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@xxxxxxxxxx> > > Acked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > > Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx> > > Acked-by: David Rientjes <rientjes@xxxxxxxxxx> > > Cc: stable@xxxxxxxxxx [2.6.36+] > > For what it's worth, the stable address has changed to > stable@xxxxxxxxxxxxxxx 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 -- 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>