__ptrace_detach: avoid task_detached(), check do_notify_parent() (9843a1e9) · Commits · 戴 / test

__ptrace_detach() relies on the current obscure behaviour of do_notify_parent(tsk) which changes tsk->exit_signal if this child should be silently reaped. That is why we check task_detached(), it is true if the task is sub-thread, or it is the group_leader but its exit_signal was changed by do_notify_parent(). This is confusing, change the code to rely on !thread_group_leader() or the value returned by do_notify_parent(). Signed-off-by:

Oleg Nesterov <oleg@redhat.com> Acked-by:

Tejun Heo <tj@kernel.org>

kernel/ptrace.c

+18 −15

Original line number	Diff line number	Diff line
		@@ -370,25 +370,28 @@ static int ignoring_children(struct sighand_struct *sigh)
		*/
		static bool __ptrace_detach(struct task_struct tracer, struct task_struct p)
		{
		bool dead;

		__ptrace_unlink(p);

		if (p->exit_state == EXIT_ZOMBIE) {
		if (!task_detached(p) && thread_group_empty(p)) {
		if (p->exit_state != EXIT_ZOMBIE)
		return false;

		dead = !thread_group_leader(p);

		if (!dead && thread_group_empty(p)) {
		if (!same_thread_group(p->real_parent, tracer))
		do_notify_parent(p, p->exit_signal);
		dead = do_notify_parent(p, p->exit_signal);
		else if (ignoring_children(tracer->sighand)) {
		__wake_up_parent(p, tracer);
		p->exit_signal = -1;
		dead = true;
		}
		}
		if (task_detached(p)) {
		/* Mark it as in the process of being reaped. */
		if (dead)
		p->exit_state = EXIT_DEAD;
		return true;
		}
		}

		return false;
		return dead;
		}

		static int ptrace_detach(struct task_struct *child, unsigned int data)

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