linux-kernel - Re: [PATCH v2 0/2] x86/mm/KASLR: Do not adapt size of the direct mapping section for SGI UV system

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Date:   Wed, 7 Jun 2017 12:35:33 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Russ Anderson <rja@....com>,
        Dimitri Sivanich <sivanich@....com>,
        "travis@....com" <travis@....com>,
        Mike Travis <mike.travis@....com>,
        Frank Ramsay <frank.ramsay@....com>,
        Thomas Garnier <thgarnie@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>
Subject: Re: [PATCH v2 0/2] x86/mm/KASLR: Do not adapt size of the direct
 mapping section for SGI UV system

Hi all,

PING!

Is there any further comment or suggetion about this patchset?

Thanks
Baoquan

On 05/20/17 at 08:02pm, Baoquan He wrote:
> This is v2 post.
> 
> This patchset is trying to fix a bug that SGI UV system casually hang
> during boot with KASLR enabled. The root cause is that mm KASLR adapts
> size of the direct mapping section only based on the system RAM size.
> Then later when map SGI UV MMIOH region into the direct mapping during
> rest_init() invocation, it might go beyond of the directing mapping
> section and step into VMALLOC or VMEMMAP area, then BUG_ON triggered.
> 
> The fix is adding a helper function is_early_uv_system to check UV system
> earlier, then call the helper function in kernel_randomize_memory() to
> check if it's a SGI UV system, if yes, we keep the size of direct mapping
> section to be 64TB just as nokslr.
> 
> With this fix, SGI UV system can have 64TB direct mapping size always,
> and the starting address of direct mapping/vmalloc/vmemmap and the padding
> between them can still be randomized to enhance the system security.
> 
> v1->v2:
>     1. Mike suggested making is_early_uv_system() an inline function and be
>     put in include/asm/uv/uv.h so that they can adjust them easier in the
>     future.
> 
>     2. Split the v1 code into uv part and mm KASLR part as Mike suggested.
> 
> Baoquan He (2):
>   x86/UV: Introduce a helper function to check UV system at earlier
>     stage
>   x86/mm/KASLR: Do not adapt the size of the direct mapping section for
>     SGI UV system
> 
>  arch/x86/include/asm/uv/uv.h | 6 ++++++
>  arch/x86/mm/kaslr.c          | 3 ++-
>  2 files changed, 8 insertions(+), 1 deletion(-)
> 
> -- 
> 2.5.5
>