Re: [PATCH 4.4 41/43] x86/mm/pat: Make set_memory_np() L1TF safe

[Guenter Roeck]

On 09/09/2018 09:46 AM, Ben Hutchings wrote:
> On Tue, 2018-08-14 at 19:18 +0200, Greg Kroah-Hartman wrote:
> > 4.4-stable review patch.ÂÂIf anyone has any objections, please let me know.
> >
> > ------------------
> >
> > From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> >
> > commit 958f79b9ee55dfaf00c8106ed1c22a2919e0028b upstream
> [...]
> > --- a/arch/x86/include/asm/pgtable.h
> > +++ b/arch/x86/include/asm/pgtable.h
> > @@ -378,12 +378,39 @@ static inline pmd_t pfn_pmd(unsigned lon
> > >  Â	return __pmd(pfn | massage_pgprot(pgprot));
> >  Â}
> >   
> > +static inline pud_t pfn_pud(unsigned long page_nr, pgprot_t pgprot)
> > +{
> > +	phys_addr_t pfn = page_nr << PAGE_SHIFT;
> > +	pfn ^= protnone_mask(pgprot_val(pgprot));
> > +	pfn &= PHYSICAL_PUD_PAGE_MASK;
> > +	return __pud(pfn | massage_pgprot(pgprot));
> > +}
> [...]
>
> This (and the backport to 4.9) are missing the fix from commit
> e14d7dfb41f5 "x86/speculation/l1tf: Fix up pte->pfn conversion for
> PAE", as that was applied earlier in the series.ÂÂBut since PAE implies
> only 3-level paging I don't know how the PUD functions get used or
> whether this actually matters.
Excellent find.

e14d7dfb41f5 (re-)applies cleanly to both 4.4.y and 4.9.y. Since most of its
changes are already applied, the only remaining change is

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index c535012bdb56..5736306bdaab 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -420,7 +420,7 @@ static inline pmd_t pfn_pmd(unsigned long page_nr, pgprot_t pgprot)

 static inline pud_t pfn_pud(unsigned long page_nr, pgprot_t pgprot)
 {
-       phys_addr_t pfn = page_nr << PAGE_SHIFT;
+       phys_addr_t pfn = (phys_addr_t)page_nr << PAGE_SHIFT;
        pfn ^= protnone_mask(pgprot_val(pgprot));
        pfn &= PHYSICAL_PUD_PAGE_MASK;
        return __pud(pfn | massage_pgprot(pgprot));

after cherry-picking it into both branches.

I think we should re-apply it to both 4.4.y and 4.9.y be on the safe side.

Thanks,
Guenter