linux-kernel - Re: [PATCH] drivers: qcom: rpmh: use struct

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Date:   Mon, 3 Sep 2018 12:07:05 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] drivers: qcom: rpmh: use struct_size() in kzalloc()

On Thu 23 Aug 18:17 PDT 2018, 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_ATOMIC);
> 
> 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_ATOMIC);
> 
> This issue was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>

Regards,
Bjorn

> ---
>  drivers/soc/qcom/rpmh.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
> index c7beb68..12c057a 100644
> --- a/drivers/soc/qcom/rpmh.c
> +++ b/drivers/soc/qcom/rpmh.c
> @@ -362,8 +362,7 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state,
>  	if (!count)
>  		return -EINVAL;
>  
> -	req = kzalloc(sizeof(*req) + count * sizeof(req->rpm_msgs[0]),
> -		      GFP_ATOMIC);
> +	req = kzalloc(struct_size(req, rpm_msgs, count), GFP_ATOMIC);
>  	if (!req)
>  		return -ENOMEM;
>  	req->count = count;
> -- 
> 2.7.4
>