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;
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);
--
2.10.0
