static int ptrace_detach(struct task_struct *child, unsigned int data)
{
- bool dead = false;
-
if (!valid_signal(data))
return -EIO;
write_lock_irq(&tasklist_lock);
/*
- * This child can be already killed. Make sure de_thread() or
- * our sub-thread doing do_wait() didn't do release_task() yet.
+ * We rely on ptrace_freeze_traced(). It can't be killed and
+ * untraced by another thread, it can't be a zombie.
*/
- if (child->ptrace) {
- child->exit_code = data;
- dead = __ptrace_detach(current, child);
- }
+ WARN_ON(!child->ptrace || child->exit_state);
+ /*
+ * tasklist_lock avoids the race with wait_task_stopped(), see
+ * the comment in ptrace_resume().
+ */
+ child->exit_code = data;
+ __ptrace_detach(current, child);
write_unlock_irq(&tasklist_lock);
proc_ptrace_connector(child, PTRACE_DETACH);
- if (unlikely(dead))
- release_task(child);
return 0;
}
static int ptrace_resume(struct task_struct *child, long request,
unsigned long data)
{
+ bool need_siglock;
+
if (!valid_signal(data))
return -EIO;
user_disable_single_step(child);
}
+ /*
+ * Change ->exit_code and ->state under siglock to avoid the race
+ * with wait_task_stopped() in between; a non-zero ->exit_code will
+ * wrongly look like another report from tracee.
+ *
+ * Note that we need siglock even if ->exit_code == data and/or this
+ * status was not reported yet, the new status must not be cleared by
+ * wait_task_stopped() after resume.
+ *
+ * If data == 0 we do not care if wait_task_stopped() reports the old
+ * status and clears the code too; this can't race with the tracee, it
+ * takes siglock after resume.
+ */
+ need_siglock = data && !thread_group_empty(current);
+ if (need_siglock)
+ spin_lock_irq(&child->sighand->siglock);
child->exit_code = data;
wake_up_state(child, __TASK_TRACED);
+ if (need_siglock)
+ spin_unlock_irq(&child->sighand->siglock);
return 0;
}