Re: [PATCH v8 1/5] kasan: support backing vmalloc space with real shadow memory

Daniel Axtens
2019-10-15T06:32:10Z

> There is a potential problem here, as Will Deacon wrote up at:
>
> https://lore.kernel.org/linux-arm-kernel/20190827131818.14724-1-will@kernel.org/
>
> ... in the section starting:
>
> | *** Other architecture maintainers -- start here! ***
>
> ... whereby the CPU can spuriously fault on an access after observing a
> valid PTE.
>
> For arm64 we handle the spurious fault, and it looks like x86 would need
> something like its vmalloc_fault() applying to the shadow region to
> cater for this.

I'm not really up on x86 - my first thought would be that their stronger
memory ordering might be sufficient but I really don't know. Reading the
thread I see arm and powerpc discussions but nothing from anyone else,
so I'm none the wiser there...

Andy, do you have any thoughts?

Regards,
Daniel

>
> Thanks,
> Mark.