tcp: Fix a data-race around sysctl_tcp_nometrics_save.

commit 87ba594f7debe5939db9c71badd898b3590eee6d upstream.

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

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 9a7d8a5998578a9e82434a3f21328a0604739dc3..0af6249a993af15a9694d5ce61a84b5ae3fc0197 100644 (file)
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -329,7 +329,7 @@ void tcp_update_metrics(struct sock *sk)
        int m;
 
        sk_dst_confirm(sk);
-       if (net->ipv4.sysctl_tcp_nometrics_save || !dst)
+       if (READ_ONCE(net->ipv4.sysctl_tcp_nometrics_save) || !dst)
                return;
 
        rcu_read_lock();