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

commit 864db232dc7036aa2de19749c3d5be0143b24f8f upstream.

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

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index dad35cd48807e925b80d7c61b5382027f9322556..f884739a0c1c72b9a9994a9065eb3f3299f27bb6 100644 (file)
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -4514,9 +4514,11 @@ 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                 * nexthops have been replaced by first new, the rest should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++;
        }