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

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Date:   Fri, 16 Feb 2018 22:02:05 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Matthew Garrett <mjg59@...gle.com>,
        "luto@...nel.org" <luto@...nel.org>
CC:     James Bottomley <James.Bottomley@...senpartnership.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "joe.konno@...ux.intel.com" <joe.konno@...ux.intel.com>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "bp@...en8.de" <bp@...en8.de>,
        linux-efi <linux-efi@...r.kernel.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        "jk@...abs.org" <jk@...abs.org>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "benjamin.drung@...fitbricks.com" <benjamin.drung@...fitbricks.com>,
        "pjones@...hat.com" <pjones@...hat.com>
Subject: RE: [PATCH 0/2] efivars: reading variables can generate SMIs

> 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.

-Tony