Re: [PATCH 2/3] crypto: hwrng remember rng chosen by user

[PrasannaKumar Muralidharan]

Hi Harald,

On 3 July 2017 at 15:33, Harald Freudenberger  wrote:
> When a user chooses a rng source via sysfs
> attribute this rng should be sticky, even
> when other sources with better quality to
> register. This patch introduces a simple way
> to remember the user's choise.
>
> Signed-off-by: Harald Freudenberger 
> ---
>  drivers/char/hw_random/core.c | 10 --
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
> index e9dda16..ffd4e36 100644
> --- a/drivers/char/hw_random/core.c
> +++ b/drivers/char/hw_random/core.c
> @@ -28,6 +28,8 @@
>  #define RNG_MODULE_NAME"hw_random"
>
>  static struct hwrng *current_rng;
> +/* the current rng has been explicitly chosen by user via sysfs */
> +static int cur_rng_set_by_user;
>  static struct task_struct *hwrng_fill;
>  /* list of registered rngs, sorted decending by quality */
>  static LIST_HEAD(rng_list);
> @@ -304,6 +306,7 @@ static ssize_t hwrng_attr_current_store(struct device 
> *dev,
> list_for_each_entry(rng, _list, list) {
> if (sysfs_streq(rng->name, buf)) {
> err = 0;
> +   cur_rng_set_by_user = 1;
> if (rng != current_rng)
> err = set_current_rng(rng);
> break;
> @@ -444,10 +447,12 @@ int hwrng_register(struct hwrng *rng)
>
> old_rng = current_rng;
> err = 0;
> -   if (!old_rng || (rng->quality > old_rng->quality)) {
> +   if (!old_rng ||
> +   (!cur_rng_set_by_user && rng->quality > old_rng->quality)) {
> /*
>  * Set new rng as current as the new rng source
> -* provides better entropy quality.
> +* provides better entropy quality and was not
> +* chosen by userspace.
>  */
> err = set_current_rng(rng);
> if (err)
> @@ -479,6 +484,7 @@ void hwrng_unregister(struct hwrng *rng)
> list_del(>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(_list)) {
> struct hwrng *new_rng;
> --
> 2.7.4
>

Looks good to me. Reviewed-by: PrasannaKumar Muralidharan
.

Regards,
PrasannaKumar

[PATCH 2/3] crypto: hwrng remember rng chosen by user

[Harald Freudenberger]

When a user chooses a rng source via sysfs
attribute this rng should be sticky, even
when other sources with better quality to
register. This patch introduces a simple way
to remember the user's choise.

Signed-off-by: Harald Freudenberger 
---
 drivers/char/hw_random/core.c | 10 --
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index e9dda16..ffd4e36 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -28,6 +28,8 @@
 #define RNG_MODULE_NAME"hw_random"
 
 static struct hwrng *current_rng;
+/* the current rng has been explicitly chosen by user via sysfs */
+static int cur_rng_set_by_user;
 static struct task_struct *hwrng_fill;
 /* list of registered rngs, sorted decending by quality */
 static LIST_HEAD(rng_list);
@@ -304,6 +306,7 @@ static ssize_t hwrng_attr_current_store(struct device *dev,
list_for_each_entry(rng, _list, list) {
if (sysfs_streq(rng->name, buf)) {
err = 0;
+   cur_rng_set_by_user = 1;
if (rng != current_rng)
err = set_current_rng(rng);
break;
@@ -444,10 +447,12 @@ int hwrng_register(struct hwrng *rng)
 
old_rng = current_rng;
err = 0;
-   if (!old_rng || (rng->quality > old_rng->quality)) {
+   if (!old_rng ||
+   (!cur_rng_set_by_user && rng->quality > old_rng->quality)) {
/*
 * Set new rng as current as the new rng source
-* provides better entropy quality.
+* provides better entropy quality and was not
+* chosen by userspace.
 */
err = set_current_rng(rng);
if (err)
@@ -479,6 +484,7 @@ void hwrng_unregister(struct hwrng *rng)
list_del(>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(_list)) {
struct hwrng *new_rng;
-- 
2.7.4