
|
}
|
|
|
|
/*
|
|
* The pipe array wraps around, so just start the new one at zero
|
|
* and adjust the indexes.
|
|
*/
|
|
if (pipe->nrbufs) {
|
|
unsigned int tail;
|
|
unsigned int head;
|
|
|
|
tail = pipe->curbuf + pipe->nrbufs;
|
|
if (tail < pipe->buffers)
|
|
tail = 0;
|
|
else
|
|
tail &= (pipe->buffers - 1);
|
|
|
|
head = pipe->nrbufs - tail;
|
|
if (head)
|
|
memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
|
|
if (tail)
|
|
memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
|
|
}
|
|
|
|
pipe->curbuf = 0;
|
|
kfree(pipe->bufs);
|
|
pipe->bufs = bufs;
|
|
pipe->buffers = nr_pages;
|
|
return nr_pages * PAGE_SIZE;
|
|
|
|
out_revert_acct:
|
|
(void) account_pipe_buffers(pipe->user, nr_pages, pipe->buffers);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
|
|
* location, so checking ->i_pipe is not enough to verify that this is a
|
|
* pipe.
|
|
*/
|
|
struct pipe_inode_info *get_pipe_info(struct file *file)
|
|
{
|
|
return file->f_op == &pipefifo_fops ? file->private_data : NULL;
|
|
}
|
|
|
|
long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
|
|
{
|
|
struct pipe_inode_info *pipe;
|
|
long ret;
|
|
|
|
pipe = get_pipe_info(file);
|
|
if (!pipe)
|
|
return -EBADF;
|
|
|
|
__pipe_lock(pipe);
|
|
|
|
switch (cmd) {
|
|
case F_SETPIPE_SZ:
|
|
ret = pipe_set_size(pipe, arg);
|
|
break;
|
|
case F_GETPIPE_SZ:
|
|
ret = pipe->buffers * PAGE_SIZE;
|
|
break;
|
|
default:
|
|
ret = -EINVAL;
|
|
break;
|
|
}
|
|
|
|
__pipe_unlock(pipe);
|
|
return ret;
|
|
}
|
|
|
|
static const struct super_operations pipefs_ops = {
|
|
.destroy_inode = free_inode_nonrcu,
|
|
.statfs = simple_statfs,
|
|
};
|
|
|
|
/*
|
|
* pipefs should _never_ be mounted by userland - too much of security hassle,
|
|
* no real gain from having the whole whorehouse mounted. So we don't need
|
|
* any operations on the root directory. However, we need a non-trivial
|
|
* d_name - pipe: will go nicely and kill the special-casing in procfs.
|
|
*/
|
|
static struct dentry *pipefs_mount(struct file_system_type *fs_type,
|
|
int flags, const char *dev_name, void *data)
|
|
{
|
|
return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
|
|
&pipefs_dentry_operations, PIPEFS_MAGIC);
|
|
}
|
|
|
|
static struct file_system_type pipe_fs_type = {
|
|
.name = "pipefs",
|
|
.mount = pipefs_mount,
|
|
.kill_sb = kill_anon_super,
|
|
};
|
|
|
|
static int __init init_pipe_fs(void)
|
|
{
|
|
int err = register_filesystem(&pipe_fs_type);
|
|
|
|
if (!err) {
|
|
pipe_mnt = kern_mount(&pipe_fs_type);
|
|
if (IS_ERR(pipe_mnt)) {
|
|
err = PTR_ERR(pipe_mnt);
|
|
unregister_filesystem(&pipe_fs_type);
|
|
}
|
|
}
|
|
return err;
|
|
}
|
|
|
|
fs_initcall(init_pipe_fs);
|