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=-8.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 02B95C4727F for ; Wed, 23 Sep 2020 22:06:57 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9D2B523787 for ; Wed, 23 Sep 2020 22:06:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9D2B523787 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id D8F5F6B0037; Wed, 23 Sep 2020 18:06:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D19A86B005A; Wed, 23 Sep 2020 18:06:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C08696B005C; Wed, 23 Sep 2020 18:06:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0116.hostedemail.com [216.40.44.116]) by kanga.kvack.org (Postfix) with ESMTP id A61036B0037 for ; Wed, 23 Sep 2020 18:06:55 -0400 (EDT) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 6A7EB8249980 for ; Wed, 23 Sep 2020 22:06:55 +0000 (UTC) X-FDA: 77295711990.12.toe60_5906a0f27159 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin12.hostedemail.com (Postfix) with ESMTP id 482F01800C87F for ; Wed, 23 Sep 2020 22:06:55 +0000 (UTC) X-HE-Tag: toe60_5906a0f27159 X-Filterd-Recvd-Size: 5648 Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by imf41.hostedemail.com (Postfix) with ESMTP for ; Wed, 23 Sep 2020 22:06:53 +0000 (UTC) IronPort-SDR: vhVoJBiwbBfWv4oRMYqDh+k6wszZACNTUD5508RySMZjHiXelA6VVYtbj11yaolmIZ3gO7jBiV lyU11vbP8C+Q== X-IronPort-AV: E=McAfee;i="6000,8403,9753"; a="158381626" X-IronPort-AV: E=Sophos;i="5.77,295,1596524400"; d="scan'208";a="158381626" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Sep 2020 15:06:51 -0700 IronPort-SDR: zLfGJI1ugyecws8SsIsL53MZ0sUWci+vJczoCgnbimmJgHSY59EFkBHYO2TCK4S8xhaVI80Tgc utWrB9C4qwTg== X-IronPort-AV: E=Sophos;i="5.77,295,1596524400"; d="scan'208";a="455088476" Received: from yyu32-mobl1.amr.corp.intel.com (HELO [10.212.121.128]) ([10.212.121.128]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Sep 2020 15:06:46 -0700 Subject: Re: [PATCH v12 8/8] x86: Disallow vsyscall emulation when CET is enabled To: Sean Christopherson , Andy Lutomirski Cc: X86 ML , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , LKML , "open list:DOCUMENTATION" , Linux-MM , linux-arch , Linux API , Arnd Bergmann , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang References: <20200918192312.25978-1-yu-cheng.yu@intel.com> <20200918192312.25978-9-yu-cheng.yu@intel.com> <24718de58ab7bc6d7288c58d3567ad802eeb6542.camel@intel.com> <20200923212925.GC15101@linux.intel.com> From: "Yu, Yu-cheng" Message-ID: Date: Wed, 23 Sep 2020 15:06:44 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20200923212925.GC15101@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 9/23/2020 2:29 PM, Sean Christopherson wrote: > On Mon, Sep 21, 2020 at 04:48:25PM -0700, Andy Lutomirski wrote: >> On Mon, Sep 21, 2020 at 3:37 PM Yu-cheng Yu wrote: >>> diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c >>> b/arch/x86/entry/vsyscall/vsyscall_64.c >>> index 44c33103a955..0131c9f7f9c5 100644 >>> --- a/arch/x86/entry/vsyscall/vsyscall_64.c >>> +++ b/arch/x86/entry/vsyscall/vsyscall_64.c >>> @@ -38,6 +38,9 @@ >>> #include >>> #include >>> #include >>> +#include >>> +#include >>> +#include >>> >>> #define CREATE_TRACE_POINTS >>> #include "vsyscall_trace.h" >>> @@ -286,6 +289,32 @@ bool emulate_vsyscall(unsigned long error_code, >>> /* Emulate a ret instruction. */ >>> regs->ip = caller; >>> regs->sp += 8; >>> + >>> + if (current->thread.cet.shstk_size || >>> + current->thread.cet.ibt_enabled) { >>> + u64 r; >>> + >>> + fpregs_lock(); >>> + if (test_thread_flag(TIF_NEED_FPU_LOAD)) >>> + __fpregs_load_activate(); >> >> Wouldn't this be nicer if you operated on the memory image, not the registers? >> >>> + >>> +#ifdef CONFIG_X86_INTEL_BRANCH_TRACKING_USER >>> + /* Fixup branch tracking */ >>> + if (current->thread.cet.ibt_enabled) { >>> + rdmsrl(MSR_IA32_U_CET, r); >>> + wrmsrl(MSR_IA32_U_CET, r & ~CET_WAIT_ENDBR); >>> + } >>> +#endif >> >> Seems reasonable on first glance. >> >>> + >>> +#ifdef CONFIG_X86_INTEL_SHADOW_STACK_USER >>> + /* Unwind shadow stack. */ >>> + if (current->thread.cet.shstk_size) { >>> + rdmsrl(MSR_IA32_PL3_SSP, r); >>> + wrmsrl(MSR_IA32_PL3_SSP, r + 8); >>> + } >>> +#endif >> >> What happens if the result is noncanonical? A quick skim of the SDM >> didn't find anything. This latter issue goes away if you operate on >> the memory image, though -- writing a bogus value is just fine, since >> the FP restore will handle it. > > #GP, the SSP MSRs do canonical checks. I think I'll add a check here for (r + 8) >= TASK_SIZE_MAX. It is better than getting a fault. Thanks, Yu-cheng