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authorMiklos Szeredi <mszeredi@suse.cz>2009-04-06 17:41:00 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-07 08:34:46 -0700
commit7bfac9ecf0585962fe13584f5cf526d8c8e76f17 (patch)
tree7e7c98311bb0d4c26e514b337216bbc8ade8d078 /fs/splice.c
parent612392307cb09e49051225092cbbd7049bd8db93 (diff)
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>
Diffstat (limited to 'fs/splice.c')
-rw-r--r--fs/splice.c25
1 files changed, 20 insertions, 5 deletions
diff --git a/fs/splice.c b/fs/splice.c
index dd727d43e5b7..c18aa7e03e2b 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;