[PATCH] eeprom: at24: use struct_size() in devm_kzalloc()

[PATCH] eeprom: at24: use struct_size() in devm_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;
    struct boo entry[];
};

size = sizeof(struct foo) + count * sizeof(struct boo);
instance = devm_kzalloc(dev, size, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

instance = devm_kzalloc(dev, struct_size(instance, entry, count), GFP_KERNEL);

Notice that, in this case, variable at24_size is not necessary, hence it
is removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/misc/eeprom/at24.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index ba8e73812644..78ba6b1917a8 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -568,7 +568,6 @@ static int at24_probe(struct i2c_client *client)
 	unsigned int i, num_addresses;
 	struct at24_data *at24;
 	struct regmap *regmap;
-	size_t at24_size;
 	bool writable;
 	u8 test_byte;
 	int err;
@@ -652,8 +651,8 @@ static int at24_probe(struct i2c_client *client)
 	if (IS_ERR(regmap))
 		return PTR_ERR(regmap);
 
-	at24_size = sizeof(*at24) + num_addresses * sizeof(struct at24_client);
-	at24 = devm_kzalloc(dev, at24_size, GFP_KERNEL);
+	at24 = devm_kzalloc(dev, struct_size(at24, client, num_addresses),
+			    GFP_KERNEL);
 	if (!at24)
 		return -ENOMEM;
 
-- 
2.21.0

Re: [PATCH] eeprom: at24: use struct_size() in devm_kzalloc()

[Bartosz Golaszewski]

śr., 29 maj 2019 o 18:30 Gustavo A. R. Silva <gustavo@embeddedor.com>
napisał(a):
>
> 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;
>     struct boo entry[];
> };
>
> size = sizeof(struct foo) + count * sizeof(struct boo);
> instance = devm_kzalloc(dev, size, GFP_KERNEL);
>
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
>
> instance = devm_kzalloc(dev, struct_size(instance, entry, count), GFP_KERNEL);
>
> Notice that, in this case, variable at24_size is not necessary, hence it
> is removed.
>
> This code was detected with the help of Coccinelle.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  drivers/misc/eeprom/at24.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> index ba8e73812644..78ba6b1917a8 100644
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -568,7 +568,6 @@ static int at24_probe(struct i2c_client *client)
>         unsigned int i, num_addresses;
>         struct at24_data *at24;
>         struct regmap *regmap;
> -       size_t at24_size;
>         bool writable;
>         u8 test_byte;
>         int err;
> @@ -652,8 +651,8 @@ static int at24_probe(struct i2c_client *client)
>         if (IS_ERR(regmap))
>                 return PTR_ERR(regmap);
>
> -       at24_size = sizeof(*at24) + num_addresses * sizeof(struct at24_client);
> -       at24 = devm_kzalloc(dev, at24_size, GFP_KERNEL);
> +       at24 = devm_kzalloc(dev, struct_size(at24, client, num_addresses),
> +                           GFP_KERNEL);
>         if (!at24)
>                 return -ENOMEM;
>
> --
> 2.21.0
>

Applied, thanks!

Bart