Re: [PATCH 1/2] x86: mm: ptdump: Calculate effective permissions correctly

[Steven Price]

On 27/05/2020 16:15, Jan Beulich wrote:
> On 21.05.2020 17:23, Steven Price wrote:
> > By switching the x86 page table dump code to use the generic code the
> > effective permissions are no longer calculated correctly because the
> > note_page() function is only called for *leaf* entries. To calculate the
> > actual effective permissions it is necessary to observe the full
> > hierarchy of the page tree.
> >
> > Introduce a new callback for ptdump which is called for every entry and
> > can therefore update the prot_levels array correctly. note_page() can
> > then simply access the appropriate element in the array.
> >
> > Reported-by: Jan Beulich <jbeulich@xxxxxxxx>
> > Fixes: 2ae27137b2db ("x86: mm: convert dump_pagetables to use walk_page_range")
> > Signed-off-by: Steven Price <steven.price@xxxxxxx>
>
> This (with the later correction) and the 2nd patch
> Tested-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> It allowed me to go and finally find why under Xen there was still
> a single W+X mapping left - another bug, another patch.
>
> Thanks, Jan

Thanks for testing (and sorry for breaking it in the first place)!

Steve