Messages in this thread | | | Date | Fri, 2 Dec 2011 21:46:13 +0100 | From | Frantisek Hrbata <> | Subject | Re: [PATCH v2 RESEND] oom: fix integer overflow of points in oom_badness |
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On Fri, Dec 02, 2011 at 11:00:19AM -0800, Greg KH wrote: > On Fri, Dec 02, 2011 at 06:45:27PM +0100, Frantisek Hrbata wrote: > > An integer overflow will happen on 64bit archs if task's sum of rss, swapents > > and nr_ptes exceeds (2^31)/1000 value. This was introduced by commit > > > > f755a04 oom: use pte pages in OOM score > > > > where the oom score computation was divided into several steps and it's no > > longer computed as one expression in unsigned long(rss, swapents, nr_pte are > > unsigned long), where the result value assigned to points(int) is in > > range(1..1000). So there could be an int overflow while computing > > > > 176 points *= 1000; > > > > and points may have negative value. Meaning the oom score for a mem hog task > > will be one. > > > > 196 if (points <= 0) > > 197 return 1; > > > > For example: > > [ 3366] 0 3366 35390480 24303939 5 0 0 oom01 > > Out of memory: Kill process 3366 (oom01) score 1 or sacrifice child > > > > Here the oom1 process consumes more than 24303939(rss)*4096~=92GB physical > > memory, but it's oom score is one. > > > > In this situation the mem hog task is skipped and oom killer kills another and > > most probably innocent task with oom score greater than one. > > > > The points variable should be of type long instead of int to prevent the int > > overflow. > > > > Signed-off-by: Frantisek Hrbata <fhrbata@redhat.com> > > Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > > Acked-by: Oleg Nesterov <oleg@redhat.com> > > Acked-by: David Rientjes <rientjes@google.com> > > Cc: stable@kernel.org [2.6.36+] > > For what it's worth, the stable address has changed to > stable@vger.kernel.org so you might want to fix that up in future > submissions.
I was not aware of this change.
> > I still catch patches that are tagged with this marking, but you will > not end up posting stuff to the list this way :)
Duly noted :)
> > thanks,
Thanks Greg!
> > greg k-h
-- Frantisek Hrbata
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