netdev - Re: [PATCH] net: make net namespace sysctls belong to container's owner

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]

Date:	Mon, 8 Aug 2016 14:54:45 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Al Viro <viro@...iv.linux.org.uk>,
	lkml <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: make net namespace sysctls belong to container's owner

On Mon, Aug 8, 2016 at 2:08 PM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
> Dmitry Torokhov <dmitry.torokhov@...il.com> writes:
>
>> If net namespace is attached to a user namespace let's make container's
>> root owner of sysctls affecting said network namespace instead of global
>> root.
>>
>> This also allows us to clean up net_ctl_permissions() because we do not
>> need to fudge permissions anymore for the container's owner since it now
>> owns the objects in question.
>
> Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>
>
> Overall this seems reasonable.  However I am not a fan of your error
> handling.
>
>> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
>> ---
>>
>> This helps when running Android CTS in a container, but I think it makes
>> sense regardless.
>
>> +static void net_ctl_set_ownership(struct ctl_table_header *head,
>> +                               struct ctl_table *table,
>> +                               kuid_t *uid, kgid_t *gid)
>> +{
>> +     struct net *net = container_of(head->set, struct net, sysctls);
>> +
>> +     *uid = make_kuid(net->user_ns, 0);
>> +     if (!uid_valid(*uid))
>> +             *uid = GLOBAL_ROOT_UID;
>> +
>> +     *gid = make_kgid(net->user_ns, 0);
>> +     if (!gid_valid(*gid))
>> +             *gid = GLOBAL_ROOT_GID;
>
> This code should eiter be:
>         *uid = make_kuid(net->user_ns, 0);
>         *gid = make_kgid(net->user_ns, 0);
>
> Or it should be:
>         tmp_uid = make_kuid(net->user_ns, 0);
>         if (uid_valid(tmp_uid))
>                 *uid = tmp_uid;
>
>         tmp_gid = make_kgid(net->user_ns, 0);
>         if (gid_valid(tmp_gid))
>                 *gid = tmp_gid;
>
> It is just very fragile to assume to know what uid and gid
> would be if this code fails.
>
> As of v4.8-rc1 INVALID_UID and INVALID_GID can be set in inode->i_uid
> and inode->i_gid without causing horrible vfs confusion (making the
> first option viable), but I expect with the mention of Android you want
> to backport this so I will ask that you ask to implement the error
> handling that doesn't assume you know better than the generic code.
>
> If you don't have a better value to set something to it really should be
> left alone.

OK, fair enough. I will adopt the 2nd option and will resubmit. I need
to also test without net namespaces support (my other change blows up
because we are getting half-initialized init_net structure when
namespaces are disabled).

Thanks.

-- 
Dmitry