[PATCH 3/5] hwrng: core - Do not register device opportunistically

Herbert Xu
2014-12-23T05:40:30Z

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>
---

drivers/char/hw_random/core.c | 23 ++++++++++++-----------
1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 42827fd..1d342f0 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");