From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5E5D5C433DF for ; Fri, 9 Oct 2020 08:19:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1EDD322251 for ; Fri, 9 Oct 2020 08:19:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732723AbgJIITG (ORCPT ); Fri, 9 Oct 2020 04:19:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52588 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732337AbgJIITF (ORCPT ); Fri, 9 Oct 2020 04:19:05 -0400 Received: from sipsolutions.net (s3.sipsolutions.net [IPv6:2a01:4f8:191:4433::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F989C0613D2; Fri, 9 Oct 2020 01:19:05 -0700 (PDT) Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.94) (envelope-from ) id 1kQncE-0029Tg-Uc; Fri, 09 Oct 2020 10:19:03 +0200 Message-ID: <1ec056cf3ec0953d2d1abaa05e37e89b29c7cc63.camel@sipsolutions.net> Subject: Re: [CRAZY-RFF] debugfs: track open files and release on remove From: Johannes Berg To: Greg KH Cc: linux-kernel@vger.kernel.org, nstange@suse.de, ap420073@gmail.com, David.Laight@aculab.com, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, rafael@kernel.org Date: Fri, 09 Oct 2020 10:19:02 +0200 In-Reply-To: <20201009081624.GA401030@kroah.com> References: <87v9fkgf4i.fsf@suse.de> <20201009095306.0d87c3aa13db.Ib3a7019bff15bb6308f6d259473a1648312a4680@changeid> <20201009080355.GA398994@kroah.com> <20201009081624.GA401030@kroah.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-1.fc32) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, 2020-10-09 at 10:16 +0200, Greg KH wrote: > On Fri, Oct 09, 2020 at 10:06:14AM +0200, Johannes Berg wrote: > > We used to say the proxy_fops weren't needed and it wasn't an issue, and > > then still implemented it. Dunno. I'm not really too concerned about it > > myself, only root can hold the files open and remove modules ... > > proxy_fops were needed because devices can be removed from the system at > any time, causing their debugfs files to want to also be removed. It > wasn't because of unloading kernel code. Indeed, that's true. Still, we lived with it for years. Anyway, like I said, I really just did this more to see that it _could_ be done, not to suggest that it _should_ :-) I think adding the .owner everywhere would be good, and perhaps we can somehow put a check somewhere like WARN_ON(is_module_address((unsigned long)fops) && !fops->owner); to prevent the issue in the future? johannes