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SubjectRe: Ugly rmap NULL ptr deref oopsie on hibernate (was Linux 2.6.34-rc3)
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On Tue, 2010-04-06 at 08:55 -0700, Linus Torvalds wrote:
> I do wonder if "page_lock_anon_vma()" should check the whole
> "page_mapped()" case _after_ taking the anon_vma lock. Because if the race
> happens, we're following a anon_vma list that has nothing to do with that
> page (it's stilla _valid_ list, since we locked the anon_vma, but will it
> be ok?)
>
> IOW, what is it that really keeps the anon_vma list reliable _and_
> relevant wrt the page? We know we may get a stale anon_vma, are we ok if
> that anon_vma list doesn't actually have anything to do with the page any
> more?

When doing the whole make i_mmap_lock/anon_vma->lock a mutex thing last
week I ran into the same issue and its on my todo list to find out wth
is happening there.

So yes I think we should move that validation check inside
page_lock_anon_vma().

I'll cook up a patch once I'm done staring at the various funny arch
mmu_gather implementations.


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