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SubjectRe: Ugly rmap NULL ptr deref oopsie on hibernate (was Linux 2.6.34-rc3)
On 04/06/2010 06:09 AM, KOSAKI Motohiro wrote:
>> (b) is also impossible. SLAB_DESTROY_BY_RCU delay the page for anon_vma
>> freeing until next rcu period. It mean rcu_read_lock()+page_mapped()
>> can see kfree()ed page. but it is safe. noone corrupt it.
>
> by the way: I haven't understand why rik's per process anon_vma concept
> works correctly with ksm. ksm increase anon_vma->ksm_refcount. but it seems
> not guranteed vma->anon_vma and page->anon_vma are the same.

KSM removes the page from its original anon_vma.

If the page gets reinstantiated (copy on write), it will be
created in the vma->anon_vma.

Am I overlooking something?


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