linux-kernel - Re: [PATCH 0/2] efivars: reading variables can generate SMIs

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Message-ID: <CACdnJuvR4NTdCwp=jT3AoW898EXuq6zakfo5hm6dd9mP-SWoGQ@mail.gmail.com>
Date:   Fri, 16 Feb 2018 22:03:37 +0000
From:   Matthew Garrett <mjg59@...gle.com>
To:     tony.luck@...el.com
Cc:     luto@...nel.org,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        joe.konno@...ux.intel.com, mingo@...nel.org, bp@...en8.de,
        linux-efi <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        jk@...abs.org, ak@...ux.intel.com, benjamin.drung@...fitbricks.com,
        pjones@...hat.com
Subject: Re: [PATCH 0/2] efivars: reading variables can generate SMIs

On Fri, Feb 16, 2018 at 2:02 PM Luck, Tony <tony.luck@...el.com> wrote:

> > If the default is 600 then it makes sense to allow a privileged service
to
> > selectively make certain variables world readable at runtime.

> As soon as you make one variable world readable you are vulnerable to
> a local user launching a DoS attack by reading that variable over and over
> generating a flood of SMIs.

I'm not terribly worried about untrusted users on my laptop, but I would
prefer to run as little code as root as possible.