On 10/27/2017 07:04 PM, PrasannaKumar Muralidharan wrote:
> User is able to select a chosen rng by writing its name to rng_current
> but there is no way to reset it without unbinding the rng. Let user
> write "" to rng_current and delesect the chosen rng.
>
> Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@xxxxxxxxx>
> ---
> drivers/char/hw_random/core.c | 51 +++++++++++++++++++++++++++----------------
> 1 file changed, 32 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
> index 9701ac7..be03024 100644
> --- a/drivers/char/hw_random/core.c
> +++ b/drivers/char/hw_random/core.c
> @@ -292,26 +292,48 @@ static struct miscdevice rng_miscdev = {
> .groups = rng_dev_groups,
> };
>
> +static int enable_best_rng(void)
> +{
> + int ret = -ENODEV;
> +
> + BUG_ON(!mutex_is_locked(&rng_mutex));
> +
> + /* rng_list is sorted by quality, use the best (=first) one */
> + if (!list_empty(&rng_list)) {
> + struct hwrng *new_rng;
> +
> + new_rng = list_entry(rng_list.next, struct hwrng, list);
> + ret = ((new_rng == current_rng) ? 0 : set_current_rng(new_rng));
> + if (!ret)
> + cur_rng_set_by_user = 0;
> + }
> +
> + return ret;
> +}
> +
> static ssize_t hwrng_attr_current_store(struct device *dev,
> struct device_attribute *attr,
> const char *buf, size_t len)
> {
> - int err;
> + int err = -ENODEV;
Two lines later err is assigned the return value of mutex_lock_interruptible().
So the -ENODEV value assignment does nothing.
> struct hwrng *rng;
>
> err = mutex_lock_interruptible(&rng_mutex);
> if (err)
> return -ERESTARTSYS;
> - err = -ENODEV;
> - list_for_each_entry(rng, &rng_list, list) {
> - if (sysfs_streq(rng->name, buf)) {
> - err = 0;
> - cur_rng_set_by_user = 1;
> - if (rng != current_rng)
> +
> + if (sysfs_streq(buf, "")) {
> + err = enable_best_rng();
> + } else {
> + list_for_each_entry(rng, &rng_list, list) {
> + if (sysfs_streq(rng->name, buf)) {
> + cur_rng_set_by_user = 1;
> err = set_current_rng(rng);
> - break;
> + break;
> + }
> }
> }
> +
> mutex_unlock(&rng_mutex);
>
> return err ? : len;
> @@ -493,17 +515,8 @@ void hwrng_unregister(struct hwrng *rng)
> mutex_lock(&rng_mutex);
>
> list_del(&rng->list);
> - if (current_rng == rng) {
> - drop_current_rng();
> - cur_rng_set_by_user = 0;
> - /* rng_list is sorted by quality, use the best (=first) one */
> - if (!list_empty(&rng_list)) {
> - struct hwrng *new_rng;
> -
> - new_rng = list_entry(rng_list.next, struct hwrng, list);
> - set_current_rng(new_rng);
> - }
> - }
> + if (current_rng == rng)
> + enable_best_rng();
>
> if (list_empty(&rng_list)) {
> mutex_unlock(&rng_mutex);
looks like for me.
reviewed-by: Harald Freudenberger <freude@xxxxxxxxxxxxxxxxxx>
