ACPICA: Namespace: add check to avoid null pointer dereference

mainline inclusion
from mainline-5.1-rc4
commit df9271d6
category: bugfix
bugzilla: 14713
CVE: NA

-------------------------------------------------

ACPICA commit 7586a625f9c34c3169efd88470192bf63119e31a

Some ACPICA userspace tools call acpi_ut_subsystem_shutdown() during
cleanup and dereference a null pointer when cleaning up the
namespace.

Link: https://github.com/acpica/acpica/commit/7586a625Signed-off-by: NErik Schmauss <erik.schmauss@intel.com>
Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NXiongfeng Wang <wangxiongfeng2@huawei.com>
Reviewed-by: NYao Hongbo <yaohongbo@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/acpi/acpica/nsalloc.c

@@ -74,6 +74,10 @@ void acpi_ns_delete_node(struct acpi_namespace_node *node)
 
 	ACPI_FUNCTION_NAME(ns_delete_node);
 
+	if (!node) {
+		return_VOID;
+	}
+
 	/* Detach an object if there is one */
 
 	acpi_ns_detach_object(node);