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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 16449C5B578 for ; Wed, 3 Jul 2019 04:36:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E1CAC21871 for ; Wed, 3 Jul 2019 04:36:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726743AbfGCEgS (ORCPT ); Wed, 3 Jul 2019 00:36:18 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:21076 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725535AbfGCEgS (ORCPT ); Wed, 3 Jul 2019 00:36:18 -0400 Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x634WSxA048943 for ; Wed, 3 Jul 2019 00:36:17 -0400 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0a-001b2d01.pphosted.com with ESMTP id 2tgkg3upbj-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 03 Jul 2019 00:36:16 -0400 Received: from localhost by e06smtp07.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 3 Jul 2019 05:36:10 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x634aAlg51445780 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 3 Jul 2019 04:36:10 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E578BAE055; Wed, 3 Jul 2019 04:36:09 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0B53FAE045; Wed, 3 Jul 2019 04:36:06 +0000 (GMT) Received: from [9.85.75.18] (unknown [9.85.75.18]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 3 Jul 2019 04:36:05 +0000 (GMT) Subject: Re: Reminder: 22 open syzbot bugs in perf subsystem To: Eric Biggers Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Song Liu , Kan Liang , Alexander Shishkin , Jiri Olsa , Namhyung Kim , syzkaller-bugs@googlegroups.com, Oleg Nesterov , Ravi Bangoria References: <20190702054342.GB27702@sol.localdomain> <5a99f556-7449-55da-d901-0249352a5e15@linux.ibm.com> <20190703035550.GA633@sol.localdomain> <4d6ce02e-9325-4247-3d9b-51cdfcfaee07@linux.ibm.com> <20190703041918.GB633@sol.localdomain> From: Ravi Bangoria Date: Wed, 3 Jul 2019 10:06:04 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190703041918.GB633@sol.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19070304-0028-0000-0000-0000037FDC73 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19070304-0029-0000-0000-0000244018F3 Message-Id: <7dd388d6-628d-23aa-0a97-84e7e0800b74@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-07-03_02:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1907030057 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/3/19 9:49 AM, Eric Biggers wrote: > On Wed, Jul 03, 2019 at 09:29:39AM +0530, Ravi Bangoria wrote: >> Hi Eric, >> >> On 7/3/19 9:25 AM, Eric Biggers wrote: >>> On Wed, Jul 03, 2019 at 09:09:55AM +0530, Ravi Bangoria wrote: >>>> >>>> >>>> On 7/2/19 11:13 AM, Eric Biggers wrote: >>>>> -------------------------------------------------------------------------------- >>>>> Title: possible deadlock in uprobe_clear_state >>>>> Last occurred: 164 days ago >>>>> Reported: 201 days ago >>>>> Branches: Mainline >>>>> Dashboard link: https://syzkaller.appspot.com/bug?id=a1ce9b3da349209c5085bb8c4fee753d68c3697f >>>>> Original thread: https://lkml.kernel.org/lkml/00000000000010a9fb057cd14174@google.com/T/#u >>>>> >>>>> Unfortunately, this bug does not have a reproducer. >>>>> >>>>> No one replied to the original thread for this bug. >>>>> >>>>> If you fix this bug, please add the following tag to the commit: >>>>> Reported-by: syzbot+1068f09c44d151250c33@syzkaller.appspotmail.com >>>>> >>>>> If you send any email or patch for this bug, please consider replying to the >>>>> original thread. For the git send-email command to use, or tips on how to reply >>>>> if the thread isn't in your mailbox, see the "Reply instructions" at >>>>> https://lkml.kernel.org/r/00000000000010a9fb057cd14174@google.com >>>>> >>>> >>>> This is false positive: >>>> https://marc.info/?l=linux-kernel&m=154925313012615&w=2 >>>> >>> >>> What do you mean "false positive"? Your patch says there can be a deadlock. >>> Also, your patch hasn't been merged yet. So doesn't it still need to be fixed? >> >> Please see Oleg's reply to the patch: >> https://marc.info/?l=linux-kernel&m=154946017315554&w=2 >> >> """ >> But this is false positive, right? if CPU1 calls update_ref_ctr() then >> either ->mm_users is already zero so binder_alloc_free_page()->mmget_not_zero() >> will fail, or the caller of update_ref_ctr() has a reference and thus >> binder_alloc_free_page()->mmput() can't trigger __mmput() ? >> """ >> > > Even if it's a lockdep false positive you can't ignore it. People rely on > lockdep to find bugs, and they will keep sending you bug reports. So someone > has to fix something. Agreed. > Did you see Oleg's suggestion to change mmput() to > mmput_async() in binder_alloc_free_page()? > https://marc.info/?l=linux-kernel&m=155119805728815&w=2 > If you believe that is the right fix, Yes, fixing it in binderfs looks right to me. > I can reassign this report to binder > subsystem and nag the binder maintainers instead... Yes please :)