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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,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 50218C47255 for ; Mon, 11 May 2020 21:07:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2582A2078A for ; Mon, 11 May 2020 21:07:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="GKJ5Eedj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731875AbgEKVHS (ORCPT ); Mon, 11 May 2020 17:07:18 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:55204 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731868AbgEKVHS (ORCPT ); Mon, 11 May 2020 17:07:18 -0400 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 04BL71iA061885; Mon, 11 May 2020 21:07:08 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2020-01-29; bh=IAJQLbVwVP5lVN0Y4tvhElORwcq/7GVBvYMoChGS9P0=; b=GKJ5EedjP3Dlo0z6HOaxnd0AT0iQfG+koP9cVjxuwSqvWOIRFSTuE168QASjdwbGHHyE sEuhck3jjNRMTswPwUxM62rY2TZOZQ6wUt6tphXOwyQihWVidpTSmCOWo7FlIkP7mFjB llYCVeLJ1SWaWoGyN6ZsjiGIByIRxJkhsEXAegdY7TiTwvVjK+rHFsxh3wY1SDAEnLHH VkiFDKN+/OB/AJD74jL5fMEwFF9SJASNeqLH2VnjRBiOhnvFpy8SRd9qtbYlRdf+1GvM KMFLSkbRd4fqxykMNeOwIa2QjFNWqJmXvRSdTgzTvpQcCqSu2qYPKOMLfQfiboo1op+v LQ== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by userp2120.oracle.com with ESMTP id 30x3mbqh5s-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 11 May 2020 21:07:07 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 04BKwEpk068680; Mon, 11 May 2020 21:07:07 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3020.oracle.com with ESMTP id 30x69rs11b-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 11 May 2020 21:07:07 +0000 Received: from abhmp0014.oracle.com (abhmp0014.oracle.com [141.146.116.20]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 04BL76pk022354; Mon, 11 May 2020 21:07:06 GMT Received: from dhcp-10-159-239-226.vpn.oracle.com (/10.159.239.226) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 11 May 2020 14:07:05 -0700 Subject: Re: [PATCH 1/2] IB/sa: Resolving use-after-free in ib_nl_send_msg. To: "Wan, Kaike" , Mark Bloch , "linux-kernel@vger.kernel.org" , "linux-rdma@vger.kernel.org" , Jason Gunthorpe Cc: Gerd Rausch , =?UTF-8?Q?H=c3=a5kon_Bugge?= , Srinivas Eeda , Rama Nichanamatlu , Doug Ledford References: <1588876487-5781-1-git-send-email-divya.indi@oracle.com> <1588876487-5781-2-git-send-email-divya.indi@oracle.com> <7572e503-312c-26a8-c8c2-05515f1c4f84@mellanox.com> From: Divya Indi Message-ID: <54a2c84e-1745-cae5-e0b5-4d63013aef32@oracle.com> Date: Mon, 11 May 2020 14:06:25 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9618 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 malwarescore=0 adultscore=0 spamscore=0 suspectscore=11 mlxscore=0 mlxlogscore=999 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005110158 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9618 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 impostorscore=0 mlxscore=0 suspectscore=11 bulkscore=0 mlxlogscore=999 phishscore=0 malwarescore=0 lowpriorityscore=0 spamscore=0 adultscore=0 clxscore=1011 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005110159 Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org Hi, Thanks for taking the time to review. Please find my comments inline - On 5/7/20 1:16 PM, Wan, Kaike wrote: > >> -----Original Message----- >> From: Mark Bloch >> Sent: Thursday, May 07, 2020 3:36 PM >> To: Divya Indi ; linux-kernel@vger.kernel.org; linux- >> rdma@vger.kernel.org; Jason Gunthorpe ; Wan, Kaike >> >> Cc: Gerd Rausch ; Håkon Bugge >> ; Srinivas Eeda ; >> Rama Nichanamatlu ; Doug Ledford >> >> Subject: Re: [PATCH 1/2] IB/sa: Resolving use-after-free in ib_nl_send_msg. >> >> >>> @@ -1123,6 +1156,18 @@ int ib_nl_handle_resolve_resp(struct sk_buff >>> *skb, >>> >>> send_buf = query->mad_buf; >>> >>> + /* >>> + * Make sure the IB_SA_NL_QUERY_SENT flag is set before >>> + * processing this query. If flag is not set, query can be accessed in >>> + * another context while setting the flag and processing the query >> will >>> + * eventually release it causing a possible use-after-free. >>> + */ >>> + if (unlikely(!ib_sa_nl_query_sent(query))) { >> Can't there be a race here where you check the flag (it isn't set) and before >> you call wait_event() the flag is set and wake_up() is called which means you >> will wait here forever? > Should wait_event() catch that? That is, if the flag is not set, wait_event() will sleep until the flag is set. > > or worse, a timeout will happen the query will be >> freed and them some other query will call wake_up() and we have again a >> use-after-free. > The request has been deleted from the request list by this time and therefore the timeout should have no impact here. > > >>> + spin_unlock_irqrestore(&ib_nl_request_lock, flags); >>> + wait_event(wait_queue, ib_sa_nl_query_sent(query)); >> What if there are two queries sent to userspace, shouldn't you check and >> make sure you got woken up by the right one setting the flag? > The wait_event() is conditioned on the specific query (ib_sa_nl_query_sent(query)), not on the wait_queue itself. > >> Other than that, the entire solution makes it very complicated to reason with >> (flags set/checked without locking etc) maybe we should just revert and fix it >> the other way? > The flag could certainly be set under the lock, which may reduce complications. We could use a lock or use atomic operations. However, the reason for not doing so was that we have 1 writer and multiple readers of the IB_SA_NL_QUERY_SENT flag and the readers wouldnt mind reading a stale value. Would it still be better to have a lock for this flag? Thanks, Divya > > Kaike >