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

[Andrey Ryabinin]

On 06/07/2017 06:35 PM, Mark Rutland wrote:
> Hi,
> 
> 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.

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


> These patches avoid the issue by doubling the stack size for kernels built with
> KASAN, as is already done for x86.
> 
> I've built and booted 4K and 64K kernels with these patches applied (and with
> KASAN enabled), and so far I haven't seen stack overflows when testing with
> Syzkaller.
> 
> Thanks,
> Mark.
> 
> Mark Rutland (2):
>   arm64: avoid open-coding THREAD_SIZE{,_ORDER}
>   arm64: use larger stacks for KASAN
> 
>  arch/arm64/include/asm/thread_info.h | 22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
>