netrom: Fix a data-race around sysctl_netrom_routing_control

[ Upstream commit b5dffcb8f71bdd02a4e5799985b51b12f4eeaf76 ]

We need to protect the reader reading the sysctl value because the
value can be changed concurrently.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/netrom/nr_route.c b/net/netrom/nr_route.c
index b8ddd8048f352c4bad595b58d820d283b535f90b..89e12e6eea2efd92ed345ccb7f630f11687a964f 100644 (file)
--- a/net/netrom/nr_route.c
+++ b/net/netrom/nr_route.c
@@ -780,7 +780,7 @@ int nr_route_frame(struct sk_buff *skb, ax25_cb *ax25)
                return ret;
        }
 
-       if (!sysctl_netrom_routing_control && ax25 != NULL)
+       if (!READ_ONCE(sysctl_netrom_routing_control) && ax25 != NULL)
                return 0;
 
        /* Its Time-To-Live has expired */