[PATCH] ACPI: video: check for error while searching for backlit device parent

[Nikita Kiryushin]

If acpi_get_parent called in acpi_video_dev_register_backlight fails
(for example, acpi_ut_acquire_mutex fails inside acpi_get_parent),
this can lead to incorrect (uninitialized) acpi_parent handler being
passed to acpi_get_pci_dev for detecting parent pci device.

Check acpi_get_parent result and set parent device only in case of success.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 9661e92c10a9 ("acpi: tie ACPI backlight devices to PCI devices if 
possible")
Signed-off-by: Nikita Kiryushin <kiryushin@xxxxxxxx>
---
 drivers/acpi/acpi_video.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index 0b7a01f38b65..1d550887349a 100644
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -1717,12 +1717,12 @@ static void 
acpi_video_dev_register_backlight(struct acpi_video_device *device)
 		return;
 	count++;
 -	acpi_get_parent(device->dev->handle, &acpi_parent);
-
-	pdev = acpi_get_pci_dev(acpi_parent);
-	if (pdev) {
-		parent = &pdev->dev;
-		pci_dev_put(pdev);
+	if (ACPI_SUCCESS(acpi_get_parent(device->dev->handle, &acpi_parent))) {
+		pdev = acpi_get_pci_dev(acpi_parent);
+		if (pdev) {
+			parent = &pdev->dev;
+			pci_dev_put(pdev);
+		}
 	}
  	memset(&props, 0, sizeof(struct backlight_properties));
--
2.34.1