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:   Thu, 01 Jun 2017 02:48:01 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Harald Welte <laforge@...monks.org>
Cc:     Cong Wang <xiyou.wangcong@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: loosing netdevices with namespaces and unshare?

Harald Welte <laforge@...monks.org> writes:

> Hi Eric,
>
> On Thu, Jun 01, 2017 at 01:32:49AM -0500, Eric W. Biederman wrote:
>
>> If a network device does not implement rntl_link_ops it is returned to
>> the initial network namespace.   Anything else will loose physical
>> devices.
>
> Thanks a lot for your statement.  This is a big relief, my line of
> thinking thus is confirmed:  We shall not loose physical devices.

Rereading that I should have said:
    We shall not lose physical devices.
We should let the loose to talk and say interesting things to the world.

>> Only for pure software based devices do we delete them.  Perhaps your
>> sub interface implements rtnl_link_ops?  Either that or something is
>> still holding a reference to your network namespace, which would prevent
>> the network device from being returned.
>
> My question is how to debug this further?  Monitoring
> /proc/*/ns/net* showed that the ID of the namespace is gone after
> terminating my processes in the namespace.  Short of adding printk() or
> playing with kprobes: to the related kernel code, how can I track the
> reference count or get an idea who might hold references?

You mentioned sub-interface.  I would first look to see if your
sub-interface might possibly implement rtnl_link_ops.

For testing I would toss in a full fledged physical interface and
see if that pops back.  Just to verify what you are seeing happening is
happening.

In your minimal test case of "unshare -Urn bash -c 'sleep 1; exit 0;'" I
can't imagine there is anything holding a reference.  So it may come
down to adding some printks or playing with kprobes.

All of macvlans and vlans and anything I can think of as sub-interface
all implement rtnl_link_ops and will get deleted when a network
namespace exits.  Which generally is what you want as it gives a very
nice cleanup.

Eric

Powered by blists - more mailing lists