Re: [PATCH 02/13] mm: Revalidate anon_vma in page_lock_anon_vma()

[Rik van Riel]

On 04/08/2010 03:17 PM, Peter Zijlstra wrote:
> There is nothing preventing the anon_vma from being detached while we
> are spinning to acquire the lock. Most (all?) current users end up
> calling something like vma_address(page, vma) on it, which has a
> fairly good chance of weeding out wonky vmas.
>
> However suppose the anon_vma got freed and re-used while we were
> waiting to acquire the lock, and the new anon_vma fits with the
> page->index (because that is the only thing vma_address() uses to
> determine if the page fits in a particular vma, we could end up
> traversing faulty anon_vma chains.
>
> Close this hole for good by re-validating that page->mapping still
> holds the very same anon_vma pointer after we acquire the lock, if not
> be utterly paranoid and retry the whole operation (which will very
> likely bail, because it's unlikely the page got attached to a different
> anon_vma in the meantime).
>
> Signed-off-by: Peter Zijlstra<a.p.zijlstra@xxxxxxxxx>
> Cc: Hugh Dickins<hugh.dickins@xxxxxxxxxxxxx>
> Cc: Linus Torvalds<torvalds@xxxxxxxxxxxxxxxxxxxx>

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/