linux-kernel - Re: [PATCH v7 3/7] mm,hugetlb: Clear HPageFreed outside of the lock

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: <b763adaf-258a-930f-d8f2-5d236e217fe7@oracle.com>
Date:   Wed, 14 Apr 2021 09:45:49 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Oscar Salvador <osalvador@...e.de>, Michal Hocko <mhocko@...e.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>,
        Muchun Song <songmuchun@...edance.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 3/7] mm,hugetlb: Clear HPageFreed outside of the lock

On 4/14/21 3:49 AM, Oscar Salvador wrote:
> On Wed, Apr 14, 2021 at 12:32:58PM +0200, Michal Hocko wrote:
>> Well, to be precise it does the very same thing with memamp struct pages
>> but that is before the initialization code you have pointed out above.
>> In this context it just poisons the allocated content which is the GB
>> page storage.
> 
> Right.
> 
>>> I checked, and when we get there in __alloc_bootmem_huge_page, page->private is
>>> still zeroed, so I guess it should be safe to assume that we do not really need
>>> to clear the flag in __prep_new_huge_page() routine?
>>
>> It would be quite nasty if the struct pages content would be undefined.
>> Maybe that is possible but then I would rather stick the initialization
>> into __alloc_bootmem_huge_page.
> 
> Yes, but I do not think that is really possible unless I missed something.
> Let us see what Mike thinks of it, if there are no objections, we can
> get rid of the clearing flag right there.
>  

Thanks for crawling through that code Oscar!

I do not think you missed anything.  Let's just get rid of the flag
clearing.
-- 
Mike Kravetz