net: ipv6: check for validity before dereferencing cfg->fc_nlinfo.nlh

nlh is being checked for validtity two times when it is dereferenced in
this function. Check for validity again when updating the flags through
nlh pointer to make the dereferencing safe.

CC: <stable@vger.kernel.org>
Addresses-Coverity: ("NULL pointer dereference")
Signed-off-by: Muhammad Usama Anjum <musamaanjum@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 1056b0229ffdc676012f7608eec52da0e752a698..373d48073106f7f1b594f4fd3df275c23bf7304a 100644 (file)
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -5209,9 +5209,11 @@ static int ip6_route_multipath_add(struct fib6_config *cfg,
                 * nexthops have been replaced by first new, the rest should
                 * be added to it.
                 */
-               cfg->fc_nlinfo.nlh->nlmsg_flags &= ~(NLM_F_EXCL |
-                                                    NLM_F_REPLACE);
-               cfg->fc_nlinfo.nlh->nlmsg_flags |= NLM_F_CREATE;
+               if (cfg->fc_nlinfo.nlh) {
+                       cfg->fc_nlinfo.nlh->nlmsg_flags &= ~(NLM_F_EXCL |
+                                                            NLM_F_REPLACE);
+                       cfg->fc_nlinfo.nlh->nlmsg_flags |= NLM_F_CREATE;
+               }
                nhn++;
        }