tcp: Fix a data-race around sysctl_tcp_probe_interval.

[ Upstream commit 2a85388f1d94a9f8b5a529118a2c5eaa0520d85c ]

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@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 0ba48c43c06f890c606a1c3f0680e28f6a8ec7b8..3fa2bfbc250d4e0529e445e02664a3477a23d8d9 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2281,7 +2281,7 @@ 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);