[Devel] [PATCH rh7 1/2] ms/fuse: Don't access pipe->buffers without pipe_lock()

[Andrey Ryabinin]

fuse_dev_splice_write() reads pipe->buffers to determine the size of
'bufs' array before taking the pipe_lock(). This is not safe as
another thread might change the 'pipe->buffers' between the allocation
and taking the pipe_lock(). So we end up with too small 'bufs' array.

Move the bufs allocations inside pipe_lock()/pipe_unlock() to fix this.

Fixes: dd3bb14f44a6 ("fuse: support splice() writing to fuse device")
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
Cc: <stable at vger.kernel.org> # v2.6.35
Signed-off-by: Miklos Szeredi <mszeredi at redhat.com>
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 fs/fuse/dev.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 707ac13ca52d..d1680b61b2a0 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -2036,11 +2036,14 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
 	if (!fud)
 		return -EPERM;
 
+	pipe_lock(pipe);
+
 	bufs = kvmalloc(pipe->buffers * sizeof(struct pipe_buffer), GFP_KERNEL);
-	if (!bufs)
+	if (!bufs) {
+		pipe_unlock(pipe);
 		return -ENOMEM;
+	}
 
-	pipe_lock(pipe);
 	nbuf = 0;
 	rem = 0;
 	for (idx = 0; idx < pipe->nrbufs && rem < len; idx++)
-- 
2.16.4