Merge tag 'acpi-6.13-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull ACPI fix from Rafael Wysocki:
 "Prevent acpi_video_device_EDID() from returning a pointer to a memory
  region that should not be passed to kfree() which causes one of its
  users to crash randomly on attempts to free it (Chris Bainbridge)"

* tag 'acpi-6.13-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  ACPI: video: Fix random crashes due to bad kfree()

2 files changed, 28 insertions, 23 deletions

diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index 8274a17872ed..a972831dbd66 100644
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -610,16 +610,28 @@ acpi_video_device_lcd_get_level_current(struct acpi_video_device *device,
 	return 0;
 }
 
+/**
+ * acpi_video_device_EDID() - Get EDID from ACPI _DDC
+ * @device: video output device (LCD, CRT, ..)
+ * @edid: address for returned EDID pointer
+ * @length: _DDC length to request (must be a multiple of 128)
+ *
+ * Get EDID from ACPI _DDC. On success, a pointer to the EDID data is written
+ * to the @edid address, and the length of the EDID is returned. The caller is
+ * responsible for freeing the edid pointer.
+ *
+ * Return the length of EDID (positive value) on success or error (negative
+ * value).
+ */
 static int
-acpi_video_device_EDID(struct acpi_video_device *device,
-		       union acpi_object **edid, int length)
+acpi_video_device_EDID(struct acpi_video_device *device, void **edid, int length)
 {
-	int status;
+	acpi_status status;
 	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
 	union acpi_object *obj;
 	union acpi_object arg0 = { ACPI_TYPE_INTEGER };
 	struct acpi_object_list args = { 1, &arg0 };
-
+	int ret;
 
 	*edid = NULL;
 
@@ -636,16 +648,17 @@ acpi_video_device_EDID(struct acpi_video_device *device,
 
 	obj = buffer.pointer;
 
-	if (obj && obj->type == ACPI_TYPE_BUFFER)
-		*edid = obj;
-	else {
+	if (obj && obj->type == ACPI_TYPE_BUFFER) {
+		*edid = kmemdup(obj->buffer.pointer, obj->buffer.length, GFP_KERNEL);
+		ret = *edid ? obj->buffer.length : -ENOMEM;
+	} else {
 		acpi_handle_debug(device->dev->handle,
 				 "Invalid _DDC data for length %d\n", length);
-		status = -EFAULT;
-		kfree(obj);
+		ret = -EFAULT;
 	}
 
-	return status;
+	kfree(obj);
+	return ret;
 }
 
 /* bus */
@@ -1435,9 +1448,7 @@ int acpi_video_get_edid(struct acpi_device *device, int type, int device_id,
 {
 	struct acpi_video_bus *video;
 	struct acpi_video_device *video_device;
-	union acpi_object *buffer = NULL;
-	acpi_status status;
-	int i, length;
+	int i, length, ret;
 
 	if (!device || !acpi_driver_data(device))
 		return -EINVAL;
@@ -1477,16 +1488,10 @@ int acpi_video_get_edid(struct acpi_device *device, int type, int device_id,
 		}
 
 		for (length = 512; length > 0; length -= 128) {
-			status = acpi_video_device_EDID(video_device, &buffer,
-							length);
-			if (ACPI_SUCCESS(status))
-				break;
+			ret = acpi_video_device_EDID(video_device, edid, length);
+			if (ret > 0)
+				return ret;
 		}
-		if (!length)
-			continue;
-
-		*edid = buffer->buffer.pointer;
-		return length;
 	}
 
 	return -ENODEV;
diff --git a/drivers/gpu/drm/nouveau/nouveau_acpi.c b/drivers/gpu/drm/nouveau/nouveau_acpi.c
index 8f0c69aad248..21b56cc7605c 100644
--- a/drivers/gpu/drm/nouveau/nouveau_acpi.c
+++ b/drivers/gpu/drm/nouveau/nouveau_acpi.c
@@ -384,7 +384,7 @@ nouveau_acpi_edid(struct drm_device *dev, struct drm_connector *connector)
 	if (ret < 0)
 		return NULL;
 
-	return kmemdup(edid, EDID_LENGTH, GFP_KERNEL);
+	return edid;
 }
 
 bool nouveau_acpi_video_backlight_use_native(void)