[PATCH 5.15.y] drm/i915/vrr: require valid min/max vfreq for VRR

From: Jani Nikula <[email protected]>

[ Upstream commit f8a9262c7a6fc2de9802e14b0228114f0333869e ]

Ensure the EDID provided min/max vfreq are valid. Most scenarios are
already covered (by coincidence) through the checks in
intel_vrr_is_capable() and intel_vrr_is_in_range(), but be more explicit
about it. At worst, a zero min_vfreq could lead to a division by zero in
intel_vrr_compute_vmax().

Discovered using AI-assisted static analysis confirmed by Intel Product
Security.

Reported-by: Martin Hodo <[email protected]>
Fixes: 117cd09ba528 ("drm/i915/display/dp: Compute VRR state in atomic_check")
Cc: [email protected] # v5.12+
Cc: Ankit Nautiyal <[email protected]>
Reviewed-by: Ankit Nautiyal <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jani Nikula <[email protected]>
(cherry picked from commit 1765cf59f517b02f3b0591fe5120930d08bddeb6)
Signed-off-by: Joonas Lahtinen <[email protected]>
[ adjusted context to 5.15's `intel_vrr_is_capable(struct drm_connector *)` form, inserting the guard before the existing compound `return HAS_VRR(i915) && ...` instead of upstream's refactored bare return. ]
Signed-off-by: Sasha Levin <[email protected]>
---
 drivers/gpu/drm/i915/display/intel_vrr.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
index c335b1dbafcf8..25abc437b6197 100644
--- a/drivers/gpu/drm/i915/display/intel_vrr.c
+++ b/drivers/gpu/drm/i915/display/intel_vrr.c
@@ -26,6 +26,10 @@ bool intel_vrr_is_capable(struct drm_connector *connector)
 	 * EDID monitor range also should be atleast 10 for reasonable
 	 * Adaptive Sync or Variable Refresh Rate end user experience.
 	 */
+	if (!info->monitor_range.min_vfreq || !info->monitor_range.max_vfreq ||
+	    info->monitor_range.min_vfreq > info->monitor_range.max_vfreq)
+		return false;
+
 	return HAS_VRR(i915) &&
 		drm_dp_sink_can_do_video_without_timing_msa(intel_dp->dpcd) &&
 		info->monitor_range.max_vfreq - info->monitor_range.min_vfreq > 10;
-- 
2.53.0