Messages in this thread | | | Date | Wed, 8 May 2019 17:25:36 +0200 | From | Oleg Nesterov <> | Subject | Re: ptrace warning due to "cgroup: get rid of cgroup_freezer_frozen_exit()" |
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On 05/07, Roman Gushchin wrote: > > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -2484,9 +2484,6 @@ bool get_signal(struct ksignal *ksig) > sigdelset(¤t->pending.signal, SIGKILL); > recalc_sigpending(); > current->jobctl &= ~JOBCTL_TRAP_FREEZE;
just noticed... perhaps it makes more sense to clear JOBCTL_TRAP_FREEZE before recalc_sigpending(). Or simply not clear it at all, see below.
> - spin_unlock_irq(&sighand->siglock); > - if (unlikely(cgroup_task_frozen(current))) > - cgroup_leave_frozen(true); > goto fatal; > } > > @@ -2608,8 +2605,10 @@ bool get_signal(struct ksignal *ksig) > continue; > } > > - spin_unlock_irq(&sighand->siglock); > fatal: > + spin_unlock_irq(&sighand->siglock); > + if (unlikely(cgroup_task_frozen(current))) > + cgroup_leave_frozen(true);
Yes, ptrace_signal() can return a fatal signal... and in this case we do not clear JOBCTL_TRAP_FREEZE. This doesn't look consistent with the code above.
I can only repeat that somehow we need to cleanup/improve the whole logic.
Say, a traced task reports syscall-enter. ptrace_stop() does enter_frozen(). The cgroup can become CGRP_FROZEN after that. Now the debugger does PTRACE_CONT, the frozen task actually starts the syscall. Obviously not good.
Heh, and if this syscall is sys_exit or sys_exit_group we can hit the same warning.
Oleg.
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