net loopback: Set loopback_dev to NULL when freed

It has recently turned up that we have a number of long standing bugs
in the network stack cleanup code with use of the loopback device
after it has been freed that have not turned up because in most cases
the storage allocated to the loopback device is not reused, when those
accesses happen.

Set looback_dev to NULL to trigger oopses instead of silent data corrupt
when we hit this class of bug.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index fcbf680c3e62f73af4933896641045de34f1f68c..a17d85a331f1ade54f9ec1834f1e8ee1c67d9b9d 100644 (file)
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -146,6 +146,7 @@ static int loopback_dev_init(struct net_device *dev)
 
 static void loopback_dev_free(struct net_device *dev)
 {
+       dev_net(dev)->loopback_dev = NULL;
        free_percpu(dev->lstats);
        free_netdev(dev);
 }