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=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,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 77EDEC4CECD for ; Sun, 15 Sep 2019 09:35:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5827C20692 for ; Sun, 15 Sep 2019 09:35:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728560AbfIOJfE (ORCPT ); Sun, 15 Sep 2019 05:35:04 -0400 Received: from mx2.yrkesakademin.fi ([85.134.45.195]:31969 "EHLO mx2.yrkesakademin.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725497AbfIOJfE (ORCPT ); Sun, 15 Sep 2019 05:35:04 -0400 Subject: Re: [PATCH 5.2 36/37] vhost: block speculation of translated descriptors To: Greg Kroah-Hartman , Stefan Lippers-Hollmann CC: , , "Michael S. Tsirkin" , Jason Wang References: <20190913130510.727515099@linuxfoundation.org> <20190913130522.155505270@linuxfoundation.org> <20190914025411.3016e3d9@mir> <20190914055050.GA489003@kroah.com> <20190914091548.230a63de@mir> <20190914080836.GB522114@kroah.com> From: Thomas Backlund Message-ID: <368d254b-dc29-6309-062d-a2d07b5dad75@mageia.org> Date: Sun, 15 Sep 2019 12:34:57 +0300 MIME-Version: 1.0 In-Reply-To: <20190914080836.GB522114@kroah.com> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-WatchGuard-Spam-ID: str=0001.0A0C020F.5D7E05C6.0029,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0 X-WatchGuard-Spam-Score: 0, clean; 0, virus threat unknown X-WatchGuard-Mail-Client-IP: 85.134.45.195 X-WatchGuard-Mail-From: tmb@mageia.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Archived-At: List-Archive: List-Post: Den 14-09-2019 kl. 11:08, skrev Greg Kroah-Hartman: > On Sat, Sep 14, 2019 at 09:15:48AM +0200, Stefan Lippers-Hollmann wrote: >> Hi >> >> On 2019-09-14, Greg Kroah-Hartman wrote: >>> On Sat, Sep 14, 2019 at 02:54:11AM +0200, Stefan Lippers-Hollmann wrote: >>>> On 2019-09-13, Greg Kroah-Hartman wrote: >>>>> From: Michael S. Tsirkin >>>>> >>>>> commit a89db445fbd7f1f8457b03759aa7343fa530ef6b upstream. >>>>> >>>>> iovec addresses coming from vhost are assumed to be >>>>> pre-validated, but in fact can be speculated to a value >>>>> out of range. >>>>> >>>>> Userspace address are later validated with array_index_nospec so we can >>>>> be sure kernel info does not leak through these addresses, but vhost >>>>> must also not leak userspace info outside the allowed memory table to >>>>> guests. >>>>> >>>>> Following the defence in depth principle, make sure >>>>> the address is not validated out of node range. >> [...] >>> Do you have the same problem with Linus's tree right now? >> >> Actually, yes I do (I had not tested i386 for 5.3~ within the last ~2 >> weeks, only amd64). Very similar kernel config, same compiler versions >> but built in a slightly different environment (built directly on the bare >> iron, in a amd64 multilib userspace, rather than a pure-i386 chroot on an >> amd64 kernel). >> >> $ git describe >> v5.3-rc8-36-ga7f89616b737 >> >> $ LANG= make ARCH=x86 -j1 bzImage modules >> CALL scripts/checksyscalls.sh >> CALL scripts/atomic/check-atomics.sh >> CHK include/generated/compile.h >> CHK kernel/kheaders_data.tar.xz >> CC [M] drivers/vhost/vhost.o >> In file included from ./include/linux/export.h:45, >> from ./include/linux/linkage.h:7, >> from ./include/linux/kernel.h:8, >> from ./include/linux/list.h:9, >> from ./include/linux/wait.h:7, >> from ./include/linux/eventfd.h:13, >> from drivers/vhost/vhost.c:13: >> drivers/vhost/vhost.c: In function 'translate_desc': >> ./include/linux/compiler.h:350:38: error: call to '__compiletime_assert_2076' declared with attribute error: BUILD_BUG_ON failed: sizeof(_s) > sizeof(long) >> 350 | _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) >> | ^ >> ./include/linux/compiler.h:331:4: note: in definition of macro '__compiletime_assert' >> 331 | prefix ## suffix(); \ >> | ^~~~~~ >> ./include/linux/compiler.h:350:2: note: in expansion of macro '_compiletime_assert' >> 350 | _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) >> | ^~~~~~~~~~~~~~~~~~~ >> ./include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert' >> 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) >> | ^~~~~~~~~~~~~~~~~~ >> ./include/linux/build_bug.h:50:2: note: in expansion of macro 'BUILD_BUG_ON_MSG' >> 50 | BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) >> | ^~~~~~~~~~~~~~~~ >> ./include/linux/nospec.h:56:2: note: in expansion of macro 'BUILD_BUG_ON' >> 56 | BUILD_BUG_ON(sizeof(_s) > sizeof(long)); \ >> | ^~~~~~~~~~~~ >> drivers/vhost/vhost.c:2076:5: note: in expansion of macro 'array_index_nospec' >> 2076 | array_index_nospec((unsigned long)(addr - node->start), >> | ^~~~~~~~~~~~~~~~~~ >> make[2]: *** [scripts/Makefile.build:281: drivers/vhost/vhost.o] Error 1 >> make[1]: *** [scripts/Makefile.build:497: drivers/vhost] Error 2 >> make: *** [Makefile:1083: drivers] Error 2 >> >> $ git revert a89db445fbd7f1f8457b03759aa7343fa530ef6b >> >> $ LANG= make ARCH=x86 -j16 bzImage modules >> CALL scripts/atomic/check-atomics.sh >> CALL scripts/checksyscalls.sh >> CHK include/generated/compile.h >> CHK kernel/kheaders_data.tar.xz >> Building modules, stage 2. >> Kernel: arch/x86/boot/bzImage is ready (#1) >> MODPOST 3464 modules >> >> $ echo $? >> 0 >> >> $ find . -name vhost\\.ko >> ./drivers/vhost/vhost.ko >> >> I've attached the affected kernel config for v5.3~/ i386. > > Ok, good, we will be "bug compatible" at the very least now :) > > When this gets fixed in Linus's tree we can backport the fix here as > well. The number of users of that compiler version/configuration is > probably pretty low at the moment to want to hold off on this fix. > This is now reverted upstream: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0d4a3f2abbef73b9e5bb5f12213c275565473588 -- Thomas