connector: send event on write to /proc/[pid]/comm

While comm change event via prctl has been reported to proc connector by
'commit f786ecba41 ("connector: add comm change event report to proc
connector")', connector listeners were missing comm changes by explicit
writes on /proc/[pid]/comm.

Let explicit writes on /proc/[pid]/comm report to proc connector.

Link: https://lkml.kernel.org/r/20210701133458epcms1p68e9eb9bd0eee8903ba26679a37d9d960@epcms1p6
Signed-off-by: Ohhoon Kwon <ohoono.kwon@samsung.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/base.c

@@ -95,6 +95,7 @@
 #include <linux/posix-timers.h>
 #include <linux/time_namespace.h>
 #include <linux/resctrl.h>
+#include <linux/cn_proc.h>
 #include <trace/events/oom.h>
 #include "internal.h"
 #include "fd.h"
@@ -1674,8 +1675,10 @@ static ssize_t comm_write(struct file *file, const char __user *buf,
 	if (!p)
 		return -ESRCH;
 
-	if (same_thread_group(current, p))
+	if (same_thread_group(current, p)) {
 		set_task_comm(p, buffer);
+		proc_comm_connector(p);
+	}
 	else
 		count = -EINVAL;