linux-kernel - [PATCH 4.19 08/86] netfilter: nft_payload: do not update layer 4 checksum when mangling fragments

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Message-Id: <20220207103757.830383880@linuxfoundation.org>
Date:   Mon,  7 Feb 2022 12:05:31 +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>,
        Florian Westphal <fw@...len.de>,
        Steffen Weinreich <steve@...nreich.org>
Subject: [PATCH 4.19 08/86] netfilter: nft_payload: do not update layer 4 checksum when mangling fragments

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

commit 4e1860a3863707e8177329c006d10f9e37e097a8 upstream.

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: Florian Westphal <fw@...len.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/netfilter/nft_payload.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -194,6 +194,9 @@ static int nft_payload_l4csum_offset(con
 				     struct sk_buff *skb,
 				     unsigned int *l4csum_offset)
 {
+	if (pkt->xt.fragoff)
+		return -1;
+
 	switch (pkt->tprot) {
 	case IPPROTO_TCP:
 		*l4csum_offset = offsetof(struct tcphdr, check);