Re: [PATCH v1] ASoC: rt5640: Fix NULL dereference on module unload

[Takashi Iwai <tiwai@suse.de>]

On Sun, 29 Dec 2019 16:04:54 +0100,
Dmitry Osipenko wrote:
> 
> The rt5640->jack is NULL if jack is already disabled at the time of
> driver's module unloading.
> 
>  Unable to handle kernel NULL pointer dereference at virtual address 00000024
>  ...
>  (rt5640_set_jack [snd_soc_rt5640]) from [<bf86f7ed>] (snd_soc_component_set_jack+0x11/0x1c [snd_soc_core])
>  (snd_soc_component_set_jack [snd_soc_core]) from [<bf8675cf>] (soc_remove_component+0x1b/0x54 [snd_soc_core])
>  (soc_remove_component [snd_soc_core]) from [<bf868859>] (soc_cleanup_card_resources+0xad/0x1cc [snd_soc_core])
>  (soc_cleanup_card_resources [snd_soc_core]) from [<bf86945f>] (snd_soc_unregister_card+0x47/0x78 [snd_soc_core])
>  (snd_soc_unregister_card [snd_soc_core]) from [<bf8b4013>] (tegra_rt5640_remove+0x13/0x1c [snd_soc_tegra_rt5640])
>  (tegra_rt5640_remove [snd_soc_tegra_rt5640]) from [<c0516d2f>] (platform_drv_remove+0x17/0x24)
>  (platform_drv_remove) from [<c0515aed>] (device_release_driver_internal+0x95/0x114)
>  (device_release_driver_internal) from [<c0515bd9>] (driver_detach+0x4d/0x90)
>  (driver_detach) from [<c0514d59>] (bus_remove_driver+0x31/0x70)
>  (bus_remove_driver) from [<bf8b4215>] (tegra_rt5640_driver_exit+0x9/0xdf4 [snd_soc_tegra_rt5640])
>  (tegra_rt5640_driver_exit [snd_soc_tegra_rt5640]) from [<c019336f>] (sys_delete_module+0xe7/0x184)
>  (sys_delete_module) from [<c0101001>] (ret_fast_syscall+0x1/0x28)
> 
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  sound/soc/codecs/rt5640.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/sound/soc/codecs/rt5640.c b/sound/soc/codecs/rt5640.c
> index adbae1f36a8a..b245c44cafbc 100644
> --- a/sound/soc/codecs/rt5640.c
> +++ b/sound/soc/codecs/rt5640.c
> @@ -2432,16 +2432,22 @@ static void rt5640_disable_jack_detect(struct snd_soc_component *component)
>  {
>  	struct rt5640_priv *rt5640 = snd_soc_component_get_drvdata(component);
>  
> -	disable_irq(rt5640->irq);
> -	rt5640_cancel_work(rt5640);
> +	/*
> +	 * soc_remove_component() force-disables jack and thus rt5640->jack
> +	 * could be NULL at the time of driver's module unloading.
> +	 */
> +	if (rt5640->jack) {
> +		disable_irq(rt5640->irq);
> +		rt5640_cancel_work(rt5640);
>  
> -	if (rt5640->jack->status & SND_JACK_MICROPHONE) {
> -		rt5640_disable_micbias1_ovcd_irq(component);
> -		rt5640_disable_micbias1_for_ovcd(component);
> -		snd_soc_jack_report(rt5640->jack, 0, SND_JACK_BTN_0);
> -	}
> +		if (rt5640->jack->status & SND_JACK_MICROPHONE) {
> +			rt5640_disable_micbias1_ovcd_irq(component);
> +			rt5640_disable_micbias1_for_ovcd(component);
> +			snd_soc_jack_report(rt5640->jack, 0, SND_JACK_BTN_0);
> +		}
>  
> -	rt5640->jack = NULL;
> +		rt5640->jack = NULL;
> +	}
>  }

I guess it's simpler just returning if rt5640->jack is already NULL.

--- a/sound/soc/codecs/rt5640.c
+++ b/sound/soc/codecs/rt5640.c
@@ -2432,6 +2432,10 @@ static void rt5640_disable_jack_detect(struct snd_soc_component *component)
 {
 	struct rt5640_priv *rt5640 = snd_soc_component_get_drvdata(component);
 
+	/* already disabled? */
+	if (!rt5640->jack)
+		return;
+
 	disable_irq(rt5640->irq);
 	rt5640_cancel_work(rt5640);
 

thanks,

Takashi