Merge branch 'pid-introduce-helper-task_is_in_root_ns'

Leo Yan says:

====================
pid: Introduce helper task_is_in_root_ns()

This patch series introduces a helper function task_is_in_init_pid_ns()
to replace open code.  The two patches are extracted from the original
series [1] for network subsystem.

As a plan, we can firstly land this patch set into kernel 5.18; there
have 5 patches are left out from original series [1], as a next step,
I will resend them for appropriate linux-next merging.

[1] https://lore.kernel.org/lkml/20211208083320.472503-1-leo.yan@linaro.org/
====================

Link: https://lore.kernel.org/r/20220126050427.605628-1-leo.yan@linaro.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/connector/cn_proc.c

@@ -358,7 +358,7 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
 	 * other namespaces.
 	 */
 	if ((current_user_ns() != &init_user_ns) ||
-	    (task_active_pid_ns(current) != &init_pid_ns))
+	    !task_is_in_init_pid_ns(current))
 		return;
 
 	/* Can only change if privileged. */

include/linux/pid_namespace.h

@@ -86,4 +86,9 @@ extern struct pid_namespace *task_active_pid_ns(struct task_struct *tsk);
 void pidhash_init(void);
 void pid_idr_init(void);
 
+static inline bool task_is_in_init_pid_ns(struct task_struct *tsk)
+{
+	return task_active_pid_ns(tsk) == &init_pid_ns;
+}
+
 #endif /* _LINUX_PID_NS_H */