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

From	Thomas Gleixner <tglx@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions
Date	2017-07-04 17:50 +0200
Message-ID	<tZyfo-1QF-17@gated-at.bofh.it> (permalink)
References	(1 earlier) <tZr4f-5Hh-19@gated-at.bofh.it> <tZwGB-Oa-15@gated-at.bofh.it> <tZx9E-12c-5@gated-at.bofh.it> <tZxjj-1fd-15@gated-at.bofh.it> <tZy5I-1N0-21@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tue, 4 Jul 2017, Matt Fleming wrote:
> 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?

No. I misread the code. The strncmp() operates on
boot_params.efi_info.efi_loader_signature itself, so yes, all is fine.

It's just Baoquans copy and paste wreckage which is busted.

Thanks,

	tglx

Thread

[PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions Baoquan He <bhe@redhat.com> - 2017-07-04 10:10 +0200
  Re: [PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized  in mirror regions Thomas Gleixner <tglx@linutronix.de> - 2017-07-04 16:10 +0200
    Re: [PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized  in mirror regions Baoquan He <bhe@redhat.com> - 2017-07-04 16:40 +0200
      Re: [PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized  in mirror regions Thomas Gleixner <tglx@linutronix.de> - 2017-07-04 16:50 +0200
        Re: [PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized  in mirror regions Matt Fleming <matt@codeblueprint.co.uk> - 2017-07-04 17:40 +0200
          Re: [PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized  in mirror regions Thomas Gleixner <tglx@linutronix.de> - 2017-07-04 17:50 +0200
            Re: [PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized  in mirror regions Baoquan He <bhe@redhat.com> - 2017-07-05 01:20 +0200

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