[PATCH][net-next] ipv6: fix dereference of rt6_ex before null check error

[Colin King]

From: Colin Ian King <colin.k...@canonical.com>

Currently rt6_ex is being dereferenced before it is null checked
hence there is a possible null dereference bug. Fix this by only
dereferencing rt6_ex after it has been null checked.

Detected by CoverityScan, CID#1457749 ("Dereference before null check")

Fixes: 81eb8447daae ("ipv6: take care of rt6_stats")
Signed-off-by: Colin Ian King <colin.k...@canonical.com>
---
 net/ipv6/route.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 606e80325b21..6db1541eaa7b 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1152,10 +1152,12 @@ static DEFINE_SPINLOCK(rt6_exception_lock);
 static void rt6_remove_exception(struct rt6_exception_bucket *bucket,
                                 struct rt6_exception *rt6_ex)
 {
-       struct net *net = dev_net(rt6_ex->rt6i->dst.dev);
+       struct net *net;
 
        if (!bucket || !rt6_ex)
                return;
+
+       net = dev_net(rt6_ex->rt6i->dst.dev);
        rt6_ex->rt6i->rt6i_node = NULL;
        hlist_del_rcu(&rt6_ex->hlist);
        rt6_release(rt6_ex->rt6i);
-- 
2.14.1