Re: Soft lockup on shutdown in nf_ct_iterate_cleanup()

[Patrick McHardy <kaber@trash.net>]

Martin Josefsson wrote:
> What about this case:
> 
> 1. Conntrack entry is created and placed on the unconfirmed list
> 2. The event cache bumps the refcount of the conntrack entry
> 3. module removal of ip_conntrack unregisters all hooks
> 4. packet is dropped by an iptables rule
> 5. packet is freed but we still have a refcount on the conntrack entry
> 
> Now there's no way to get that refcount to decrease as that only happens
> when the event cache receives another packet or the current packet makes
> it through the stack as you wrote above. And neither of this will happen
> since we unregistered the hooks providing the packets and dropped the
> packet.

The event cache is flushed on conntrack module unload after the hooks
have been unregistered, which should release all references.