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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 DF03AC43441 for ; Thu, 15 Nov 2018 04:07:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B263E20671 for ; Thu, 15 Nov 2018 04:07:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B263E20671 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728257AbeKOOMv (ORCPT ); Thu, 15 Nov 2018 09:12:51 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:48600 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726574AbeKOOMv (ORCPT ); Thu, 15 Nov 2018 09:12:51 -0500 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id wAF43ixi117778 for ; Wed, 14 Nov 2018 23:06:42 -0500 Received: from e06smtp01.uk.ibm.com (e06smtp01.uk.ibm.com [195.75.94.97]) by mx0a-001b2d01.pphosted.com with ESMTP id 2nrw9q8k1n-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 14 Nov 2018 23:06:41 -0500 Received: from localhost by e06smtp01.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) Thu, 15 Nov 2018 04:06:33 -0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id wAF46W9l6553870 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 15 Nov 2018 04:06:32 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6F9BA52051; Thu, 15 Nov 2018 04:06:32 +0000 (GMT) Received: from [9.124.35.153] (unknown [9.124.35.153]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id 2391A52054; Thu, 15 Nov 2018 04:06:28 +0000 (GMT) Subject: Re: [PATCH] Uprobes: Fix kernel oops with delayed_uprobe_remove() To: Oleg Nesterov Cc: srikar@linux.vnet.ibm.com, rostedt@goodmis.org, mhiramat@kernel.org, liu.song.a23@gmail.com, peterz@infradead.org, mingo@redhat.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, linux-kernel@vger.kernel.org, ananth@linux.vnet.ibm.com, alexis.berlemont@gmail.com, naveen.n.rao@linux.vnet.ibm.com, linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org, linux@armlinux.org.uk, ralf@linux-mips.org, paul.burton@mips.com, Ravi Bangoria References: <20181114081921.26484-1-ravi.bangoria@linux.ibm.com> <20181114160600.GD13885@redhat.com> From: Ravi Bangoria Date: Thu, 15 Nov 2018 09:36:42 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: <20181114160600.GD13885@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 18111504-4275-0000-0000-000002E13020 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18111504-4276-0000-0000-000037EE4688 Message-Id: <556c2aa5-550d-d96f-7ed2-549d8f3d803b@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-11-15_01:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=987 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1811150034 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Oleg, On 11/14/18 9:36 PM, Oleg Nesterov wrote: > On 11/14, Ravi Bangoria wrote: >> >> syzbot reported a kernel crash with delayed_uprobe_remove(): >> https://lkml.org/lkml/2018/11/1/1244 >> >> Backtrace mentioned in the link points to a race between process >> exit and uprobe_unregister(). Fix it by locking delayed_uprobe_lock >> before calling delayed_uprobe_remove() from put_uprobe(). > > The patch looks good to me, but could you update the changelog? > > Please explain that the exiting task calls uprobe_clear_state() which > can race with delayed_uprobe_remove(). IIUC this is the only problem > solved by this patch, right? Right. Is this better: There could be a race between task exit and probe unregister: exit_mm() mmput() __mmput() uprobe_unregister() uprobe_clear_state() put_uprobe() delayed_uprobe_remove() delayed_uprobe_remove() put_uprobe() is calling delayed_uprobe_remove() without taking delayed_uprobe_lock and thus the race sometimes results in a kernel crash. Fix this by taking delayed_uprobe_lock before calling delayed_uprobe_remove() from put_uprobe(). Detailed crash log can be found at: https://lkml.org/lkml/2018/11/1/1244