linux-kernel - Re: [PATCH][next] net: dsa: sja1105: Use struct

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Date:   Fri, 19 Jun 2020 22:38:41 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: Re: [PATCH][next] net: dsa: sja1105: Use struct_size() in kzalloc()

Hi Gustavo,

On Fri, 19 Jun 2020 at 21:04, Gustavo A. R. Silva <gustavoars@...nel.org> wrote:
>
> Make use of the struct_size() helper instead of an open-coded version
> in order to avoid any potential type mistakes.
>
> This code was detected with the help of Coccinelle and, audited and
> fixed manually.
>
> Addresses-KSPP-ID: https://github.com/KSPP/linux/issues/83
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>  drivers/net/dsa/sja1105/sja1105_tas.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/net/dsa/sja1105/sja1105_tas.c b/drivers/net/dsa/sja1105/sja1105_tas.c
> index 3aa1a8b5f766..31d8acff1f01 100644
> --- a/drivers/net/dsa/sja1105/sja1105_tas.c
> +++ b/drivers/net/dsa/sja1105/sja1105_tas.c
> @@ -475,8 +475,7 @@ bool sja1105_gating_check_conflicts(struct sja1105_private *priv, int port,
>         if (list_empty(&gating_cfg->entries))
>                 return false;
>
> -       dummy = kzalloc(sizeof(struct tc_taprio_sched_entry) * num_entries +
> -                       sizeof(struct tc_taprio_qopt_offload), GFP_KERNEL);
> +       dummy = kzalloc(struct_size(dummy, entries, num_entries), GFP_KERNEL);

Before, I could read this line and I knew what it did. Now, I have to
look it up.
But if it's in the interest of kernel coding style, what can I say.

Acked-by: Vladimir Oltean <vladimir.oltean@....com>

>         if (!dummy) {
>                 NL_SET_ERR_MSG_MOD(extack, "Failed to allocate memory");
>                 return true;
> --
> 2.27.0
>