From 696e1a48b1a1b01edad542a1ef293665864a4dd0 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Wed, 11 Jan 2023 17:07:33 +0100 Subject: netfilter: nft_payload: incorrect arithmetics when fetching VLAN header bits If the offset + length goes over the ethernet + vlan header, then the length is adjusted to copy the bytes that are within the boundaries of the vlan_ethhdr scratchpad area. The remaining bytes beyond ethernet + vlan header are copied directly from the skbuff data area. Fix incorrect arithmetic operator: subtract, not add, the size of the vlan header in case of double-tagged packets to adjust the length accordingly to address CVE-2023-0179. Reported-by: Davide Ornaghi Fixes: f6ae9f120dad ("netfilter: nft_payload: add C-VLAN support") Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nft_payload.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/netfilter/nft_payload.c') diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c index 17b418a5a593..3a3c7746e88f 100644 --- a/net/netfilter/nft_payload.c +++ b/net/netfilter/nft_payload.c @@ -63,7 +63,7 @@ nft_payload_copy_vlan(u32 *d, const struct sk_buff *skb, u8 offset, u8 len) return false; if (offset + len > VLAN_ETH_HLEN + vlan_hlen) - ethlen -= offset + len - VLAN_ETH_HLEN + vlan_hlen; + ethlen -= offset + len - VLAN_ETH_HLEN - vlan_hlen; memcpy(dst_u8, vlanh + offset - vlan_hlen, ethlen); -- cgit