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

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Date:   Fri, 16 Feb 2018 21:58:35 +0000
From:   Matthew Garrett <mjg59@...gle.com>
To:     luto@...nel.org
Cc:     tony.luck@...el.com,
        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 1:45 PM Andy Lutomirski <luto@...nel.org> wrote:
> I'm going to go out on a limb and suggest that the fact that
> unprivileged users can read efi variables at all is a mistake
> regardless of SMI issues.

Why? They should never contain sensitive material.

> Also, chmod() just shouldn't work on efi variables, and the mode
> passed to creat() should be ignored.  After all, there's no backing
> store for the mode.

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