Messages in this thread Patch in this message | | | From | Naoya Horiguchi <> | Subject | 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) | Date | Thu, 5 Mar 2015 08:09:49 +0000 |
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On Thu, Mar 05, 2015 at 08:02:27AM +0000, Horiguchi Naoya(堀口 直也) wrote: ... > --- > From 107fa3fb256bddff40a882c90af717af9863aed7 Mon Sep 17 00:00:00 2001 > From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> > Date: Thu, 5 Mar 2015 16:37:37 +0900 > Subject: [PATCH] mm: pagewalk: prevent positive return value of > walk_page_test() from being passed to callers > > 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()")
This is not a right tag. To be precise, the bug was introduced by commit fafaa4264eba ("pagewalk: improve vma handling"), so
Fixes fafaa4264eba ("pagewalk: improve vma handling")
is right.
Thanks, Naoya Horiguchi
> Reported-by: Kazutomo Yoshii <kazutomo.yoshii@gmail.com> > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> > --- > mm/pagewalk.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/mm/pagewalk.c b/mm/pagewalk.c > index 75c1f2878519..29f2f8b853ae 100644 > --- a/mm/pagewalk.c > +++ b/mm/pagewalk.c > @@ -265,8 +265,15 @@ int walk_page_range(unsigned long start, unsigned long end, > vma = vma->vm_next; > > err = walk_page_test(start, next, walk); > - if (err > 0) > + if (err > 0) { > + /* > + * positive return values are purely for > + * controlling the pagewalk, so should never > + * be passed to the callers. > + */ > + err = 0; > continue; > + } > if (err < 0) > break; > } > -- > 1.9.3 > | |