[PATCH 6.1 457/473] netfilter: nft_payload: rebuild vlan header on h_proto access

Greg Kroah-Hartman
2024-06-06T14:20:36Z

From: Florian Westphal <fw@strlen.de>

[ Upstream commit af84f9e447a65b4b9f79e7e5d69e19039b431c56 ]

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>
Stable-dep-of: 33c563ebf8d3 ("netfilter: nft_payload: skbuff vlan metadata mangle support")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 74777a687eb5f..eaa629c6d7da6 100644
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -109,6 +109,17 @@ static 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)
@@ -127,7 +138,7 @@ 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;
--
2.43.0