linux-kernel - Re: [PATCH 4.4 41/43] x86/mm/pat: Make set_memory

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Date:   Sun, 9 Sep 2018 10:06:06 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Ben Hutchings <ben.hutchings@...ethink.co.uk>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Michal Hocko <mhocko@...e.cz>
Cc:     stable@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4.4 41/43] x86/mm/pat: Make set_memory_np() L1TF safe

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.  If anyone has any objections, please let me know.
>>
>> ------------------
>>
>> From: Andi Kleen <ak@...ux.intel.com>
>>
>> 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
>>>   	return __pmd(pfn | massage_pgprot(pgprot));
>>   }
>>   
>> +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.  But 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