linux-kernel - Re: [PATCH v2] platform/x86: think-lmi: Fix memory leak when showing current settings

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Message-Id: <2233a8da-aaad-4265-b583-f3db27f75667@app.fastmail.com>
Date:   Fri, 31 Mar 2023 15:14:13 -0400
From:   "Mark Pearson" <mpearson-lenovo@...ebb.ca>
To:     "Armin Wolf" <W_Armin@....de>,
        "Mark Pearson" <markpearson@...ovo.com>,
        "Mirsad Goran Todorovac" <mirsad.todorovac@....unizg.hr>
Cc:     "Hans de Goede" <hdegoede@...hat.com>,
        "markgross@...nel.org" <markgross@...nel.org>,
        Thomas Weißschuh <thomas@...ch.de>,
        "Greg KH" <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] platform/x86: think-lmi: Fix memory leak when showing current
 settings

Hi Armin

On Fri, Mar 31, 2023, at 2:09 PM, Armin Wolf wrote:
> When retriving a item string with tlmi_setting(), the result has to be
> freed using kfree(). In current_value_show() however, malformed
> item strings are not freed, causing a memory leak.
> Fix this by eliminating the early return responsible for this.
>
> Reported-by: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
> Link: 
> https://lore.kernel.org/platform-driver-x86/01e920bc-5882-ba0c-dd15-868bf0eca0b8@alu.unizg.hr/T/#t
> Fixes: a40cd7ef22fb ("platform/x86: think-lmi: Add WMI interface 
> support on Lenovo platforms")
> Signed-off-by: Armin Wolf <W_Armin@....de>
> ---
> Changes in v2:
> - Add Reported-by: and Link: tags
> ---
>  drivers/platform/x86/think-lmi.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/platform/x86/think-lmi.c 
> b/drivers/platform/x86/think-lmi.c
> index cc66f7cbccf2..8cafb9d4016c 100644
> --- a/drivers/platform/x86/think-lmi.c
> +++ b/drivers/platform/x86/think-lmi.c
> @@ -930,10 +930,12 @@ static ssize_t current_value_show(struct kobject 
> *kobj, struct kobj_attribute *a
>  	/* validate and split from `item,value` -> `value` */
>  	value = strpbrk(item, ",");
>  	if (!value || value == item || !strlen(value + 1))
> -		return -EINVAL;
> +		ret = -EINVAL;
> +	else
> +		ret = sysfs_emit(buf, "%s\n", value + 1);
>
> -	ret = sysfs_emit(buf, "%s\n", value + 1);
>  	kfree(item);
> +
>  	return ret;
>  }
>
> --
> 2.30.2

Thanks for doing this - it was on my todo list but you beat me to it.

As a minor note - the Fixes tag should, I think, be
Fixes: 0fdf10e5fc96 ("platform/x86: think-lmi: Split current_value to reflect only the value")

As that's when I believe I introduced the issue.

Mark