linux-kernel - Re: [PATCH v2 RESEND 2/2] x86/mm/KASLR: Fix the size of vmemmap section

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Date:   Fri, 26 Apr 2019 17:23:48 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Borislav Petkov <bp@...en8.de>, keescook@...omium.org
Cc:     kirill@...temov.name, linux-kernel@...r.kernel.org, x86@...nel.org,
        tglx@...utronix.de, mingo@...nel.org, hpa@...or.com,
        keescook@...omium.org, peterz@...radead.org, thgarnie@...gle.com,
        herbert@...dor.apana.org.au, mike.travis@....com,
        frank.ramsay@....com, yamada.masahiro@...ionext.com
Subject: Re: [PATCH v2 RESEND 2/2] x86/mm/KASLR: Fix the size of vmemmap
 section

Hi Boris,

On 04/15/19 at 09:47pm, Borislav Petkov wrote:
> On Sun, Apr 14, 2019 at 03:28:04PM +0800, Baoquan He wrote:
> > kernel_randomize_memory() hardcodes the size of vmemmap section as 1 TB,
> > to support the maximum amount of system RAM in 4-level paging mode, 64 TB.
> > 
> > However, 1 TB is not enough for vmemmap in 5-level paging mode. Assuming
> > the size of struct page is 64 Bytes, to support 4 PB system RAM in 5-level,
> > 64 TB of vmemmap area is needed. The wrong hardcoding may cause vmemmap
> > stamping into the following cpu_entry_area section, if KASLR puts vmemmap
> > very close to cpu_entry_area, and the actual area of vmemmap is much bigger
> > than 1 TB.
 
> 
> Kirill, ack?

I sent private mail to Kirill and Kees. Kirill haven't replied yet, he
could be busy with something else as he doesn't show up recently on
lkml.

Kees kindly replied, and said he couldn't find this mail thread. He told
I can add his Reviewed-by, as he has acked this patchset in v2
thread. I just updated later to tune log and correct typos.
http://lkml.kernel.org/r/CAGXu5j+o4aSx9mMDJqTMOp-VrvWes-2YEwR1f29z8dm0rUfzGQ@mail.gmail.com

Can this be picked into tip with Kees' ack?

Thanks
Baoquan