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. This patch puts the computation of points back in one expression, so the int overflow will not happen. My understanding is that we may just change the type of points variable from int to long and keep the current imho clearer(better readable) computation. There should not be an overflow on 32bit and there is a plenty of space for 64bit. If you like this solution better I will post the patch as v2. Signed-off-by: Frantisek Hrbata <fhrbata@xxxxxxxxxx> --- mm/oom_kill.c | 6 ++---- 1 files changed, 2 insertions(+), 4 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 626303b..d029e9b 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -192,11 +192,9 @@ unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem, * The baseline for the badness score is the proportion of RAM that each * task's rss, pagetable and swap space use. */ - points = get_mm_rss(p->mm) + p->mm->nr_ptes; - points += get_mm_counter(p->mm, MM_SWAPENTS); + points = (int)((get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) + + p->mm->nr_ptes) * 1000UL / totalpages); - points *= 1000; - points /= totalpages; task_unlock(p); /* -- 1.7.6.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>