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Commit 9843a1e9 authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

__ptrace_detach: avoid task_detached(), check do_notify_parent() 



__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: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
parent 45cdf5cc

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)