[PATCH net 1/2] geneve: should not call rt6_lookup() when ipv6 was disabled

[Hangbin Liu]

When we add a new GENEVE device with IPv6 remote, checking only for
IS_ENABLED(CONFIG_IPV6) is not enough as we may disable IPv6 in kernel
cmd(ipv6.disable=1), which will cause a NULL pointer dereference.

Reported-by: Jianlin Shi <ji...@redhat.com>
Signed-off-by: Hangbin Liu <liuhang...@gmail.com>
---
 drivers/net/geneve.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index 58bbba8582b0..0658715581e3 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -1512,6 +1512,10 @@ static void geneve_link_config(struct net_device *dev,
        }
 #if IS_ENABLED(CONFIG_IPV6)
        case AF_INET6: {
+               struct inet6_dev *idev = in6_dev_get(dev);
+               if (!idev)
+                       break;
+
                struct rt6_info *rt = rt6_lookup(geneve->net,
                                                 &info->key.u.ipv6.dst, NULL, 0,
                                                 NULL, 0);
@@ -1519,6 +1523,8 @@ static void geneve_link_config(struct net_device *dev,
                if (rt && rt->dst.dev)
                        ldev_mtu = rt->dst.dev->mtu - GENEVE_IPV6_HLEN;
                ip6_rt_put(rt);
+
+               in6_dev_put(idev);
                break;
        }
 #endif
-- 
2.19.2