Re: [PATCH 1/3] driver core: class: Fix wild pointer dereference in API class_dev_iter_next()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Nov 05, 2024 at 08:20:22AM +0800, Zijun Hu wrote:
> From: Zijun Hu <quic_zijuhu@quicinc.com>
> 
> class_dev_iter_init(struct class_dev_iter *iter, struct class *class, ...)
> has return type void, but it does not initialize its output parameter @iter
> when suffers class_to_subsys(@class) error, so caller can not detect the
> error and call API class_dev_iter_next(@iter) which will dereference wild
> pointers of @iter's members as shown by below typical usage:
> 
> // @iter's members are wild pointers
> struct class_dev_iter iter;
> 
> // No change in @iter when the error happens.
> class_dev_iter_init(&iter, ...);
> 
> // dereference these wild member pointers here.
> while (dev = class_dev_iter_next(&iter)) { ... }.
> 
> Actually, all callers of the API have such usage pattern in kernel tree.
> Fix by memset() @iter in API *_init() and error checking @iter in *_next().
> 
> Fixes: 7b884b7f24b4 ("driver core: class.c: convert to only use class_to_subsys")
> Cc: stable@vger.kernel.org

There is no in-kernel broken users of this from what I can tell, right?
Otherwise things would have blown up by now, so why is this needed in
stable kernels?

thanks,

greg k-h