From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: Wed, 5 Jan 2022 15:09:57 +0000 (+0100)
Subject: netfilter: nft_payload: do not update layer 4 checksum when mangling fragments
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=4e1860a3863707e8177329c006d10f9e37e097a8;p=linux.git

netfilter: nft_payload: do not update layer 4 checksum when mangling fragments

IP fragments do not come with the transport header, hence skip bogus
layer 4 checksum updates.

Fixes: 1814096980bb ("netfilter: nft_payload: layer 4 checksum adjustment for pseudoheader fields")
Reported-and-tested-by: Steffen Weinreich <steve@weinreich.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---

diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c
index bd689938a2e0c..58e96a0fe0b4c 100644
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -546,6 +546,9 @@ static int nft_payload_l4csum_offset(const struct nft_pktinfo *pkt,
 				     struct sk_buff *skb,
 				     unsigned int *l4csum_offset)
 {
+	if (pkt->fragoff)
+		return -1;
+
 	switch (pkt->tprot) {
 	case IPPROTO_TCP:
 		*l4csum_offset = offsetof(struct tcphdr, check);