Messages in this thread | | | Date | Sat, 09 Jun 2012 18:25:46 -0400 | From | KOSAKI Motohiro <> | Subject | Re: [patch for-3.5-rc1] mm, oom: fix badness score underflow |
| |
(6/8/12 4:21 PM), David Rientjes wrote: > If the privileges given to root threads (3% of allowable memory) or a > negative value of /proc/pid/oom_score_adj happen to exceed the amount of > rss of a thread, its badness score overflows as a result of a7f638f999ff > ("mm, oom: normalize oom scores to oom_score_adj scale only for > userspace"). > > Fix this by making the type signed and return 1, meaning the thread is > still eligible for kill, if the value is negative. > > Reported-by: Dave Jones<davej@redhat.com> > Acked-by: Oleg Nesterov<oleg@redhat.com> > Signed-off-by: David Rientjes<rientjes@google.com> > --- > mm/oom_kill.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -183,7 +183,7 @@ static bool oom_unkillable_task(struct task_struct *p, > unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, > const nodemask_t *nodemask, unsigned long totalpages) > { > - unsigned long points; > + long points; > > if (oom_unkillable_task(p, memcg, nodemask)) > return 0; > @@ -223,7 +223,7 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, > * Never return 0 for an eligible task regardless of the root bonus and > * oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here). > */ > - return points ? points : 1; > + return points> 0 ? points : 1; > }
Use long long. following line is dangerous.
points += p->signal->oom_score_adj * totalpages / 1000;
maximum oom_score_adj is 1000. then if system has >8G memory on 32bit (i.e. LONG_MAX [pages] * 4096 [pagesize] / 1000), it might get an overflow.
Or, don't use normalized oom_score_adj. i.e, oom_score_adj_write() convert oom_score_adj into rss based modifier.
This is oom-killer code. A micro optimization don't bring us a performance benefit.
| |