Exemple #1
0
/*
 * Check that we have indeed attached to the thing..
 */
int ptrace_check_attach(struct task_struct *child, int kill)
{
	int ret = -ESRCH;

	/*
	 * We take the read lock around doing both checks to close a
	 * possible race where someone else was tracing our child and
	 * detached between these two checks.  After this locked check,
	 * we are sure that this is our traced child and that can only
	 * be changed by us so it's not changing right after this.
	 */
	read_lock(&tasklist_lock);
	if ((child->ptrace & PT_PTRACED) && child->parent == current) {
		ret = 0;
		/*
		 * child->sighand can't be NULL, release_task()
		 * does ptrace_unlink() before __exit_signal().
		 */
		spin_lock_irq(&child->sighand->siglock);
		if (task_is_stopped(child))
			child->state = TASK_TRACED;
		else if (!task_is_traced(child) && !kill)
			ret = -ESRCH;
		spin_unlock_irq(&child->sighand->siglock);
	}
	read_unlock(&tasklist_lock);

	if (!ret && !kill)
		ret = wait_task_inactive(child, TASK_TRACED) ? 0 : -ESRCH;

	/* All systems go.. */
	return ret;
}
Exemple #2
0
static int ptrace_attach(struct task_struct *task)
{
	bool wait_trap = false;
	int retval;

	audit_ptrace(task);

	retval = -EPERM;
	if (unlikely(task->flags & PF_KTHREAD))
		goto out;
	if (same_thread_group(task, current))
		goto out;

	/*
	 * Protect exec's credential calculations against our interference;
	 * interference; SUID, SGID and LSM creds get determined differently
	 * under ptrace.
	 */
	retval = -ERESTARTNOINTR;
	if (mutex_lock_interruptible(&task->signal->cred_guard_mutex))
		goto out;

	task_lock(task);
	retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
	task_unlock(task);
	if (retval)
		goto unlock_creds;

	write_lock_irq(&tasklist_lock);
	retval = -EPERM;
	if (unlikely(task->exit_state))
		goto unlock_tasklist;
	if (task->ptrace)
		goto unlock_tasklist;

	task->ptrace = PT_PTRACED;
	if (task_ns_capable(task, CAP_SYS_PTRACE))
		task->ptrace |= PT_PTRACE_CAP;

	__ptrace_link(task, current);
	send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);

	spin_lock(&task->sighand->siglock);

	/*
	 * If the task is already STOPPED, set GROUP_STOP_PENDING and
	 * TRAPPING, and kick it so that it transits to TRACED.  TRAPPING
	 * will be cleared if the child completes the transition or any
	 * event which clears the group stop states happens.  We'll wait
	 * for the transition to complete before returning from this
	 * function.
	 *
	 * This hides STOPPED -> RUNNING -> TRACED transition from the
	 * attaching thread but a different thread in the same group can
	 * still observe the transient RUNNING state.  IOW, if another
	 * thread's WNOHANG wait(2) on the stopped tracee races against
	 * ATTACH, the wait(2) may fail due to the transient RUNNING.
	 *
	 * The following task_is_stopped() test is safe as both transitions
	 * in and out of STOPPED are protected by siglock.
	 */
	if (task_is_stopped(task)) {
		task->group_stop |= GROUP_STOP_PENDING | GROUP_STOP_TRAPPING;
		signal_wake_up(task, 1);
		wait_trap = true;
	}

	spin_unlock(&task->sighand->siglock);

	retval = 0;
unlock_tasklist:
	write_unlock_irq(&tasklist_lock);
unlock_creds:
	mutex_unlock(&task->signal->cred_guard_mutex);
out:
	if (wait_trap)
		wait_event(current->signal->wait_chldexit,
			   !(task->group_stop & GROUP_STOP_TRAPPING));
	return retval;
}