From 7bfac9ecf0585962fe13584f5cf526d8c8e76f17 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Mon, 6 Apr 2009 17:41:00 +0200 Subject: 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 Acked-by: Mark Fasheh Acked-by: Jens Axboe Cc: stable@kernel.org Signed-off-by: Linus Torvalds --- fs/ocfs2/file.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'fs/ocfs2') diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c index a5887df2cd8..8672b953603 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; -- cgit v1.2.3-18-g5258