Re: [PATCH NETFILTER v2] netfilter: gre: nf_ct_gre_keymap_flush() removal
From: Pablo Neira Ayuso
Date: Thu Jul 01 2021 - 20:56:36 EST
On Thu, Jul 01, 2021 at 08:02:24AM +0300, Vasily Averin wrote:
> nf_ct_gre_keymap_flush() is useless.
> It is called from nf_conntrack_cleanup_net_list() only and tries to remove
> nf_ct_gre_keymap entries from pernet gre keymap list. Though:
> a) at this point the list should already be empty, all its entries were
> deleted during the conntracks cleanup, because
> nf_conntrack_cleanup_net_list() executes nf_ct_iterate_cleanup(kill_all)
> before nf_conntrack_proto_pernet_fini():
> +- nf_ct_iterate_cleanup
> | nf_ct_put
> | nf_conntrack_put
> | nf_conntrack_destroy
> | destroy_conntrack
> | destroy_gre_conntrack
> | nf_ct_gre_keymap_destroy
> `- nf_conntrack_proto_pernet_fini
> b) Let's say we find that the keymap list is not empty. This means netns
> still has a conntrack associated with gre, in which case we should not free
> its memory, because this will lead to a double free and related crashes.
> However I doubt it could have gone unnoticed for years, obviously
> this does not happen in real life. So I think we can remove
> both nf_ct_gre_keymap_flush() and nf_conntrack_proto_pernet_fini().
I think nf_ct_gre_keymap_flush() became useless when the GRE was
de-modularized (built-in into nf_conntrack).