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netfilter: nft_payload: sanitize offset and length before calling skb_checksum()

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If access to offset + length is larger than the skbuff length, then
skb_checksum() triggers BUG_ON().

skb_checksum() internally subtracts the length parameter while iterating
over skbuff, BUG_ON(len) at the end of it checks that the expected
length to be included in the checksum calculation is fully consumed.

Fixes: 7ec3f7b47b ("netfilter: nft_payload: add packet mangling support")
Reported-by: Slavin Liu <slavin-ayu@qq.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso 2024-10-30 23:13:48 +01:00
parent 4ed234fe79
commit d5953d680f
1 changed files with 3 additions and 0 deletions
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3
net/netfilter/nft_payload.c
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@ -904,6 +904,9 @@ static void nft_payload_set_eval(const struct nft_expr *expr,
((priv->base != NFT_PAYLOAD_TRANSPORT_HEADER &&
priv->base != NFT_PAYLOAD_INNER_HEADER) ||
skb->ip_summed != CHECKSUM_PARTIAL)) {
if (offset + priv->len > skb->len)
goto err;
fsum = skb_checksum(skb, offset, priv->len, 0);
tsum = csum_partial(src, priv->len, 0);