fib, fib6: reject invalid feature bits

Feature bits that are invalid should not be accepted by the kernel,
only the lower 4 bits may be configured, but not the remaining ones.
Even from these 4, 2 of them are unused.
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/uapi/linux/rtnetlink.h

@@ -418,10 +418,13 @@ enum {
 
 #define RTAX_MAX (__RTAX_MAX - 1)
 
-#define RTAX_FEATURE_ECN	0x00000001
-#define RTAX_FEATURE_SACK	0x00000002
-#define RTAX_FEATURE_TIMESTAMP	0x00000004
-#define RTAX_FEATURE_ALLFRAG	0x00000008
+#define RTAX_FEATURE_ECN	(1 << 0)
+#define RTAX_FEATURE_SACK	(1 << 1)
+#define RTAX_FEATURE_TIMESTAMP	(1 << 2)
+#define RTAX_FEATURE_ALLFRAG	(1 << 3)
+
+#define RTAX_FEATURE_MASK	(RTAX_FEATURE_ECN | RTAX_FEATURE_SACK | \
+				 RTAX_FEATURE_TIMESTAMP | RTAX_FEATURE_ALLFRAG)
 
 struct rta_session {
 	__u8	proto;

net/ipv4/fib_semantics.c

@@ -908,6 +908,8 @@ fib_convert_metrics(struct fib_info *fi, const struct fib_config *cfg)
 			val = 65535 - 40;
 		if (type == RTAX_MTU && val > 65535 - 15)
 			val = 65535 - 15;
+		if (type == RTAX_FEATURES && (val & ~RTAX_FEATURE_MASK))
+			return -EINVAL;
 		fi->fib_metrics[type - 1] = val;
 	}
 

net/ipv6/route.c

@@ -1728,6 +1728,8 @@ static int ip6_convert_metrics(struct mx6_config *mxc,
 		} else {
 			val = nla_get_u32(nla);
 		}
+		if (type == RTAX_FEATURES && (val & ~RTAX_FEATURE_MASK))
+			goto err;
 
 		mp[type - 1] = val;
 		__set_bit(type - 1, mxc->mx_valid);