linux-kernel - Re: [PATCH v2 0/8] x86/kaslr: Cleanup and small bugfixes

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Date:   Tue, 28 Jul 2020 13:06:17 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Arvind Sankar <nivedita@...m.mit.edu>
Cc:     Kees Cook <keescook@...omium.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/8] x86/kaslr: Cleanup and small bugfixes


* Arvind Sankar <nivedita@...m.mit.edu> wrote:

> The first 7 patches are cleanup and minor bugfixes on the x86 KASLR
> code.
> 
> The last one is a bit of an RFC. The memory regions used for KASLR are
> stored as 64-bit even on a 32-bit kernel. However there are still a few
> local variables that are 32-bit, but should be ok as far as I can see
> because they are assigned values that have been already limited to
> 32-bit. It does make it a little harder to verify that the code is
> correct. Since KASLR cannot actually use 64-bit regions for the 32-bit
> kernel, the patch reduces regions to their below-4G segment when
> creating them, making the actual variables 32-bit. Alternatively, the
> few local variables could be upgraded to 64-bit.
> 
> v1->v2:
> - Fix a bug in the bugfix 5/8: overlap.start can be smaller than
>   region.start, so shouldn't subtract before comparing.
> 
> Arvind Sankar (8):
>   x86/kaslr: Make command line handling safer
>   x86/kaslr: Remove bogus warning and unnecessary goto
>   x86/kaslr: Fix process_efi_entries comment
>   x86/kaslr: Initialize mem_limit to the real maximum address
>   x86/kaslr: Simplify __process_mem_region
>   x86/kaslr: Simplify process_gb_huge_pages
>   x86/kaslr: Clean up slot handling
>   x86/kaslr: Don't use 64-bit mem_vector for 32-bit kernel
> 
>  arch/x86/boot/compressed/acpi.c  |   7 +-
>  arch/x86/boot/compressed/kaslr.c | 228 ++++++++++++-------------------
>  arch/x86/boot/compressed/misc.h  |  19 ++-
>  3 files changed, 111 insertions(+), 143 deletions(-)

I've applied patches 1-4 to x86/kaslr and will push them out if they 
pass testing - see the review feedback for the others.

Thanks,

	Ingo