Re: [PATCH v2 for 4.4] x86/mm/pat: Fix L1TF stable backport for CPA, 2nd call

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Sep 07, 2018 at 11:13:07AM +0200, Jiri Slaby wrote:
> Mostly recycling the commit log from adaba23ccd7d which fixed
> populate_pmd, but did not fix populate_pud. The same problem exists
> there.
> 
> Stable trees reverted the following patch:
>   Revert "x86/mm/pat: Ensure cpa->pfn only contains page frame numbers"
> 
>     This reverts commit 87e2bd898d3a79a8c609f183180adac47879a2a4 which is
>     commit edc3b9129cecd0f0857112136f5b8b1bc1d45918 upstream.
> 
> but the L1TF patch 02ff2769edbc backported here
> 
>   x86/mm/pat: Make set_memory_np() L1TF safe
> 
>     commit 958f79b9ee55dfaf00c8106ed1c22a2919e0028b upstream
> 
>     set_memory_np() is used to mark kernel mappings not present, but it has
>     it's own open coded mechanism which does not have the L1TF protection of
>     inverting the address bits.
> 
> assumed that cpa->pfn contains a PFN. With the above patch reverted
> it does not, which causes the PUD to be set to an incorrect address
> shifted by 12 bits, which can cause various failures.
> 
> Convert the address to a PFN before passing it to pud_pfn().
> 
> This is a 4.4 stable only patch to fix the L1TF patches backport there.
> 
> Cc: stable@vger.kernel.org # 4.4-only
> Cc: Andi Kleen <ak@linux.intel.com>
> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
> ---
>  arch/x86/mm/pageattr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Thanks for this, now queued up.

greg k-h