fib_frontend: fix possible NULL pointer dereference

hartkopp · davem330 · commit a0065f266a9b · 2014-01-24T15:51:26.000-08:00
The two commits 0115e8e (net: remove delay at device dismantle) and 748e2d9 (net: reinstate rtnl in call_netdevice_notifiers()) silently removed a NULL pointer check for in_dev since Linux 3.7. This patch re-introduces this check as it causes crashing the kernel when setting small mtu values on non-ip capable netdevices. Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
@@ -1047,6 +1047,8 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
 	}
 
 	in_dev = __in_dev_get_rtnl(dev);
+	if (!in_dev)
+		return NOTIFY_DONE;
 
 	switch (event) {
 	case NETDEV_UP:

Original file line number	Diff line number	Diff line change
`@@ -1047,6 +1047,8 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo`
`1047`	`1047`	`}`
`1048`	`1048`
`1049`	`1049`	`in_dev = __in_dev_get_rtnl(dev);`
	`1050`	`+ if (!in_dev)`
	`1051`	`+ return NOTIFY_DONE;`
`1050`	`1052`
`1051`	`1053`	`switch (event) {`
`1052`	`1054`	`case NETDEV_UP:`