netfilter: nf_tables: reduce nft_pktinfo by 8 bytes

structure is reduced from 32 to 24 bytes.  While at it, also check
that iphdrlen is sane, this is guaranteed for NFPROTO_IPV4 but not
for ingress or bridge, so add checks for this.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_tables.h

@@ -32,8 +32,8 @@ struct nft_pktinfo {
 	u8				flags;
 	u8				tprot;
 	u16				fragoff;
-	unsigned int			thoff;
-	unsigned int			inneroff;
+	u16				thoff;
+	u16				inneroff;
 };
 
 static inline struct sock *nft_sk(const struct nft_pktinfo *pkt)

include/net/netfilter/nf_tables_ipv4.h

@@ -35,6 +35,8 @@ static inline int __nft_set_pktinfo_ipv4_validate(struct nft_pktinfo *pkt)
 		return -1;
 	else if (len < thoff)
 		return -1;
+	else if (thoff < sizeof(*iph))
+		return -1;
 
 	pkt->flags = NFT_PKTINFO_L4PROTO;
 	pkt->tprot = iph->protocol;
@@ -69,6 +71,8 @@ static inline int nft_set_pktinfo_ipv4_ingress(struct nft_pktinfo *pkt)
 		return -1;
 	} else if (len < thoff) {
 		goto inhdr_error;
+	} else if (thoff < sizeof(*iph)) {
+		return -1;
 	}
 
 	pkt->flags = NFT_PKTINFO_L4PROTO;

include/net/netfilter/nf_tables_ipv6.h

@@ -13,7 +13,7 @@ static inline void nft_set_pktinfo_ipv6(struct nft_pktinfo *pkt)
 	unsigned short frag_off;
 
 	protohdr = ipv6_find_hdr(pkt->skb, &thoff, -1, &frag_off, &flags);
-	if (protohdr < 0) {
+	if (protohdr < 0 || thoff > U16_MAX) {
 		nft_set_pktinfo_unspec(pkt);
 		return;
 	}
@@ -47,7 +47,7 @@ static inline int __nft_set_pktinfo_ipv6_validate(struct nft_pktinfo *pkt)
 		return -1;
 
 	protohdr = ipv6_find_hdr(pkt->skb, &thoff, -1, &frag_off, &flags);
-	if (protohdr < 0)
+	if (protohdr < 0 || thoff > U16_MAX)
 		return -1;
 
 	pkt->flags = NFT_PKTINFO_L4PROTO;
@@ -93,7 +93,7 @@ static inline int nft_set_pktinfo_ipv6_ingress(struct nft_pktinfo *pkt)
 	}
 
 	protohdr = ipv6_find_hdr(pkt->skb, &thoff, -1, &frag_off, &flags);
-	if (protohdr < 0)
+	if (protohdr < 0 || thoff > U16_MAX)
 		goto inhdr_error;
 
 	pkt->flags = NFT_PKTINFO_L4PROTO;