From 5fd0628918977a0afdc2e6bc562d8751b5d3b8c5 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Mon, 26 Aug 2024 12:45:22 +0200 Subject: [PATCH 1/2] netfilter: nf_tables: restore IP sanity checks for netdev/egress Subtract network offset to skb->len before performing IPv4 header sanity checks, then adjust transport offset from offset from mac header. Jorge Ortiz says: When small UDP packets (< 4 bytes payload) are sent from eth0, `meta l4proto udp` condition is not met because `NFT_PKTINFO_L4PROTO` is not set. This happens because there is a comparison that checks if the transport header offset exceeds the total length. This comparison does not take into account the fact that the skb network offset might be non-zero in egress mode (e.g., 14 bytes for Ethernet header). Fixes: 0ae8e4cca787 ("netfilter: nf_tables: set transport offset from mac header for netdev/egress") Reported-by: Jorge Ortiz Signed-off-by: Pablo Neira Ayuso --- include/net/netfilter/nf_tables_ipv4.h | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/include/net/netfilter/nf_tables_ipv4.h b/include/net/netfilter/nf_tables_ipv4.h index 60a7d0ce308046..fcf967286e37cb 100644 --- a/include/net/netfilter/nf_tables_ipv4.h +++ b/include/net/netfilter/nf_tables_ipv4.h @@ -19,7 +19,7 @@ static inline void nft_set_pktinfo_ipv4(struct nft_pktinfo *pkt) static inline int __nft_set_pktinfo_ipv4_validate(struct nft_pktinfo *pkt) { struct iphdr *iph, _iph; - u32 len, thoff; + u32 len, thoff, skb_len; iph = skb_header_pointer(pkt->skb, skb_network_offset(pkt->skb), sizeof(*iph), &_iph); @@ -30,8 +30,10 @@ static inline int __nft_set_pktinfo_ipv4_validate(struct nft_pktinfo *pkt) return -1; len = iph_totlen(pkt->skb, iph); - thoff = skb_network_offset(pkt->skb) + (iph->ihl * 4); - if (pkt->skb->len < len) + thoff = iph->ihl * 4; + skb_len = pkt->skb->len - skb_network_offset(pkt->skb); + + if (skb_len < len) return -1; else if (len < thoff) return -1; @@ -40,7 +42,7 @@ static inline int __nft_set_pktinfo_ipv4_validate(struct nft_pktinfo *pkt) pkt->flags = NFT_PKTINFO_L4PROTO; pkt->tprot = iph->protocol; - pkt->thoff = thoff; + pkt->thoff = skb_network_offset(pkt->skb) + thoff; pkt->fragoff = ntohs(iph->frag_off) & IP_OFFSET; return 0; From 70c261d500951cf3ea0fcf32651aab9a65a91471 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Mon, 26 Aug 2024 15:03:23 +0200 Subject: [PATCH 2/2] 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 --- include/net/netfilter/nf_tables_ipv6.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/include/net/netfilter/nf_tables_ipv6.h b/include/net/netfilter/nf_tables_ipv6.h index 467d59b9e5334c..a0633eeaec977b 100644 --- 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);