[IPSEC]: Fix BEET output

The IPv6 BEET output function is incorrectly including the inner
header in the payload to be protected.  This causes a crash as
the packet doesn't actually have that many bytes for a second
header.

The IPv4 BEET output on the other hand is broken when it comes
to handling an inner IPv6 header since it always assumes an
inner IPv4 header.

This patch fixes both by making sure that neither BEET output
function touches the inner header at all.  All access is now
done through the protocol-independent cb structure.  Two new
attributes are added to make this work, the IP header length
and the IPv4 option length.  They're filled in by the inner
mode's output function.

Thanks to Joakim Koskela for finding this problem.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/xfrm.h

@@ -552,6 +552,9 @@ struct xfrm_mode_skb_cb {
 	__be16 id;
 	__be16 frag_off;
 
+	/* IP header length (excluding options or extension headers). */
+	u8 ihl;
+
 	/* TOS for IPv4, class for IPv6. */
 	u8 tos;
 
@@ -561,6 +564,9 @@ struct xfrm_mode_skb_cb {
 	/* Protocol for IPv4, NH for IPv6. */
 	u8 protocol;
 
+	/* Option length for IPv4, zero for IPv6. */
+	u8 optlen;
+
 	/* Used by IPv6 only, zero for IPv4. */
 	u8 flow_lbl[3];
 };

net/ipv4/xfrm4_mode_beet.c

@@ -39,13 +39,11 @@ static void xfrm4_beet_make_header(struct sk_buff *skb)
 static int xfrm4_beet_output(struct xfrm_state *x, struct sk_buff *skb)
 {
 	struct ip_beet_phdr *ph;
-	struct iphdr *iph, *top_iph;
+	struct iphdr *top_iph;
 	int hdrlen, optlen;
 
-	iph = ip_hdr(skb);
-
 	hdrlen = 0;
-	optlen = iph->ihl * 4 - sizeof(*iph);
+	optlen = XFRM_MODE_SKB_CB(skb)->optlen;
 	if (unlikely(optlen))
 		hdrlen += IPV4_BEET_PHMAXLEN - (optlen & 4);
 
@@ -53,11 +51,12 @@ static int xfrm4_beet_output(struct xfrm_state *x, struct sk_buff *skb)
 				    hdrlen);
 	skb->mac_header = skb->network_header +
 			  offsetof(struct iphdr, protocol);
-	skb->transport_header = skb->network_header + sizeof(*iph);
+	skb->transport_header = skb->network_header + sizeof(*top_iph);
 
 	xfrm4_beet_make_header(skb);
 
-	ph = (struct ip_beet_phdr *)__skb_pull(skb, sizeof(*iph) - hdrlen);
+	ph = (struct ip_beet_phdr *)
+		__skb_pull(skb, XFRM_MODE_SKB_CB(skb)->ihl - hdrlen);
 
 	top_iph = ip_hdr(skb);
 

net/ipv4/xfrm4_state.c

@@ -52,10 +52,12 @@ int xfrm4_extract_header(struct sk_buff *skb)
 {
 	struct iphdr *iph = ip_hdr(skb);
 
+	XFRM_MODE_SKB_CB(skb)->ihl = sizeof(*iph);
 	XFRM_MODE_SKB_CB(skb)->id = iph->id;
 	XFRM_MODE_SKB_CB(skb)->frag_off = iph->frag_off;
 	XFRM_MODE_SKB_CB(skb)->tos = iph->tos;
 	XFRM_MODE_SKB_CB(skb)->ttl = iph->ttl;
+	XFRM_MODE_SKB_CB(skb)->optlen = iph->ihl * 4 - sizeof(*iph);
 	memset(XFRM_MODE_SKB_CB(skb)->flow_lbl, 0,
 	       sizeof(XFRM_MODE_SKB_CB(skb)->flow_lbl));
 

net/ipv6/xfrm6_mode_beet.c

@@ -45,6 +45,7 @@ static int xfrm6_beet_output(struct xfrm_state *x, struct sk_buff *skb)
 	skb->mac_header = skb->network_header +
 			  offsetof(struct ipv6hdr, nexthdr);
 	skb->transport_header = skb->network_header + sizeof(*top_iph);
+	__skb_pull(skb, XFRM_MODE_SKB_CB(skb)->ihl);
 
 	xfrm6_beet_make_header(skb);
 

net/ipv6/xfrm6_state.c

@@ -174,10 +174,12 @@ int xfrm6_extract_header(struct sk_buff *skb)
 {
 	struct ipv6hdr *iph = ipv6_hdr(skb);
 
+	XFRM_MODE_SKB_CB(skb)->ihl = sizeof(*iph);
 	XFRM_MODE_SKB_CB(skb)->id = 0;
 	XFRM_MODE_SKB_CB(skb)->frag_off = htons(IP_DF);
 	XFRM_MODE_SKB_CB(skb)->tos = ipv6_get_dsfield(iph);
 	XFRM_MODE_SKB_CB(skb)->ttl = iph->hop_limit;
+	XFRM_MODE_SKB_CB(skb)->optlen = 0;
 	memcpy(XFRM_MODE_SKB_CB(skb)->flow_lbl, iph->flow_lbl,
 	       sizeof(XFRM_MODE_SKB_CB(skb)->flow_lbl));