linux-kernel - Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions

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Message-ID: <20170728080640.GK24304@x1>
Date:   Fri, 28 Jul 2017 16:06:40 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Matt Fleming <matt@...eblueprint.co.uk>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        keescook@...omium.org, tglx@...utronix.de, hpa@...or.com,
        izumi.taku@...fujitsu.com, fanc.fnst@...fujitsu.com,
        thgarnie@...gle.com, n-horiguchi@...jp.nec.com
Subject: Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be
 randomized in mirror regions

Hi Ingo,

On 07/24/17 at 02:34pm, Matt Fleming wrote:
> On Fri, 21 Jul, at 09:19:56PM, Baoquan He wrote:
> >
> > There are places where the efi map is getting and used like this. E.g
> > in efi_high_alloc() of drivers/firmware/efi/libstub/efi-stub-helper.c.
> > EFI developers worry the size of efi_memory_desc_t could not be the same
> > as e->efi_memdesc_size?
> > 
> > Hi Matt,
> > 
> > Could you help have a look at this?
> 
> You're exactly right. The code guards against the size of the
> efi_memory_desc_t struct changing. The UEFI spec says to traverse the
> memory map this way.

I saw your new comment in v7 post. Matt has helped to confirm it.
The EFI code was made to get efi memmap in that way on purpose. There
are several sub-threads about this patch, it could be missed.

Thanks
Baoquan