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

Bartosz Golaszewski
2017-12-13T09:57:02Z

2017-12-13 10:32 GMT+01:00 Lars-Peter Clausen <lars@metafoo.de>:
> 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().
>

Nice! Another useful kernel interface I wasn't aware of. I'll wait
some more for any potential comments from others and include that in
v2.

Thanks,
Bartosz

>> + 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);
>>
>