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Date: Wed, 25 Jan 2017 11:41:13 -0800
From: Kees Cook <>
To: Hoeun Ryu <>
Cc: "" <>
Subject: Re: I'd like to contribute to this project.

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'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!


Kees Cook
Nexus Security

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