libceph: do not dereference a NULL bio pointer

Commit f38a5181d9f3 ("ceph: Convert to immutable biovecs") introduced
a NULL pointer dereference, which broke rbd in -rc1.  Fix it.

Cc: Kent Overstreet <kmo@daterainc.com>
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 0e478a0..30efc5c 100644 (file)
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -840,9 +840,13 @@ static bool ceph_msg_data_bio_advance(struct ceph_msg_data_cursor *cursor,
 
        if (!cursor->bvec_iter.bi_size) {
                bio = bio->bi_next;
-               cursor->bvec_iter = bio->bi_iter;
+               cursor->bio = bio;
+               if (bio)
+                       cursor->bvec_iter = bio->bi_iter;
+               else
+                       memset(&cursor->bvec_iter, 0,
+                              sizeof(cursor->bvec_iter));
        }
-       cursor->bio = bio;
 
        if (!cursor->last_piece) {
                BUG_ON(!cursor->resid);