[PATCH 1/1] ACPI: video: Use acpi_video_device for cooling-dev driver data - Linux-stable-mirror

27 Nov 2023

The acpi_video code was storing the acpi_video_device as driver-data
in the acpi_device children of the acpi_video_bus acpi_device.
But the acpi_video driver only binds to the bus acpi_device.
It uses, but does not bind to, the children. Since it is not
the driver it should not be using the driver_data of the children's
acpi_device-s.
Since commit 0d16710146a1 ("ACPI: bus: Set driver_data to NULL every
time .add() fails") the childen's driver_data ends up getting set
to NULL after a driver fails to bind to the children leading to a NULL
pointer deref in video_get_max_state when registering the cooling-dev:
[    3.148958] BUG: kernel NULL pointer dereference, address: 0000000000000090
<snip>
[    3.149015] Hardware name: Sony Corporation VPCSB2X9R/VAIO, BIOS R2087H4 06/15/2012
[    3.149021] RIP: 0010:video_get_max_state+0x17/0x30 [video]
<snip>
[    3.149105] Call Trace:
[    3.149110]  <TASK>
[    3.149114]  ? __die+0x23/0x70
[    3.149126]  ? page_fault_oops+0x171/0x4e0
[    3.149137]  ? exc_page_fault+0x7f/0x180
[    3.149147]  ? asm_exc_page_fault+0x26/0x30
[    3.149158]  ? video_get_max_state+0x17/0x30 [video 9b6f3f0d19d7b4a0e2df17a2d8b43bc19c2ed71f]
[    3.149176]  ? __pfx_video_get_max_state+0x10/0x10 [video 9b6f3f0d19d7b4a0e2df17a2d8b43bc19c2ed71f]
[    3.149192]  __thermal_cooling_device_register.part.0+0xf2/0x2f0
[    3.149205]  acpi_video_bus_register_backlight.part.0.isra.0+0x414/0x570 [video 9b6f3f0d19d7b4a0e2df17a2d8b43bc19c2ed71f]
[    3.149227]  acpi_video_register_backlight+0x57/0x80 [video 9b6f3f0d19d7b4a0e2df17a2d8b43bc19c2ed71f]
[    3.149245]  intel_acpi_video_register+0x68/0x90 [i915 1f3a758130b32ef13d301d4f8f78c7d766d57f2a]
[    3.149669]  intel_display_driver_register+0x28/0x50 [i915 1f3a758130b32ef13d301d4f8f78c7d766d57f2a]
[    3.150064]  i915_driver_probe+0x790/0xb90 [i915 1f3a758130b32ef13d301d4f8f78c7d766d57f2a]
[    3.150402]  local_pci_probe+0x45/0xa0
[    3.150412]  pci_device_probe+0xc1/0x260
<snip>
Fix this by directly using the acpi_video_device as devdata for
the cooling-device, which avoids the need to set driver-data on
the children at all.
Fixes: 0d16710146a1 ("ACPI: bus: Set driver_data to NULL every time .add() fails")
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/9718
Cc: Michal Wilczynski michal.wilczynski@intel.com
Cc: 6.6+ stable@vger.kernel.org # 6.6+
Signed-off-by: Hans de Goede hdegoede@redhat.com
---
 drivers/acpi/acpi_video.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index 5eded14f8853..7cd91e85c62a 100644
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -253,8 +253,7 @@ static const struct backlight_ops acpi_backlight_ops = {
 static int video_get_max_state(struct thermal_cooling_device *cooling_dev,
    		       unsigned long *state)
 {
-	struct acpi_device *device = cooling_dev->devdata;
-	struct acpi_video_device *video = acpi_driver_data(device);
+	struct acpi_video_device *video = cooling_dev->devdata;
*state = video->brightness->count - ACPI_VIDEO_FIRST_LEVEL - 1;
    return 0;
@@ -263,8 +262,7 @@ static int video_get_max_state(struct thermal_cooling_device *cooling_dev,
 static int video_get_cur_state(struct thermal_cooling_device *cooling_dev,
    		       unsigned long *state)
 {
-	struct acpi_device *device = cooling_dev->devdata;
-	struct acpi_video_device *video = acpi_driver_data(device);
+	struct acpi_video_device *video = cooling_dev->devdata;
    unsigned long long level;
    int offset;
@@ -283,8 +281,7 @@ static int video_get_cur_state(struct thermal_cooling_device *cooling_dev,
 static int
 video_set_cur_state(struct thermal_cooling_device *cooling_dev, unsigned long state)
 {
-	struct acpi_device *device = cooling_dev->devdata;
-	struct acpi_video_device *video = acpi_driver_data(device);
+	struct acpi_video_device *video = cooling_dev->devdata;
    int level;
if (state >= video->brightness->count - ACPI_VIDEO_FIRST_LEVEL)
@@ -1125,7 +1122,6 @@ static int acpi_video_bus_get_one_device(struct acpi_device *device, void *arg)
strcpy(acpi_device_name(device), ACPI_VIDEO_DEVICE_NAME);
    strcpy(acpi_device_class(device), ACPI_VIDEO_CLASS);
-	device->driver_data = data;
data->device_id = device_id;
    data->video = video;
@@ -1747,8 +1743,8 @@ static void acpi_video_dev_register_backlight(struct acpi_video_device *device)
    device->backlight->props.brightness =
    		acpi_video_get_brightness(device->backlight);
-	device->cooling_dev = thermal_cooling_device_register("LCD",
-				device->dev, &video_cooling_ops);
+	device->cooling_dev = thermal_cooling_device_register("LCD", device,
+							      &video_cooling_ops);
    if (IS_ERR(device->cooling_dev)) {
    	/*
    	 * Set cooling_dev to NULL so we don't crash trying to free it.
-- 
2.43.0



    