Messages in this thread | | | Subject | Re: Ugly rmap NULL ptr deref oopsie on hibernate (was Linux 2.6.34-rc3) | From | Minchan Kim <> | Date | Mon, 05 Apr 2010 01:12:55 +0900 |
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Hi, Rik.
On Fri, 2010-04-02 at 18:01 -0400, Rik van Riel wrote: > On 04/02/2010 02:37 PM, Linus Torvalds wrote: > > On Fri, 2 Apr 2010, Andrew Morton wrote: > >> On Fri, 2 Apr 2010 11:09:14 -0700 (PDT) Linus Torvalds<torvalds@linux-foundation.org> wrote: > >> > >>> > >>> I think this is likely due to the new scalable anon_vma linking by Rik. > >> > >> Similar to https://bugzilla.kernel.org/show_bug.cgi?id=15680 > > > > Yup, looks like the same thing, except that bugzilla entry was due to > > swapping rather than hibernation and memory shrinking. But same end > > result, just different reasons for why we were trying to shrink the page > > lists. > > Interesting that it is a null pointer dereference, given > that we do not zero out the anon_vma_chain structs before > freeing them. > > Page_referenced_anon() takes the anon_vma->lock before > walking the list. The three places where we modify the > anon_vma_chain->same_anon_vma list, we also hold the > lock. > > No doubt something in mm/ is doing something silly, but > I have not found anything yet :( > > If I had to guess, I'd say maybe we got one of the > mprotect & vma_adjust cases wrong. Maybe a page stayed > around in the LRU (and in a process?) after its anon_vma > already got freed?
While I review the code again due to this BUG, I found some strange thing.
In anon_vma_fork, if anon_vma_clone is successful but anon_vma_alloc is failed, what happens? Parent VMA's anon_vmas have anon_vma_chain which has vma which is destroyed. I couldn't find any clean routine to remove this garbage. I am missing something?
But I think it isn't related to this bug because oops point is not vma_address but anon_vma_chain.next.
-- Kind regards, Minchan Kim
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