Re: [Intel-gfx] [PATCH] drm/i915/debugfs: HDCP capability enc NULL check

[Imre Deak <imre.deak@intel.com>]

On Fri, Jan 29, 2021 at 01:30:43PM +0530, Anshuman Gupta wrote:
> DP-MST connector encoder initializes at modeset
> Adding a connector->encoder NULL check in order to
> avoid any NULL pointer dereference.
> intel_hdcp_enable() already handle this but debugfs
> can also invoke the intel_{hdcp,hdcp2_capable}.
> Handling it gracefully.
> 
> Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_hdcp.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
> index ae1371c36a32..58af323d189a 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdcp.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
> @@ -135,11 +135,16 @@ int intel_hdcp_read_valid_bksv(struct intel_digital_port *dig_port,
>  /* Is HDCP1.4 capable on Platform and Sink */
>  bool intel_hdcp_capable(struct intel_connector *connector)
>  {
> -	struct intel_digital_port *dig_port = intel_attached_dig_port(connector);
> +	struct intel_digital_port *dig_port;
>  	const struct intel_hdcp_shim *shim = connector->hdcp.shim;
>  	bool capable = false;
>  	u8 bksv[5];
>  
> +	if (!connector->encoder)
> +		return -ENODEV;

I assume this is needed when called from i915_hdcp_sink_capability
debugfs entry. That one is lacking the locking for the connector, but is
that entry really needed? We print the same info already from the
i915_display_info entry which has the proper locking and encoder check.

> +
> +	dig_port = intel_attached_dig_port(connector);
> +
>  	if (!shim)
>  		return capable;
>  
> @@ -156,11 +161,16 @@ bool intel_hdcp_capable(struct intel_connector *connector)
>  /* Is HDCP2.2 capable on Platform and Sink */
>  bool intel_hdcp2_capable(struct intel_connector *connector)
>  {
> -	struct intel_digital_port *dig_port = intel_attached_dig_port(connector);
> +	struct intel_digital_port *dig_port;
>  	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
>  	struct intel_hdcp *hdcp = &connector->hdcp;
>  	bool capable = false;
>  
> +	if (!connector->encoder)
> +		return -ENODEV;
> +
> +	dig_port = intel_attached_dig_port(connector);
> +
>  	/* I915 support for HDCP2.2 */
>  	if (!hdcp->hdcp2_supported)
>  		return false;
> -- 
> 2.26.2
> 
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