Re: [PATCH] hwmon: (hp-wmi-sensors) Fix use-after-free in fungible_show()

[James Seo]

On Wed, Sep 16, 2026 at 05:29:26AM +0500, Muhammad Bilal wrote:
> hp_wmi_update_info() takes state->lock internally and releases it
> before returning, so by the time fungible_show() dereferences
> nsensor->current_state in seq_printf(), no lock is held. Two
> processes reading a sensor's current_state debugfs entry at
> overlapping times (or one reading it while another read of the same
> sensor triggers a refresh) can race: one thread's seq_printf() can
> be part-way through printing the string at the moment another
> thread's call into update_numeric_sensor_from_wobj() frees it with
> devm_kfree() and installs a new pointer, causing a use-after-free
> read.
Thanks for identifying this issue.

> Take state->lock around the read in fungible_show() as well, so it
> can never run concurrently with the free-and-replace in
> update_numeric_sensor_from_wobj().
> 
> Fixes: 23902f98f8d4 ("hwmon: add HP WMI Sensors driver")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Muhammad Bilal <meatuni001@xxxxxxxxx>
> ---
>  drivers/hwmon/hp-wmi-sensors.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/hwmon/hp-wmi-sensors.c b/drivers/hwmon/hp-wmi-sensors.c
> index 03c684b..55aee16 100644
> --- a/drivers/hwmon/hp-wmi-sensors.c
> +++ b/drivers/hwmon/hp-wmi-sensors.c
> @@ -1247,7 +1247,9 @@ static int fungible_show(struct seq_file *seqf, enum hp_wmi_property prop)
>  		break;
>  
>  	case HP_WMI_PROPERTY_CURRENT_STATE:
> +		mutex_lock(&state->lock);
>  		seq_printf(seqf, "%s\n", nsensor->current_state);
> +		mutex_unlock(&state->lock);
>  		break;
>  
>  	case HP_WMI_PROPERTY_UNIT_MODIFIER:
> -- 
> 2.43.0
>
Fine with me.

Acked-by: James Seo <james@xxxxxxxxxx>