Re: [PATCH V6 1/2] soc: imx: Add SCU SoC info driver support

[Russell King - ARM Linux admin]

On Thu, May 23, 2019 at 04:53:46AM +0000, Anson Huang wrote:
> Add i.MX SCU SoC info driver to support i.MX8QXP SoC, introduce
> driver dependency into Kconfig as CONFIG_IMX_SCU must be
> selected to support i.MX SCU SoC driver, also need to use
> platform driver model to make sure IMX_SCU driver is probed
> before i.MX SCU SoC driver.

This seems buggy...

> +static int imx_scu_soc_probe(struct platform_device *pdev)
> +{
> +	struct soc_device_attribute *soc_dev_attr;
> +	struct soc_device *soc_dev;
> +	u32 id, val;
> +	int ret;
> +
> +	ret = imx_scu_get_handle(&soc_ipc_handle);
> +	if (ret)
> +		return ret;
> +
> +	soc_dev_attr = devm_kzalloc(&pdev->dev, sizeof(*soc_dev_attr),
> +				    GFP_KERNEL);
> +	if (!soc_dev_attr)
> +		return -ENOMEM;
> +
> +	soc_dev_attr->family = "Freescale i.MX";
> +
> +	ret = of_property_read_string(of_root,
> +				      "model",
> +				      &soc_dev_attr->machine);
> +	if (ret)
> +		return ret;
> +
> +	id = imx_scu_soc_id();
> +
> +	/* format soc_id value passed from SCU firmware */
> +	val = id & 0x1f;
> +	soc_dev_attr->soc_id = val ? kasprintf(GFP_KERNEL, "0x%x", val)
> +			       : "unknown";

soc_id can either be an allocated string, or it can be a static string
of "unknown".

> +	if (!soc_dev_attr->soc_id)
> +		return -ENOMEM;
> +
> +	/* format revision value passed from SCU firmware */
> +	val = (id >> 5) & 0xf;
> +	val = (((val >> 2) + 1) << 4) | (val & 0x3);
> +	soc_dev_attr->revision = val ? kasprintf(GFP_KERNEL,
> +						 "%d.%d",
> +						 (val >> 4) & 0xf,
> +						 val & 0xf) : "unknown";

revision here is the same.

> +	if (!soc_dev_attr->revision) {
> +		ret = -ENOMEM;
> +		goto free_soc_id;
> +	}
> +
> +	soc_dev = soc_device_register(soc_dev_attr);
> +	if (IS_ERR(soc_dev)) {
> +		ret = PTR_ERR(soc_dev);
> +		goto free_revision;
> +	}
> +
> +	return 0;
> +
> +free_revision:
> +	kfree(soc_dev_attr->revision);
> +free_soc_id:
> +	kfree(soc_dev_attr->soc_id);

Yet here you blindly kfree(), which means you could be doing in effect
kfree("unknown") - which will likely result in a kernel oops.

Either always make revision/soc_id an allocated string, or use some
static storage for the strings (they're only small, static storage is
likely to be much more efficient in this case, and there can only be
one of these in any case.)

> +	return ret;
> +}
> +
> +static struct platform_driver imx_scu_soc_driver = {
> +	.driver = {
> +		.name = IMX_SCU_SOC_DRIVER_NAME,
> +	},
> +	.probe = imx_scu_soc_probe,
> +};
> +
> +static int __init imx_scu_soc_init(void)
> +{
> +	struct platform_device *imx_scu_soc_pdev;
> +	struct device_node *np;
> +	int ret;
> +
> +	np = of_find_compatible_node(NULL, NULL, "fsl,imx-scu");
> +	if (!np)
> +		return -ENODEV;
> +
> +	of_node_put(np);
> +
> +	ret = platform_driver_register(&imx_scu_soc_driver);
> +	if (ret)
> +		return ret;
> +
> +	imx_scu_soc_pdev =
> +		platform_device_register_simple(IMX_SCU_SOC_DRIVER_NAME,
> +						-1,
> +						NULL,
> +						0);
> +	if (IS_ERR(imx_scu_soc_pdev))
> +		platform_driver_unregister(&imx_scu_soc_driver);
> +
> +	return PTR_ERR_OR_ZERO(imx_scu_soc_pdev);
> +}
> +device_initcall(imx_scu_soc_init);
> -- 
> 2.7.4
> 
> 
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