Merge tag 'exynos-drm-next-for-v6.20' of git://git.kernel.org/pub/scm/linux/kernel/git/daeinki/drm-exynos into drm-next

Fix three regressions
. Fix a regression where vidi_connection_ioctl() used the wrong device
  to look up the vidi context. It stores the vidi device in exynos_drm_private
  and uses it in ioctl(), preventing invalid pointer access and related bugs.
. Fix a security regression where vidi_connection_ioctl() directly dereferenced
  a user pointer for EDID data. It copies EDID from user space
  with copy_from_user() into kernel memory before use, preventing arbitrary
  kernel memory access.
. Fix a concurrency regression where vidi_context members related
  to EDID memory were accessed without locking. It protects alloc/free and
  state updates with ctx->lock, preventing race conditions and use-after-free bugs.

Signed-off-by: Dave Airlie <[email protected]>

From: Inki Dae <[email protected]>
Link: https://patch.msgid.link/[email protected]

Author: airlied

drivers/gpu/drm/exynos/exynos_drm_drv.h

@@ -199,6 +199,7 @@ struct drm_exynos_file_private {
 struct exynos_drm_private {
 	struct device *g2d_dev;
 	struct device *dma_dev;
+	struct device *vidi_dev;
 	void *mapping;
 
 	/* for atomic commit */

drivers/gpu/drm/exynos/exynos_drm_vidi.c

@@ -187,29 +187,37 @@ static ssize_t vidi_store_connection(struct device *dev,
 				const char *buf, size_t len)
 {
 	struct vidi_context *ctx = dev_get_drvdata(dev);
-	int ret;
+	int ret, new_connected;
 
-	ret = kstrtoint(buf, 0, &ctx->connected);
+	ret = kstrtoint(buf, 0, &new_connected);
 	if (ret)
 		return ret;
-
-	if (ctx->connected > 1)
+	if (new_connected > 1)
 		return -EINVAL;
 
+	mutex_lock(&ctx->lock);
+
 	/*
 	 * Use fake edid data for test. If raw_edid is set then it can't be
 	 * tested.
 	 */
 	if (ctx->raw_edid) {
 		DRM_DEV_DEBUG_KMS(dev, "edid data is not fake data.\n");
-		return -EINVAL;
+		ret = -EINVAL;
+		goto fail;
 	}
 
+	ctx->connected = new_connected;
+	mutex_unlock(&ctx->lock);
+
 	DRM_DEV_DEBUG_KMS(dev, "requested connection.\n");
 
 	drm_helper_hpd_irq_event(ctx->drm_dev);
 
 	return len;
+fail:
+	mutex_unlock(&ctx->lock);
+	return ret;
 }
 
 static DEVICE_ATTR(connection, 0644, vidi_show_connection,
@@ -224,9 +232,14 @@ ATTRIBUTE_GROUPS(vidi);
 int vidi_connection_ioctl(struct drm_device *drm_dev, void *data,
 				struct drm_file *file_priv)
 {
-	struct vidi_context *ctx = dev_get_drvdata(drm_dev->dev);
+	struct exynos_drm_private *priv = drm_dev->dev_private;
+	struct device *dev = priv ? priv->vidi_dev : NULL;
+	struct vidi_context *ctx = dev ? dev_get_drvdata(dev) : NULL;
 	struct drm_exynos_vidi_connection *vidi = data;
 
+	if (!ctx)
+		return -ENODEV;
+
 	if (!vidi) {
 		DRM_DEV_DEBUG_KMS(ctx->dev,
 				  "user data for vidi is null.\n");
@@ -239,21 +252,38 @@ int vidi_connection_ioctl(struct drm_device *drm_dev, void *data,
 		return -EINVAL;
 	}
 
+	mutex_lock(&ctx->lock);
 	if (ctx->connected == vidi->connection) {
+		mutex_unlock(&ctx->lock);
 		DRM_DEV_DEBUG_KMS(ctx->dev,
 				  "same connection request.\n");
 		return -EINVAL;
 	}
+	mutex_unlock(&ctx->lock);
 
 	if (vidi->connection) {
 		const struct drm_edid *drm_edid;
-		const struct edid *raw_edid;
+		const void __user *edid_userptr = u64_to_user_ptr(vidi->edid);
+		void *edid_buf;
+		struct edid hdr;
 		size_t size;
 
