ceph: Fix oops when handling mdsmap that decreases max_mds

When i >= newmap->m_max_mds, ceph_mdsmap_get_addr(newmap, i) return
NULL. Passing NULL to memcmp() triggers oops.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Sage Weil <sage@inktank.com>

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index a5a7354..1bcf712 100644 (file)
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -2625,7 +2625,8 @@ static void check_new_map(struct ceph_mds_client *mdsc,
                     ceph_mdsmap_is_laggy(newmap, i) ? " (laggy)" : "",
                     session_state_name(s->s_state));
 
-               if (memcmp(ceph_mdsmap_get_addr(oldmap, i),
+               if (i >= newmap->m_max_mds ||
+                   memcmp(ceph_mdsmap_get_addr(oldmap, i),
                           ceph_mdsmap_get_addr(newmap, i),
                           sizeof(struct ceph_entity_addr))) {
                        if (s->s_state == CEPH_MDS_SESSION_OPENING) {