platform/x86: dell-wmi-sysman: Fix WMI data block retrieval in sysfs callbacks

After retrieving WMI data blocks in sysfs callbacks, check for the
validity of them before dereferencing their content.

Reported-by: Jan Graczyk <[e-mail]>
Closes: https://lore.kernel.org/r/CAHk-=wgMiSKXf7SvQrfEnxVtmT=QVQPjJdNjfm3aXS7wc=[e-mail]/
Fixes: e8a60aa7404b ("platform/x86: Introduce support for Systems Management Driver over WMI for Dell Systems")
Suggested-by: Linus Torvalds <[e-mail]>
Reviewed-by: Armin Wolf <[e-mail]>
Signed-off-by: Kurt Borja <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Ilpo Järvinen <[e-mail]>
Signed-off-by: Ilpo Järvinen <[e-mail]>

drivers/platform/x86/dell/dell-wmi-sysman/dell-wmi-sysman.h

···
 
 enum { ENUM, INT, STR, PO };
 
+#define ENUM_MIN_ELEMENTS		8
+#define INT_MIN_ELEMENTS		9
+#define STR_MIN_ELEMENTS		8
+#define PO_MIN_ELEMENTS			4
+
 enum {
 	ATTR_NAME,
 	DISPL_NAME_LANG_CODE,

drivers/platform/x86/dell/dell-wmi-sysman/enum-attributes.c

···
 	obj = get_wmiobj_pointer(instance_id, DELL_WMI_BIOS_ENUMERATION_ATTRIBUTE_GUID);
 	if (!obj)
 		return -EIO;
-	if (obj->package.elements[CURRENT_VAL].type != ACPI_TYPE_STRING) {
+	if (obj->type != ACPI_TYPE_PACKAGE || obj->package.count < ENUM_MIN_ELEMENTS ||
+	    obj->package.elements[CURRENT_VAL].type != ACPI_TYPE_STRING) {
 		kfree(obj);
-		return -EINVAL;
+		return -EIO;
 	}
 	ret = snprintf(buf, PAGE_SIZE, "%s\n", obj->package.elements[CURRENT_VAL].string.pointer);
 	kfree(obj);

drivers/platform/x86/dell/dell-wmi-sysman/int-attributes.c

···
 	obj = get_wmiobj_pointer(instance_id, DELL_WMI_BIOS_INTEGER_ATTRIBUTE_GUID);
 	if (!obj)
 		return -EIO;
-	if (obj->package.elements[CURRENT_VAL].type != ACPI_TYPE_INTEGER) {
+	if (obj->type != ACPI_TYPE_PACKAGE || obj->package.count < INT_MIN_ELEMENTS ||
+	    obj->package.elements[CURRENT_VAL].type != ACPI_TYPE_INTEGER) {
 		kfree(obj);
-		return -EINVAL;
+		return -EIO;
 	}
 	ret = snprintf(buf, PAGE_SIZE, "%lld\n", obj->package.elements[CURRENT_VAL].integer.value);
 	kfree(obj);

drivers/platform/x86/dell/dell-wmi-sysman/passobj-attributes.c

···
 	obj = get_wmiobj_pointer(instance_id, DELL_WMI_BIOS_PASSOBJ_ATTRIBUTE_GUID);
 	if (!obj)
 		return -EIO;
-	if (obj->package.elements[IS_PASS_SET].type != ACPI_TYPE_INTEGER) {
+	if (obj->type != ACPI_TYPE_PACKAGE || obj->package.count < PO_MIN_ELEMENTS ||
+	    obj->package.elements[IS_PASS_SET].type != ACPI_TYPE_INTEGER) {
 		kfree(obj);
-		return -EINVAL;
+		return -EIO;
 	}
 	ret = snprintf(buf, PAGE_SIZE, "%lld\n", obj->package.elements[IS_PASS_SET].integer.value);
 	kfree(obj);

drivers/platform/x86/dell/dell-wmi-sysman/string-attributes.c

···
 	obj = get_wmiobj_pointer(instance_id, DELL_WMI_BIOS_STRING_ATTRIBUTE_GUID);
 	if (!obj)
 		return -EIO;
-	if (obj->package.elements[CURRENT_VAL].type != ACPI_TYPE_STRING) {
+	if (obj->type != ACPI_TYPE_PACKAGE || obj->package.count < STR_MIN_ELEMENTS ||
+	    obj->package.elements[CURRENT_VAL].type != ACPI_TYPE_STRING) {
 		kfree(obj);
-		return -EINVAL;
+		return -EIO;
 	}
 	ret = snprintf(buf, PAGE_SIZE, "%s\n", obj->package.elements[CURRENT_VAL].string.pointer);
 	kfree(obj);

drivers/platform/x86/dell/dell-wmi-sysman/sysman.c

···
 		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;
+	case ENUM:	min_elements = ENUM_MIN_ELEMENTS;	break;
+	case INT:	min_elements = INT_MIN_ELEMENTS;	break;
+	case STR:	min_elements = STR_MIN_ELEMENTS;	break;
+	case PO:	min_elements = PO_MIN_ELEMENTS;		break;
 	default:
 		pr_err("Error: Unknown attr_type: %d\n", attr_type);
 		return -EINVAL;