linux-kernel - Re: [PATCH] platform/x86: wmi: Add Null check for device

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Message-ID: <ff53debd-05bd-3a7f-89a5-2110b8103fad@linux.intel.com>
Date: Fri, 14 Mar 2025 13:41:42 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Chenyuan Yang <chenyuan0y@...il.com>
cc: W_Armin@....de, Hans de Goede <hdegoede@...hat.com>, 
    platform-driver-x86@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] platform/x86: wmi: Add Null check for device

On Thu, 13 Mar 2025, Chenyuan Yang wrote:

Hi,

Could you please be consistent in style and write "NULL" also in the 
shortlog in the subject.

> Not all devices have an ACPI companion fwnode, so device might be NULL.
> This is similar to the commit cd2fd6eab480
> ("platform/x86: int3472: Check for adev == NULL").

Please fold the paragraph normally.

> Add a check for device not being set and return -ENODEV in that case to
> avoid a possible NULL pointer deref in parse_wdg().
> 
> Note, acpi_wmi_probe() under the same file has such a check.

Hmm, is this a bogus fix, as parse_wdg() is only called from 
acpi_wmi_probe() so how can ACPI companion turn NULL in between??

How was this problem found??

> Signed-off-by: Chenyuan Yang <chenyuan0y@...il.com>
> ---
>  drivers/platform/x86/wmi.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
> index 646370bd6b03..54e697838c1e 100644
> --- a/drivers/platform/x86/wmi.c
> +++ b/drivers/platform/x86/wmi.c
> @@ -1091,6 +1091,9 @@ static int parse_wdg(struct device *wmi_bus_dev, struct platform_device *pdev)
>  	u32 i, total;
>  	int retval;
>  
> +	if (!device)
> +		return -ENODEV;
> +
>  	status = acpi_evaluate_object(device->handle, "_WDG", NULL, &out);
>  	if (ACPI_FAILURE(status))
>  		return -ENXIO;
> 

-- 
 i.