Re: [PATCH 1/2] x86/mm/KASLR: Fix the wrong calculation of kalsr region initial size

Baoquan He
2018-09-08T13:33:46Z

On 09/08/18 at 02:10pm, Thomas Gleixner wrote:
> On Wed, 29 Aug 2018, Baoquan He wrote:
>
> > In memory KASLR, __PHYSICAL_MASK_SHIFT is taken to calculate the
> > initial size of the direct mapping region. This is right in the
> > old code where __PHYSICAL_MASK_SHIFT was equal to MAX_PHYSMEM_BITS,
> > 46bit, and only 4-level mode was supported.
> >
> > Later, in commit:
> > b83ce5ee91471d ("x86/mm/64: Make __PHYSICAL_MASK_SHIFT always 52"),
> > __PHYSICAL_MASK_SHIFT was changed to be 52 always, no matter it's
> > 5-level or 4-level. This is wrong for 4-level paging. Then when
> > adapt phyiscal memory region size based on available memory, it
> > will overflow if the amount of system RAM and the padding is bigger
> > than 64TB.
> >
> > In fact, here MAX_PHYSMEM_BITS should be used instead. Fix it by
> > by replacing __PHYSICAL_MASK_SHIFT with MAX_PHYSMEM_BITS.
> >
> > Signed-off-by: Baoquan He <bhe@redhat.com>
>
> This lacks a fixes tag .....

Sure, I will add fix tag in this patch, and arrange a new patchset
according to discussion with Kirill after test.

Thanks
Baoquan