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

commit a2477b0e67c52f4364a47c3ad70902bc2a61bd4c upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 261fd13..f3f6cd3 100644 (file)
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1941,11 +1941,14 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
        if (!fud)
                return -EPERM;
 
+       pipe_lock(pipe);
+
        bufs = kmalloc(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++)