linux-kernel - [PATCH 3/3] drm/atomic: verify that gamma/degamma LUTs are not too big

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Message-Id: <20251115-drm-fix-lut-checks-v1-3-3586f5855bc7@oss.qualcomm.com>
Date: Sat, 15 Nov 2025 05:42:51 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Harry Wentland <harry.wentland@....com>, Leo Li <sunpeng.li@....com>,
        Rodrigo Siqueira <siqueira@...lia.com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        amd-gfx@...ts.freedesktop.org
Subject: [PATCH 3/3] drm/atomic: verify that gamma/degamma LUTs are not too
 big

The kernel specifies LUT table sizes in a separate property, however it
doesn't enforce it as a maximum. Some drivers implement max suze check
on their own in the atomic_check path. Other drivers simply ignore the
issue. Perform LUT size validation in the generic place.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
---
 drivers/gpu/drm/drm_atomic_uapi.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
index 7d2076f1006e976de73c898a838ceb4b5c4370e4..178d983b2378e1910a8afff4da24e090f02f3bd4 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -384,11 +384,19 @@ static int drm_atomic_crtc_set_property(struct drm_crtc *crtc,
 	} else if (property == config->prop_vrr_enabled) {
 		state->vrr_enabled = val;
 	} else if (property == config->degamma_lut_property) {
+		u64 lut_size;
+
+		ret = drm_object_immutable_property_get_value(&crtc->base,
+							      config->degamma_lut_size_property,
+							      &lut_size);
+		if (ret)
+			return ret;
+
 		ret = drm_property_replace_blob_from_id(dev,
 					&state->degamma_lut,
 					val,
 					-1, sizeof(struct drm_color_lut),
-					0,
+					sizeof(struct drm_color_lut) * lut_size,
 					&replaced);
 		state->color_mgmt_changed |= replaced;
 		return ret;
@@ -401,11 +409,19 @@ static int drm_atomic_crtc_set_property(struct drm_crtc *crtc,
 		state->color_mgmt_changed |= replaced;
 		return ret;
 	} else if (property == config->gamma_lut_property) {
+		u64 lut_size;
+
+		ret = drm_object_immutable_property_get_value(&crtc->base,
+							      config->gamma_lut_size_property,
+							      &lut_size);
+		if (ret)
+			return ret;
+
 		ret = drm_property_replace_blob_from_id(dev,
 					&state->gamma_lut,
 					val,
 					-1, sizeof(struct drm_color_lut),
-					0,
+					sizeof(struct drm_color_lut) * lut_size,
 					&replaced);
 		state->color_mgmt_changed |= replaced;
 		return ret;

-- 
2.47.3