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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 09537C25B08 for ; Wed, 10 Aug 2022 08:50:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230419AbiHJIuZ (ORCPT ); Wed, 10 Aug 2022 04:50:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45042 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231232AbiHJIuY (ORCPT ); Wed, 10 Aug 2022 04:50:24 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 667B0FD17 for ; Wed, 10 Aug 2022 01:50:22 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id A8C8DB81B3A for ; Wed, 10 Aug 2022 08:50:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A221DC433B5; Wed, 10 Aug 2022 08:50:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1660121420; bh=apg3OEJoYJrBH0EU36EwV5KUXtmT9zQg9lbHi1C/AIo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=x7qurrStAn97EAjHJ8iDG8RnHtIdeAAPTkv0F69A3h5KWR3d/wB3ilwXKm9LzLIxK 544u+I+FjouJZdBs5gJhMwd29p4XFWRE7huaOV7F4uhgfnwStJGjZ/lgjckPahAy6A TdjDnh0SOOBuME/MXlm/8mlTEVZvMVkAl1eMKCXg= Date: Wed, 10 Aug 2022 10:21:49 +0200 From: Greg KH To: Krzysztof Kozlowski , Stephen Hemminger Cc: Bjorn Helgaas , bhelgaas@google.com, linux-pci@vger.kernel.org, regressions@lists.linux.dev Subject: Re: [REGRESSION] changes to driver_override parsing broke DPDK script Message-ID: References: <20220809192102.GA1331186@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Wed, Aug 10, 2022 at 08:11:33AM +0200, Greg KH wrote: > On Wed, Aug 10, 2022 at 08:54:36AM +0300, Krzysztof Kozlowski wrote: > > On 09/08/2022 22:21, Bjorn Helgaas wrote: > > > [+cc regressions list] > > > > > > 23d99baf9d72 appeared in v5.19-rc1. > > > > > > On Tue, Aug 09, 2022 at 11:29:43AM -0700, Stephen Hemminger wrote: > > >> This commit broke the driver override script in DPDK. > > >> This is an API/ABI breakage, please revert or fix the commit. > > >> > > >> Report of problem: > > >> http://mails.dpdk.org/archives/dev/2022-August/247794.html > > > > Thanks for the report. I'll take a look. > > > > >> > > >> > > >> commit 23d99baf9d729ca30b2fb6798a7b403a37bfb800 > > >> Author: Krzysztof Kozlowski > > >> Date: Tue Apr 19 13:34:28 2022 +0200 > > >> > > >> PCI: Use driver_set_override() instead of open-coding > > >> > > >> Use a helper to set driver_override to the reduce amount of duplicated > > >> code. Make the driver_override field const char, because it is not > > >> modified by the core and it matches other subsystems. > > >> > > >> Reviewed-by: Andy Shevchenko > > >> Acked-by: Bjorn Helgaas > > >> Signed-off-by: Krzysztof Kozlowski > > >> Link: https://lore.kernel.org/r/20220419113435.246203-6-krzysztof.kozlowski@linaro.org > > >> Signed-off-by: Greg Kroah-Hartman > > >> > > >> > > >> The script is sending single nul character to remove override > > >> and that no longer works. > > > > The sysfs API clearly states: > > "and > > may be cleared with an empty string (echo > driver_override)." > > Documentation/ABI/testing/sysfs-bus-pci > > > > Sending other data and expecting the same result is not conforming to > > API. Therefore we have usual example of some undocumented behavior which > > user-space started relying on and instead using API, user-space expect > > that undocumented behavior to be back. > > > > Yay! I wonder what is the point to even describe the ABI if user-space > > can simply ignore it? > > One can argue that a string of just '\0' is an "empty string" and we > should be able to properly handle this in the kernel. Heck, > "\0\0\0\0\0\0" is also an "empty string", right? > > I don't have an issue with fixing the kernel up here, it should be able > to handle this. Stephen, does the patch below fix this for you? thanks, greg k-h ----------------- diff --git a/drivers/base/driver.c b/drivers/base/driver.c index 15a75afe6b84..676b6275d5b5 100644 --- a/drivers/base/driver.c +++ b/drivers/base/driver.c @@ -63,6 +63,12 @@ int driver_set_override(struct device *dev, const char **override, if (len >= (PAGE_SIZE - 1)) return -EINVAL; + /* + * Compute the real length of the string in case userspace sends us a + * bunch of \0 characters like python likes to do. + */ + len = strlen(s); + if (!len) { /* Empty string passed - clear override */ device_lock(dev);