Re: Ugly rmap NULL ptr deref oopsie on hibernate (was Linux2.6.34-rc3)

From: Linus Torvalds
Date: Tue Apr 06 2010 - 12:36:58 EST

On Wed, 7 Apr 2010, Minchan Kim wrote:
> >
> > I don't think so. That isn't the racy case. We're working with a
> > anon_vma_chain, so the anonvma is all there.
> But the anon_vma is using for another anon_vma.

No, that can only happen if somebody has done "anon_vma_free()" on it. And
nobody does that if the anonvma still has a non-empty'&anon_vma->head'.

So as long as the anon_vma has a anon_vma_chain entry associated with it
(or a ksm refcount, but that's a separate issue), it's not going to be
re-allocated for any other use, because it's not going to be free'd.

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