Re: Bug report about KASLR and ZONE_MOVABLE

[Baoquan He]

On 07/11/18 at 06:41pm, Baoquan He wrote:
 
> Hmm, it's an issue, worth fixing it. Otherwise the size of
> movable area will be smaller than we expect when add "kernel_core="
> or "movable_core=".
> 
> Add a check in find_zone_movable_pfns_for_nodes(), and use min() to get
> the starting address of movable area between aligned '_etext'
> and start_pfn. It will go to label 'restart' to calculate the 2nd round
> if not satisfiled. 
> 
> Hi Chao,
> 
> Could you check if below patch works for you?
> 
> 
> From ab6e47c6a78d1a4ccb577b995b7b386f3149732f Mon Sep 17 00:00:00 2001
> From: Baoquan He <bhe@xxxxxxxxxx>
> Date: Wed, 11 Jul 2018 18:30:04 +0800
> Subject: [PATCH] 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@xxxxxxxxxx>
> ---
>  mm/page_alloc.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> 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: