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

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

On Fri, Feb 05, 2021 at 10:16:30AM +0200, Gupta, Anshuman wrote:
> > -----Original Message-----
> > From: Imre Deak <imre.deak@intel.com>
> > Sent: Thursday, February 4, 2021 11:58 PM
> > To: Gupta, Anshuman <anshuman.gupta@intel.com>
> > Cc: intel-gfx@lists.freedesktop.org
> > Subject: Re: [Intel-gfx] [PATCH] drm/i915/debugfs: HDCP capability enc NULL
> > check
> > 
> > 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.
>
> Historically HDCP capability added to i915_display_info later to debug
> CI machine as i915_display_info available as CI logs.  Now the plans
> i915_display_info  should only show the monitor capability.  and
> i915_hdcp_sink_capability will check both sink and platform
> capability.

Ok, in any case the encoder NULL check and the required locking should
be done in i915_hdcp_sink_capability_show().

> 
> Thanks,
> Anshuman Gupta.
> > 
> > > +
> > > +	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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> > > Intel-gfx@lists.freedesktop.org
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