problem with /proc/sysrq-trigger

[Gao feng <gaofeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>]

Hi all

when I using the container, I found the /proc/sysrq-trigger is not isolated with the host.
when exec echo c > /proc/sysrq-trigger in the container,
the host will crash too.

I don't know if it's correct.
And if it's incorrect,can I fix this by just like this?

diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index 05728894..da4d812 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -865,6 +865,10 @@ EXPORT_SYMBOL(unregister_sysrq_key);
 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
                                   size_t count, loff_t *ppos)
 {
+       if (current->nsproxy != &init_nsproxy)
+               return -EFAULT;

        if (count) {
                char c;