Re: [PATCH v3 05/17] arm64, hibernate: check pgd table allocation

[James Morse]

Hi Pavel,

On 21/08/2019 19:31, Pavel Tatashin wrote:
> There is a bug in create_safe_exec_page(), when page table is allocated
> it is not checked that table is allocated successfully:
> 
> But it is dereferenced in: pgd_none(READ_ONCE(*pgdp)).

If there is a bug, it shouldn't be fixed part way through a series. This makes it
difficult to backport the fix.

Please split this out as an independent patch with a 'Fixes:' tag for the commit that
introduced the bug.


> Another issue,

So this patch does two things? That is rarely a good idea. Again, this makes it difficult
to backport the fix.


> is that phys_to_ttbr() uses an offset in page table instead
> of pgd directly.

If you were going to reuse this, that would be a bug. But because the only page that is
being mapped, is mapped to PAGE_SIZE, all the top bits will be 0. The offset calls are
boiler-plate. It doesn't look intentional, but its harmless.


Please separate out the potential NULL-dereference bits so there is a clean stand-alone
fix that can be sent to the stable trees.


Thanks,

James