[PATCH] Input: mcs_touchkey - use struct_size() in kzalloc()

[PATCH] Input: mcs_touchkey - use struct_size() in kzalloc()

[Gustavo A. R. Silva]

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/input/keyboard/mcs_touchkey.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/input/keyboard/mcs_touchkey.c b/drivers/input/keyboard/mcs_touchkey.c
index be56d4f262a7..b132662201a4 100644
--- a/drivers/input/keyboard/mcs_touchkey.c
+++ b/drivers/input/keyboard/mcs_touchkey.c
@@ -113,9 +113,8 @@ static int mcs_touchkey_probe(struct i2c_client *client,
 		return -EINVAL;
 	}
 
-	data = kzalloc(sizeof(struct mcs_touchkey_data) +
-			sizeof(data->keycodes[0]) * (pdata->key_maxval + 1),
-			GFP_KERNEL);
+	data = kzalloc(struct_size(data, keycodes, pdata->key_maxval + 1),
+		       GFP_KERNEL);
 	input_dev = input_allocate_device();
 	if (!data || !input_dev) {
 		dev_err(&client->dev, "Failed to allocate memory\n");
-- 
2.20.1

Re: [PATCH] Input: mcs_touchkey - use struct_size() in kzalloc()

[Dmitry Torokhov]

On Tue, Jan 08, 2019 at 03:15:56PM -0600, 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>

Applied, thank you.

> ---
>  drivers/input/keyboard/mcs_touchkey.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/input/keyboard/mcs_touchkey.c b/drivers/input/keyboard/mcs_touchkey.c
> index be56d4f262a7..b132662201a4 100644
> --- a/drivers/input/keyboard/mcs_touchkey.c
> +++ b/drivers/input/keyboard/mcs_touchkey.c
> @@ -113,9 +113,8 @@ static int mcs_touchkey_probe(struct i2c_client *client,
>  		return -EINVAL;
>  	}
>  
> -	data = kzalloc(sizeof(struct mcs_touchkey_data) +
> -			sizeof(data->keycodes[0]) * (pdata->key_maxval + 1),
> -			GFP_KERNEL);
> +	data = kzalloc(struct_size(data, keycodes, pdata->key_maxval + 1),
> +		       GFP_KERNEL);
>  	input_dev = input_allocate_device();
>  	if (!data || !input_dev) {
>  		dev_err(&client->dev, "Failed to allocate memory\n");
> -- 
> 2.20.1
> 

-- 
Dmitry

Re: [PATCH] Input: mcs_touchkey - use struct_size() in kzalloc()

[Gustavo A. R. Silva]

On 1/14/19 12:31 AM, Dmitry Torokhov wrote:

>>
>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> 
> Applied, thank you.
> 

Thanks, Dmitry.

--
Gustavo