Re: [PATCH] mm: pagewalk: prevent positive return value of walk_page_test() from being passed to callers (Re: [PATCH] mm: fix do_mbind return value)

[David Rientjes <rientjes@google.com>]

On Thu, 5 Mar 2015, Naoya Horiguchi wrote:

> walk_page_test() is purely pagewalk's internal stuff, and its positive return
> values are not intended to be passed to the callers of pagewalk. However, in
> the current code if the last vma in the do-while loop in walk_page_range()
> happens to return a positive value, it leaks outside walk_page_range().
> So the user visible effect is invalid/unexpected return value (according to
> the reporter, mbind() causes it.)
> 
> This patch fixes it simply by reinitializing the return value after checked.
> 
> Another exposed interface, walk_page_vma(), already returns 0 for such cases
> so no problem.
> 
> Fixes: 6f4576e3687b ("mempolicy: apply page table walker on queue_pages_range()")
> Reported-by: Kazutomo Yoshii <kazutomo.yoshii@gmail.com>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

Acked-by: David Rientjes <rientjes@google.com>

This is exactly what I had in mind, thanks for fixing it up so fast!

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