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=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 4ED67C43462 for ; Wed, 31 Mar 2021 21:02:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2169861076 for ; Wed, 31 Mar 2021 21:02:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232372AbhCaVC0 (ORCPT ); Wed, 31 Mar 2021 17:02:26 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:37660 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230284AbhCaVBu (ORCPT ); Wed, 31 Mar 2021 17:01:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1617224509; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VK3wZ2uZxurW5NHYBbFfGkqs4fcBNPjrFax0D4qhIZg=; b=EYa8Cibp1d+Tah81lcga/f3ImhkRWT32tjnCscpyEXnOxq8GQ0E+A30265OK/yWj2hi7ei G29maTvVzp6G0BRJKA5b4mr/K/JcCtNXekdPdmas+16Ni8Pw33cVf1xlOrfVE9ffYuI9U6 owLOBc1mnP/xqdhOBRLU7+AMhREohQo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-111-nqaMPqcBPYiIv5xBLk0AZQ-1; Wed, 31 Mar 2021 17:01:45 -0400 X-MC-Unique: nqaMPqcBPYiIv5xBLk0AZQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 94E93501F8; Wed, 31 Mar 2021 21:01:43 +0000 (UTC) Received: from ovpn-112-207.phx2.redhat.com (ovpn-112-207.phx2.redhat.com [10.3.112.207]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4B7E059451; Wed, 31 Mar 2021 21:01:42 +0000 (UTC) Message-ID: Subject: Re: [PATCH v2] nvme-tcp: Check if request has started before processing it From: "Ewan D. Milne" To: Hannes Reinecke , Keith Busch , Sagi Grimberg Cc: Daniel Wagner , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, Jens Axboe , Christoph Hellwig Date: Wed, 31 Mar 2021 17:01:41 -0400 In-Reply-To: References: <20210301175601.116405-1-dwagner@suse.de> <6b51a989-5551-e243-abda-5872411ec3ff@grimberg.me> <20210311094345.ogm2lxqfuszktuhp@beryllium.lan> <70af5b02-10c1-ab0b-1dfc-5906216871b4@grimberg.me> <2fc7a320c86f75507584453dd2fbd744de5c170d.camel@redhat.com> <20210330232813.GA1935968@dhcp-10-100-145-180.wdc.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2021-03-31 at 09:11 +0200, Hannes Reinecke wrote: > On 3/31/21 1:28 AM, Keith Busch wrote: > > On Tue, Mar 30, 2021 at 10:34:25AM -0700, Sagi Grimberg wrote: > > > > > > > > It is, but in this situation, the controller is sending a > > > > > second > > > > > completion that results in a use-after-free, which makes the > > > > > transport irrelevant. Unless there is some other flow (which > > > > > is > > > > > unclear > > > > > to me) that causes this which is a bug that needs to be fixed > > > > > rather > > > > > than hidden with a safeguard. > > > > > > > > > > > > > The kernel should not crash regardless of any network traffic > > > > that is > > > > sent to the system. It should not be possible to either > > > > intentionally > > > > of mistakenly contruct packets that will deny service in this > > > > way. > > > > > > This is not specific to nvme-tcp. I can build an rdma or pci > > > controller > > > that can trigger the same crash... I saw a similar patch from > > > Hannes > > > implemented in the scsi level, and not the individual scsi > > > transports.. > > > > If scsi wants this too, this could be made generic at the blk-mq > > level. > > We just need to make something like blk_mq_tag_to_rq(), but return > > NULL > > if the request isn't started. > > > > > I would also mention, that a crash is not even the scariest issue > > > that > > > we can see here, because if the request happened to be reused we > > > are > > > in the silent data corruption realm... > > > > If this does happen, I think we have to come up with some way to > > mitigate it. We're not utilizing the full 16 bits of the > > command_id, so > > maybe we can append something like a generation sequence number > > that can > > be checked for validity. > > > > ... which will be near impossible. > We can protect against crashing on invalid frames. > We can _not_ protect against maliciously crafted packets referencing > any > random _existing_ tag; that's what TLS is for. > > What we can do, though, is checking the 'state' field in the tcp > request, and only allow completions for commands which are in a state > allowing for completions. > > Let's see if I can whip up a patch. That would be great. BTW in the crash dump I am looking at now, it looks like pdu->command_id was zero in nvme_tcp_recv_data(), and blk_mq_tag_to_rq() returned a request struct that had not been used. So I think we do need to check that the tag was actually allocated. -Ewan > > Cheers, > > Hannes