xfrm6: fix the proto and ports decode of sctp protocol

The SCTP pushed the skb above the sctp chunk header, so the
check of pskb_may_pull(skb, nh + offset + 1 - skb->data) in
_decode_session6() will never return 0 and the ports decode
of sctp will always fail. (nh + offset + 1 - skb->data < 0)

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/xfrm6_policy.c b/net/ipv6/xfrm6_policy.c
index b4b16a4..3a3c677 100644 (file)
--- a/net/ipv6/xfrm6_policy.c
+++ b/net/ipv6/xfrm6_policy.c
@@ -157,7 +157,8 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse)
        ipv6_addr_copy(&fl->fl6_dst, reverse ? &hdr->saddr : &hdr->daddr);
        ipv6_addr_copy(&fl->fl6_src, reverse ? &hdr->daddr : &hdr->saddr);
 
-       while (pskb_may_pull(skb, nh + offset + 1 - skb->data)) {
+       while (nh + offset + 1 < skb->data ||
+              pskb_may_pull(skb, nh + offset + 1 - skb->data)) {
                nh = skb_network_header(skb);
                exthdr = (struct ipv6_opt_hdr *)(nh + offset);
 
@@ -177,7 +178,8 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse)
                case IPPROTO_TCP:
                case IPPROTO_SCTP:
                case IPPROTO_DCCP:
-                       if (!onlyproto && pskb_may_pull(skb, nh + offset + 4 - skb->data)) {
+                       if (!onlyproto && (nh + offset + 4 < skb->data ||
+                            pskb_may_pull(skb, nh + offset + 4 - skb->data))) {
                                __be16 *ports = (__be16 *)exthdr;
 
                                fl->fl_ip_sport = ports[!!reverse];