linux-kernel - Re: [PATCH 1/2] fs/efivarfs: restrict inode permissions

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Message-ID: <CA+55aFy8JMLjpDk+sU6pirSZdVqqHtw5oocDAEC7wcHuo5Vssw@mail.gmail.com>
Date:   Tue, 20 Feb 2018 16:49:14 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     Joe Konno <joe.konno@...ux.intel.com>, linux-efi@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Matthew Garrett <matthew.garrett@...ula.com>,
        Jeremy Kerr <jk@...abs.org>, Andi Kleen <ak@...ux.intel.com>,
        Matthew Garrett <mjg59@...gle.com>,
        Peter Jones <pjones@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        James Bottomley <james.bottomley@...senpartnership.com>
Subject: Re: [PATCH 1/2] fs/efivarfs: restrict inode permissions

On Tue, Feb 20, 2018 at 3:30 PM, Luck, Tony <tony.luck@...el.com> wrote:
>
> Too much weasel there.  Should say:
>
> EFI[1] stinks. Reading any file in /sys/firmware/efi/efivars/ generates
> 4 (yes FOUR!) SMIs.

Is that actualkly the normal implementation?

Also, if these are just synchronous SMI's, then don't we just end up
correctly assigning the CPU load to the reader, and it doesn't
actually matter? Where's the DoS?

                 Linus