Messages in this thread |  | | | Date | Wed, 7 Dec 2011 19:44:57 -0800 (PST) | | From | David Rientjes <> | | Subject | Re: [PATCH v2 RESEND] oom: fix integer overflow of points in oom_badness |
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On Fri, 2 Dec 2011, 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+]
Andrew, this looks like 3.2-rc5 material.
> --- > mm/oom_kill.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 626303b..e9a1785 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -162,7 +162,7 @@ static bool oom_unkillable_task(struct task_struct *p, > unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem, > const nodemask_t *nodemask, unsigned long totalpages) > { > - int points; > + long points; > > if (oom_unkillable_task(p, mem, nodemask)) > return 0;
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