tcp: Fix a data-race around sysctl_tcp_probe_threshold.

BugLink: https://bugs.launchpad.net/bugs/1988479
[ 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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index b4a8a5b9350faff0be9202123778f07228416b09..0ba48c43c06f890c606a1c3f0680e28f6a8ec7b8 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2363,7 +2363,7 @@ 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.
                 */