drm/i915/opregion: check port number bounds for SWSCI display power state

commit ea958422291de248b9e2eaaeea36004e84b64043 upstream.

The mapping from enum port to whatever port numbering scheme is used by
the SWSCI Display Power State Notification is odd, and the memory of it
has faded. In any case, the parameter only has space for ports numbered
[0..4], and UBSAN reports bit shift beyond it when the platform has port
F or more.

Since the SWSCI functionality is supposed to be obsolete for new
platforms (i.e. ones that might have port F or more), just bail out
early if the mapped and mangled port number is beyond what the Display
Power State Notification can support.

Fixes: 9c4b0a683193 ("drm/i915: add opregion function to notify bios of encoder enable/disable")
Cc: <stable@vger.kernel.org> # v3.13+
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/4800
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/cc363f42d6b5a5932b6d218fefcc8bdfb15dbbe5.1644489329.git.jani.nikula@intel.com
(cherry picked from commit 24a644ebbfd3b13cda702f98907f9dd123e34bf9)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/display/intel_opregion.c b/drivers/gpu/drm/i915/display/intel_opregion.c
index 3855fba709807727d4b019e313e17d76d97f9d10..f7f49b69830fafd1fb81a81cd4432233437325eb 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_opregion.c
+++ b/drivers/gpu/drm/i915/display/intel_opregion.c
@@ -361,6 +361,21 @@ int intel_opregion_notify_encoder(struct intel_encoder *intel_encoder,
                port++;
        }
 
+       /*
+        * The port numbering and mapping here is bizarre. The now-obsolete
+        * swsci spec supports ports numbered [0..4]. Port E is handled as a
+        * special case, but port F and beyond are not. The functionality is
+        * supposed to be obsolete for new platforms. Just bail out if the port
+        * number is out of bounds after mapping.
+        */
+       if (port > 4) {
+               drm_dbg_kms(&dev_priv->drm,
+                           "[ENCODER:%d:%s] port %c (index %u) out of bounds for display power state notification\n",
+                           intel_encoder->base.base.id, intel_encoder->base.name,
+                           port_name(intel_encoder->port), port);
+               return -EINVAL;
+       }
+
        if (!enable)
                parm |= 4 << 8;