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On no-so-small systems, it is possible for a single process to cause an OOM condition by filling large pipes with data that are never read. A typical process filling 4000 pipes with 1 MB of data will use 4 GB of memory. On small systems it may be tricky to set the pipe max size to prevent this from happening. This patch makes it possible to enforce a per-user soft limit above which new pipes will be limited to a single page, effectively limiting them to 4 kB each, as well as a hard limit above which no new pipes may be created for this user. This has the effect of protecting the system against memory abuse without hurting other users, and still allowing pipes to work correctly though with less data at once. The limit are controlled by two new sysctls : pipe-user-pages-soft, and pipe-user-pages-hard. Both may be disabled by setting them to zero. The default soft limit allows the default number of FDs per process (1024) to create pipes of the default size (64kB), thus reaching a limit of 64MB before starting to create only smaller pipes. With 256 processes limited to 1024 FDs each, this results in 1024*64kB + (256*1024 - 1024) * 4kB = 1084 MB of memory allocated for a user. The hard limit is disabled by default to avoid breaking existing applications that make intensive use of pipes (eg: for splicing). Reported-by: socketpair@gmail.com Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Mitigates: CVE-2013-4312 (Linux 2.0+) Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Willy Tarreau <w@1wt.eu> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
154 lines
5.1 KiB
C
154 lines
5.1 KiB
C
#ifndef _LINUX_PIPE_FS_I_H
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#define _LINUX_PIPE_FS_I_H
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#define PIPE_DEF_BUFFERS 16
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#define PIPE_BUF_FLAG_LRU 0x01 /* page is on the LRU */
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#define PIPE_BUF_FLAG_ATOMIC 0x02 /* was atomically mapped */
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#define PIPE_BUF_FLAG_GIFT 0x04 /* page is a gift */
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#define PIPE_BUF_FLAG_PACKET 0x08 /* read() as a packet */
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/**
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* struct pipe_buffer - a linux kernel pipe buffer
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* @page: the page containing the data for the pipe buffer
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* @offset: offset of data inside the @page
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* @len: length of data inside the @page
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* @ops: operations associated with this buffer. See @pipe_buf_operations.
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* @flags: pipe buffer flags. See above.
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* @private: private data owned by the ops.
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**/
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struct pipe_buffer {
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struct page *page;
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unsigned int offset, len;
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const struct pipe_buf_operations *ops;
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unsigned int flags;
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unsigned long private;
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};
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/**
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* struct pipe_inode_info - a linux kernel pipe
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* @mutex: mutex protecting the whole thing
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* @wait: reader/writer wait point in case of empty/full pipe
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* @nrbufs: the number of non-empty pipe buffers in this pipe
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* @buffers: total number of buffers (should be a power of 2)
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* @curbuf: the current pipe buffer entry
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* @tmp_page: cached released page
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* @readers: number of current readers of this pipe
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* @writers: number of current writers of this pipe
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* @files: number of struct file referring this pipe (protected by ->i_lock)
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* @waiting_writers: number of writers blocked waiting for room
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* @r_counter: reader counter
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* @w_counter: writer counter
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* @fasync_readers: reader side fasync
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* @fasync_writers: writer side fasync
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* @bufs: the circular array of pipe buffers
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* @user: the user who created this pipe
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**/
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struct pipe_inode_info {
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struct mutex mutex;
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wait_queue_head_t wait;
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unsigned int nrbufs, curbuf, buffers;
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unsigned int readers;
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unsigned int writers;
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unsigned int files;
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unsigned int waiting_writers;
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unsigned int r_counter;
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unsigned int w_counter;
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struct page *tmp_page;
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struct fasync_struct *fasync_readers;
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struct fasync_struct *fasync_writers;
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struct pipe_buffer *bufs;
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struct user_struct *user;
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};
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/*
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* Note on the nesting of these functions:
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*
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* ->confirm()
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* ->steal()
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* ...
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* ->map()
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* ...
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* ->unmap()
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*
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* That is, ->map() must be called on a confirmed buffer,
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* same goes for ->steal(). See below for the meaning of each
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* operation. Also see kerneldoc in fs/pipe.c for the pipe
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* and generic variants of these hooks.
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*/
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struct pipe_buf_operations {
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/*
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* This is set to 1, if the generic pipe read/write may coalesce
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* data into an existing buffer. If this is set to 0, a new pipe
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* page segment is always used for new data.
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*/
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int can_merge;
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/*
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* ->confirm() verifies that the data in the pipe buffer is there
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* and that the contents are good. If the pages in the pipe belong
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* to a file system, we may need to wait for IO completion in this
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* hook. Returns 0 for good, or a negative error value in case of
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* error.
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*/
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int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
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/*
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* When the contents of this pipe buffer has been completely
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* consumed by a reader, ->release() is called.
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*/
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void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
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/*
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* Attempt to take ownership of the pipe buffer and its contents.
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* ->steal() returns 0 for success, in which case the contents
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* of the pipe (the buf->page) is locked and now completely owned
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* by the caller. The page may then be transferred to a different
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* mapping, the most often used case is insertion into different
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* file address space cache.
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*/
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int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
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/*
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* Get a reference to the pipe buffer.
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*/
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void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
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};
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/* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
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memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
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#define PIPE_SIZE PAGE_SIZE
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/* Pipe lock and unlock operations */
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void pipe_lock(struct pipe_inode_info *);
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void pipe_unlock(struct pipe_inode_info *);
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void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
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extern unsigned int pipe_max_size, pipe_min_size;
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extern unsigned long pipe_user_pages_hard;
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extern unsigned long pipe_user_pages_soft;
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int pipe_proc_fn(struct ctl_table *, int, void __user *, size_t *, loff_t *);
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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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struct pipe_inode_info *alloc_pipe_info(void);
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void free_pipe_info(struct pipe_inode_info *);
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/* Generic pipe buffer ops functions */
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void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
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int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
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int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
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void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
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extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
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/* for F_SETPIPE_SZ and F_GETPIPE_SZ */
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long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
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struct pipe_inode_info *get_pipe_info(struct file *file);
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int create_pipe_files(struct file **, int);
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#endif
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