Re: [PATCH 3/3] regmap: duplicate the name string stored in regmap

Lars-Peter Clausen
2017-12-13T09:32:49Z

On 12/13/2017 10:28 AM, Bartosz Golaszewski wrote:
> Currently we just copy over the pointer passed to regmap_init() in
> the regmap config struct. To be on the safe side: duplicate the string
> so that if an unaware user passes an address to a stack-allocated
> buffer, we won't crash.
>
> Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
> ---
> drivers/base/regmap/regmap.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
> index a2a02ce58824..3952e5d7638a 100644
> --- a/drivers/base/regmap/regmap.c
> +++ b/drivers/base/regmap/regmap.c
> @@ -672,6 +672,14 @@ struct regmap *__regmap_init(struct device *dev,
> goto err;
> }
>
> + if (config->name) {
> + map->name = kstrdup(config->name, GFP_KERNEL);

To get the best of both worlds: kstrdup_const(), this will not make a copy
when it is in a read-only section (like most strings will be). Needs to be
matched with kfree_const().

> + if (!map->name) {
> + ret = -ENOMEM;
> + goto err_map;
> + }
> + }
> +
> if (config->disable_locking) {
> map->locking_disabled = true;
> map->lock = map->unlock = regmap_lock_unlock_none;
> @@ -763,7 +771,6 @@ struct regmap *__regmap_init(struct device *dev,
> map->volatile_reg = config->volatile_reg;
> map->precious_reg = config->precious_reg;
> map->cache_type = config->cache_type;
> - map->name = config->name;
>
> spin_lock_init(&map->async_lock);
> INIT_LIST_HEAD(&map->async_list);
> @@ -1308,6 +1315,7 @@ void regmap_exit(struct regmap *map)
> }
> if (map->hwlock)
> hwspin_lock_free(map->hwlock);
> + kfree(map->name);
> kfree(map);
> }
> EXPORT_SYMBOL_GPL(regmap_exit);
>