odp-util: Stop parse odp actions if nlattr is overflow

`encap = nl_msg_start_nested(key, OVS_KEY_ATTR_ENCAP)` ensures that
key->size >= (encap + NLA_HDRLEN), so the `if` statement is safe.

Reported-at: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=11306
Signed-off-by: Yifeng Sun <pkusunyifeng@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

lib/odp-util.c

@@ -2318,6 +2318,10 @@ parse_odp_key_mask_attr(const char *s, const struct simap *port_names,
             if (retval < 0) {
                 return retval;
             }
+
+            if (nl_attr_oversized(key->size - encap - NLA_HDRLEN)) {
+                return -E2BIG;
+            }
             s += retval;
         }
         s++;