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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 CB251C433E0 for ; Sat, 23 May 2020 09:23:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 922BB20727 for ; Sat, 23 May 2020 09:23:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="W6i4bXYb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387753AbgEWJX6 (ORCPT ); Sat, 23 May 2020 05:23:58 -0400 Received: from mail.skyhub.de ([5.9.137.197]:39588 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387678AbgEWJX6 (ORCPT ); Sat, 23 May 2020 05:23:58 -0400 Received: from zn.tnic (p200300ec2f1b96004c59f332ede330a0.dip0.t-ipconnect.de [IPv6:2003:ec:2f1b:9600:4c59:f332:ede3:30a0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id D4F011EC00F8; Sat, 23 May 2020 11:23:56 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1590225837; 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:in-reply-to:in-reply-to: references:references; bh=RhlLOpWrzFCYAA5wjrrTkxDaFVK4ufjSSsBDJauVbXs=; b=W6i4bXYbASIdWPDlvAWA9Sw9TKs/imch2CRIvLqZAZ4AKkFkjp/UuQi1aiIvRsUqpb/Ijj rhKqdXWe1V8tbZrsV+ydJdjBXCSo3iOhh1eYx5fNwk/T/wLPMiQnd007L0F2AmgC3CZUHh n/hVT/CyRpJEn0ufXVLgJKYXhQaudvg= Date: Sat, 23 May 2020 11:23:51 +0200 From: Borislav Petkov To: Joerg Roedel Cc: x86@kernel.org, hpa@zytor.com, Andy Lutomirski , Dave Hansen , Peter Zijlstra , Thomas Hellstrom , Jiri Slaby , Dan Williams , Tom Lendacky , Juergen Gross , Kees Cook , David Rientjes , Cfir Cohen , Erdem Aktas , Masami Hiramatsu , Mike Stunes , Joerg Roedel , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH v3 49/75] x86/sev-es: Handle instruction fetches from user-space Message-ID: <20200523092351.GE27431@zn.tnic> References: <20200428151725.31091-1-joro@8bytes.org> <20200428151725.31091-50-joro@8bytes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200428151725.31091-50-joro@8bytes.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 28, 2020 at 05:16:59PM +0200, Joerg Roedel wrote: > From: Joerg Roedel > > When a #VC exception is triggered by user-space the instruction decoder > needs to read the instruction bytes from user addresses. Enhance > vc_decode_insn() to safely fetch kernel and user instructions. > > Signed-off-by: Joerg Roedel > --- > arch/x86/kernel/sev-es.c | 31 ++++++++++++++++++++++--------- > 1 file changed, 22 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c > index 85027fb4177e..c2223c2a28c2 100644 > --- a/arch/x86/kernel/sev-es.c > +++ b/arch/x86/kernel/sev-es.c > @@ -165,17 +165,30 @@ static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt) > enum es_result ret; > int res; > > - res = vc_fetch_insn_kernel(ctxt, buffer); > - if (unlikely(res == -EFAULT)) { Let's also test for 0 in case the probe_read* guts get changed and start returning so other errval besides -EFAULT. > - ctxt->fi.vector = X86_TRAP_PF; > - ctxt->fi.error_code = 0; > - ctxt->fi.cr2 = ctxt->regs->ip; > - return ES_EXCEPTION; > + if (!user_mode(ctxt->regs)) { Flip that check so that it reads more naturally: if (user_mode(..) insn_fetch_from_user() ... } else { vc_fetch_insn_kernel() } > + res = vc_fetch_insn_kernel(ctxt, buffer); > + if (unlikely(res == -EFAULT)) { > + ctxt->fi.vector = X86_TRAP_PF; > + ctxt->fi.error_code = 0; > + ctxt->fi.cr2 = ctxt->regs->ip; > + return ES_EXCEPTION; > + } > + > + insn_init(&ctxt->insn, buffer, MAX_INSN_SIZE - res, 1); > + insn_get_length(&ctxt->insn); > + } else { > + res = insn_fetch_from_user(ctxt->regs, buffer); > + if (res == 0) { if (!res) -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette