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

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Message-ID: <20170724133410.GC11076@codeblueprint.co.uk>
Date:   Mon, 24 Jul 2017 14:34:10 +0100
From:   Matt Fleming <matt@...eblueprint.co.uk>
To:     Baoquan He <bhe@...hat.com>
Cc:     Ingo Molnar <mingo@...nel.org>, 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

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.