netdev - Re: [PATCH net-next v2 1/2] rswitch: Use unsigned int for array index

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Date: Mon, 16 Oct 2023 21:56:05 +0200
From: Simon Horman <horms@...nel.org>
To: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Cc: s.shtylyov@....ru, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org,
	Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH net-next v2 1/2] rswitch: Use unsigned int for array index

+ Geert Uytterhoeven

On Fri, Oct 13, 2023 at 09:19:35PM +0900, Yoshihiro Shimoda wrote:
> The array index should not be negative, so modify the condition of
> rswitch_for_each_enabled_port_continue_reverse() macro, and then
> use unsigned int instead.
> 
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
> ---
>  drivers/net/ethernet/renesas/rswitch.c | 8 +++++---
>  drivers/net/ethernet/renesas/rswitch.h | 2 +-
>  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/renesas/rswitch.c b/drivers/net/ethernet/renesas/rswitch.c
> index 112e605f104a..7640144db79b 100644
> --- a/drivers/net/ethernet/renesas/rswitch.c
> +++ b/drivers/net/ethernet/renesas/rswitch.c
> @@ -1405,7 +1405,8 @@ static void rswitch_ether_port_deinit_one(struct rswitch_device *rdev)
>  
>  static int rswitch_ether_port_init_all(struct rswitch_private *priv)
>  {
> -	int i, err;
> +	unsigned int i;
> +	int err;
>  
>  	rswitch_for_each_enabled_port(priv, i) {
>  		err = rswitch_ether_port_init_one(priv->rdev[i]);
> @@ -1786,7 +1787,8 @@ static void rswitch_device_free(struct rswitch_private *priv, int index)
>  
>  static int rswitch_init(struct rswitch_private *priv)
>  {
> -	int i, err;
> +	unsigned int i;
> +	int err;
>  
>  	for (i = 0; i < RSWITCH_NUM_PORTS; i++)
>  		rswitch_etha_init(priv, i);

Hi Shimoda-san,

Immediately below this hunk, the following code appears.

                if (err < 0) {
                        for (i--; i >= 0; i--)
                                rswitch_device_free(priv, i);
                        goto err_device_alloc;
                } 

I suspect that the for loop should be updated in a similar way to
that in rswitch_for_each_enabled_port_continue_reverse as,
now that i is unsigned, i >= 0 will always be true.

As flagged by Smatch and Coccinelle.

Otherwise this patch-set looks good to me.

> @@ -1959,7 +1961,7 @@ static int renesas_eth_sw_probe(struct platform_device *pdev)
>  
>  static void rswitch_deinit(struct rswitch_private *priv)
>  {
> -	int i;
> +	unsigned int i;
>  
>  	rswitch_gwca_hw_deinit(priv);
>  	rcar_gen4_ptp_unregister(priv->ptp_priv);
> diff --git a/drivers/net/ethernet/renesas/rswitch.h b/drivers/net/ethernet/renesas/rswitch.h
> index 04f49a7a5843..27c9d3872c0e 100644
> --- a/drivers/net/ethernet/renesas/rswitch.h
> +++ b/drivers/net/ethernet/renesas/rswitch.h
> @@ -20,7 +20,7 @@
>  		else
>  
>  #define rswitch_for_each_enabled_port_continue_reverse(priv, i)	\
> -	for (i--; i >= 0; i--)					\
> +	for (; i-- > 0; )					\
>  		if (priv->rdev[i]->disabled)			\
>  			continue;				\
>  		else

-- 
pw-bot: changes-requested