[PATCH 0/2] arm64: avoid KASAN stack overflows

[mark.rutland@arm.com (Mark Rutland)]

On Wed, Jun 07, 2017 at 07:12:30PM +0300, Andrey Ryabinin wrote:
> On 06/07/2017 06:35 PM, Mark Rutland wrote:
> > I recently tried building the kernel with a GCC 7.1.0 toolchain, and
> > encountered a number of new and surprising failures on kernels buitl with
> > KASAN.
> > 
> > It looks like this is due to stack instrumentation, which my prior toolchain
> > didn't support. KASAN's stack instrumentation significantly bloats the stack
> > significantly, leading to stack overflows and subsequent failures as a result
> > of the data corruption they cause.
> 
> This is caused by -fsanitize-address-use-after-scope which is added in gcc 7.
> Arnd reported that sometimes it causes enormously huge stack growth.

Ah. Sorry for the bogus attribution, then.

> Given that we haven't found any single use-after-scope bug so far, I wouldn't object
> removing it completely.  

FWIW, I saw a single use-after-scope splat when testing with syzkaller
(prior to these patches), but that may have been a result of things
going wrong after a stack overflow. Unfortuantely I threw away all of
the results of that run.

I'll see if anything triggers overnight with this patch.

Otherwise, I'm also happy for use-after-scope checks to be disabled.

Thanks,
Mark.