Re: [PATCH 2/2] test: check copy_to/from_user boundary validation

[Andrew Morton <akpm@linux-foundation.org>]

On Tue,  3 Dec 2013 13:27:34 -0800 Kees Cook <keescook@chromium.org> wrote:

> To help avoid an architecture failing to correctly check kernel/user
> boundaries when handling copy_to_user, copy_from_user, put_user, or
> get_user, perform some simple tests and fail to load if any of them
> behave unexpectedly.
> 
> Specifically, this is to make sure there is a way to notice if things
> like what was fixed in 8404663f81d212918ff85f493649a7991209fa04 ("ARM:
> 7527/1: uaccess: explicitly check __user pointer when !CPU_USE_DOMAINS")
> ever regresses again, for any architecture.

I guess the challenge will be to get anyone to remember to run this.

Really, this could be viewed as a candidate for
tools/testing/selftests.  The tests in there are userspace tests, and
your userspace test would consist of "modprobe test_user_copy".  The
advantage of this is that your test will get included whenever someone
runs the selftest suite.  This is better than having it stranded over
in ./kernel/.

> ---
>  kernel/Makefile         |    1 +
>  kernel/test_user_copy.c |  103 +++++++++++++++++++++++++++++++++++++++++++++++
>  lib/Kconfig.debug       |   13 ++++++

We already have a whole pile of test modules - seven of them reside in
lib/ and I think there's an RCU one somewhere.  Can we bring order to
all of this?  Some form of integration under tools/testing would be one
approach.

If you're disinclined to undertake such a project at this time, I'd
suggest these two go into lib/ so they are known about if/when someone
goes for the big cleanup.