Re: [PATCH] x86/mm/pti: in pti_clone_pgtable() don't increase addr by PUD_SIZE

Thomas Gleixner
2019-08-20T13:39:41Z

On Tue, 20 Aug 2019, Song Liu wrote:
> > On Aug 20, 2019, at 4:16 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> >
> > On Tue, 20 Aug 2019, Peter Zijlstra wrote:
> >> What that code wants to do is skip to the end of the pud, a pmd_size
> >> increase will not do that. And right below this, there's a second
> >> instance of this exact pattern.
> >>
> >> Did I get the below right?
> >>
> >> ---
> >> diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
> >> index b196524759ec..32b20b3cb227 100644
> >> --- a/arch/x86/mm/pti.c
> >> +++ b/arch/x86/mm/pti.c
> >> @@ -330,12 +330,14 @@ pti_clone_pgtable(unsigned long start, unsigned long end,
> >>
> >> pud = pud_offset(p4d, addr);
> >> if (pud_none(*pud)) {
> >> + addr &= PUD_MASK;
> >> addr += PUD_SIZE;
> >
> > round_up(addr, PUD_SIZE);
>
> I guess we need "round_up(addr + PMD_SIZE, PUD_SIZE)".

Right you are.