Return-Path: linux-nfs-owner@vger.kernel.org Received: from mout.gmx.net ([212.227.17.20]:65518 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750902Ab3G1P00 (ORCPT ); Sun, 28 Jul 2013 11:26:26 -0400 Received: from [80.171.226.78] ([80.171.226.78]) by mail.gmx.com (mrgmx003) with ESMTPSA (Nemesis) id 0LhOvA-1UH9c00Z4i-00mYab for ; Sun, 28 Jul 2013 17:26:24 +0200 Message-ID: <51F5381D.1080904@gmx.de> Date: Sun, 28 Jul 2013 17:26:21 +0200 From: =?UTF-8?B?VG9yYWxmIEbDtnJzdGVy?= MIME-Version: 1.0 To: Oleg Nesterov CC: "Serge E. Hallyn" , Andrey Vagin , "Eric W. Biederman" , Al Viro , Linux NFS mailing list Subject: Re: fuzz tested user mode linux core dumps in fs/lockd/clntproc.c:131 References: <51F39AE8.3090401@gmx.de> <20130727170051.GA31447@redhat.com> In-Reply-To: <20130727170051.GA31447@redhat.com> Content-Type: text/plain; charset=UTF-8 Sender: linux-nfs-owner@vger.kernel.org List-ID: The attached patch works - applied on top of current git - at least the issue cannot be reproduced then. On 07/27/2013 07:00 PM, Oleg Nesterov wrote: > On 07/27, Toralf Förster wrote: >> >> I do have a user mode linux image (stable 32 bit Gentoo Linux ) which erratically crashes >> while fuzz tested with trinity if the victim files are located on a NFS share. >> >> The back trace of the core dumps always looks like the attached. >> >> To bisect it is hard. However after few attempts in the last weeks the following >> commit is either the first bad commit or at least the upper limit (less likely). >> >> >> commit 8aac62706adaaf0fab02c4327761561c8bda9448 >> Author: Oleg Nesterov >> Date: Fri Jun 14 21:09:49 2013 +0200 >> >> move exit_task_namespaces() outside of exit_notify() >> >> #15 nlmclnt_setlockargs (req=0x48e18860, fl=0x48f27c8c) at fs/lockd/clntproc.c:131 > > Thanks. > > So nlmclnt_setlockargs()->utsname() crashes and we probably need > the patch below. > > But is it correct? I know _absolutely_ nothing about nfs/sunrpc/etc and > I never looked into this code before, most probably I am wrong. > > But it seems that __nlm_async_call() relies on workqueues. > nlmclnt_async_call() does rpc_wait_for_completion_task(), but what if > the caller is killed? > > nlm_rqst can't go away, ->a_count was incremented. But can't the caller > exit before call->name is used? In this case the memory it points to > can be already freed. > > Oleg. > > --- x/kernel/exit.c > +++ x/kernel/exit.c > @@ -783,8 +783,8 @@ void do_exit(long code) > exit_shm(tsk); > exit_files(tsk); > exit_fs(tsk); > - exit_task_namespaces(tsk); > exit_task_work(tsk); > + exit_task_namespaces(tsk); > check_stack_usage(); > exit_thread(); > > > -- MfG/Sincerely Toralf Förster pgp finger print: 7B1A 07F4 EC82 0F90 D4C2 8936 872A E508 7DB6 9DA3