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 <[email protected]>
---
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");
Herbert Xu <[email protected]> writes:
> 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.
Does this break userspace by creating a device which will just return
-ENODEV on read? Sure, callers *should* handle it...
I far prefer this (simpler) model, though.
Thanks,
Rusty.
>
> Signed-off-by: Herbert Xu <[email protected]>
> ---
>
> 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");
On Wed, Dec 24, 2014 at 09:59:41AM +1030, Rusty Russell wrote:
>
> Does this break userspace by creating a device which will just return
> -ENODEV on read? Sure, callers *should* handle it...
If somebody complains we could easily fix this by making open
fail. In fact, if such applications exist then they're likely
to want to hold onto a reference to the RNG after then open...
Cheers,
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt