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netfilter: nft_payload: incorrect arithmetics when fetching VLAN header bits

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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: f6ae9f120d ("netfilter: nft_payload: add C-VLAN support")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso 2023-01-11 17:07:33 +01:00
parent 9ea4b476ce
commit 696e1a48b1
1 changed files with 1 additions and 1 deletions
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2
net/netfilter/nft_payload.c
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@ -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);