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Date: Thu, 26 Jan 2017 23:49:00 +0900
From: Hoeun Ryu <>
To: Kees Cook <>
Cc: "" <>
Subject: Re: I'd like to contribute to this project.

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 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.

> -Kees
> --
> Kees Cook
> Nexus Security

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