iommu/amd: Fix NULL dereference bug in match_hid_uid

jira LE-1907
Rebuild_History Non-Buildable kernel-3.10.0-1160.118.1.el7
commit-author Aaron Ma <[email protected]>
commit bb6bccb

Add a non-NULL check to fix potential NULL pointer dereference
Cleanup code to call function once.

	Signed-off-by: Aaron Ma <[email protected]>
Fixes: 2bf9a0a ('iommu/amd: Add iommu support for ACPI HID devices')
	Signed-off-by: Joerg Roedel <[email protected]>
(cherry picked from commit bb6bccb)
	Signed-off-by: Jonathan Maple <[email protected]>

Author: PlaidCat

drivers/iommu/amd_iommu.c

@@ -179,10 +179,14 @@ static struct lock_class_key reserved_rbtree_key;
 static inline int match_hid_uid(struct device *dev,
 				struct acpihid_map_entry *entry)
 {
+	struct acpi_device *adev = ACPI_COMPANION(dev);
 	const char *hid, *uid;
 
-	hid = acpi_device_hid(ACPI_COMPANION(dev));
-	uid = acpi_device_uid(ACPI_COMPANION(dev));
+	if (!adev)
+		return -ENODEV;
+
+	hid = acpi_device_hid(adev);
+	uid = acpi_device_uid(adev);
 
 	if (!hid || !(*hid))
 		return -ENODEV;