netrom: Fix a data-race around sysctl_netrom_routing_control

JasonXing · Paolo Abeni · commit b5dffcb8f71b · 2024-03-07T10:36:58.000+01:00
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 &lt;kernelxing@tencent.com&gt;
Signed-off-by: Paolo Abeni &lt;pabeni@redhat.com&gt;
diff --git 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 */

Original file line number	Diff line number	Diff line change
`@@ -780,7 +780,7 @@ int nr_route_frame(struct sk_buff skb, ax25_cb ax25)`
`780`	`780`	`return ret;`
`781`	`781`	`}`
`782`	`782`
`783`		`- if (!sysctl_netrom_routing_control && ax25 != NULL)`
	`783`	`+ if (!READ_ONCE(sysctl_netrom_routing_control) && ax25 != NULL)`
`784`	`784`	`return 0;`
`785`	`785`
`786`	`786`	`/* Its Time-To-Live has expired */`