Commit 01cc9ab6 authored Mar 29, 2021 by Eric Dumazet Committed by Greg Kroah-Hartman May 22, 2021

sit: proper dev_{hold|put} in ndo_[un]init methods



commit 6289a98f0817a4a457750d6345e754838eae9439 upstream.

After adopting CONFIG_PCPU_DEV_REFCNT=n option, syzbot was able to trigger
a warning [1]

Issue here is that:

- all dev_put() should be paired with a corresponding prior dev_hold().

- A driver doing a dev_put() in its ndo_uninit() MUST also
  do a dev_hold() in its ndo_init(), only when ndo_init()
  is returning 0.

Otherwise, register_netdevice() would call ndo_uninit()
in its error path and release a refcount too soon.

Fixes: 919067cc845f ("net: add CONFIG_PCPU_DEV_REFCNT")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 2dc72d6a

net/ipv6/sit.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -215,8 +215,6 @@ static int ipip6_tunnel_create(struct net_device *dev)

		ipip6_tunnel_clone_6rd(dev, sitn);

		dev_hold(dev);

		ipip6_tunnel_link(sitn, t);
		return 0;

		@@ -1407,7 +1405,7 @@ static int ipip6_tunnel_init(struct net_device *dev)
		dev->tstats = NULL;
		return err;
		}

		dev_hold(dev);
		return 0;
		}