[PATCH] Drivers: hv: vmbus: Check ACPI companion before use

[Jiale Yao <yaojiale02@163.com>]

Platform drivers can be forced to bind to devices outside their match
tables through driver_override. vmbus_acpi_add() assumes that every bound
device has an ACPI companion and dereferences it without checking.

Return -ENODEV when the companion is absent to avoid a NULL pointer
dereference.

Signed-off-by: Jiale Yao <yaojiale02@163.com>
---
 drivers/hv/vmbus_drv.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 4692687cdbf3..28f459679406 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -2571,10 +2571,14 @@ EXPORT_SYMBOL_GPL(vmbus_free_mmio);
 #ifdef CONFIG_ACPI
 static int vmbus_acpi_add(struct platform_device *pdev)
 {
+	struct acpi_device *ancestor;
+	struct acpi_device *device;
 	acpi_status result;
 	int ret_val = -ENODEV;
-	struct acpi_device *ancestor;
-	struct acpi_device *device = ACPI_COMPANION(&pdev->dev);
+
+	device = ACPI_COMPANION(&pdev->dev);
+	if (!device)
+		return -ENODEV;
 
 	vmbus_root_device = &device->dev;
 
-- 
2.34.1