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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 92646C18E5A for ; Tue, 10 Mar 2020 15:16:09 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5017920727 for ; Tue, 10 Mar 2020 15:16:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5017920727 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=xmission.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E79676B000D; Tue, 10 Mar 2020 11:16:08 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E03396B000E; Tue, 10 Mar 2020 11:16:08 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CA3D96B0010; Tue, 10 Mar 2020 11:16:08 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0041.hostedemail.com [216.40.44.41]) by kanga.kvack.org (Postfix) with ESMTP id ABA436B000D for ; Tue, 10 Mar 2020 11:16:08 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 88BC4180AD804 for ; Tue, 10 Mar 2020 15:16:08 +0000 (UTC) X-FDA: 76579803216.14.drum48_3587226c70246 X-HE-Tag: drum48_3587226c70246 X-Filterd-Recvd-Size: 8543 Received: from out01.mta.xmission.com (out01.mta.xmission.com [166.70.13.231]) by imf37.hostedemail.com (Postfix) with ESMTP for ; Tue, 10 Mar 2020 15:16:07 +0000 (UTC) Received: from in02.mta.xmission.com ([166.70.13.52]) by out01.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jBgby-0004CF-1k; Tue, 10 Mar 2020 09:16:02 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1jBgbx-0004Li-5P; Tue, 10 Mar 2020 09:16:01 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Bernd Edlinger Cc: Christian Brauner , Kees Cook , Jann Horn , Jonathan Corbet , Alexander Viro , Andrew Morton , Alexey Dobriyan , Thomas Gleixner , Oleg Nesterov , Frederic Weisbecker , Andrei Vagin , Ingo Molnar , "Peter Zijlstra \(Intel\)" , Yuyang Du , David Hildenbrand , Sebastian Andrzej Siewior , Anshuman Khandual , David Howells , James Morris , Greg Kroah-Hartman , Shakeel Butt , Jason Gunthorpe , Christian Kellner , Andrea Arcangeli , Aleksa Sarai , "Dmitry V. Levin" , "linux-doc\@vger.kernel.org" , "linux-kernel\@vger.kernel.org" , "linux-fsdevel\@vger.kernel.org" , "linux-mm\@kvack.org" , "stable\@vger.kernel.org" , "linux-api\@vger.kernel.org" References: <87r1y8dqqz.fsf@x220.int.ebiederm.org> <87tv32cxmf.fsf_-_@x220.int.ebiederm.org> <87v9ne5y4y.fsf_-_@x220.int.ebiederm.org> <87zhcq4jdj.fsf_-_@x220.int.ebiederm.org> <878sk94eay.fsf@x220.int.ebiederm.org> <87r1y12yc7.fsf@x220.int.ebiederm.org> <87k13t2xpd.fsf@x220.int.ebiederm.org> <87d09l2x5n.fsf@x220.int.ebiederm.org> <871rq12vxu.fsf@x220.int.ebiederm.org> <877dzt1fnf.fsf@x220.int.ebiederm.org> Date: Tue, 10 Mar 2020 10:13:42 -0500 In-Reply-To: (Bernd Edlinger's message of "Tue, 10 Mar 2020 14:43:41 +0100") Message-ID: <87d09kxmxl.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1jBgbx-0004Li-5P;;;mid=<87d09kxmxl.fsf@x220.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/eOO49tMC1vtWTUcFarj2ncADp1TyDOKs= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH 1/4] exec: Fix a deadlock in ptrace X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Bernd Edlinger writes: > This fixes a deadlock in the tracer when tracing a multi-threaded > application that calls execve while more than one thread are running. > > I observed that when running strace on the gcc test suite, it always > blocks after a while, when expect calls execve, because other threads > have to be terminated. They send ptrace events, but the strace is no > longer able to respond, since it is blocked in vm_access. > > The deadlock is always happening when strace needs to access the > tracees process mmap, while another thread in the tracee starts to > execve a child process, but that cannot continue until the > PTRACE_EVENT_EXIT is handled and the WIFEXITED event is received: Overall this looks good. Mind if I change the subject to: "exec: Fix a deadlock in strace" ? Eric > > strace D 0 30614 30584 0x00000000 > Call Trace: > __schedule+0x3ce/0x6e0 > schedule+0x5c/0xd0 > schedule_preempt_disabled+0x15/0x20 > __mutex_lock.isra.13+0x1ec/0x520 > __mutex_lock_killable_slowpath+0x13/0x20 > mutex_lock_killable+0x28/0x30 > mm_access+0x27/0xa0 > process_vm_rw_core.isra.3+0xff/0x550 > process_vm_rw+0xdd/0xf0 > __x64_sys_process_vm_readv+0x31/0x40 > do_syscall_64+0x64/0x220 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > expect D 0 31933 30876 0x80004003 > Call Trace: > __schedule+0x3ce/0x6e0 > schedule+0x5c/0xd0 > flush_old_exec+0xc4/0x770 > load_elf_binary+0x35a/0x16c0 > search_binary_handler+0x97/0x1d0 > __do_execve_file.isra.40+0x5d4/0x8a0 > __x64_sys_execve+0x49/0x60 > do_syscall_64+0x64/0x220 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > This changes mm_access to use the new exec_update_mutex > instead of cred_guard_mutex. > > This patch is based on the following patch by Eric W. Biederman: > "[PATCH 0/5] Infrastructure to allow fixing exec deadlocks" > Link: https://lore.kernel.org/lkml/87v9ne5y4y.fsf_-_@x220.int.ebiederm.org/ > > Signed-off-by: Bernd Edlinger > --- > kernel/fork.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index c12595a..5720ff3 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -1224,7 +1224,7 @@ struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) > struct mm_struct *mm; > int err; > > - err = mutex_lock_killable(&task->signal->cred_guard_mutex); > + err = mutex_lock_killable(&task->signal->exec_update_mutex); > if (err) > return ERR_PTR(err); > > @@ -1234,7 +1234,7 @@ struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) > mmput(mm); > mm = ERR_PTR(-EACCES); > } > - mutex_unlock(&task->signal->cred_guard_mutex); > + mutex_unlock(&task->signal->exec_update_mutex); > > return mm; > }