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 486A2C4332F for ; Tue, 7 Nov 2023 09:26:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233809AbjKGJ0p (ORCPT ); Tue, 7 Nov 2023 04:26:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40864 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233701AbjKGJ0m (ORCPT ); Tue, 7 Nov 2023 04:26:42 -0500 X-Greylist: delayed 1815 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Tue, 07 Nov 2023 01:26:38 PST Received: from 9.mo561.mail-out.ovh.net (9.mo561.mail-out.ovh.net [87.98.184.141]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B769C106 for ; Tue, 7 Nov 2023 01:26:38 -0800 (PST) Received: from director9.ghost.mail-out.ovh.net (unknown [10.109.156.38]) by mo561.mail-out.ovh.net (Postfix) with ESMTP id 6784829264 for ; Tue, 7 Nov 2023 08:56:21 +0000 (UTC) Received: from ghost-submission-6684bf9d7b-xtvm8 (unknown [10.110.103.4]) by director9.ghost.mail-out.ovh.net (Postfix) with ESMTPS id DF8911FE4C; Tue, 7 Nov 2023 08:56:20 +0000 (UTC) Received: from RCM-web8.webmail.mail.ovh.net ([151.80.29.22]) by ghost-submission-6684bf9d7b-xtvm8 with ESMTPSA id 5ldYNbT7SWV8SwAAy7z86g (envelope-from ); Tue, 07 Nov 2023 08:56:20 +0000 MIME-Version: 1.0 Date: Tue, 07 Nov 2023 10:56:20 +0200 From: =?UTF-8?Q?Jos=C3=A9_Pekkarinen?= To: Greg KH Cc: rafael@kernel.org, len.brown@intel.com, pavel@ucw.cz, skhan@linuxfoundation.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, syzbot+95f2e2439b97575ec3c0@syzkaller.appspotmail.com Subject: Re: [PATCH] drivers core: lookup sysfs power group before removal In-Reply-To: <2023110353-bring-contented-c9f8@gregkh> References: <20231101173627.2658-1-jose.pekkarinen@foxhound.fi> <2023110139-dupe-snipping-5700@gregkh> <835b2930c710381b8da38eca821aa92d@foxhound.fi> <2023110353-bring-contented-c9f8@gregkh> User-Agent: Roundcube Webmail/1.4.15 Message-ID: X-Sender: jose.pekkarinen@foxhound.fi Organization: Foxhound Ltd. X-Originating-IP: 91.132.144.59 X-Webmail-UserID: jose.pekkarinen@foxhound.fi Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Ovh-Tracer-Id: 18137403077422261763 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: -100 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedvkedrudduhedguddvfecutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfqggfjpdevjffgvefmvefgnecuuegrihhlohhuthemucehtddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpeggfffhvfevufgjfhgfkfigohhitgfgsehtkehjtddtreejnecuhfhrohhmpeflohhsrocurfgvkhhkrghrihhnvghnuceojhhoshgvrdhpvghkkhgrrhhinhgvnhesfhhogihhohhunhgurdhfiheqnecuggftrfgrthhtvghrnhepkefhgeduudefgedvleegtddvffeghedvtdekveekjeevvdegiedtfeelhedtiedtnecukfhppeduvdejrddtrddtrddupdeluddrudefvddrudeggedrheelpdduhedurdektddrvdelrddvvdenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepihhnvghtpeduvdejrddtrddtrddupdhmrghilhhfrhhomhepoehjohhsvgdrphgvkhhkrghrihhnvghnsehfohighhhouhhnugdrfhhiqedpnhgspghrtghpthhtohepuddprhgtphhtthhopehlihhnuhigqdhkvghrnhgvlhesvhhgvghrrdhkvghrnhgvlhdrohhrghdpoffvtefjohhsthepmhhoheeiuddpmhhouggvpehsmhhtphhouhht Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023-11-03 20:36, Greg KH wrote: > On Fri, Nov 03, 2023 at 07:49:39PM +0200, José Pekkarinen wrote: >> On 2023-11-01 19:54, Greg KH wrote: >> > On Wed, Nov 01, 2023 at 07:36:27PM +0200, José Pekkarinen wrote: >> > > Hinted by syzboot, there is a few cases where the sysfs power group >> > > may >> > > not be there, like the failure while adding it, or adding its runtime >> > > group, or when the sysfs firmware loader fallback fail to populate. In >> > > the last case, the device_del function will be called leading to >> > > attempt >> > > to remove the sysfs group. This patch will lookup for it in advance to >> > > grant that it is effectively there before cleaning it up. >> > > >> > > Reported-by: syzbot+95f2e2439b97575ec3c0@syzkaller.appspotmail.com >> > > >> > > Signed-off-by: José Pekkarinen >> > > --- >> > > drivers/base/power/sysfs.c | 4 +++- >> > > 1 file changed, 3 insertions(+), 1 deletion(-) >> > > >> > > diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c >> > > index a1474fb67db9..6601729c4698 100644 >> > > --- a/drivers/base/power/sysfs.c >> > > +++ b/drivers/base/power/sysfs.c >> > > @@ -834,5 +834,7 @@ void dpm_sysfs_remove(struct device *dev) >> > > dev_pm_qos_constraints_destroy(dev); >> > > rpm_sysfs_remove(dev); >> > > sysfs_unmerge_group(&dev->kobj, &pm_wakeup_attr_group); >> > > - sysfs_remove_group(&dev->kobj, &pm_attr_group); >> > > + >> > > + if (kernfs_find_and_get((&dev->kobj)->sd, pm_attr_group.name)) >> > > + sysfs_remove_group(&dev->kobj, &pm_attr_group); >> > >> > What's to keep it from going away right after finding it? >> > >> > In other words, what is wrong with removing a group that is not there? >> > What error happens? It should be fine, or are you seeing real code >> > failures somewhere? >> >> No, this is just hitting a warning that sysbot complains about by >> setting panic on warning, no big deal, though it can be a wrong >> behaviour >> in ueagle-atm driver, since it defines to disconnect the device if the >> firmware is not there, no matter the sysfs fallback. > > Then fix the driver please. I'm afraid I was wrong in the assumption that the probe return value of the driver would influence the testing result, so this no longer seems fixable from driver side. It may be fixed here in the base, in the sysfs or not to fix it at all since this seem to be a very difficult to reach situation. I'm fine with any approach, and I can do the work, I'd just like to read what are your preferences on the topic. Thanks! José.