From: Igor Stoppa <igor.stoppa@huawei.com>
To: Jerome Glisse <jglisse@redhat.com>, Michal Hocko <mhocko@kernel.org>
Cc: Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
<linux-security-module@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Kees Cook <keescook@google.com>
Subject: Re: [RFC] Tagging of vmalloc pages for supporting the pmalloc allocator
Date: Thu, 3 Aug 2017 18:06:11 +0300 [thread overview]
Message-ID: <ab4809cd-0efc-a79d-6852-4bd2349a2b3f@huawei.com> (raw)
In-Reply-To: <20170803144746.GA9501@redhat.com>
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
next prev parent reply other threads:[~2017-08-03 15:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-02 15:14 [RFC] Tagging of vmalloc pages for supporting the pmalloc allocator Igor Stoppa
2017-08-02 17:08 ` Jerome Glisse
2017-08-03 10:11 ` Igor Stoppa
2017-08-03 11:48 ` Michal Hocko
2017-08-03 12:20 ` Igor Stoppa
2017-08-03 13:55 ` Michal Hocko
2017-08-03 14:41 ` Igor Stoppa
2017-08-03 14:47 ` Jerome Glisse
2017-08-03 15:06 ` Igor Stoppa [this message]
2017-08-03 15:15 ` Michal Hocko
2017-08-04 8:02 ` Igor Stoppa
2017-08-04 8:12 ` Michal Hocko
2017-08-07 11:26 ` Igor Stoppa
2017-08-07 11:34 ` Michal Hocko
2017-08-07 13:31 ` Jerome Glisse
2017-08-07 14:13 ` Igor Stoppa
2017-08-07 19:12 ` Jerome Glisse
2017-08-08 12:59 ` Igor Stoppa
2017-08-08 23:15 ` Jerome Glisse
2017-08-09 7:27 ` Igor Stoppa
2017-08-10 7:14 ` Michal Hocko
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