netdev - Re: [PATCH] ip6_gre: don't allow to remove the fb_tunnel

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <534CE668.9060509@6wind.com>
Date:	Tue, 15 Apr 2014 09:57:28 +0200
From:	Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:	David Miller <davem@...emloft.net>
CC:	netdev@...r.kernel.org, xeb@...l.ru
Subject: Re: [PATCH] ip6_gre: don't allow to remove the fb_tunnel_dev

Le 15/04/2014 06:04, David Miller a écrit :
> From: Nicolas Dichtel <nicolas.dichtel@...nd.com>
> Date: Mon, 14 Apr 2014 17:11:38 +0200
>
>> It's possible to remove the FB tunnel with the command 'ip link del ip6gre0' but
>> this is unsafe, the module always supposes that this device exists. For example,
>> ip6gre_tunnel_lookup() may use it unconditionally.
>>
>> Let's add a rtnl handler for dellink, which will never remove the FB tunnel (we
>> let ip6gre_destroy_tunnels() do the job).
>>
>> Introduced by commit c12b395a4664 ("gre: Support GRE over IPv6").
>>
>> CC: Dmitry Kozlov <xeb@...l.ru>
>> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>
>
> I don't see how we ever get rid of fb_tunnel_dev and can therefore
> remove the module successfully.
>
> It is created by the per-netns initialization, but since it isn't
> added to the hashes I don't see how the per-netns exit code can
> end up unregistering and freeing it up.
>
> How is this supposed to work?
It is added to the hashes in ip6gre_init_net() in bucket [0][0]:
#define tunnels_wc      tunnels[0]
[snip]
         rcu_assign_pointer(ign->tunnels_wc[0],
                            netdev_priv(ign->fb_tunnel_dev));

Thus the tunnel is deleted by the loop in ip6gre_destroy_tunnels().
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html