Oleg Nesterov <o...@redhat.com> writes:
> On 04/26, Eric W. Biederman wrote:
>>
>> @@ -253,7 +252,7 @@ static int ptrace_check_attach(struct task_struct
>> *child, bool ignore_state)
>> */
>> if (lock_task_sighand(child, &flags)) {
>> if (child->ptrace && child->parent == current) {
>> - WARN_ON(READ_ONCE(child->__state) == __TASK_TRACED);
>> + WARN_ON(child->jobctl & JOBCTL_DELAY_WAKEKILL);
>
> This WARN_ON() doesn't look right.
>
> It is possible that this child was traced by another task and
> PTRACE_DETACH'ed,
> but it didn't clear DELAY_WAKEKILL.
That would be a bug. That would mean that PTRACE_DETACHED process can
not be SIGKILL'd.
> If the new debugger attaches and calls ptrace() before the child takes siglock
> ptrace_freeze_traced() will fail, but we can hit this WARN_ON().
Eric
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