-		raw_edid = (const struct edid *)(unsigned long)vidi->edid;
-		size = (raw_edid->extensions + 1) * EDID_LENGTH;
+		if (copy_from_user(&hdr, edid_userptr, sizeof(hdr)))
+			return -EFAULT;
+
+		size = (hdr.extensions + 1) * EDID_LENGTH;
+
+		edid_buf = kmalloc(size, GFP_KERNEL);
+		if (!edid_buf)
+			return -ENOMEM;
 
-		drm_edid = drm_edid_alloc(raw_edid, size);
+		if (copy_from_user(edid_buf, edid_userptr, size)) {
+			kfree(edid_buf);
+			return -EFAULT;
+		}
+
+		drm_edid = drm_edid_alloc(edid_buf, size);
+		kfree(edid_buf);
 		if (!drm_edid)
 			return -ENOMEM;
 
@@ -263,14 +293,21 @@ int vidi_connection_ioctl(struct drm_device *drm_dev, void *data,
 					  "edid data is invalid.\n");
 			return -EINVAL;
 		}
+		mutex_lock(&ctx->lock);
 		ctx->raw_edid = drm_edid;
+		mutex_unlock(&ctx->lock);
 	} else {
 		/* with connection = 0, free raw_edid */
+		mutex_lock(&ctx->lock);
 		drm_edid_free(ctx->raw_edid);
 		ctx->raw_edid = NULL;
+		mutex_unlock(&ctx->lock);
 	}
 
+	mutex_lock(&ctx->lock);
 	ctx->connected = vidi->connection;
+	mutex_unlock(&ctx->lock);
+
 	drm_helper_hpd_irq_event(ctx->drm_dev);
 
 	return 0;
@@ -285,7 +322,7 @@ static enum drm_connector_status vidi_detect(struct drm_connector *connector,
 	 * connection request would come from user side
 	 * to do hotplug through specific ioctl.
 	 */
-	return ctx->connected ? connector_status_connected :
+	return READ_ONCE(ctx->connected) ? connector_status_connected :
 			connector_status_disconnected;
 }
 
@@ -308,11 +345,15 @@ static int vidi_get_modes(struct drm_connector *connector)
 	const struct drm_edid *drm_edid;
 	int count;
 
+	mutex_lock(&ctx->lock);
+
 	if (ctx->raw_edid)
 		drm_edid = drm_edid_dup(ctx->raw_edid);
 	else
 		drm_edid = drm_edid_alloc(fake_edid_info, sizeof(fake_edid_info));
 
+	mutex_unlock(&ctx->lock);
+
 	drm_edid_connector_update(connector, drm_edid);
 
 	count = drm_edid_connector_add_modes(connector);
@@ -372,13 +413,16 @@ static int vidi_bind(struct device *dev, struct device *master, void *data)
 {
 	struct vidi_context *ctx = dev_get_drvdata(dev);
 	struct drm_device *drm_dev = data;
+	struct exynos_drm_private *priv = drm_dev->dev_private;
 	struct drm_encoder *encoder = &ctx->encoder;
 	struct exynos_drm_plane *exynos_plane;
 	struct exynos_drm_plane_config plane_config = { 0 };
 	unsigned int i;
 	int ret;
 
 	ctx->drm_dev = drm_dev;
+	if (priv)
+		priv->vidi_dev = dev;
 
 	plane_config.pixel_formats = formats;
 	plane_config.num_pixel_formats = ARRAY_SIZE(formats);
@@ -424,8 +468,12 @@ static int vidi_bind(struct device *dev, struct device *master, void *data)
 static void vidi_unbind(struct device *dev, struct device *master, void *data)
 {
 	struct vidi_context *ctx = dev_get_drvdata(dev);
+	struct drm_device *drm_dev = data;
+	struct exynos_drm_private *priv = drm_dev->dev_private;
 
 	timer_delete_sync(&ctx->timer);
+	if (priv)
+		priv->vidi_dev = NULL;
 }
 
 static const struct component_ops vidi_component_ops = {
@@ -457,9 +505,13 @@ static void vidi_remove(struct platform_device *pdev)
 {
 	struct vidi_context *ctx = platform_get_drvdata(pdev);
 
+	mutex_lock(&ctx->lock);
+
 	drm_edid_free(ctx->raw_edid);
 	ctx->raw_edid = NULL;
 
+	mutex_unlock(&ctx->lock);
+
 	component_del(&pdev->dev, &vidi_component_ops);
 }