xfrm: Fix xfrm sel prefix length validation

Family of src/dst can be different from family of selector src/dst.
Use xfrm selector family to validate address prefix length,
while verifying new sa from userspace.

Validated patch with this command:
ip xfrm state add src 1.1.6.1 dst 1.1.6.2 proto esp spi 4260196 \
reqid 20004 mode tunnel aead "rfc4106(gcm(aes))" \
0x1111016400000000000000000000000044440001 128 \
sel src 1011:1:4::2/128 sel dst 1021:1:4::2/128 dev Port5

Fixes: 07bf790 ("xfrm: Validate address prefix lengths in the xfrm selector.")
Signed-off-by: Anirudh Gupta <anirudh.gupta@sophos.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/xfrm/xfrm_user.c

@@ -150,6 +150,22 @@ static int verify_newsa_info(struct xfrm_usersa_info *p,
 
 	err = -EINVAL;
 	switch (p->family) {
+	case AF_INET:
+		break;
+
+	case AF_INET6:
+#if IS_ENABLED(CONFIG_IPV6)
+		break;
+#else
+		err = -EAFNOSUPPORT;
+		goto out;
+#endif
+
+	default:
+		goto out;
+	}
+
+	switch (p->sel.family) {
 	case AF_INET:
 		if (p->sel.prefixlen_d > 32 || p->sel.prefixlen_s > 32)
 			goto out;