linux-kernel - [PATCH] netfilter: seqadj: check seq offset before update

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Date:   Fri, 24 Dec 2021 10:37:13 +0800
From:   zhang kai <zhangkaiheb@....com>
To:     pablo@...filter.org, kadlec@...filter.org, fw@...len.de,
        davem@...emloft.net, kuba@...nel.org,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     zhang kai <zhangkaiheb@....com>
Subject: [PATCH] netfilter: seqadj: check seq offset before update

if seq/ack offset is zero, don't update

Signed-off-by: zhang kai <zhangkaiheb@....com>
---
 net/netfilter/nf_conntrack_seqadj.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/net/netfilter/nf_conntrack_seqadj.c b/net/netfilter/nf_conntrack_seqadj.c
index 3066449f8bd8..d35e272a2e36 100644
--- a/net/netfilter/nf_conntrack_seqadj.c
+++ b/net/netfilter/nf_conntrack_seqadj.c
@@ -186,11 +186,13 @@ int nf_ct_seq_adjust(struct sk_buff *skb,
 	else
 		seqoff = this_way->offset_before;
 
-	newseq = htonl(ntohl(tcph->seq) + seqoff);
-	inet_proto_csum_replace4(&tcph->check, skb, tcph->seq, newseq, false);
-	pr_debug("Adjusting sequence number from %u->%u\n",
-		 ntohl(tcph->seq), ntohl(newseq));
-	tcph->seq = newseq;
+	if (seqoff) {
+		newseq = htonl(ntohl(tcph->seq) + seqoff);
+		inet_proto_csum_replace4(&tcph->check, skb, tcph->seq, newseq, false);
+		pr_debug("Adjusting sequence number from %u->%u\n",
+			 ntohl(tcph->seq), ntohl(newseq));
+		tcph->seq = newseq;
+	}
 
 	if (!tcph->ack)
 		goto out;
@@ -201,6 +203,9 @@ int nf_ct_seq_adjust(struct sk_buff *skb,
 	else
 		ackoff = other_way->offset_before;
 
+	if (!ackoff)
+		goto out;
+
 	newack = htonl(ntohl(tcph->ack_seq) - ackoff);
 	inet_proto_csum_replace4(&tcph->check, skb, tcph->ack_seq, newack,
 				 false);
-- 
2.17.1