Re: [PATCH v2] media: qcom: camss: fix VFE pm domain off

[Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>]

On 11/28/24 21:39, Barnabás Czémán wrote:
> Fix NULL pointer check before device_link_del
> is called.
> 
> Unable to handle kernel NULL pointer dereference at virtual address 000000000000032c
> Call trace:
>   device_link_put_kref+0xc/0xb8
>   device_link_del+0x30/0x48
>   vfe_pm_domain_off+0x24/0x38 [qcom_camss]
>   vfe_put+0x9c/0xd0 [qcom_camss]
>   vfe_set_power+0x48/0x58 [qcom_camss]
>   pipeline_pm_power_one+0x154/0x158 [videodev]
>   pipeline_pm_power+0x74/0xfc [videodev]
>   v4l2_pipeline_pm_use+0x54/0x90 [videodev]
>   v4l2_pipeline_pm_put+0x14/0x34 [videodev]
>   video_release+0x2c/0x44 [qcom_camss]
>   v4l2_release+0xe4/0xec [videodev]
> 
> Fixes: eb73facec2c2 ("media: qcom: camss: Use common VFE pm_domain_on/pm_domain_off where applicable")
> Tested-by: Yassine Oudjana <y.oudjana@protonmail.com>
> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
> Signed-off-by: Barnabás Czémán <barnabas.czeman@mainlining.org>
> ---
> Changes in v2:
> - Add backtrace to the commit message.
> - Link to v1: https://lore.kernel.org/r/20241122-vfe_pm_domain_off-v1-1-81d18f56563d@mainlining.org
> ---
>   drivers/media/platform/qcom/camss/camss-vfe.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/qcom/camss/camss-vfe.c b/drivers/media/platform/qcom/camss/camss-vfe.c
> index 80a62ba11295042802cbaec617fb87c492ea6a55..1bf1473331f63b9ab106d21ea263c84d851c8a31 100644
> --- a/drivers/media/platform/qcom/camss/camss-vfe.c
> +++ b/drivers/media/platform/qcom/camss/camss-vfe.c
> @@ -595,7 +595,7 @@ void vfe_isr_reset_ack(struct vfe_device *vfe)
>    */
>   void vfe_pm_domain_off(struct vfe_device *vfe)
>   {
> -	if (!vfe->genpd)
> +	if (!vfe->genpd_link)
>   		return;
>   
>   	device_link_del(vfe->genpd_link);
> 

I object to this change, there might be a problem in the code, however it
is not yet identified.

vfe->genpd is not NULL, if vfe_pm_domain_on()/vfe_pm_domain_off() are
called appropriately, the "fix" does not fix the real problem, it veils it.

--
Best wishes,
Vladimir