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Date: Thu, 26 Jan 2017 13:36:19 -0800
From: Kees Cook <>
To: Hoeun Ryu <>
Cc: "" <>, 
	Richard Weinberger <>
Subject: Re: I'd like to contribute to this project.

On Thu, Jan 26, 2017 at 6:49 AM, Hoeun Ryu <> wrote:
> On Thu, Jan 26, 2017 at 4:41 AM, Kees Cook <> wrote:
>> On Wed, Jan 25, 2017 at 6:01 AM, Hoeun Ryu <> wrote:
>>> Hi. I'm Hoeun Ryu.
>> Hi! Nice to meet you!
>>> I've been reading arm/arm64 and mm/fs kernel code for the last few years.
>>> I stumbled upon the wiki page for this project and found this project seems
>>> very interesting.
>>> I think I can start to contibute to this project from porting small parts of
>>> PAX/GRSEC features that you guys haven't worked on yet.
>> Sure, that would be very welcome. Are there features you're especially
>> interested in?
> I tried to find out what features PAX/GRKERNSEC provides reading
> grsecurity wiki pages and the patch file today.
> It might take a week or two to find adequate features for me to tackle.
> But my guess after few hours of a brief investigation is `Deter
> exploit bruteforcing (GRKERNSEC_BRUTE)`
> Do you think the feature is worth it to you guys ? If not, please
> recommend others.

I'd really like to see this, yes. There have been attempts in the past
that got derailed. I strongly think it should be part of the kernel
(and not glibc, as got proposed):

I think it's worth trying it again.

>>> I'd like to start from something trivial so I can do it in my free time.
>>> It's also ok to work with someone who are working on a big patch series if
>>> you need help.
>> Just looking through the list of things on the wiki, how about this?
>> - add zeroing of copy_from_user on failure test to test_usercopy.c
>> The issue here is that when a copy_from_user() call fails (for
>> whatever reason), the kernel is supposed to clear the destination
>> buffer with zeros to make sure nothing is accidentally exposed later
>> (if, say, it is copied back to userspace at a later time). We saw a
>> few instances where this protective copying wasn't happening, but
>> there was no regression test for it.
>> Adding a test to lib/test_usercopy.c for the zeroing would be nice to
>> have, and should be a relatively small change.
>> Let me know if that sounds good to you, and thanks!
> It sounds good, of course. I can work on it.
> Your help during my struggle for it will be appreciated.

Cool, let us know how we can help. :)


Kees Cook
Nexus Security

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