Re: [PATCH] cpufreq: e_powersaver: Use struct_size() in kzalloc()

Gustavo A. R. Silva
2019-01-24T17:33:52Z

On 1/24/19 4:34 AM, Rafael J. Wysocki wrote:
> On Tuesday, January 8, 2019 6:00:56 AM CET Viresh Kumar wrote:
>> On 07-01-19, 11:33, Gustavo A. R. Silva wrote:
>>> One of the more common cases of allocation size calculations is finding the
>>> size of a structure that has a zero-sized array at the end, along with memory
>>> for some number of elements for that array. For example:
>>>
>>> struct foo {
>>> int stuff;
>>> void *entry[];
>>> };
>>>
>>> instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);
>>>
>>> Instead of leaving these open-coded and prone to type mistakes, we can now
>>> use the new struct_size() helper:
>>>
>>> instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);
>>>
>>> This code was detected with the help of Coccinelle.
>>>
>>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
>>> ---
>>> drivers/cpufreq/e_powersaver.c | 5 ++---
>>> 1 file changed, 2 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/cpufreq/e_powersaver.c b/drivers/cpufreq/e_powersaver.c
>>> index 60bea302abbe..2d3ef208dd70 100644
>>> --- a/drivers/cpufreq/e_powersaver.c
>>> +++ b/drivers/cpufreq/e_powersaver.c
>>> @@ -323,9 +323,8 @@ static int eps_cpu_init(struct cpufreq_policy *policy)
>>> states = 2;
>>>
>>> /* Allocate private data and frequency table for current cpu */
>>> - centaur = kzalloc(sizeof(*centaur)
>>> - + (states + 1) * sizeof(struct cpufreq_frequency_table),
>>> - GFP_KERNEL);
>>> + centaur = kzalloc(struct_size(centaur, freq_table, states + 1),
>>> + GFP_KERNEL);
>>> if (!centaur)
>>> return -ENOMEM;
>>> eps_cpu[0] = centaur;
>>
>> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
>
> Patch applied, thanks!
>

Thank you both, Viresh and Rafael.

--
Gustavo