From: jsg <jsg@openbsd.org>
Date: Mon, 7 Oct 2024 05:30:12 +0000 (+0000)
Subject: drm/amd/display: Validate backlight caps are sane
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=2fb364bbd4aaa613131449e6f7a68a341c0ac5ab;p=openbsd

drm/amd/display: Validate backlight caps are sane

From Mario Limonciello
c886061bbdd1f37190939b11926055413e86a56c in linux-6.6.y/6.6.54
327e62f47eb57ae5ff63de82b0815557104e439a in mainline linux
---

diff --git a/sys/dev/pci/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/sys/dev/pci/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 9688dc53952..a74f6e9489e 100644
--- a/sys/dev/pci/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/sys/dev/pci/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4041,6 +4041,7 @@ static int amdgpu_dm_mode_config_init(struct amdgpu_device *adev)
 
 #define AMDGPU_DM_DEFAULT_MIN_BACKLIGHT 12
 #define AMDGPU_DM_DEFAULT_MAX_BACKLIGHT 255
+#define AMDGPU_DM_MIN_SPREAD ((AMDGPU_DM_DEFAULT_MAX_BACKLIGHT - AMDGPU_DM_DEFAULT_MIN_BACKLIGHT) / 2)
 #define AUX_BL_DEFAULT_TRANSITION_TIME_MS 50
 
 static void amdgpu_dm_update_backlight_caps(struct amdgpu_display_manager *dm,
@@ -4055,6 +4056,21 @@ static void amdgpu_dm_update_backlight_caps(struct amdgpu_display_manager *dm,
 		return;
 
 	amdgpu_acpi_get_backlight_caps(&caps);
+
+	/* validate the firmware value is sane */
+	if (caps.caps_valid) {
+		int spread = caps.max_input_signal - caps.min_input_signal;
+
+		if (caps.max_input_signal > AMDGPU_DM_DEFAULT_MAX_BACKLIGHT ||
+		    caps.min_input_signal < AMDGPU_DM_DEFAULT_MIN_BACKLIGHT ||
+		    spread > AMDGPU_DM_DEFAULT_MAX_BACKLIGHT ||
+		    spread < AMDGPU_DM_MIN_SPREAD) {
+			DRM_DEBUG_KMS("DM: Invalid backlight caps: min=%d, max=%d\n",
+				      caps.min_input_signal, caps.max_input_signal);
+			caps.caps_valid = false;
+		}
+	}
+
 	if (caps.caps_valid) {
 		dm->backlight_caps[bl_idx].caps_valid = true;
 		if (caps.aux_support)