linux-kernel - Re: [PATCH v2] mm/page_alloc.c: avoid accessing uninitialized pcp page migratetype

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Message-ID: <dc9fa24b-cd9e-fb7c-047b-75d7e5cb0c1e@suse.cz>
Date:   Thu, 2 Sep 2021 14:09:11 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org
Cc:     peterz@...radead.org, mgorman@...hsingularity.net,
        david@...hat.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/page_alloc.c: avoid accessing uninitialized pcp
 page migratetype

On 9/2/21 13:54, Miaohe Lin wrote:
> If it's not prepared to free unref page, the pcp page migratetype is
> unset. Thus We will get rubbish from get_pcppage_migratetype() and
> might list_del &page->lru again after it's already deleted from the
> list leading to grumble about data corruption.
> 
> Fixes: df1acc856923 ("mm/page_alloc: avoid conflating IRQs disabled with zone->lock")
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> Acked-by: Mel Gorman <mgorman@...hsingularity.net>
> Cc: <stable@...r.kernel.org>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  mm/page_alloc.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 9c09dcb24149..a3c6acafa478 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3420,8 +3420,10 @@ void free_unref_page_list(struct list_head *list)
>  	/* Prepare pages for freeing */
>  	list_for_each_entry_safe(page, next, list, lru) {
>  		pfn = page_to_pfn(page);
> -		if (!free_unref_page_prepare(page, pfn, 0))
> +		if (!free_unref_page_prepare(page, pfn, 0)) {
>  			list_del(&page->lru);
> +			continue;
> +		}
>  
>  		/*
>  		 * Free isolated pages directly to the allocator, see
>