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From 07fa6df737871f5e491ec70f499963aedd679f2a Mon Sep 17 00:00:00 2001
From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: Wed, 11 Jan 2023 17:07:33 +0100
Subject: [PATCH 4/5] netfilter: nft_payload: incorrect arithmetics when
fetching VLAN header bits
commit 696e1a48b1a1b01edad542a1ef293665864a4dd0 upstream.
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 <d.ornaghi97@gmail.com>
Fixes: f6ae9f120dad ("netfilter: nft_payload: add C-VLAN support")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/netfilter/nft_payload.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c
index 4edd899aeb9b..d7de2ecb287e 100644
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -62,7 +62,7 @@ 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);
--
2.39.0
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