Re: [RESEND][PATCH] kbuild: Abort build on bad stack protector flag

From: Kees Cook
Date: Tue Jul 26 2016 - 17:23:01 EST

On Tue, Jul 26, 2016 at 2:06 PM, Michal Marek <mmarek@xxxxxxxx> wrote:
> On Tue, Jul 12, 2016 at 03:30:43PM -0700, Kees Cook wrote:
>> Before, the stack protector flag was sanity checked before .config had
>> been reprocessed. This meant the build couldn't be aborted early, and
>> only a warning could be emitted followed later by the compiler blowing
>> up with an unknown flag. This has caused a lot of confusion over time,
>> so this splits the flag selection from sanity checking and performs the
>> sanity checking after the make has been restarted from a reprocessed
>> .config, so builds can be aborted as early as possible now.
>> Additionally moves the x86-specific sanity check to the same location,
>> since it suffered from the same warn-then-wait-for-compiler-failure
>> problem.
>> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Hi Kees,
> sorry for the late review.
>> +# Find arch-specific stack protector compiler sanity-checking script.
>> + stackp-path := $(srctree)/scripts/gcc-$(ARCH)_$(BITS)
> You need to use SRCARCH here if you want "x86" on x86.
>> + ifneq ($(wildcard $(stackp-path)),)
>> + stackp-check := $(stackp-path)
>> + endif
> stackp-check := $(wildcard $(stackp-path))
> is more straightforward. But the long version is correct as well.

Ah! Yes, thanks. I was thinking I needed to handle "defined but
empty", but that's not true for Makefiles. I'll send a v2 with this
and SRCARCH fixed.


Kees Cook
Chrome OS & Brillo Security