From af84f9e447a65b4b9f79e7e5d69e19039b431c56 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Fri, 29 Sep 2023 10:42:10 +0200 Subject: [PATCH] netfilter: nft_payload: rebuild vlan header on h_proto access nft can perform merging of adjacent payload requests. This means that: ether saddr 00:11 ... ether type 8021ad ... is a single payload expression, for 8 bytes, starting at the ethernet source offset. Check that offset+length is fully within the source/destination mac addersses. This bug prevents 'ether type' from matching the correct h_proto in case vlan tag got stripped. Fixes: de6843be3082 ("netfilter: nft_payload: rebuild vlan header when needed") Reported-by: David Ward Signed-off-by: Florian Westphal --- net/netfilter/nft_payload.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c index 8cb8009..120f6d3 100644 --- a/net/netfilter/nft_payload.c +++ b/net/netfilter/nft_payload.c @@ -154,6 +154,17 @@ int nft_payload_inner_offset(const struct nft_pktinfo *pkt) return pkt->inneroff; } +static bool nft_payload_need_vlan_copy(const struct nft_payload *priv) +{ + unsigned int len = priv->offset + priv->len; + + /* data past ether src/dst requested, copy needed */ + if (len > offsetof(struct ethhdr, h_proto)) + return true; + + return false; +} + void nft_payload_eval(const struct nft_expr *expr, struct nft_regs *regs, const struct nft_pktinfo *pkt) @@ -172,7 +183,7 @@ void nft_payload_eval(const struct nft_expr *expr, goto err; if (skb_vlan_tag_present(skb) && - priv->offset >= offsetof(struct ethhdr, h_proto)) { + nft_payload_need_vlan_copy(priv)) { if (!nft_payload_copy_vlan(dest, skb, priv->offset, priv->len)) goto err; -- 2.7.4