Re: [PATCH 05/23] x86, kaiser: unmap kernel from userspace page tables (core patch)

Dave Hansen
2018-01-05T06:29:56Z

On 01/04/2018 10:16 PM, Yisheng Xie wrote:
> BTW, we have just reported a bug caused by kaiser[1], which looks like
> caused by SMEP. Could you please help to have a look?
>
> [1] https://lkml.org/lkml/2018/1/5/3

Please report that to your kernel vendor. Your EFI page tables have the
NX bit set on the low addresses. There have been a bunch of iterations
of this, but you need to make sure that the EFI kernel mappings don't
get _PAGE_NX set on them. Look at what __pti_set_user_pgd() does in
mainline.