driver core: class: Fix wild pointer dereferences in API class_dev_iter_next()

In the Linux kernel, the following vulnerability has been resolved: driver core: class: Fix wild pointer dereferences in API class_dev_iter_next() There are a potential wild pointer dereferences issue regarding APIs class_dev_iter_(init|next|exit)(), as explained by below typical usage: // All members of @iter are wild pointers. struct class_dev_iter iter; // class_dev_iter_init(@iter, @class, ...) checks parameter @class for // potential class_to_subsys() error, and it returns void type and does // not initialize its output parameter @iter, so caller can not detect // the error and continues to invoke class_dev_iter_next(@iter) even if // @iter still contains wild pointers. class_dev_iter_init(&iter, ...); // Dereference these wild pointers in @iter here once suffer the error. while (dev = class_dev_iter_next(&iter)) { ... }; // Also dereference these wild pointers here. class_dev_iter_exit(&iter); Actually, all callers of these APIs have such usage pattern in kernel tree. Fix by: - Initialize output parameter @iter by memset() in class_dev_iter_init() and give callers prompt by pr_crit() for the error. - Check if @iter is valid in class_dev_iter_next().