diff --git a/sys/net/if.c b/sys/net/if.c
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -1453,6 +1453,11 @@
 	ifgl->ifgl_group = ifg;
 	ifgm->ifgm_ifp = ifp;
 
+	/*
+	 * Ensure that all pointed-to objects are visible to readers before the
+	 * holding structures are added to the lists under the lock.
+	 */
+	atomic_thread_fence_seq_cst();
 	IF_ADDR_WLOCK(ifp);
 	CK_STAILQ_INSERT_TAIL(&ifg->ifg_members, ifgm, ifgm_next);
 	CK_STAILQ_INSERT_TAIL(&ifp->if_groups, ifgl, ifgl_next);