linux-kernel - Re: [PATCH v2] mm/swapfile: unuse_pte can map random data if swap read fails

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: <87k0bkk2rp.fsf@nvdebian.thelocal>
Date:   Wed, 20 Apr 2022 10:25:02 +1000
From:   Alistair Popple <apopple@...dia.com>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     akpm@...ux-foundation.org, willy@...radead.org, vbabka@...e.cz,
        dhowells@...hat.com, neilb@...e.de, david@...hat.com,
        surenb@...gle.com, minchan@...nel.org, peterx@...hat.com,
        sfr@...b.auug.org.au, rcampbell@...dia.com,
        naoya.horiguchi@....com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/swapfile: unuse_pte can map random data if swap
 read fails

Miaohe Lin <linmiaohe@...wei.com> writes:

> On 2022/4/19 15:53, Alistair Popple wrote:
>> Also in madvise_free_pte_range() you could just remove the swap entry as it's no
>> longer needed.
>>
>
> This swap entry will be removed in madvise_dontneed_single_vma().
> And in madvise_free_pte_range(), we may need to keep it as same as
> hwpoison entry. Or am I supposed to remove it even if hwpoison entry
> is reused later?

Why would we need to keep it for MADV_FREE though? It only works on private
anonymous memory, and 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 entry. I think that applies equally to a
hwpoison entry too - there's no reason to kill the process if it has called
MADV_FREE on the range.

>
> Thanks!
>
>> Alistair Popple <apopple@...dia.com> writes:
>>
>>> Miaohe Lin <linmiaohe@...wei.com> writes:
>>>
> ...