[Intel-gfx] [bug report] drm/i915/tc: Fix TypeC PHY connect/disconnect logic on ADL-P

[Ville Syrjälä]

On Fri, Oct 01, 2021 at 04:25:35PM +0300, Dan Carpenter wrote:
> Hello Imre Deak,
> 
> This is a semi-automatic email about new static checker warnings.
> 
> The patch 3e0abc7661c8: "drm/i915/tc: Fix TypeC PHY 
> connect/disconnect logic on ADL-P" from Sep 29, 2021, leads to the 
> following Smatch complaint:
> 
>     drivers/gpu/drm/i915/display/intel_ddi.c:4028 intel_ddi_encoder_destroy()
>     warn: variable dereferenced before check 'dig_port' (see line 4020)
> 
> drivers/gpu/drm/i915/display/intel_ddi.c
>   4019		struct intel_digital_port *dig_port = enc_to_dig_port(to_intel_encoder(encoder));
>   4020		enum phy phy = intel_port_to_phy(i915, dig_port->base.port);
>                                                        ^^^^^^^^^^^^^^^^^^^
> The patch adds a new unchecked dereference.
> 
>   4021	
>   4022		intel_dp_encoder_flush_work(encoder);
>   4023		if (intel_phy_is_tc(i915, phy))
>   4024			intel_tc_port_flush_work(dig_port);
>   4025		intel_display_power_flush_work(i915);
>   4026	
>   4027		drm_encoder_cleanup(encoder);
>   4028		if (dig_port)
>                     ^^^^^^^^
> But the existing code checked for NULL.

That check is nonsense. Feel free to nuke it.

> 
>   4029			kfree(dig_port->hdcp_port_data.streams);
>   4030		kfree(dig_port);
> 
> regards,
> dan carpenter

-- 
Ville Syrjälä
Intel