[IPCOMP]: Fetch nexthdr before ipch is destroyed

When I moved the nexthdr setting out of IPComp I accidently moved
the reading of ipch->nexthdr after the decompression.  Unfortunately
this means that we'd be reading from a stale ipch pointer which
doesn't work very well.

This patch moves the reading up so that we get the correct nexthdr
value.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ipcomp.c

@@ -74,6 +74,7 @@ static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb)
 
 static int ipcomp_input(struct xfrm_state *x, struct sk_buff *skb)
 {
+	int nexthdr;
 	int err = -ENOMEM;
 	struct ip_comp_hdr *ipch;
 
@@ -84,13 +85,15 @@ static int ipcomp_input(struct xfrm_state *x, struct sk_buff *skb)
 
 	/* Remove ipcomp header and decompress original payload */
 	ipch = (void *)skb->data;
+	nexthdr = ipch->nexthdr;
+
 	skb->transport_header = skb->network_header + sizeof(*ipch);
 	__skb_pull(skb, sizeof(*ipch));
 	err = ipcomp_decompress(x, skb);
 	if (err)
 		goto out;
 
-	err = ipch->nexthdr;
+	err = nexthdr;
 
 out:
 	return err;

net/ipv6/ipcomp6.c

@@ -64,6 +64,7 @@ static LIST_HEAD(ipcomp6_tfms_list);
 
 static int ipcomp6_input(struct xfrm_state *x, struct sk_buff *skb)
 {
+	int nexthdr;
 	int err = -ENOMEM;
 	struct ip_comp_hdr *ipch;
 	int plen, dlen;
@@ -79,6 +80,8 @@ static int ipcomp6_input(struct xfrm_state *x, struct sk_buff *skb)
 
 	/* Remove ipcomp header and decompress original payload */
 	ipch = (void *)skb->data;
+	nexthdr = ipch->nexthdr;
+
 	skb->transport_header = skb->network_header + sizeof(*ipch);
 	__skb_pull(skb, sizeof(*ipch));
 
@@ -108,7 +111,7 @@ static int ipcomp6_input(struct xfrm_state *x, struct sk_buff *skb)
 	skb->truesize += dlen - plen;
 	__skb_put(skb, dlen - plen);
 	skb_copy_to_linear_data(skb, scratch, dlen);
-	err = ipch->nexthdr;
+	err = nexthdr;
 
 out_put_cpu:
 	put_cpu();