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 CFD74C43334 for ; Tue, 5 Jul 2022 05:37:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229805AbiGEFhc (ORCPT ); Tue, 5 Jul 2022 01:37:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51238 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229814AbiGEFh3 (ORCPT ); Tue, 5 Jul 2022 01:37:29 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5AEB913CFD; Mon, 4 Jul 2022 22:37:28 -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 sin.source.kernel.org (Postfix) with ESMTPS id BD691CE1A3C; Tue, 5 Jul 2022 05:37:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5E86FC341C7; Tue, 5 Jul 2022 05:37:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1656999444; bh=mvpa4gKzseUX82ww/tYk5JY4OCyIABqzLqgbEy8cqIM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qHhaEiDKMW7LBlP9x/Cw0CgekdwLm+FQNdCoiPVPg8333K7x/fm94BVs1aCHXot5J rIQh3fg3xCTs3FpXsT8muVTTdK4tFUGH1eUUAOqibQsWfFj89vXqrc64FJZVwSsEfB W+gONI6dDMT3wayLok7FhHmaKM0cq+BUjH6I4jKY= Date: Tue, 5 Jul 2022 07:37:21 +0200 From: Greg KH To: Tetsuo Handa Cc: "Rafael J. Wysocki" , Len Brown , Pavel Machek , arnd@arndb.de, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Wedson Almeida Filho Subject: Re: [PATCH] char: misc: make misc_open() and misc_register() killable Message-ID: References: <000000000000d9ff3a05bb37069e@google.com> <72e74af9-f1b6-e383-a2c3-6ee8a0aea5e0@I-love.SAKURA.ne.jp> <100f445e-9fa8-4f37-76aa-8359f0008c59@I-love.SAKURA.ne.jp> <01a93294-e323-b9ca-7e95-a33d4b89dc47@I-love.SAKURA.ne.jp> <617f64e3-74c8-f98b-3430-bd476867e483@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <617f64e3-74c8-f98b-3430-bd476867e483@I-love.SAKURA.ne.jp> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 05, 2022 at 02:21:17PM +0900, Tetsuo Handa wrote: > On 2022/07/04 23:31, Greg KH wrote: > > I don't understand what you are trying to "fix" here. What is userspace > > doing (as a normal user) that is causing a problem, and what problem is > > it causing and for what device/hardware/driver is this a problem? > > Currently the root cause is unknown. > This might be another example of deadlock hidden by device_initialize(). > > We can see from https://syzkaller.appspot.com/text?tag=CrashReport&x=11feb7e0080000 that > when khungtaskd reports that a process is blocked waiting for misc_mtx at misc_open(), > there is a process which is holding system_transition_mutex from snapshot_open(). /dev/snapshot is not read/writable by anyone but root for obvious reasons. And perhaps it's something that syzbot shouldn't be fuzzing unless it wants to take the system down easily :) thanks, greg k-h