Messages in this thread | | | Date | Fri, 13 May 2011 20:34:16 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 10/11] ptrace: move JOBCTL_TRAPPING wait to wait(2) and ptrace_check_attach() |
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On 05/13, Tejun Heo wrote: > > On Thu, May 12, 2011 at 08:20:06PM +0200, Oleg Nesterov wrote: > > Now about GROUP_STOP_TRAPPING. To simplify the discussion, lets > > forget about this series, > > > > ... > > > > Problem: TRAPPING can be set outside of do_signal_stop() paths, and > > I think we should avoid this as much as possible. > > For PTRACE_DETACH, this was true but it isn't true for notification > re-traps. Notification re-traps happen iff JOBCTL_TRAPPED
Yes I see, and task_clear_jobctl_trapping() was moved into get_signal_to_deliver().
So, if we return to this series then "outside of do_signal_stop()" is not accurate.
> > (I am ignoring the problem this patch addresses temporary, I think > > we can fix it a bit differently). > > Just leaving it alone also is an option. We can just mandate > ptrace(2) users to always perform sleeping wait(2) after PTRACE_SEIZE. > If it can be fixed easily, sure. If not, let's leave it alone.
Let's leave it alone in this thread, unless I missed something this is simple. Or I missed something and it is not that simple ;)
> > Say, the thread group was stopped, the tracer PTRACE_CONT's T1, it calls > > sys_execve() and reports the trap from syscall_trace_enter(). > > > > The tracer does ptrace(T1, DETACH) + ptrace(T1, SEIZE) and hangs forever. > > > > Once again, this is only one example. coredump, vfork, probably something > > else. In short: I think that TRAPPING-outside-of-do_signal_stop is the > > can of worms. > > Yeap, fully agreed. We need something different for detach case; > however, for re-trap, tracee is known to be in signal delivery path > and should be okay, I think. Right?
I think this is right, but there were so many issues, that is why I suggested to ignore this series temporary. And, to be honest, because I was a bit confused, somehow I thought you are going to add more TRAPPING's.
So, we agree that we can only set TRAPPING iff we know what the tracee should do "really soon". Great.
I have other concerns, but I noticed you have already sent V2. Let's continue there.
Oleg.
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