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From:   ebiederm@xmission.com (Eric W. Biederman)
To:     Matt Bennett <matt.bennett@alliedtelesis.co.nz>
Cc:     netdev@vger.kernel.org, zbr@ioremap.net,
        linux-kernel@vger.kernel.org,
        Linux Containers <containers@lists.linux-foundation.org>
References: <20200702002635.8169-1-matt.bennett@alliedtelesis.co.nz>
Date:   Thu, 02 Jul 2020 13:59:59 -0500
In-Reply-To: <20200702002635.8169-1-matt.bennett@alliedtelesis.co.nz> (Matt
        Bennett's message of "Thu, 2 Jul 2020 12:26:30 +1200")
Message-ID: <87k0zlspxs.fsf@x220.int.ebiederm.org>
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Subject: Re: [PATCH 0/5] RFC: connector: Add network namespace awareness
Sender: linux-kernel-owner@vger.kernel.org
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Matt Bennett <matt.bennett@alliedtelesis.co.nz> writes:

> Previously the connector functionality could only be used by processes running in the
> default network namespace. This meant that any process that uses the connector functionality
> could not operate correctly when run inside a container. This is a draft patch series that
> attempts to now allow this functionality outside of the default network namespace.
>
> I see this has been discussed previously [1], but am not sure how my changes relate to all
> of the topics discussed there and/or if there are any unintended side
> effects from my draft

In a quick skim this patchset does not look like it approaches a correct
conversion to having code that works in multiple namespaces.

I will take the changes to proc_id_connector for example.
You report the values in the callers current namespaces.

Which means an unprivileged user can create a user namespace and get
connector to report whichever ids they want to users in another
namespace.  AKA lie.

So this appears to make connector completely unreliable.

Eric


> changes.
>
> Thanks.
>
> [1] https://marc.info/?l=linux-kernel&m=150806196728365&w=2
>
> Matt Bennett (5):
>   connector: Use task pid helpers
>   connector: Use 'current_user_ns' function
>   connector: Ensure callback entry is released
>   connector: Prepare for supporting multiple namespaces
>   connector: Create connector per namespace
>
>  Documentation/driver-api/connector.rst |   6 +-
>  drivers/connector/cn_proc.c            | 110 +++++++-------
>  drivers/connector/cn_queue.c           |   9 +-
>  drivers/connector/connector.c          | 192 ++++++++++++++++++++-----
>  drivers/hv/hv_fcopy.c                  |   1 +
>  drivers/hv/hv_utils_transport.c        |   6 +-
>  drivers/md/dm-log-userspace-transfer.c |   6 +-
>  drivers/video/fbdev/uvesafb.c          |   8 +-
>  drivers/w1/w1_netlink.c                |  19 +--
>  include/linux/connector.h              |  38 +++--
>  include/net/net_namespace.h            |   4 +
>  kernel/exit.c                          |   2 +-
>  samples/connector/cn_test.c            |   6 +-
>  13 files changed, 286 insertions(+), 121 deletions(-)