commit 78eb166cdefcc3221c8c7c1e2d514e91a2eb5014
author Kuniyuki Iwashima <kuniyu@amazon.com> Wed Jul 13 13:52:02 2022 -0700
committer David S. Miller <davem@davemloft.net> Fri Jul 15 11:49:56 2022 +0100
tree 9fe160afb4da1305add732aae094e74918218bda
parent 88d78bc097cd8ebc6541e93316c9d9bf651b13e8

tcp: Fix data-races around sysctl_tcp_min_snd_mss.

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

Fixes: 5f3e2bf008c2 ("tcp: add tcp_min_snd_mss sysctl")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_timer.c

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 04063c7..39107bb 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -173,7 +173,7 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
 		mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
 		mss = min(READ_ONCE(net->ipv4.sysctl_tcp_base_mss), mss);
 		mss = max(mss, net->ipv4.sysctl_tcp_mtu_probe_floor);
-		mss = max(mss, net->ipv4.sysctl_tcp_min_snd_mss);
+		mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_min_snd_mss));
 		icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
 	}
 	tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);