linux-kernel - Re: kdbus_proc_permission (Re: [GIT PULL] kdbus updates for Greg)

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Message-ID: <CANq1E4TnH9WeHFwKPnZQ6i4rY2cKWxgjhNvqsbM5WPiORXxyBA@mail.gmail.com>
Date:	Mon, 31 Aug 2015 18:22:38 +0200
From:	David Herrmann <dh.herrmann@...il.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg KH <gregkh@...uxfoundation.org>
Subject: Re: kdbus_proc_permission (Re: [GIT PULL] kdbus updates for Greg)

Hi

On Mon, Aug 31, 2015 at 5:37 PM, Andy Lutomirski <luto@...capital.net> wrote:
> On Mon, Aug 24, 2015 at 2:52 AM, David Herrmann <dh.herrmann@...il.com> wrote:
>> On Mon, Aug 10, 2015 at 4:42 AM, Andy Lutomirski <luto@...capital.net> wrote:
>>> I haven't checked the context in which it's used, but in order for
>>> kdbus_proc_permission to do what it claims to do, it appears to be
>>> missing calls to security_inode_permission and
>>> security_file_permission.
>>
>> Both are expected to be added by lsm patches (both hooks you mentioned
>> are empty if no lsm is selected).
>
> Will that mean that existing MAC policies stop being fully enforced
> (in effect) if kdbus is installed?

It means kdbus messages carry information about the sender, which LSMs
might prevent you to read via /proc. Just like you can send dbus
messages to a peer, which LSM-enhanced dbus-daemon might not allow. If
you use LSMs, we clearly advise you to wait for kdbus to gain LSM
support. We explicitly support legacy dbus1-compat for exactly such
reasons.

Thanks
David
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