On Tue, 9 Jan 2018, Kees Cook wrote:

-static void report_usercopy(unsigned long len, bool to_user, const char *type)
+int report_usercopy(const char *name, const char *detail, bool to_user,
+		    unsigned long offset, unsigned long len)
 {
-	pr_emerg("kernel memory %s attempt detected %s '%s' (%lu bytes)\n",
+	pr_emerg("kernel memory %s attempt detected %s %s%s%s%s (offset %lu, size %lu)\n",
 		to_user ? "exposure" : "overwrite",
-		to_user ? "from" : "to", type ? : "unknown", len);
+		to_user ? "from" : "to",
+		name ? : "unknown?!",
+		detail ? " '" : "", detail ? : "", detail ? "'" : "",
+		offset, len);
 	/*
 	 * For greater effect, it would be nice to do do_group_exit(),
 	 * but BUG() actually hooks all the lock-breaking and per-arch
 	 * Oops code, so that is used here instead.
 	 */
 	BUG();

Should this be a WARN() or so? Or some configuration that changes
BUG() behavior? Otherwise

+
+	return -1;

This return code will never be returned.

Why a return code at all? Maybe I will see that in the following patches?