linux-kernel - Re: [PATCH] i2c: mux: demux-pinctrl: handle failure case of devm

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Message-ID: <549eba3a-28b9-e4b0-f680-8fb51b160879@axentia.se>
Date:   Tue, 4 Dec 2018 11:16:59 +0000
From:   Peter Rosin <peda@...ntia.se>
To:     Nicholas Mc Guire <hofrat@...dl.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>
CC:     "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i2c: mux: demux-pinctrl: handle failure case of
 devm_kstrdup()

Hi!

This patch looks like a good idea. However, a nitpick below.

On 2018-12-01 11:01, Nicholas Mc Guire wrote:
> devm_kstrdup() may return NULL if internal allocation failed.
> Thus using  name, value  is unsafe without being checked. As
> i2c_demux_pinctrl_probe() can return -ENOMEM in other cases
> a dev_err() message is included to make the failure location
> clear.
> 
> Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
> Fixes: e35478eac030 ("i2c: mux: demux-pinctrl: run properly with multiple instances")
> ---
> 
> Problem located with experimental coccinelle script
> 
> Q: The use of devm_kstrdup() seems a bit odd while technically not wrong,
>    personally I think devm_kasprintf() would be more suitable here.
> 
> Patch was compile tested with: multi_v7_defconfig 
> (implies I2C_DEMUX_PINCTRL=y)
> 
> Patch is against 4.20-rc4 (localversion-next is next-20181130)
> 
>  drivers/i2c/muxes/i2c-demux-pinctrl.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/i2c/muxes/i2c-demux-pinctrl.c b/drivers/i2c/muxes/i2c-demux-pinctrl.c
> index 035032e..c466999 100644
> --- a/drivers/i2c/muxes/i2c-demux-pinctrl.c
> +++ b/drivers/i2c/muxes/i2c-demux-pinctrl.c
> @@ -244,6 +244,12 @@ static int i2c_demux_pinctrl_probe(struct platform_device *pdev)
>  
>  		props[i].name = devm_kstrdup(&pdev->dev, "status", GFP_KERNEL);
>  		props[i].value = devm_kstrdup(&pdev->dev, "ok", GFP_KERNEL);
> +		if (!props[i].name || !props[i].value) {
> +			dev_err(&pdev->dev,
> +				"chan %d name, value allocation failed\n", i);

Please drop this memory allocation failure message. You should get such a
message from devm_kstrdup.

Cheers,
Peter

> +			err = -ENOMEM;
> +			goto err_rollback;
> +		}
>  		props[i].length = 3;
>  
>  		of_changeset_init(&priv->chan[i].chgset);
>