ipv4: Check attribute length for RTA_GATEWAY in multipath route

syzbot reported uninit-value: ============================================================ BUG: KMSAN: uninit-value in fib_get_nhs+0xac4/0x1f80 net/ipv4/fib_semantics.c:708 fib_get_nhs+0xac4/0x1f80 net/ipv4/fib_semantics.c:708 fib_create_info+0x2411/0x4870 net/ipv4/fib_semantics.c:1453 fib_table_insert+0x45c/0x3a10 net/ipv4/fib_trie.c:1224 inet_rtm_newroute+0x289/0x420 net/ipv4/fib_frontend.c:886 Add helper to validate RTA_GATEWAY length before using the attribute. Fixes: 4e902c5 ("[IPv4]: FIB configuration using struct fib_config") Reported-by: [email protected] Signed-off-by: David Ahern <[email protected]> Cc: Thomas Graf <[email protected]> Signed-off-by: David S. Miller <[email protected]>
bignaux · Dec 31, 2021 · 7a3429b · 7a3429b
1 parent 74c78b4
commit 7a3429b
Showing 1 changed file with 26 additions and 3 deletions.
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
@@ -662,6 +662,19 @@ static int fib_count_nexthops(struct rtnexthop *rtnh, int remaining,
 	return nhs;
 }
 
+static int fib_gw_from_attr(__be32 *gw, struct nlattr *nla,
+			    struct netlink_ext_ack *extack)
+{
+	if (nla_len(nla) < sizeof(*gw)) {
+		NL_SET_ERR_MSG(extack, "Invalid IPv4 address in RTA_GATEWAY");
+		return -EINVAL;
+	}
+
+	*gw = nla_get_in_addr(nla);
+
+	return 0;
+}
+
 /* only called when fib_nh is integrated into fib_info */
 static int fib_get_nhs(struct fib_info *fi, struct rtnexthop *rtnh,
 		       int remaining, struct fib_config *cfg,
@@ -704,7 +717,11 @@ static int fib_get_nhs(struct fib_info *fi, struct rtnexthop *rtnh,
 				return -EINVAL;
 			}
 			if (nla) {
-				fib_cfg.fc_gw4 = nla_get_in_addr(nla);
+				ret = fib_gw_from_attr(&fib_cfg.fc_gw4, nla,
+						       extack);
+				if (ret)
+					goto errout;
+
 				if (fib_cfg.fc_gw4)
 					fib_cfg.fc_gw_family = AF_INET;
 			} else if (nlav) {
@@ -902,6 +919,7 @@ int fib_nh_match(struct net *net, struct fib_config *cfg, struct fib_info *fi,
 		attrlen = rtnh_attrlen(rtnh);
 		if (attrlen > 0) {
 			struct nlattr *nla, *nlav, *attrs = rtnh_attrs(rtnh);
+			int err;
 
 			nla = nla_find(attrs, attrlen, RTA_GATEWAY);
 			nlav = nla_find(attrs, attrlen, RTA_VIA);
@@ -912,12 +930,17 @@ int fib_nh_match(struct net *net, struct fib_config *cfg, struct fib_info *fi,
 			}
 
 			if (nla) {
+				__be32 gw;
+
+				err = fib_gw_from_attr(&gw, nla, extack);
+				if (err)
+					return err;
+
 				if (nh->fib_nh_gw_family != AF_INET ||
-				    nla_get_in_addr(nla) != nh->fib_nh_gw4)
+				    gw != nh->fib_nh_gw4)
 					return 1;
 			} else if (nlav) {
 				struct fib_config cfg2;
-				int err;
 
 				err = fib_gw_from_via(&cfg2, nlav, extack);
 				if (err)