diff --git a/net/ipv4/xfrm4_policy.c b/net/ipv4/xfrm4_policy.c
index 60d918c96a4fff19c0d4062558ea8c594fa9bef2..0071ee6f441f1236d953f6a2f0f6b3cd8d67e758 100644
--- a/net/ipv4/xfrm4_policy.c
+++ b/net/ipv4/xfrm4_policy.c
@@ -136,7 +136,8 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
 		case IPPROTO_TCP:
 		case IPPROTO_SCTP:
 		case IPPROTO_DCCP:
-			if (pskb_may_pull(skb, xprth + 4 - skb->data)) {
+			if (xprth + 4 < skb->data ||
+			    pskb_may_pull(skb, xprth + 4 - skb->data)) {
 				__be16 *ports = (__be16 *)xprth;
 
 				fl->fl_ip_sport = ports[!!reverse];