Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/tools/testing/selftests/gpio/gpio-mockup-chardev.c b/tools/testing/selftests/gpio/gpio-mockup-chardev.c
index f8d468f..73ead88 100644
--- a/tools/testing/selftests/gpio/gpio-mockup-chardev.c
+++ b/tools/testing/selftests/gpio/gpio-mockup-chardev.c
@@ -1,18 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * GPIO chardev test helper
  *
  * Copyright (C) 2016 Bamvor Jian Zhang
- *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 as published by
- * the Free Software Foundation.
  */
 
 #define _GNU_SOURCE
 #include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <stdio.h>
 #include <errno.h>
 #include <string.h>
 #include <fcntl.h>
@@ -37,7 +33,7 @@
 	struct libmnt_table *tb;
 	struct libmnt_iter *itr = NULL;
 	struct libmnt_fs *fs;
-	int found = 0;
+	int found = 0, ret;
 
 	cxt = mnt_new_context();
 	if (!cxt)
@@ -58,8 +54,11 @@
 			break;
 		}
 	}
-	if (found)
-		asprintf(path, "%s/gpio", mnt_fs_get_target(fs));
+	if (found) {
+		ret = asprintf(path, "%s/gpio", mnt_fs_get_target(fs));
+		if (ret < 0)
+			err(EXIT_FAILURE, "failed to format string");
+	}
 
 	mnt_free_iter(itr);
 	mnt_free_context(cxt);