On Fri, 10 Jun 2011 12:19:49 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > On Fri, 10 Jun 2011 11:33:11 +0900 > KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > > On Thu, 9 Jun 2011 18:30:49 -0700 (PDT) > > Hugh Dickins <hughd@xxxxxxxxxx> wrote: > > > > 781cc621 <mem_cgroup_from_task>: > > > 781cc621: 55 push %ebp > > > 781cc622: 31 c0 xor %eax,%eax > > > 781cc624: 89 e5 mov %esp,%ebp > > > 781cc626: 8b 55 08 mov 0x8(%ebp),%edx > > > 781cc629: 85 d2 test %edx,%edx > > > 781cc62b: 74 09 je 781cc636 <mem_cgroup_from_task+0x15> > > > 781cc62d: 8b 82 fc 08 00 00 mov 0x8fc(%edx),%eax > > > 781cc633: 8b 40 1c mov 0x1c(%eax),%eax <========== > > > 781cc636: c9 leave > > > 781cc637: c3 ret > > > > > > > then, access to task->cgroups->subsys[?] causes access to 6b6b6b87... > > > > Then, task->cgroups or task->cgroups->subsys contains bad pointer. > > Considering khugepaged, it grabs mm_struct and memcg make an access to > > (mm->owner)->cgroups->subsys. > > > > Then, from memcg's point of view, we need to doubt mm->owner is valid or not > > for this kind of tasks. > > > > Dave's log shows 6b6b6b6b6b..., too. > > I guess it as "POISON_FREE" of slab object. Then, task->cgroups may used after free. > Ah, sorry. 0x1c(%eax) == 6b6b6b87 means %eax was 0x6b6b6b6b. The %eax was the contents of [task->cgroups]....hmm, then, task itself is freed pointer (and poisoned). So, it seems a problem of accessing mm->owner.. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx 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>