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netfilter: nft_payload: rebuild vlan header on h_proto access

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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 <david.ward@ll.mit.edu>
Signed-off-by: Florian Westphal <fw@strlen.de>
This commit is contained in:
Florian Westphal 2023-09-29 10:42:10 +02:00
parent 51e7a66666
commit af84f9e447
1 changed files with 12 additions and 1 deletions
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13
net/netfilter/nft_payload.c
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@ -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;