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

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Message-ID: <CAMRc=MfyURSh98ds0B2tO5xV9SK5d5D4FoZq5nOPhYH2aGJ9hg@mail.gmail.com>
Date:   Wed, 13 Dec 2017 10:56:58 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Lars-Peter Clausen <lars@...afoo.de>
Cc:     Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH 3/3] regmap: duplicate the name string stored in regmap

2017-12-13 10:32 GMT+01:00 Lars-Peter Clausen <lars@...afoo.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@...ev.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);
>>
>