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

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Message-ID: <CAGXu5jJP4UbFbfRmLiDLT5Bq3CzBum7tRdXMXY3nPDQQ+bZZmQ@mail.gmail.com>
Date:   Thu, 23 Aug 2018 20:05:06 -0700
From:   Kees Cook <keescook@...omium.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,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drivers: qcom: rpmh: use struct_size() in kzalloc()

On Thu, Aug 23, 2018 at 6:17 PM, Gustavo A. R. Silva
<gustavo@...eddedor.com> 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: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  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
>



-- 
Kees Cook
Pixel Security