Messages in this thread | | | Date | Wed, 5 Apr 2017 14:30:45 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCHv2] ptrace: fix PTRACE_LISTEN race corrupting task->state |
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On 04/04, bsegall@google.com wrote: > > v2: slight clarification in comments, put the conditional around the > whole wakeup area
Acked-by: Oleg Nesterov <oleg@redhat.com>
and I think this should go to -stable.
> Oleg mentioned a preference for making LISTEN unfreeze instead; I have > no preference there,
Yes, but I won't insist if you prefer this more simple fix,
> just wanted to make sure that this doesn't get > forgotten entirely.
And you are right, I forgot about this bug. Thanks!
Oleg.
> kernel/ptrace.c | 14 ++++++++++---- > 1 file changed, 10 insertions(+), 4 deletions(-) > > diff --git a/kernel/ptrace.c b/kernel/ptrace.c > index 0af928712174..7cc49c3e73af 100644 > --- a/kernel/ptrace.c > +++ b/kernel/ptrace.c > @@ -184,11 +184,17 @@ static void ptrace_unfreeze_traced(struct task_struct *task) > > WARN_ON(!task->ptrace || task->parent != current); > > + /* > + * PTRACE_LISTEN can allow ptrace_trap_notify to wake us up > + * remotely. Recheck state under the lock to close this race. > + */ > spin_lock_irq(&task->sighand->siglock); > - if (__fatal_signal_pending(task)) > - wake_up_state(task, __TASK_TRACED); > - else > - task->state = TASK_TRACED; > + if (task->state == __TASK_TRACED) { > + if (__fatal_signal_pending(task)) > + wake_up_state(task, __TASK_TRACED); > + else > + task->state = TASK_TRACED; > + } > spin_unlock_irq(&task->sighand->siglock); > } > > -- > 2.12.2.715.g7642488e1d-goog >
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