Re: [PATCH] Kconfig.debug: disable CONFIG_FRAME_WARN for KASAN_STACK && CC_IS_CLANG by default

[Tudor Ambarus]

Hi, Arnd,

On 4/21/23 15:30, Arnd Bergmann wrote:
> On Fri, Apr 21, 2023, at 15:01, Tudor Ambarus wrote:
> 
>> The conclusion is that when KASAN is enabled the stack usage increases a
>> bit, but nothing unmanageable ~30-70 bytes, whereas when enabling
>> KASAN_STACK the stack usage is excessive, from ~1.7K to ~5.8K for these
>> cases.
>>
>> Disable CONFIG_FRAME_WARN for KASAN_STACK && CC_IS_CLANG by default.
>> Adventurers can still override the default value by input prompt or
>> explicit values in defconfigs in case they feel that some real warnings
>> are missed.
>>
>> Signed-off-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxx>
> 
> I think we are still better off with the warning enabled. When someone
> really wants to run a kernel with KASAN_STACK enabled, they should have
> a chance to see what they are getting into and not report any runtime
> bugs that come from stack overflow. 
> 

Are such stack overflows warnings reliable when we know that stack
instrumentation causes excessive stack usage? Until clang is fixed one
shall hunt frame-larger-than warnings with KASAN_STACK disabled.

Cheers,
ta