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author | Miklos Szeredi <mszeredi@suse.cz> | 2009-04-06 15:41:00 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-04-07 15:34:46 (GMT) |
commit | 7bfac9ecf0585962fe13584f5cf526d8c8e76f17 (patch) | |
tree | 7e7c98311bb0d4c26e514b337216bbc8ade8d078 | |
parent | 612392307cb09e49051225092cbbd7049bd8db93 (diff) | |
download | linux-fsl-qoriq-7bfac9ecf0585962fe13584f5cf526d8c8e76f17.tar.xz |
splice: fix deadlock in splicing to file
There's a possible deadlock in generic_file_splice_write(),
splice_from_pipe() and ocfs2_file_splice_write():
- task A calls generic_file_splice_write()
- this calls inode_double_lock(), which locks i_mutex on both
pipe->inode and target inode
- ordering depends on inode pointers, can happen that pipe->inode is
locked first
- __splice_from_pipe() needs more data, calls pipe_wait()
- this releases lock on pipe->inode, goes to interruptible sleep
- task B calls generic_file_splice_write(), similarly to the first
- this locks pipe->inode, then tries to lock inode, but that is
already held by task A
- task A is interrupted, it tries to lock pipe->inode, but fails, as
it is already held by task B
- ABBA deadlock
Fix this by explicitly ordering locks: the outer lock must be on
target inode and the inner lock (which is later unlocked and relocked)
must be on pipe->inode. This is OK, pipe inodes and target inodes
form two nonoverlapping sets, generic_file_splice_write() and friends
are not called with a target which is a pipe.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Acked-by: Mark Fasheh <mfasheh@suse.com>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | fs/ocfs2/file.c | 8 | ||||
-rw-r--r-- | fs/splice.c | 25 |
2 files changed, 26 insertions, 7 deletions
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c index a5887df..8672b95 100644 --- a/fs/ocfs2/file.c +++ b/fs/ocfs2/file.c @@ -1926,7 +1926,7 @@ static ssize_t ocfs2_file_splice_write(struct pipe_inode_info *pipe, out->f_path.dentry->d_name.len, out->f_path.dentry->d_name.name); - inode_double_lock(inode, pipe->inode); + mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT); ret = ocfs2_rw_lock(inode, 1); if (ret < 0) { @@ -1941,12 +1941,16 @@ static ssize_t ocfs2_file_splice_write(struct pipe_inode_info *pipe, goto out_unlock; } + if (pipe->inode) + mutex_lock_nested(&pipe->inode->i_mutex, I_MUTEX_CHILD); ret = generic_file_splice_write_nolock(pipe, out, ppos, len, flags); + if (pipe->inode) + mutex_unlock(&pipe->inode->i_mutex); out_unlock: ocfs2_rw_unlock(inode, 1); out: - inode_double_unlock(inode, pipe->inode); + mutex_unlock(&inode->i_mutex); mlog_exit(ret); return ret; diff --git a/fs/splice.c b/fs/splice.c index dd727d4..c18aa7e 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -737,10 +737,19 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out, * ->write_end. Most of the time, these expect i_mutex to * be held. Since this may result in an ABBA deadlock with * pipe->inode, we have to order lock acquiry here. + * + * Outer lock must be inode->i_mutex, as pipe_wait() will + * release and reacquire pipe->inode->i_mutex, AND inode must + * never be a pipe. */ - inode_double_lock(inode, pipe->inode); + WARN_ON(S_ISFIFO(inode->i_mode)); + mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT); + if (pipe->inode) + mutex_lock_nested(&pipe->inode->i_mutex, I_MUTEX_CHILD); ret = __splice_from_pipe(pipe, &sd, actor); - inode_double_unlock(inode, pipe->inode); + if (pipe->inode) + mutex_unlock(&pipe->inode->i_mutex); + mutex_unlock(&inode->i_mutex); return ret; } @@ -831,11 +840,17 @@ generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out, }; ssize_t ret; - inode_double_lock(inode, pipe->inode); + WARN_ON(S_ISFIFO(inode->i_mode)); + mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT); ret = file_remove_suid(out); - if (likely(!ret)) + if (likely(!ret)) { + if (pipe->inode) + mutex_lock_nested(&pipe->inode->i_mutex, I_MUTEX_CHILD); ret = __splice_from_pipe(pipe, &sd, pipe_to_file); - inode_double_unlock(inode, pipe->inode); + if (pipe->inode) + mutex_unlock(&pipe->inode->i_mutex); + } + mutex_unlock(&inode->i_mutex); if (ret > 0) { unsigned long nr_pages; |