Re: [PATCH 0/7] test_user_copy improvements

On Wed, Aug 5, 2015 at 8:48 AM, James Hogan [off-list ref] wrote:

These patches extend the test_user_copy test module to handle lots more
cases of user accessors which architectures can override separately, and
in particular those which are important for checking the MIPS Enhanced
Virtual Addressing (EVA) implementations, which need to handle
overlapping user and kernel address spaces, with special instructions
for accessing user address space from kernel mode.

- Checking that kernel pointers are accepted when user address limit is
  set to KERNEL_DS, as done by the kernel when it internally invokes
  system calls with kernel pointers.
- Checking of the unchecked accessors (which don't call access_ok()).
  Some of the tests are special cased for EVA at the moment which has
  stricter hardware guarantees for bad user accesses than other
  configurations.
- Checking of other sets of user accessors, including the inatomic user
  copies, copy_in_user, clear_user, the user string accessors, and the
  user checksum functions, all of which need special handling in arch
  code with EVA.

Tested on MIPS with and without EVA, and on x86_64.

James Hogan (7):
  test_user_copy: Check legit kernel accesses
  test_user_copy: Check unchecked accessors
  test_user_copy: Check __clear_user()/clear_user()
  test_user_copy: Check __copy_in_user()/copy_in_user()
  test_user_copy: Check __copy_{to,from}_user_inatomic()
  test_user_copy: Check user string accessors
  test_user_copy: Check user checksum functions

 lib/test_user_copy.c | 221 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 221 insertions(+)

Cc: Kees Cook <redacted>
Cc: Andrew Morton <akpm@linux-foundation.org>

Ooooh! Nice! This is great, thank you. :) Great to hear it helped find
a bug too. :)

I'm wondering if we need to macro-ize any of these. Probably not, but
it just feels like there's a lot of repeated stuff now. But I think
it's a bit of an illusion since each test is ever so slightly
different from the others.

Acked-by: Kees Cook <redacted>

-Kees

-- 
Kees Cook
Chrome OS Security