netdev - [PATCH v1 net 12/15] tcp: Fix a data-race around sysctl_tcp_tw

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Message-ID: <20220715171755.38497-13-kuniyu@amazon.com>
Date:   Fri, 15 Jul 2022 10:17:52 -0700
From:   Kuniyuki Iwashima <kuniyu@...zon.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        David Ahern <dsahern@...nel.org>
CC:     Kuniyuki Iwashima <kuniyu@...zon.com>,
        Kuniyuki Iwashima <kuni1840@...il.com>,
        <netdev@...r.kernel.org>
Subject: [PATCH v1 net 12/15] tcp: Fix a data-race around sysctl_tcp_tw_reuse.

While reading sysctl_tcp_tw_reuse, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its reader.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 net/ipv4/tcp_ipv4.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index da5a3c44c4fb..d16e6e40f47b 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -108,10 +108,10 @@ static u32 tcp_v4_init_ts_off(const struct net *net, const struct sk_buff *skb)
 
 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp)
 {
+	int reuse = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tw_reuse);
 	const struct inet_timewait_sock *tw = inet_twsk(sktw);
 	const struct tcp_timewait_sock *tcptw = tcp_twsk(sktw);
 	struct tcp_sock *tp = tcp_sk(sk);
-	int reuse = sock_net(sk)->ipv4.sysctl_tcp_tw_reuse;
 
 	if (reuse == 2) {
 		/* Still does not detect *everything* that goes through
-- 
2.30.2