Re: [PATCH] selftests/lkdtm: Disable CONFIG_UBSAN_TRAP in test config

[Kees Cook <keescook@chromium.org>]

On Tue, Aug 01, 2023 at 11:43:29AM +0200, Ricardo Cañuelo wrote:
> The lkdtm selftest config fragment enables CONFIG_UBSAN_TRAP to make the
> ARRAY_BOUNDS test kill the calling process when an out-of-bound access
> is detected by UBSAN. However, after this [1] commit, UBSAN is triggered
> under many new scenarios that weren't detected before, such as in struct
> definitions with fixed-size trailing arrays used as flexible arrays. As
> a result, CONFIG_UBSAN_TRAP=y has become a very aggressive option to
> enable except for specific situations.

Yeah, that's fair. We need to actually get these issues reported and
TRAP doesn't help with that.

> 
> `make kselftest-merge` applies CONFIG_UBSAN_TRAP=y to the kernel config
> for all selftests, which makes many of them fail because of system hangs
> during boot.
> 
> This change removes the config option from the lkdtm kselftest and also
> the ARRAY_BOUNDS test to skip it rather than have it failing. If
> out-of-bound array accesses need to be checked, there's
> CONFIG_TEST_UBSAN for that.

I *think* instead, we can turn off TRAP but retain the ARRAY_BOUNDS
kselftest by looking for either WARN or TRAP results:

-ARRAY_BOUNDS
+ARRAY_BOUNDS call trace:|UBSAN: array-index-out-of-bounds

Can test that and send a v2?

-Kees

-- 
Kees Cook