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: 7ec3f7b47b8d ("netfilter: nft_payload: add packet mangling support")
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
net/netfilter/nft_payload.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c
index 330609a76fb2..7dfc5343dae4 100644
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -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);
--
2.30.2
