platform/x86: dell-wmi-sysman: Make init_bios_attributes() ACPI object parsing more...

Make init_bios_attributes() ACPI object parsing more robust:
1. Always check that the type of the return ACPI object is package, rather
   then only checking this for instance_id == 0
2. Check that the package has the minimum amount of elements which will
   be consumed by the populate_foo_data() for the attr_type

Note/TODO: The populate_foo_data() functions should also be made more
robust. The should check the type of each of the elements matches the
type which they expect and in case of populate_enum_data()
obj->package.count should be passed to it as an argument and it should
re-check this itself since it consume a variable number of elements.

Fixes: e8a60aa7404b ("platform/x86: Introduce support for Systems Management Driver over WMI for Dell Systems")
Cc: Divya Bharathi <Divya_Bharathi@dell.com>
Cc: Mario Limonciello <mario.limonciello@dell.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20210321121607.35717-1-hdegoede@redhat.com

diff --git a/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c b/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c
index 7410cca..a90ae6b 100644 (file)
--- a/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c
+++ b/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c
@@ -399,6 +399,7 @@ static int init_bios_attributes(int attr_type, const char *guid)
        union acpi_object *obj = NULL;
        union acpi_object *elements;
        struct kset *tmp_set;
+       int min_elements;
 
        /* instance_id needs to be reset for each type GUID
         * also, instance IDs are unique within GUID but not across
@@ -409,14 +410,38 @@ static int init_bios_attributes(int attr_type, const char *guid)
        retval = alloc_attributes_data(attr_type);
        if (retval)
                return retval;
+
+       switch (attr_type) {
+       case ENUM:      min_elements = 8;       break;
+       case INT:       min_elements = 9;       break;
+       case STR:       min_elements = 8;       break;
+       case PO:        min_elements = 4;       break;
+       default:
+               pr_err("Error: Unknown attr_type: %d\n", attr_type);
+               return -EINVAL;
+       }
+
        /* need to use specific instance_id and guid combination to get right data */
        obj = get_wmiobj_pointer(instance_id, guid);
-       if (!obj || obj->type != ACPI_TYPE_PACKAGE)
+       if (!obj)
                return -ENODEV;
-       elements = obj->package.elements;
 
        mutex_lock(&wmi_priv.mutex);
-       while (elements) {
+       while (obj) {
+               if (obj->type != ACPI_TYPE_PACKAGE) {
+                       pr_err("Error: Expected ACPI-package type, got: %d\n", obj->type);
+                       retval = -EIO;
+                       goto err_attr_init;
+               }
+
+               if (obj->package.count < min_elements) {
+                       pr_err("Error: ACPI-package does not have enough elements: %d < %d\n",
+                              obj->package.count, min_elements);
+                       goto nextobj;
+               }
+
+               elements = obj->package.elements;
+
                /* sanity checking */
                if (elements[ATTR_NAME].type != ACPI_TYPE_STRING) {
                        pr_debug("incorrect element type\n");
@@ -481,7 +506,6 @@ nextobj:
                kfree(obj);
                instance_id++;
                obj = get_wmiobj_pointer(instance_id, guid);
-               elements = obj ? obj->package.elements : NULL;
        }
 
        mutex_unlock(&wmi_priv.mutex);