From patchwork Thu May 26 21:08:09 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 12862794 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2E410C433EF for ; Thu, 26 May 2022 21:24:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348775AbiEZVYV (ORCPT ); Thu, 26 May 2022 17:24:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44412 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229835AbiEZVYS (ORCPT ); Thu, 26 May 2022 17:24:18 -0400 Received: from mail-pf1-x449.google.com (mail-pf1-x449.google.com [IPv6:2607:f8b0:4864:20::449]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DAEC75F27A for ; Thu, 26 May 2022 14:24:17 -0700 (PDT) Received: by mail-pf1-x449.google.com with SMTP id i19-20020aa79093000000b0050d44b83506so1472179pfa.22 for ; Thu, 26 May 2022 14:24:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=reply-to:date:message-id:mime-version:subject:from:to:cc; bh=mOpI/+KYEZdbicuZlQkRSCxZ1y9mz9g1l8prxAxeWBQ=; b=WsfHkiW/udderPR0r7wqNd2MXukeGBYWW7b/3FjGwLvQvLB7HuDmwuCi+T2GLYkgo/ GwZxyWANLG5Teqq7jC1OKUr7S0Ag/hjj4osE7NLbe4dWfKwRXSbQXrmohE5C73XYwLbk r27+HcOalBxWxQ0rTHQYScxcIRyAP3wxbZr5OV+XZAIjpawDTjyCdormq0QKaDHlKJ7d bkEnd4QmrejzO3Eu5lJZ3YA9Yxs3eeGJX5hloedjrj1i7MtekfY2AW7/aQ2n7vybUmxN 6UoYnaKeehZN5gYCwKskPn1sN//Fh4x7SunC79xIjeHSvcwZe+fKYzcByy91G2RXum7X chEA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:reply-to:date:message-id:mime-version:subject :from:to:cc; bh=mOpI/+KYEZdbicuZlQkRSCxZ1y9mz9g1l8prxAxeWBQ=; b=Z1hvpqykV+f+cue5gTOvz39jn3nizaER51tY6XUdl7KaAgNJrI/aJZcDHz3Egi+Icp 7Nh2CJv8U+PAMIvrQWlBCNupx0E4yCU7J26s8C6+iJUOARgyXWX6BtAT3FUmx1DHLcT7 q09Gv3X/6unKZKU+0u9D2cIxxLYzh06qRILO1AqSdbMBExih1y8YDMIZ0r3pGtyCY+vG wZ7C0Bi5+oXW5TkaBwAntGVXHJa8pHBy8PtJeYckYId6+/UWoB4mHHas/NP+0Oeu5GZP CKH7HAhtzNGhTtcku0KVxsuif6wXRChxxJeqRFEY9iDxUoaco1+DTMa8Fjf2852RPJ6d CNmA== X-Gm-Message-State: AOAM530WokiDilnZFMiPeZYmXgCEgRcAh7bS6QRP5VcTxYtiRclcrNco fObqHKTCCdEoQsNdEXdRXev5VsOKu4I= X-Google-Smtp-Source: ABdhPJxzk5JajMO4kk7EeMLmpp0YUvfoHhz1BHLMWcZFnj442UGh2Ej356Klhh6wHL6kvWZRRscH1w1jr+U= X-Received: from seanjc.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:3e5]) (user=seanjc job=sendgmr) by 2002:a05:6a00:170e:b0:519:3571:903e with SMTP id h14-20020a056a00170e00b005193571903emr581498pfc.30.1653600257340; Thu, 26 May 2022 14:24:17 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 26 May 2022 21:08:09 +0000 Message-Id: <20220526210817.3428868-1-seanjc@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.36.1.255.ge46751e96f-goog Subject: [PATCH v2 0/8] KVM: x86: Emulator _regs fixes and cleanups From: Sean Christopherson To: Paolo Bonzini Cc: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Kees Cook , Robert Dinse Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Clean up and harden the use of the x86_emulate_ctxt._regs, which is surrounded by a fair bit of magic. This series was prompted by bug reports by Kees and Robert where GCC-12 flags an out-of-bounds _regs access. The warning is a false positive due to a now-known GCC bug, but it's cheap and easy to harden the _regs usage, and doing so minimizing the risk of more precisely handling 32-bit vs. 64-bit GPRs. I didn't tag patch 2 with Fixes or Cc: stable@. It does remedy the GCC-12 warning, but AIUI the GCC-12 bug affects other KVM paths that already have explicit guardrails, i.e. fixing this one case doesn't guarantee happiness when building with CONFIG_KVM_WERROR=y, let alone CONFIG_WERROR=y. That said, it might be worth sending to the v5.18 stable tree[*] as it does appear to make some configs/setups happy. [*] KVM hasn't changed, but the warning=>error was introduced in v5.18 by commit e6148767825c ("Makefile: Enable -Warray-bounds"). v2: - Collect reviews and tests. [Vitaly, Kees, Robert] - Tweak patch 1's changelog to explicitly call out that dirty_regs is a 4 byte field. [Vitaly] - Add Reported-by for Kees and Robert since this does technically fix a build breakage. - Use a raw literal for NR_EMULATOR_GPRS instead of VCPU_REGS_R15+1 to play nice with 32-bit builds. [kernel test robot] - Reduce the number of emulated GPRs to 8 for 32-bit builds. - Add and use KVM_EMULATOR_BUG_ON() to bug/kill the VM when an emulator bug is detected. [Vitaly] v1: https://lore.kernel.org/all/20220525222604.2810054-1-seanjc@google.com Sean Christopherson (8): KVM: x86: Grab regs_dirty in local 'unsigned long' KVM: x86: Harden _regs accesses to guard against buggy input KVM: x86: Omit VCPU_REGS_RIP from emulator's _regs array KVM: x86: Use 16-bit fields to track dirty/valid emulator GPRs KVM: x86: Reduce the number of emulator GPRs to '8' for 32-bit KVM KVM: x86: Bug the VM if the emulator accesses a non-existent GPR KVM: x86: Bug the VM if the emulator generates a bogus exception vector KVM: x86: Bug the VM on an out-of-bounds data read arch/x86/kvm/emulate.c | 26 ++++++++++++++++++++------ arch/x86/kvm/kvm_emulate.h | 28 +++++++++++++++++++++++++--- arch/x86/kvm/x86.c | 9 +++++++++ 3 files changed, 54 insertions(+), 9 deletions(-) base-commit: 90bde5bea810d766e7046bf5884f2ccf76dd78e9