linux-kernel - Re: [PATCH 1/1] ACPI: fix acpi table use after free

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Message-ID: <e8593eae-40b8-bc9a-78db-529d28d2be88@redhat.com>
Date:   Wed, 10 Mar 2021 20:10:42 +0100
From:   David Hildenbrand <david@...hat.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     George Kennedy <george.kennedy@...cle.com>,
        Robert Moore <robert.moore@...el.com>,
        Erik Kaneda <erik.kaneda@...el.com>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Len Brown <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "open list:ACPI COMPONENT ARCHITECTURE (ACPICA)" <devel@...ica.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Dhaval Giani <dhaval.giani@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Oscar Salvador <osalvador@...e.de>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        Pankaj Gupta <pankaj.gupta.linux@...il.com>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH 1/1] ACPI: fix acpi table use after free


>>> Memory gets allocated and used in a different order, which seems to have
>>> exposed (yet another) latent BUG.
>>
>> Well, you can call it that, or you can say that things worked under
>> certain assumptions regarding the memory allocation order which are
>> not met any more.
>>
>>> The same could be reproduced via zone shuffling with a little luck.
>>
>> But nobody does that in practice.
>>

Dan will most certainly object. And I don't know what makes you speak in 
absolute words here.

>> This would be relatively straightforward to address if ACPICA was not
>> involved in it, but unfortunately that's not the case.
>>
>> Changing this part of ACPICA is risky, because such changes may affect
>> other OSes using it, so that requires some serious consideration.
>> Alternatively, the previous memory allocation order in Linux could be
>> restored.
> 
> Of course, long-term this needs to be addressed in the ACPI
> initialization code, because it clearly is not robust enough, but in
> the meantime there's practical breakage observable in the field, so
> what can be done about that?

*joke* enable zone shuffling.

No seriously, fix the latent BUG. What again is problematic about 
excluding these pages from the page allcoator, for example, via 
memblock_reserve()?

@Mike?

-- 
Thanks,

David / dhildenb