tcp: Fix a data-race around sysctl_tcp_probe_threshold.

[ 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@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 b0d49317b2216e7376acbb0f4a2f0a3a61c5cf14..7a8c8de458182fc0e736bb293b8f2148b7385e45 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2360,7 +2360,7 @@ 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.
                 */