linux-kernel - Re: firmware: dmi-sysfs: why is the access mode of dmi sysfs entries restricted to 0400?

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Date:   Wed, 4 Dec 2019 10:29:42 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Guoheyi <guoheyi@...wei.com>
Cc:     Mike Waychison <mikew@...gle.com>, linux-kernel@...r.kernel.org,
        wanghaibin 00208455 <wanghaibin.wang@...wei.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: firmware: dmi-sysfs: why is the access mode of dmi sysfs entries
 restricted to 0400?

On Wed, Dec 04, 2019 at 05:01:06PM +0800, Guoheyi wrote:
> 
> 在 2019/12/4 15:41, Greg Kroah-Hartman 写道:
> > On Wed, Dec 04, 2019 at 03:31:22PM +0800, Guoheyi wrote:
> > > Hi,
> > > 
> > > Why is the access mode of dmi sysfs entries restricted to 0400? Is it for
> > > security concern? If it is, which information do we consider as privacy?
> > There's lots of "interesting" information in dmi entries that you
> > probably do not want all processes reading, which is why they are
> > restricted.
> > 
> > > We would like to fetch CPU information from non-root application, is there
> > > feasible way to do that?
> > What specific CPU information is not currently exported in /proc/cpuinfo
> > that only shows up in DMI entries that you are interested in?
> 
> We'd like to get processor manufacturer, speed and version, and pass the
> information to qemu virtual machine, for users of VM might be happy to see
> this instead of "unknown xxx", while qemu may run as non-root.

Careful about this as if you move that virtual machine around, those
values will change and if userspace was depending on them being static
(set up at program start time), then you might have problems.

good luck!

greg k-h