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,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 CAD1AC4727F for ; Wed, 23 Sep 2020 21:29:31 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5DA7523772 for ; Wed, 23 Sep 2020 21:29:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5DA7523772 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 D2F586B0003; Wed, 23 Sep 2020 17:29:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CB8346B0037; Wed, 23 Sep 2020 17:29:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B7F646B005A; Wed, 23 Sep 2020 17:29:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0177.hostedemail.com [216.40.44.177]) by kanga.kvack.org (Postfix) with ESMTP id 9DEB06B0003 for ; Wed, 23 Sep 2020 17:29:30 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 58DD12466 for ; Wed, 23 Sep 2020 21:29:30 +0000 (UTC) X-FDA: 77295617700.17.hope02_5f06d6327159 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin17.hostedemail.com (Postfix) with ESMTP id 3725D180D0180 for ; Wed, 23 Sep 2020 21:29:30 +0000 (UTC) X-HE-Tag: hope02_5f06d6327159 X-Filterd-Recvd-Size: 5333 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by imf05.hostedemail.com (Postfix) with ESMTP for ; Wed, 23 Sep 2020 21:29:28 +0000 (UTC) IronPort-SDR: U+Yuw8UbovnqIoomVzgG+mM/QSbtYI81vSMm3Bm4Wi5ij/GsACXlgjaCGJ/pjIi88tzOqgN4nC RH4r9VsIS2PA== X-IronPort-AV: E=McAfee;i="6000,8403,9753"; a="161946644" X-IronPort-AV: E=Sophos;i="5.77,295,1596524400"; d="scan'208";a="161946644" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Sep 2020 14:29:27 -0700 IronPort-SDR: oG/dfcX9c8XEBHsFy+RgMu7uZo6ZO+S0IAC+V6fq3JjdHtLd9yuY9OIQq98sXgJkkBW5Ee18W0 mA5hSNUsfgUg== X-IronPort-AV: E=Sophos;i="5.77,295,1596524400"; d="scan'208";a="511797445" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.160]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Sep 2020 14:29:26 -0700 Date: Wed, 23 Sep 2020 14:29:25 -0700 From: Sean Christopherson To: Andy Lutomirski Cc: Yu-cheng Yu , 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 Subject: Re: [PATCH v12 8/8] x86: Disallow vsyscall emulation when CET is enabled Message-ID: <20200923212925.GC15101@linux.intel.com> References: <20200918192312.25978-1-yu-cheng.yu@intel.com> <20200918192312.25978-9-yu-cheng.yu@intel.com> <24718de58ab7bc6d7288c58d3567ad802eeb6542.camel@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) 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 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.