linux-kernel - Re: /dev/mem and secure boot

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190906121510.GA17328@kroah.com>
Date:   Fri, 6 Sep 2019 14:15:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Jean Delvare <jdelvare@...e.de>
Cc:     Arnd Bergmann <arnd@...db.de>, Thomas <trenn@...e.de>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: /dev/mem and secure boot

On Fri, Sep 06, 2019 at 01:02:21PM +0200, Jean Delvare wrote:
> I've been bitten recently by mcelog not working on machines started in
> secure boot mode. mcelog tries to read DMI information from /dev/mem
> and fails to open it.

What do you mean by "secure boot"?  Is this matthew's patchset that
restricts /dev/mem/ or something else?

> This made me wonder: if not even root can read /dev/mem (nor, I
> suppose, /dev/kmem and /dev/port) in secure boot mode, why are we
> creating these device nodes at all in the first place? Can't we detect
> that we are in secure boot mode and skip that step, and reap the rewards
> (faster boot, lower memory footprint and less confusion)?

Sure, feel free to not register it at all if the mode is enabled.

thanks,

greg k-h