linux-kernel - Re: SMBIOS/DMI data under CONFIG_STRICT

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Date:	Sat, 17 Jan 2015 17:56:32 -0500
From:	Jon Masters <jcm@...hat.com>
To:	Olof Johansson <olof@...om.net>
CC:	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: SMBIOS/DMI data under CONFIG_STRICT_DEVMEM

On 01/17/2015 05:52 PM, Jon Masters wrote:
> Hi Olof,
> 
> On 01/17/2015 04:10 PM, Olof Johansson wrote:
>> Hi,
>>
>> On Sat, Jan 17, 2015 at 12:12 PM, Jon Masters <jcm@...hat.com> wrote:
>>> Hi Catalin, all,
>>>
>>> I would like to ensure that the SMBIOS data provided by firmware is
>>> always readable from userspace on AArch64, through /dev/mem.
>>
>> Seems like this would be a good opportunity for cleanup and fixing
>> userspace to use /sys/firmware/dmi interfaces instead of having to go
>> poking through /dev/mem. That way they don't have to be privileged
>> process any more and is a general security benefit for everybody.
> 
> I don't disagree :)
> 
> Indeed, I was pushing within RH years ago to help get it into
> /sys/firmware/dmi where it lives today. Someone went over this code for
> us a few months ago and the determination was that there's a chunk of
> refactoring that needs doing to get it to do the right thing. I think in
> the interim some of the vendor kernels might need another solution, but
> I've already asked that Linaro refactor the tool to do it right.
> 
> There's probably good reasons to be able to poke at the tables directly
> from userspace under certain circumstances too. For example, one of the
> reference platforms I am using has bogus checksums in the tables so they
> fail to load in the Linux interpreter which means you never see the
> entries in /sys/firmware/dmi being created and could not debug why if
> you had no direct access to read the raw ones. That means that probably
> people would still carry hacks to allow such access.

(the reference platform in question above will be corrected shortly)


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