ipv6: fix dereference of rt6_ex before null check error

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.king@canonical.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 13b0d6d..c1c44f4 100644 (file)
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1142,10 +1142,12 @@ 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);