Re: [PATCH v2 17/33] mm: kfence: Disable KMSAN when checking the canary

[Alexander Potapenko]

On Fri, Dec 8, 2023 at 1:53 PM Alexander Potapenko <glider@xxxxxxxxxx> wrote:
>
> On Tue, Nov 21, 2023 at 11:02 PM Ilya Leoshkevich <iii@xxxxxxxxxxxxx> wrote:
> >
> > KMSAN warns about check_canary() accessing the canary.
> >
> > The reason is that, even though set_canary() is properly instrumented
> > and sets shadow, slub explicitly poisons the canary's address range
> > afterwards.
> >
> > Unpoisoning the canary is not the right thing to do: only
> > check_canary() is supposed to ever touch it. Instead, disable KMSAN
> > checks around canary read accesses.
> >
> > Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
> Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>

and even

Tested-by: Alexander Potapenko <glider@xxxxxxxxxx>