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" <redacted>
---
 drivers/net/loopback.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index fcbf680..a17d85a 100644
--- 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);
 }

-- 
1.7.5.4