From: Miklos Szeredi Date: Tue, 7 Apr 2009 16:25:02 +0000 (+0000) Subject: splice: fix deadlock in splicing to file X-Git-Tag: v2.6.28.10~59 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=af85932753d252ac37a01b00ab857197ee0bac16;p=thirdparty%2Fkernel%2Fstable.git splice: fix deadlock in splicing to file upstream commit: 7bfac9ecf0585962fe13584f5cf526d8c8e76f17 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 Signed-off-by: Linus Torvalds Signed-off-by: Chris Wright Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c index e2570a3bc2b20..3f39a2a16db9c 100644 --- a/fs/ocfs2/file.c +++ b/fs/ocfs2/file.c @@ -1943,7 +1943,7 @@ 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) { @@ -1958,12 +1958,16 @@ 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 1eaef06442b6d..8074867696f6c 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -735,10 +735,19 @@ 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; } @@ -829,11 +838,17 @@ 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;