linux-kernel - Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into KASLR VA space for randomization

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Message-ID: <20170324094656.r2nln4vbidj5jhqt@pd.tnic>
Date:   Fri, 24 Mar 2017 10:46:56 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Ingo Molnar <mingo@...nel.org>, Dave Young <dyoung@...hat.com>,
        Baoquan He <bhe@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        Thomas Garnier <thgarnie@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Bhupesh Sharma <bhsharma@...hat.com>
Subject: Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into
 KASLR VA space for randomization

On Fri, Mar 24, 2017 at 09:42:40AM +0000, Ard Biesheuvel wrote:
> That is a different matter. If the regions are only mapped while
> runtime services invocations are in progress (as we do on ARM), I am
> not sure if it matters that much, given how rarely that occurs in
> normal use.

Question is, is there anything worth protecting with ASLR or we don't
care? I wanna say, we should randomize just in case, especially as it
shouldn't be that expensive to do.

Also, how does the whole EFI-in-the-kexec-ed-kernel work on ARM? Runtime
services get mapped on-demand in the kexec-ed kernel too?

-- 
Regards/Gruss,
    Boris.

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