linux-kernel - Re: [PATCH] mm/hugetlb: fix potential race in __update_and_free_hugetlb

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Message-Id: <AEF4F0F8-B3F5-4650-8B21-CCCE28FC0FCD@linux.dev>
Date: Mon, 8 Jul 2024 15:08:44 +0800
From: Muchun Song <muchun.song@...ux.dev>
To: Miaohe Lin <linmiaohe@...wei.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Linux-MM <linux-mm@...ck.org>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/hugetlb: fix potential race in
 __update_and_free_hugetlb_folio()



> On Jul 8, 2024, at 10:51, Miaohe Lin <linmiaohe@...wei.com> wrote:
> 
> There is a potential race between __update_and_free_hugetlb_folio() and
> try_memory_failure_hugetlb():
> 
> CPU1 CPU2
> __update_and_free_hugetlb_folio try_memory_failure_hugetlb
> folio_test_hugetlb
>  -- It's still hugetlb folio.
>  folio_clear_hugetlb_hwpoison
>    spin_lock_irq(&hugetlb_lock);
>   __get_huge_page_for_hwpoison
>    folio_set_hugetlb_hwpoison
>  spin_unlock_irq(&hugetlb_lock);
>  spin_lock_irq(&hugetlb_lock);
>  __folio_clear_hugetlb(folio);
>   -- Hugetlb flag is cleared but too late.
>  spin_unlock_irq(&hugetlb_lock);
> 
> When above race occurs, raw error page info will be leaked. Even worse,
> raw error pages won't have hwpoisoned flag set and hit pcplists/buddy.
> Fix this issue by deferring folio_clear_hugetlb_hwpoison() until
> __folio_clear_hugetlb() is done. So all raw error pages will have
> hwpoisoned flag set.
> 
> Fixes: 32c877191e02 ("hugetlb: do not clear hugetlb dtor until allocating vmemmap")
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>

Acked-by: Muchun Song <muchun.song@...ux.dev>

Thanks.