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

commit f4032d615f90970d6c3ac1d9c0bce3351eb4445c 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: 6f99612e2500 ("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>

diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c
index 5c86598..30e9539 100644 (file)
--- a/drivers/char/tpm/tpm_vtpm_proxy.c
+++ b/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;
-               goto err_vtpmx_cleanup;
+               return -ENOMEM;
        }
 
-       return 0;
-
-err_vtpmx_cleanup:
-       vtpmx_cleanup();
+       rc = misc_register(&vtpmx_miscdev);
+       if (rc) {
+               pr_err("couldn't create vtpmx device\n");
+               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);