linux-kernel - Re: Bug report about KASLR and ZONE

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Date:   Wed, 11 Jul 2018 20:41:55 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Chao Fan <fanc.fnst@...fujitsu.com>, akpm@...ux-foundation.org,
        linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        yasu.isimatu@...il.com, keescook@...omium.org,
        indou.takao@...fujitsu.com, caoj.fnst@...fujitsu.com,
        douly.fnst@...fujitsu.com, mhocko@...e.com, vbabka@...e.cz,
        mgorman@...hsingularity.net
Subject: Re: Bug report about KASLR and ZONE_MOVABLE

On 07/11/18 at 06:49pm, Baoquan He wrote:
> On 07/11/18 at 06:41pm, Baoquan He wrote:
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 1521100..fe346b4 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -6678,6 +6678,8 @@ static void __init find_zone_movable_pfns_for_nodes(void)
> >  			unsigned long size_pages;
> >  
> >  			start_pfn = max(start_pfn, zone_movable_pfn[nid]);
> > +			/* KASLR may put kernel after 'start_pfn', start after kernel */
> > +			start_pfn = max(start_pfn, PAGE_ALIGN(_etext));
> 
> Sorry, I used wrong function.
> 
> Please try this one:
> 
> From 005435407a331ecf2803e5ebfdc44b8f5f8f9748 Mon Sep 17 00:00:00 2001
> From: Baoquan He <bhe@...hat.com>
> Date: Wed, 11 Jul 2018 18:30:04 +0800
> Subject: [PATCH v2] mm, page_alloc: find movable zone after kernel text
> 
> In find_zone_movable_pfns_for_nodes(), when try to find the starting
> PFN movable zone begins in each node, kernel text position is not
> considered. KASLR may put kernel after which movable zone begins.
> 
> Fix it by finding movable zone after kernel text.
> 
> Signed-off-by: Baoquan He <bhe@...hat.com>
> ---
>  mm/page_alloc.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 1521100..17584cc 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6678,6 +6678,8 @@ static void __init find_zone_movable_pfns_for_nodes(void)
>  			unsigned long size_pages;
>  
>  			start_pfn = max(start_pfn, zone_movable_pfn[nid]);
> +			/* KASLR may put kernel after 'start_pfn', start after kernel */
> +			start_pfn = max(start_pfn, PFN_UP(_etext));

It's wrong again, NACK, have posted v3 in this thread.

>  			if (start_pfn >= end_pfn)
>  				continue;
>  
> -- 
> 2.1.0
>