fuse: Don't access pipe->buffers without pipe_lock()

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@virtuozzo.com>
Cc: <stable@vger.kernel.org> # v2.6.35
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index ec83b107c1a0..4a9ace7280b9 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1955,12 +1955,15 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
         if (!fud)
                 return -EPERM;
 
+        pipe_lock(pipe);
+
         bufs = kmalloc_array(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++)