Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 13 May 2020 18:26:04 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Luis Chamberlain <mcgrof@kernel.org>
Cc:     "Eric W. Biederman" <ebiederm@xmission.com>,
        Josh Triplett <josh@joshtriplett.org>, viro@zeniv.linux.org.uk,
        rafael@kernel.org, jeyu@kernel.org, jmorris@namei.org,
        keescook@chromium.org, paul@paul-moore.com,
        stephen.smalley.work@gmail.com, eparis@parisplace.org,
        nayna@linux.ibm.com, zohar@linux.ibm.com,
        scott.branden@broadcom.com, dan.carpenter@oracle.com,
        skhan@linuxfoundation.org, geert@linux-m68k.org,
        tglx@linutronix.de, bauerman@linux.ibm.com, dhowells@redhat.com,
        linux-integrity@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        kexec@lists.infradead.org, linux-security-module@vger.kernel.org,
        selinux@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] security: add symbol namespace for reading file data
Message-ID: <20200513162604.GE1362525@kroah.com>
References: <20200513152108.25669-1-mcgrof@kernel.org>
 <20200513152108.25669-3-mcgrof@kernel.org>
 <87k11fonbk.fsf@x220.int.ebiederm.org>
 <20200513161622.GS11244@42.do-not-panic.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200513161622.GS11244@42.do-not-panic.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, May 13, 2020 at 04:16:22PM +0000, Luis Chamberlain wrote:
> On Wed, May 13, 2020 at 10:40:31AM -0500, Eric W. Biederman wrote:
> > Luis Chamberlain <mcgrof@kernel.org> writes:
> > 
> > > Certain symbols are not meant to be used by everybody, the security
> > > helpers for reading files directly is one such case. Use a symbol
> > > namespace for them.
> > >
> > > This will prevent abuse of use of these symbols in places they were
> > > not inteded to be used, and provides an easy way to audit where these
> > > types of operations happen as a whole.
> > 
> > Why not just remove the ability for the firmware loader to be a module?
> > 
> > Is there some important use case that requires the firmware loader
> > to be a module?
> > 
> > We already compile the code in by default.  So it is probably just
> > easier to remove the modular support all together.  Which would allow
> > the export of the security hooks to be removed as well.
> 
> Yeah, that's a better solution. The only constaint I am aware of is
> we *cannot* change the name of the module from firmware_class since the
> old fallback sysfs loader depends on the module name. So, so long as we
> take care with that on built-in and document this very well, I think
> we should be good.
> 
> I checked the commit logs and this was tristate since the code was added
> upstream, so I cannot see any good reason it was enabled as modular.
> 
> Speaking with a *backports experience* hat on, we did have a use case
> to use a module for it in case a new feature was added upstream which
> was not present on older kernels. However I think that using a separate
> symbol prefix would help with that.
> 
> Would any Android stakeholders / small / embedded folks whave any issue
> with this?

Android has build in the firmware loading logic for a while now.  Well,
always, they have not had kernel modules for many years.  That is
changing but this logic is not getting moved to a kernel module as that
would just be silly :)

thanks,

greg k-h