On Tue, Feb 10, 2009 at 4:45 AM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > On Tue, Feb 10, 2009 at 02:15:36AM -0800, Paul Menage wrote: >> On Tue, Feb 10, 2009 at 1:31 AM, Li Zefan <lizf@xxxxxxxxxxxxxx> wrote: >> > In cgroup_kill_sb(), root is freed before sb is detached from the list, >> > so another sget() may find this sb and call cgroup_test_super(), >> > which will access the root that has been freed. >> >> I think that I'd assumed that by the time we get to cgroup_kill_sb() >> there's no chance of the sb being resurrected by sget(). > > There is none. grab_super() will fail to get it, so sget() will go > through retry logics. Which doesn't mean that test won't be called > on it in the meanwhile. OK, so Zefan's patch looks like the safest way to fix this particular issue. I think I see some other potential races with cgroup_test_super() though - we probably need to synchronize against the changing of a root's subsys_bits in rebind_subsystems(). Taking cgroup_mutex around the call to sget() would certainly provide that, but I'd have to check whether it causes locking cycles. Paul _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
