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

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Message-ID: <20170914014451.GK12824@x1>
Date:   Thu, 14 Sep 2017 09:44:51 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     mingo@...hat.com, tglx@...utronix.de, hpa@...or.com,
        thgarnie@...gle.com, keescook@...omium.org,
        akpm@...ux-foundation.org, yamada.masahiro@...ionext.com,
        rja@....com, frank.ramsay@....com
Subject: Re: [PATCH v2 RESEND 0/2] x86/mm/KASLR: Do not adapt the size of the
 direct mapping section for SGI UV system

Hi all,

PING!

Do anyone has any suggestion about this issue? This bug blocks SGI
system's boot, KASLR has to be disabled on SGI system if they want to
run tests.

Thanks
Baoquan

On 09/07/17 at 03:42pm, Baoquan He wrote:
> This is v2 post RESEND. Add Mike's Acked-by to patch 2/2 as he suggested
> in private mail. And update patches log slightly.
> 
> 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
>