linux-kernel - RE: [PATCH] pinctrl: imx: fix unsigned check if nfuncs with less than or equal zero

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Message-ID: <AM3PR04MB3063FA8C1B267634A8B1A5180C10@AM3PR04MB306.eurprd04.prod.outlook.com>
Date:   Mon, 26 Feb 2018 13:14:59 +0000
From:   "A.s. Dong" <aisheng.dong@....com>
To:     Colin King <colin.king@...onical.com>,
        Fabio Estevam <festevam@...il.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Stefan Agner <stefan@...er.ch>,
        inus Walleij <linus.walleij@...aro.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
CC:     "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] pinctrl: imx: fix unsigned check if nfuncs with less than
 or equal zero

> -----Original Message-----
> From: Colin King [mailto:colin.king@...onical.com]
> Sent: Monday, February 26, 2018 8:04 PM
> To: A.s. Dong <aisheng.dong@....com>; Fabio Estevam
> <festevam@...il.com>; Shawn Guo <shawnguo@...nel.org>; Stefan
> Agner <stefan@...er.ch>; inus Walleij <linus.walleij@...aro.org>; linux-
> gpio@...r.kernel.org
> Cc: kernel-janitors@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: [PATCH] pinctrl: imx: fix unsigned check if nfuncs with less than or
> equal zero
> 
> From: Colin Ian King <colin.king@...onical.com>
> 
> The unsigned integer nfuncs is being error checked with a value less or equal
> to zero; this is always false if of_get_child_count returns a -ve for an error
> condition since nfuncs is not signed. Fix this by making variables nfuncs and i
> signed integers.
> 
> Detected with Coccinelle:
> drivers/pinctrl/freescale/pinctrl-imx.c:620:6-12: WARNING: Unsigned
> expression compared with zero: nfuncs <= 0
> 
> Fixes: ae75ff814538 ("pinctrl: pinctrl-imx: add imx pinctrl core driver")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/pinctrl/freescale/pinctrl-imx.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pinctrl/freescale/pinctrl-imx.c
> b/drivers/pinctrl/freescale/pinctrl-imx.c
> index 24aaddd760a0..1e8ca83352d0 100644
> --- a/drivers/pinctrl/freescale/pinctrl-imx.c
> +++ b/drivers/pinctrl/freescale/pinctrl-imx.c
> @@ -605,8 +605,8 @@ static int imx_pinctrl_probe_dt(struct
> platform_device *pdev,
>  	struct device_node *np = pdev->dev.of_node;
>  	struct device_node *child;
>  	struct pinctrl_dev *pctl = ipctl->pctl;
> -	u32 nfuncs = 0;
> -	u32 i = 0;
> +	int nfuncs = 0;
> +	int i = 0;
>  	bool flat_funcs;
> 

I saw 'i', later used, is converted to u32 unconditionally. (GCC did not complain)
e.g.
radix_tree_insert
imx_pinctrl_parse_functions

And of_get_child_count seems can't  return a minor value.

So does something like below look better?

diff --git a/drivers/pinctrl/freescale/pinctrl-imx.c b/drivers/pinctrl/freescale/pinctrl-imx.c
index c976ffe..4259209 100644
--- a/drivers/pinctrl/freescale/pinctrl-imx.c
+++ b/drivers/pinctrl/freescale/pinctrl-imx.c
@@ -612,7 +612,7 @@ static int imx_pinctrl_probe_dt(struct platform_device *pdev,
                nfuncs = 1;
        } else {
                nfuncs = of_get_child_count(np);
-               if (nfuncs <= 0) {
+               if (nfuncs == 0) {
                        dev_err(&pdev->dev, "no functions defined\n");
                        return -EINVAL;
                }

Regards
Dong Aisheng

>  	if (!np)
> --
> 2.15.1