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 55C5DC4332F for ; Wed, 1 Nov 2023 17:54:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232365AbjKARyR (ORCPT ); Wed, 1 Nov 2023 13:54:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37484 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231258AbjKARyR (ORCPT ); Wed, 1 Nov 2023 13:54:17 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 00553109; Wed, 1 Nov 2023 10:54:10 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1C845C433C9; Wed, 1 Nov 2023 17:54:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1698861250; bh=JAumfjAMArYws76N389UqFy89DYhXF68dhxExokMXXI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=gp/1JaVgjaX0aErHXARToRP3jqVB4mU1rKyb6acTpxhiky76TB9Au9YxcUcD2wkVf oQ0d2jabJM17qBhkJCxYSHCiUyVLvQm4o4onpY/I4xrc7/ku06ZJRZkOp/RPqQxAiu 1jzYI9CoeyudoOCLekiRugVrhVBBv6+BxDVgLgrM= Date: Wed, 1 Nov 2023 18:54:07 +0100 From: Greg KH To: =?iso-8859-1?Q?Jos=E9?= Pekkarinen 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 Message-ID: <2023110139-dupe-snipping-5700@gregkh> References: <20231101173627.2658-1-jose.pekkarinen@foxhound.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20231101173627.2658-1-jose.pekkarinen@foxhound.fi> Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org 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? Also, I think you just leaked a reference count here, how was this tested? thanks, greg k-h