tpm: tpm_vtpm_proxy: fix a race condition in /dev/vtpmx creation

commit f4032d615f upstream.

/dev/vtpmx is made visible before 'workqueue' is initialized, which can
lead to a memory corruption in the worst case scenario.

Address this by initializing 'workqueue' as the very first step of the
driver initialization.

Cc: stable@vger.kernel.org
Fixes: 6f99612e25 ("tpm: Proxy driver for supporting multiple emulated TPMs")
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@tuni.fi>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/char/tpm/tpm_vtpm_proxy.c

@@ -683,37 +683,21 @@ static struct miscdevice vtpmx_miscdev = {
 	.fops = &vtpmx_fops,
 };
 
-static int vtpmx_init(void)
-{
-	return misc_register(&vtpmx_miscdev);
-}
-
-static void vtpmx_cleanup(void)
-{
-	misc_deregister(&vtpmx_miscdev);
-}
-
 static int __init vtpm_module_init(void)
 {
 	int rc;
 
-	rc = vtpmx_init();
-	if (rc) {
-		pr_err("couldn't create vtpmx device\n");
-		return rc;
-	}
-
 	workqueue = create_workqueue("tpm-vtpm");
 	if (!workqueue) {
 		pr_err("couldn't create workqueue\n");
-		rc = -ENOMEM;
+		return -ENOMEM;
-		goto err_vtpmx_cleanup;
 	}
 
-	return 0;
+	rc = misc_register(&vtpmx_miscdev);
-
+	if (rc) {
-err_vtpmx_cleanup:
+		pr_err("couldn't create vtpmx device\n");
-	vtpmx_cleanup();
+		destroy_workqueue(workqueue);
+	}
 
 	return rc;
 }
@@ -721,7 +705,7 @@ err_vtpmx_cleanup:
 static void __exit vtpm_module_exit(void)
 {
 	destroy_workqueue(workqueue);
-	vtpmx_cleanup();
+	misc_deregister(&vtpmx_miscdev);
 }
 
 module_init(vtpm_module_init);