[PATCH 5.4 25/87] tcp: Fix a data-race around sysctl_tcp_probe_threshold.

[Greg Kroah-Hartman]

From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>

[ Upstream commit 92c0aa4175474483d6cf373314343d4e624e882a ]

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

Fixes: 6b58e0a5f32d ("ipv4: Use binary search to choose tcp PMTU probe_size")
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 7c0b96319fc0..e60cb69d00a4 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2134,7 +2134,7 @@ static int tcp_mtu_probe(struct sock *sk)
 	 * probing process by not resetting search range to its orignal.
 	 */
 	if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
-		interval < net->ipv4.sysctl_tcp_probe_threshold) {
+	    interval < READ_ONCE(net->ipv4.sysctl_tcp_probe_threshold)) {
 		/* Check whether enough time has elaplased for
 		 * another round of probing.
 		 */
-- 
2.35.1