ipv6: Check attribute length for RTA_GATEWAY in multipath route

Commit referenced in the Fixes tag used nla_memcpy for RTA_GATEWAY as
does the current nla_get_in6_addr. nla_memcpy protects against accessing
memory greater than what is in the attribute, but there is no check
requiring the attribute to have an IPv6 address. Add it.

Fixes: 51ebd3181572 ("ipv6: add support of equal cost multipath (ECMP)")
Signed-off-by: David Ahern <dsahern@kernel.org>
Cc: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 42d60c7..d16599c 100644 (file)
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -5224,6 +5224,19 @@ out:
        return should_notify;
 }
 
+static int fib6_gw_from_attr(struct in6_addr *gw, struct nlattr *nla,
+                            struct netlink_ext_ack *extack)
+{
+       if (nla_len(nla) < sizeof(*gw)) {
+               NL_SET_ERR_MSG(extack, "Invalid IPv6 address in RTA_GATEWAY");
+               return -EINVAL;
+       }
+
+       *gw = nla_get_in6_addr(nla);
+
+       return 0;
+}
+
 static int ip6_route_multipath_add(struct fib6_config *cfg,
                                   struct netlink_ext_ack *extack)
 {
@@ -5264,7 +5277,13 @@ static int ip6_route_multipath_add(struct fib6_config *cfg,
 
                        nla = nla_find(attrs, attrlen, RTA_GATEWAY);
                        if (nla) {
-                               r_cfg.fc_gateway = nla_get_in6_addr(nla);
+                               int ret;
+
+                               ret = fib6_gw_from_attr(&r_cfg.fc_gateway, nla,
+                                                       extack);
+                               if (ret)
+                                       return ret;
+
                                r_cfg.fc_flags |= RTF_GATEWAY;
                        }
                        r_cfg.fc_encap = nla_find(attrs, attrlen, RTA_ENCAP);