Re: [PATCH 12/32] kmsan: Allow disabling KMSAN checks for the current task

Ilya Leoshkevich
2023-11-16T09:17:54Z

On Thu, 2023-11-16 at 09:56 +0100, Alexander Potapenko wrote:
> On Wed, Nov 15, 2023 at 9:34 PM Ilya Leoshkevich <iii@linux.ibm.com>
> wrote:
> >
> > Like for KASAN, it's useful to temporarily disable KMSAN checks
> > around,
> > e.g., redzone accesses.
>
> This example is incorrect, because KMSAN does not have redzones.
> You are calling these functions from "mm: slub: Let KMSAN access
> metadata", which mentiones redzones in kfree(), but the description
> is
> still somewhat unclear.
> Can you provide more insight about what is going on? Maybe we can fix
> those accesses instead of disabling KMSAN?

It's about SLUB redzones, which appear when compiling with
CONFIG_DEBUG_SLAB.

I think that from KMSAN's point of view they should be considered
poisoned, but then the question is what to do with functions that check
them. I noticed that there was special handling for KASAN there
already, so I figured that the best solution would be to do the same
thing for KMSAN.