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

On Fri, Sep 6, 2019 at 11:17 AM James Morse [off-list ref] wrote:

Hi Pavel,

On 21/08/2019 19:31, Pavel Tatashin wrote:

quoted

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.

quoted

Another issue,

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

quoted

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.

Yes, it is harmless otherwise the code would not work. But it is
confusing to read, and looks broken. I will separate this change as
two patches as you suggested.

Thank you,
Pasha

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