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: <7308d733-1e0b-7d2e-bc34-0757555d39d6@redhat.com>
Date:   Tue, 19 Apr 2022 14:12:41 +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,
        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

On 19.04.22 14:00, Miaohe Lin wrote:
> On 2022/4/19 19:46, David Hildenbrand wrote:
> ...
>>> Do you mean that we should set the pfn to 0 for the hwpoison marker so that we can
>>> distinguish swapin error case from real hwpoison case?
>>
>> I am not sure if we really have to distinguish. However, "0" seems to
>> make sense to indicate "this is not an actual problematic PFN, the
>> information is simply no longer around due to a hardware issue.
>>
> 
> IMHO, we have to distinguish. For example, we might need to return VM_FAULT_SIGBUS
> instead of VM_FAULT_HWPOISON when user accesses the error page. Or should we simply
> return VM_FAULT_HWPOISON to simplify the handling?

Hm, you're right. In e.g., x86 do_sigbus() we would send an BUS_MCEERR_AR.

So yes, if we reuse is_hwpoison_entry() we'd have to convert to either
VM_FAULT_HWPOISON or VM_FAULT_SIGBUS.

Something like "is_error_entry()" that can further be refined to
hwpoison or swapin could make sense. But what you have here is straight
forward to me as well. Whatever you/others prefer.

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


NIT: I'd make the terminology make_swapin_error_entry() consistent with
SWAP_READ_ERROR and especially existing SWP_.

For example, calling the latter SWP_SWAPIN_ERROR

-- 
Thanks,

David / dhildenb