netfilter: nf_tables_ipv6: consider network offset in netdev/egress validation

From netdev/egress, skb->len can include the ethernet header, therefore,
subtract network offset from skb->len when validating IPv6 packet length.

Fixes: 42df6e1d221d ("netfilter: Introduce egress hook")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/include/net/netfilter/nf_tables_ipv6.h b/include/net/netfilter/nf_tables_ipv6.h
index 467d59b9e5334c17ca673e7cdb19b80a71b48fdb..a0633eeaec977bd014355873fac8c56657c0118a 100644 (file)
--- a/include/net/netfilter/nf_tables_ipv6.h
+++ b/include/net/netfilter/nf_tables_ipv6.h
@@ -31,8 +31,8 @@ static inline int __nft_set_pktinfo_ipv6_validate(struct nft_pktinfo *pkt)
        struct ipv6hdr *ip6h, _ip6h;
        unsigned int thoff = 0;
        unsigned short frag_off;
+       u32 pkt_len, skb_len;
        int protohdr;
-       u32 pkt_len;
 
        ip6h = skb_header_pointer(pkt->skb, skb_network_offset(pkt->skb),
                                  sizeof(*ip6h), &_ip6h);
@@ -43,7 +43,8 @@ static inline int __nft_set_pktinfo_ipv6_validate(struct nft_pktinfo *pkt)
                return -1;
 
        pkt_len = ntohs(ip6h->payload_len);
-       if (pkt_len + sizeof(*ip6h) > pkt->skb->len)
+       skb_len = pkt->skb->len - skb_network_offset(pkt->skb);
+       if (pkt_len + sizeof(*ip6h) > skb_len)
                return -1;
 
        protohdr = ipv6_find_hdr(pkt->skb, &thoff, -1, &frag_off, &flags);