linux-kernel - Re: [PATCH v2 3/3] mm/madvise: free hwpoison and swapin error entry in madvise_free_pte

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <0a793d7c-0591-28bc-5c36-a908c9d4900d@redhat.com>
Date:   Thu, 21 Apr 2022 15:25:07 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org
Cc:     willy@...radead.org, vbabka@...e.cz, dhowells@...hat.com,
        neilb@...e.de, apopple@...dia.com, surenb@...gle.com,
        minchan@...nel.org, peterx@...hat.com, sfr@...b.auug.org.au,
        naoya.horiguchi@....com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] mm/madvise: free hwpoison and swapin error entry
 in madvise_free_pte_range

On 21.04.22 14:53, Miaohe Lin wrote:
> Once the MADV_FREE operation has succeeded, callers can expect they might
> get zero-fill pages if accessing the memory again. Therefore it should be
> safe to delete the hwpoison entry and swapin error entry. There is no
> reason to kill the process if it has called MADV_FREE on the range.
> 
> Suggested-by: Alistair Popple <apopple@...dia.com>
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  mm/madvise.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 4d6592488b51..5f4537511532 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -624,11 +624,14 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
>  			swp_entry_t entry;
>  
>  			entry = pte_to_swp_entry(ptent);
> -			if (non_swap_entry(entry))
> -				continue;
> -			nr_swap--;
> -			free_swap_and_cache(entry);
> -			pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
> +			if (!non_swap_entry(entry)) {
> +				nr_swap--;
> +				free_swap_and_cache(entry);
> +				pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
> +			} else if (is_hwpoison_entry(entry) ||
> +				   is_swapin_error_entry(entry)) {
> +				pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
> +			}
>  			continue;
>  		}
>  

Reading the man page that should be fine, but might not be required.

"[...] the kernel can free the pages at any time. Once pages in the
range have been freed, the caller will see zero-fill-on-demand pages
upon subsequent page references."


LGTM

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb