On 06/17, Sukadev Bhattiprolu wrote: > > Prevent container-inits from using CLONE_PARENT > > If a container-init creates a sibling (using CLONE_PARENT), pid namespace > semantics become complicated: > > - the "active pid namespace" of the sibling will be the descendant > container, but its not obvious if that is correct. > > - if container-init exits, it will terminate the sibling, but again > its not clear if that is the correct behavior. > > - the sibling exists in both parent and child containers while current > pid namespace semantics assume that only container-init can exist > in both parent/child containers. > > - the parent of the sibling is not a descendant of container-init > (while pid namespaces assume that all processes in the container > are descendants of the container-init) I agree, this all a bit strange and perhaps should be fixed. But afaics, nothing bad can happen? I mean, if the sub-namespace does stupid things it can't do a harm to the parent namespace? Or I missed something? > - When the sibling dies, the SIGCHLD is sent to its parent (if > alive), i.e the signal escapes the container to a parent container. The same if container-init exits, we send SIGCHLD up. But yes, I agree, this is a bit strange. > (if the parent of the sibling exits, the container-init then becomes > the reaper of the sibling). Again, strange but harmless. > To keep pid namespace semantics simple, prevent container-inits from using > CLONE_PARENT at least until we have a better understanding of CLONE_PARENT > and pid-namespace interactions. Yes, perhaps makes sense. > --- linux-mmotm.orig/kernel/fork.c 2009-06-17 18:23:23.000000000 -0700 > +++ linux-mmotm/kernel/fork.c 2009-06-17 19:17:54.000000000 -0700 > @@ -974,6 +974,14 @@ static struct task_struct *copy_process( > if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) > return ERR_PTR(-EINVAL); > > + /* > + * To keep pid namespace semantics simple, prevent container-inits > + * from creating siblings. > + */ > + if ((clone_flags & CLONE_PARENT) && > + is_container_init(current) && !is_global_init(current)) Both is_ checks are not right afaics. There are per-thread. This means that container-init can do clone(CLONE_THREAD), and then this thread does CLONE_PARENT and fools copy_process(). As for !is_global_init(). I never understood what should we do if the global init does CLONE_PARENT, this attaches another process to swapper, not good. Oleg. _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
