2019-01-08 17:28:56

by Gustavo A. R. Silva

Subject: [PATCH] qtnfmac: use struct_size() in kzalloc()

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 <[email protected]>
---
drivers/net/wireless/quantenna/qtnfmac/commands.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/quantenna/qtnfmac/commands.c b/drivers/net/wireless/quantenna/qtnfmac/commands.c
index 659e7649fe22..cf386f579060 100644
--- a/drivers/net/wireless/quantenna/qtnfmac/commands.c
+++ b/drivers/net/wireless/quantenna/qtnfmac/commands.c
@@ -914,9 +914,8 @@ qtnf_cmd_resp_proc_hw_info(struct qtnf_bus *bus,
if (WARN_ON(resp->n_reg_rules > NL80211_MAX_SUPP_REG_RULES))
return -E2BIG;

- hwinfo->rd = kzalloc(sizeof(*hwinfo->rd)
- + sizeof(struct ieee80211_reg_rule)
- * resp->n_reg_rules, GFP_KERNEL);
+ hwinfo->rd = kzalloc(struct_size(hwinfo->rd, reg_rules,
+ resp->n_reg_rules), GFP_KERNEL);

if (!hwinfo->rd)
return -ENOMEM;
--
2.20.1

2019-01-09 09:11:23

by Sergey Matyukevich

Subject: Re: [PATCH] qtnfmac: use struct_size() in kzalloc()

> 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[];
> };

...

> Signed-off-by: Gustavo A. R. Silva <[email protected]>
> ---
> drivers/net/wireless/quantenna/qtnfmac/commands.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/wireless/quantenna/qtnfmac/commands.c b/drivers/net/wireless/quantenna/qtnfmac/commands.c
> index 659e7649fe22..cf386f579060 100644
> --- a/drivers/net/wireless/quantenna/qtnfmac/commands.c
> +++ b/drivers/net/wireless/quantenna/qtnfmac/commands.c
> @@ -914,9 +914,8 @@ qtnf_cmd_resp_proc_hw_info(struct qtnf_bus *bus,
> if (WARN_ON(resp->n_reg_rules > NL80211_MAX_SUPP_REG_RULES))
> return -E2BIG;
>
> - hwinfo->rd = kzalloc(sizeof(*hwinfo->rd)
> - + sizeof(struct ieee80211_reg_rule)
> - * resp->n_reg_rules, GFP_KERNEL);
> + hwinfo->rd = kzalloc(struct_size(hwinfo->rd, reg_rules,
> + resp->n_reg_rules), GFP_KERNEL);
>
> if (!hwinfo->rd)
> return -ENOMEM;

Thanks!

Reviewed-by: Sergey Matyukevich <[email protected]>

Regards,
Sergey

2019-02-01 12:10:49

by Kalle Valo

Subject: Re: [PATCH] qtnfmac: use struct_size() in kzalloc()

"Gustavo A. R. Silva" <[email protected]> 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 <[email protected]>
> Reviewed-by: Sergey Matyukevich <[email protected]>

Patch applied to wireless-drivers-next.git, thanks.

db040dfa53e2 qtnfmac: use struct_size() in kzalloc()

--
https://patchwork.kernel.org/patch/10752601/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches