6.6-stable review patch. If anyone has any objections, please let me know.
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From: Pablo Neira Ayuso pablo@netfilter.org
[ Upstream commit 5fd0628918977a0afdc2e6bc562d8751b5d3b8c5 ]
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 jorge.ortiz.escribano@gmail.com Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 60a7d0ce30804..fcf967286e37c 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;