hwrng: core - Do not register device opportunistically

Currently we only register the device when a valid RNG is added.
However the way it's done is buggy because we test whether there
is a current RNG to determine whether we need to register.  As
the current RNG may be missing due to a reinitialisation error
this can lead to a reregistration of the device.

As the device already has to handle a NULL current RNG anyway,
let's just register the device always and remove the complexity.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 12 insertions, 11 deletions

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 42827fd5f38d..1d342f0cb0c1 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -372,14 +372,14 @@ static DEVICE_ATTR(rng_available, S_IRUGO,
                    NULL);
 
 
-static void unregister_miscdev(void)
+static void __exit unregister_miscdev(void)
 {
         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
         misc_deregister(&rng_miscdev);
 }
 
-static int register_miscdev(void)
+static int __init register_miscdev(void)
 {
         int err;
 
@@ -484,12 +484,6 @@ int hwrng_register(struct hwrng *rng)
                 if (err)
                         goto out_unlock;
                 set_current_rng(rng);
-
-                err = register_miscdev();
-                if (err) {
-                        drop_current_rng();
-                        goto out_unlock;
-                }
         }
         list_add_tail(&rng->list, &rng_list);
 
@@ -530,7 +524,6 @@ void hwrng_unregister(struct hwrng *rng)
 
         if (list_empty(&rng_list)) {
                 mutex_unlock(&rng_mutex);
-                unregister_miscdev();
                 if (hwrng_fill)
                         kthread_stop(hwrng_fill);
         } else
@@ -540,16 +533,24 @@ void hwrng_unregister(struct hwrng *rng)
 }
 EXPORT_SYMBOL_GPL(hwrng_unregister);
 
-static void __exit hwrng_exit(void)
+static int __init hwrng_modinit(void)
+{
+        return register_miscdev();
+}
+
+static void __exit hwrng_modexit(void)
 {
         mutex_lock(&rng_mutex);
         BUG_ON(current_rng);
         kfree(rng_buffer);
         kfree(rng_fillbuf);
         mutex_unlock(&rng_mutex);
+
+        unregister_miscdev();
 }
 
-module_exit(hwrng_exit);
+module_init(hwrng_modinit);
+module_exit(hwrng_modexit);
 
 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
 MODULE_LICENSE("GPL");