Commit 14578923 authored by Chris Bainbridge's avatar Chris Bainbridge Committed by Rafael J. Wysocki
Browse files

ACPI: video: Fix random crashes due to bad kfree() 



Commit c6a83708 ("drm/amd/display: Fetch the EDID from _DDC if
available for eDP") added function dm_helpers_probe_acpi_edid(), which
fetches the EDID from the BIOS by calling acpi_video_get_edid().

acpi_video_get_edid() returns a pointer to the EDID, but this pointer
does not originate from kmalloc() - it is actually the internal
"pointer" field from an acpi_buffer struct (which did come from
kmalloc()).

dm_helpers_probe_acpi_edid() then attempts to kfree() the EDID pointer,
resulting in memory corruption which leads to random, intermittent
crashes (e.g. 4% of boots will fail with some Oops).

Fix this by allocating a new array (which can be safely freed) for the
EDID data, and correctly freeing the acpi_buffer pointer.

The only other caller of acpi_video_get_edid() is nouveau_acpi_edid():
remove the extraneous kmemdup() here as the EDID data is now copied in
acpi_video_device_EDID().

Signed-off-by: default avatarChris Bainbridge <chris.bainbridge@gmail.com>
Fixes: c6a83708 ("drm/amd/display: Fetch the EDID from _DDC if available for eDP")
Reviewed-by: default avatarHans de Goede <hdegoede@redhat.com>
Reviewed-by: default avatarMario Limonciello <mario.limonciello@amd.com>
Reported-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Tested-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Closes: https://lore.kernel.org/amd-gfx/20250110175252.GBZ4FedNKqmBRaY4T3@fat_crate.local/T/#m324a23eb4c4c32fa7e89e31f8ba96c781e496fb1
Link: https://patch.msgid.link/Z4K_oQL7eA9Owkbs@debian.local


[ rjw: Changed function description comment into a kerneldoc one ]
[ rjw: Subject and changelog edits ]
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 5bc55a33

drivers/acpi/acpi_video.c

+27 −22
Original line number Diff line number Diff line
@@ -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;

drivers/gpu/drm/nouveau/nouveau_acpi.c

+1 −1
Original line number Diff line number Diff line
@@ -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)