linux-kernel - [PATCH 5.15 314/846] netfilter: nft_payload: do not update layer 4 checksum when mangling fragments

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Date:   Mon, 24 Jan 2022 19:37:11 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Pablo Neira Ayuso <pablo@...filter.org>,
        Sasha Levin <sashal@...nel.org>,
        Steffen Weinreich <steve@...nreich.org>
Subject: [PATCH 5.15 314/846] netfilter: nft_payload: do not update layer 4 checksum when mangling fragments

From: Pablo Neira Ayuso <pablo@...filter.org>

[ Upstream commit 4e1860a3863707e8177329c006d10f9e37e097a8 ]

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@...nreich.org>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 a44b14f6c0dc0..132875cd7fff2 100644
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -502,6 +502,9 @@ 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);
-- 
2.34.1