Re: [PATCH v2 0/3] special_mapping_fault() is broken

[Andrew Morton]

On Fri, 10 Jul 2015 18:51:21 +0200 Oleg Nesterov <oleg@xxxxxxxxxx> wrote:

> special_mapping_fault() is absolutely broken. It seems it was always
> wrong, but this didn't matter until vdso/vvar started to use more than
> one page.
> 
> The patches are the same, just 1/3 was re-diffed on top of the recent
> 6b7339f4c31ad "mm: avoid setting up anonymous pages into file mapping"
> from Kirill.
> 
> And after this change vma_is_anonymous() becomes really trivial, it
> simply checks vm_ops == NULL. However, I do think the helper makes
> sense. There are a lot of ->vm_ops != NULL checks, the helper makes
> the caller's code more understandable (self-documented) and this is
> more grep-friendly.

I'm trying to work out which kernel version(s) this should go into,
without a lot of success.

What do we think the worst-case effects of the bug?
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