linux-kernel - Re: [PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions

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Message-ID: <20170704153633.GA3149@codeblueprint.co.uk>
Date:   Tue, 4 Jul 2017 16:36:33 +0100
From:   Matt Fleming <matt@...eblueprint.co.uk>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Baoquan He <bhe@...hat.com>, LKML <linux-kernel@...r.kernel.org>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Ingo Molnar <mingo@...nel.org>,
        Kees Cook <keescook@...omium.org>, thgarnie@...gle.com,
        caoj.fnst@...fujitsu.com, izumi.taku@...fujitsu.com
Subject: Re: [PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized
 in mirror regions

On Tue, 04 Jul, at 04:46:58PM, Thomas Gleixner wrote:
> On Tue, 4 Jul 2017, Baoquan He wrote:
>  
> > In fact I just referred to code in setup_arch(). Now I have a question,
> > though CONFIG_EFI=y but efi firmware is not enabled,
> > boot_params.efi_info.efi_loader_signature should be initilized to 0.
> > Then below code is also problematic.
> >
> > #ifdef CONFIG_EFI
> >         if (!strncmp((char *)&boot_params.efi_info.efi_loader_signature,                                                                         
> >                      EFI32_LOADER_SIGNATURE, 4)) {
> >                 set_bit(EFI_BOOT, &efi.flags);
> >         } else if (!strncmp((char *)&boot_params.efi_info.efi_loader_signature,
> >                      EFI64_LOADER_SIGNATURE, 4)) {
> >                 set_bit(EFI_BOOT, &efi.flags);
> >                 set_bit(EFI_64BIT, &efi.flags);
> >         }
> > 
> >         if (efi_enabled(EFI_BOOT))
> >                 efi_memblock_x86_reserve_range();
> > #endif
> 
> Indeed. Matt?

It's possibly that I'm missing some context, but boot_params should be
zero'd -- the x86 boot protocol requires that the entire data
structure be zero'd on allocation.

Have I missed something?