linux-kernel - Re: [PATCH] platform/x86: dell-pc: avoid double free and invalid unregistration

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Date: Tue, 04 Jun 2024 20:46:29 -0600
From: Lyndon Sanche <lsanche@...deno.ca>
To: Thomas Weißschuh <linux@...ssschuh.net>
Cc: Hans de Goede <hdegoede@...hat.com>, Ilpo Järvinen
	<ilpo.jarvinen@...ux.intel.com>, platform-driver-x86@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] platform/x86: dell-pc: avoid double free and invalid
 unregistration



On Tue, Jun 4 2024 at 11:41:24 PM +02:00:00, Thomas Weißschuh 
<linux@...ssschuh.net> wrote:
> If platform_profile_register() fails it does kfree(thermal_handler) 
> and
> leaves the pointer value around.
> Any call to thermal_cleanup() will try to kfree(thermal_handler) 
> again.
> This will happen right away in dell_init().
> In addition, platform_profile_remove() will be called although no
> profile is registered.
> 
> NULL out the thermal_handler, so thermal_cleanup() avoids the double 
> free.
> 
> Fixes: 996ad4129810 ("platform/x86: dell-pc: Implement 
> platform_profile")
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> ---
> Currently the call to thermal_cleanup() in dell_init() is completely
> unnecessary. But I guess more functionality will be handled by the
> driver and then this structure makes sense.
> 
> This is untested.
> ---
>  drivers/platform/x86/dell/dell-pc.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/dell/dell-pc.c 
> b/drivers/platform/x86/dell/dell-pc.c
> index dfe09c463d03..972385ca1990 100644
> --- a/drivers/platform/x86/dell/dell-pc.c
> +++ b/drivers/platform/x86/dell/dell-pc.c
> @@ -261,8 +261,10 @@ static int thermal_init(void)
> 
>  	/* Clean up if failed */
>  	ret = platform_profile_register(thermal_handler);
> -	if (ret)
> +	if (ret) {
>  		kfree(thermal_handler);
> +		thermal_handler = NULL;
> +	}
> 
>  	return ret;
>  }
> 
> ---
> base-commit: 0da7a954480cc99978e3570c991e3779e56fc736
> change-id: 20240604-dell-pc-double-free-e8cf2aa9b2fb
> 
> Best regards,
> --
> Thomas Weißschuh <linux@...ssschuh.net>

Thank you for this patch. I was able to apply your patch and compile 
successfully. I have not had a chance to try it on my hardware.

I agree with the change, and it looks good to me.

Thanks,

Reviewed-by: Lyndon Sanche <lsanche@...deno.ca>