linux-kernel - Re: [RFC] Tagging of vmalloc pages for supporting the pmalloc allocator

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: <ab4809cd-0efc-a79d-6852-4bd2349a2b3f@huawei.com>
Date:   Thu, 3 Aug 2017 18:06:11 +0300
From:   Igor Stoppa <igor.stoppa@...wei.com>
To:     Jerome Glisse <jglisse@...hat.com>,
        Michal Hocko <mhocko@...nel.org>
CC:     Linux-MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        <linux-security-module@...r.kernel.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        Kees Cook <keescook@...gle.com>
Subject: Re: [RFC] Tagging of vmalloc pages for supporting the pmalloc
 allocator

On 03/08/17 17:47, Jerome Glisse wrote:
> On Thu, Aug 03, 2017 at 03:55:50PM +0200, Michal Hocko wrote:
>> On Thu 03-08-17 15:20:31, Igor Stoppa wrote:

[...]

>>> I am confused about this: if "private2" is a pointer, but when I get an
>>> address, I do not even know if the address represents a valid pmalloc
>>> page, how can i know when it's ok to dereference "private2"?
>>
>> because you can make all pages which back vmalloc mappings have vm_area
>> pointer set.
> 
> Note that i think this might break some device driver that use vmap()
> i think some of them use private field to store device driver specific
> informations. But there likely is an unuse field in struct page that
> can be use for that.

This increases the unease from my side ... it looks like there is no way
to fully understand if a field is really used or not, without having
deep intimate knowledge of lots of code that is only marginally involved :-/

Similarly, how would I be able to specify what would be the correct way
to decide the member of the union to use for handling the field?

If there were either some sort of non-multiplexed tag/cookie field or a
function, that would specify how to treat the various unions, then it
would be easier to multiplex the remaining data, according to how the
page is used.

--
igor