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

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Message-ID: <20220713205205.15735-16-kuniyu@amazon.com>
Date:   Wed, 13 Jul 2022 13:52:05 -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>, Fan Du <fan.du@...el.com>
Subject: [PATCH v1 net 15/15] tcp: Fix a data-race around sysctl_tcp_probe_interval.

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

Fixes: 05cbc0db03e8 ("ipv4: Create probe timer for tcp PMTU as per RFC4821")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
CC: Fan Du <fan.du@...el.com>
---
 net/ipv4/tcp_output.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index aa757c74dad4..02ab3a9c6657 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2283,7 +2283,7 @@ static inline void tcp_mtu_check_reprobe(struct sock *sk)
 	u32 interval;
 	s32 delta;
 
-	interval = net->ipv4.sysctl_tcp_probe_interval;
+	interval = READ_ONCE(net->ipv4.sysctl_tcp_probe_interval);
 	delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp;
 	if (unlikely(delta >= interval * HZ)) {
 		int mss = tcp_current_mss(sk);
-- 
2.30.2