From patchwork Fri May 17 07:57:21 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yuxuan Luo X-Patchwork-Id: 1936304 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lists.ubuntu.com (client-ip=185.125.189.65; helo=lists.ubuntu.com; envelope-from=kernel-team-bounces@lists.ubuntu.com; receiver=patchwork.ozlabs.org) Received: from lists.ubuntu.com (lists.ubuntu.com [185.125.189.65]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4VgfTr05R6z1ydW for ; Fri, 17 May 2024 17:58:24 +1000 (AEST) Received: from localhost ([127.0.0.1] helo=lists.ubuntu.com) by lists.ubuntu.com with esmtp (Exim 4.86_2) (envelope-from ) id 1s7sTr-0005l9-1Q; Fri, 17 May 2024 07:58:19 +0000 Received: from smtp-relay-internal-1.internal ([10.131.114.114] helo=smtp-relay-internal-1.canonical.com) by lists.ubuntu.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1s7sTp-0005hD-8j for kernel-team@lists.ubuntu.com; Fri, 17 May 2024 07:58:17 +0000 Received: from mail-ej1-f71.google.com (mail-ej1-f71.google.com [209.85.218.71]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by smtp-relay-internal-1.canonical.com (Postfix) with ESMTPS id 3C89E3F363 for ; Fri, 17 May 2024 07:58:15 +0000 (UTC) Received: by mail-ej1-f71.google.com with SMTP id a640c23a62f3a-a59a17f35c8so544460766b.0 for ; Fri, 17 May 2024 00:58:15 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1715932694; x=1716537494; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=MfIN7DDJmgNd+ZjkMMwGoQozdPmlNW2rJhXz9rgb9kA=; b=fFVzhA53Pvmq5z5pIK0QJhaSX7g6HixODnWkgtM0gDuWgcOKWHqSmalZb4FTyDD57/ O+hdIVhvvx84Xwf7Kf7/d++TJ/QRH+AQ8bbKspTpAX2cDQrt9hNa3MhWKmxgf2SpQTKR Z818Xh0tZ6mHzk4bx04Uy0hDLFTWqscAOVpidMzRQe4CD9QgghEmlk3q3gkfNAvjiUa3 fRo4jr6FJQgcR13WJ96ESj+KWFF5OUuMSZJSx2+35oijgvcczlFVZRcy+04AgvCRPy2E 4heCjNZy9IZ+3tPI9dOV93Zfb2GY3VK0tLIKbCD4HN61s9HLPbnWPe2360TRkOlWqp0v bwUw== X-Gm-Message-State: AOJu0YxhplzSolfDPVZeS7b1vcjttbGlhmKPdme6izopCA5rNvALnFSo 9T6H4e1GBTa4ny7TbyPHks4j2OvS2Wvm9veQ9mAmo/mHWNe+svafdtVmhqdhcSh4wInuxwj4FZQ E8Eowpl4d51eJLyk3kUw9RsqT2b7Wu1SBhTUqRGzb4JBHOA2BeBnvVhAAjg4kDZ5TCZz5yhUDhR Mb2i9RlA2McGKw X-Received: by 2002:a17:907:76d3:b0:a59:c7d7:8b0f with SMTP id a640c23a62f3a-a5a2d57a717mr1266141666b.29.1715932694057; Fri, 17 May 2024 00:58:14 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHdsUK/6wF3V6zg9X/e6i01zPdBLC7yDC9h39HUcNTqiLMQ3CKMlTvTGMlHuloIZtyCC2UpPg== X-Received: by 2002:a17:907:76d3:b0:a59:c7d7:8b0f with SMTP id a640c23a62f3a-a5a2d57a717mr1266141066b.29.1715932693734; Fri, 17 May 2024 00:58:13 -0700 (PDT) Received: from localhost.localdomain ([2001:67c:1562:8007::aac:4795]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a5a17b179f1sm1080016966b.212.2024.05.17.00.58.12 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 May 2024 00:58:12 -0700 (PDT) From: Yuxuan Luo To: kernel-team@lists.ubuntu.com Subject: [PATCH 08/15] x86/bhi: Mitigate KVM by default Date: Fri, 17 May 2024 03:57:21 -0400 Message-Id: <20240517075728.9722-9-yuxuan.luo@canonical.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240517075728.9722-1-yuxuan.luo@canonical.com> References: <20240517075728.9722-1-yuxuan.luo@canonical.com> MIME-Version: 1.0 X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.20 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: "kernel-team" From: Pawan Gupta BHI mitigation mode spectre_bhi=auto does not deploy the software mitigation by default. In a cloud environment, it is a likely scenario where userspace is trusted but the guests are not trusted. Deploying system wide mitigation in such cases is not desirable. Update the auto mode to unconditionally mitigate against malicious guests. Deploy the software sequence at VMexit in auto mode also, when hardware mitigation is not available. Unlike the force =on mode, software sequence is not deployed at syscalls in auto mode. Suggested-by: Alexandre Chartre Signed-off-by: Pawan Gupta Signed-off-by: Daniel Sneddon Signed-off-by: Thomas Gleixner Reviewed-by: Alexandre Chartre Reviewed-by: Josh Poimboeuf (cherry picked from commit 95a6ccbdc7199a14b71ad8901cb788ba7fb5167b) CVE-2024-2201 Signed-off-by: Yuxuan Luo --- Documentation/admin-guide/hw-vuln/spectre.rst | 7 +++++-- Documentation/admin-guide/kernel-parameters.txt | 5 +++-- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/include/asm/nospec-branch.h | 5 +++++ arch/x86/kernel/cpu/bugs.c | 9 ++++++++- arch/x86/kvm/vmx/vmenter.S | 2 +- 6 files changed, 23 insertions(+), 6 deletions(-) diff --git a/Documentation/admin-guide/hw-vuln/spectre.rst b/Documentation/admin-guide/hw-vuln/spectre.rst index 1cf9356bbfe28..8e003eb6ac0fd 100644 --- a/Documentation/admin-guide/hw-vuln/spectre.rst +++ b/Documentation/admin-guide/hw-vuln/spectre.rst @@ -439,10 +439,12 @@ The possible values in this file are: - System is protected by retpoline * - BHI: BHI_DIS_S - System is protected by BHI_DIS_S - * - BHI: SW loop + * - BHI: SW loop; KVM SW loop - System is protected by software clearing sequence * - BHI: Syscall hardening - Syscalls are hardened against BHI + * - BHI: Syscall hardening; KVM: SW loop + - System is protected from userspace attacks by syscall hardening; KVM is protected by software clearing sequence Full mitigation might require a microcode update from the CPU vendor. When the necessary microcode is not available, the kernel will @@ -711,7 +713,8 @@ For user space mitigation: unconditionally disable. auto enable if hardware mitigation - control(BHI_DIS_S) is available. + control(BHI_DIS_S) is available, otherwise + enable alternate mitigation in KVM. For spectre_v2_user see Documentation/admin-guide/kernel-parameters.txt diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index c97f8435f86c7..9b38050fdf5f0 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4613,8 +4613,9 @@ on - unconditionally enable. off - unconditionally disable. - auto - (default) enable only if hardware mitigation - control(BHI_DIS_S) is available. + auto - (default) enable hardware mitigation + (BHI_DIS_S) if available, otherwise enable + alternate mitigation in KVM. spectre_v2= [X86] Control mitigation of Spectre variant 2 (indirect branch speculation) vulnerability. diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 2e823723c2b42..9db06d306f5d7 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -391,6 +391,7 @@ #define X86_FEATURE_CLEAR_BHB_LOOP (21*32+ 1) /* "" Clear branch history at syscall entry using SW loop */ #define X86_FEATURE_BHI_CTRL (21*32+ 2) /* "" BHI_DIS_S HW control available */ #define X86_FEATURE_CLEAR_BHB_HW (21*32+ 3) /* "" BHI_DIS_S HW control enabled */ +#define X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT (21*32+ 4) /* "" Clear branch history at vmexit using SW loop */ /* * BUG word(s) diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index d6824fb49080d..6ba7faf8b938c 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -179,8 +179,13 @@ .macro CLEAR_BRANCH_HISTORY ALTERNATIVE "", "call clear_bhb_loop", X86_FEATURE_CLEAR_BHB_LOOP .endm + +.macro CLEAR_BRANCH_HISTORY_VMEXIT + ALTERNATIVE "", "call clear_bhb_loop", X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT +.endm #else #define CLEAR_BRANCH_HISTORY +#define CLEAR_BRANCH_HISTORY_VMEXIT #endif #else /* __ASSEMBLY__ */ diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index b43c29c3f0a72..cd69490b65722 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1428,9 +1428,14 @@ static void __init bhi_select_mitigation(void) if (!IS_ENABLED(CONFIG_X86_64)) return; + /* Mitigate KVM by default */ + setup_force_cpu_cap(X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT); + pr_info("Spectre BHI mitigation: SW BHB clearing on vm exit\n"); + if (bhi_mitigation == BHI_MITIGATION_AUTO) return; + /* Mitigate syscalls when the mitigation is forced =on */ setup_force_cpu_cap(X86_FEATURE_CLEAR_BHB_LOOP); pr_info("Spectre BHI mitigation: SW BHB clearing on syscall\n"); } @@ -2349,10 +2354,12 @@ static const char * const spectre_bhi_state(void) else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_HW)) return "; BHI: BHI_DIS_S"; else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_LOOP)) - return "; BHI: SW loop"; + return "; BHI: SW loop, KVM: SW loop"; else if (boot_cpu_has(X86_FEATURE_RETPOLINE) && !(x86_read_arch_cap_msr() & ARCH_CAP_RRSBA)) return "; BHI: Retpoline"; + else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT)) + return "; BHI: Syscall hardening, KVM: SW loop"; return "; BHI: Vulnerable (Syscall hardening enabled)"; } diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S index 8cbebde85a4f6..15737a22d67f7 100644 --- a/arch/x86/kvm/vmx/vmenter.S +++ b/arch/x86/kvm/vmx/vmenter.S @@ -198,7 +198,7 @@ SYM_INNER_LABEL(vmx_vmexit, SYM_L_GLOBAL) call vmx_spec_ctrl_restore_host - CLEAR_BRANCH_HISTORY + CLEAR_BRANCH_HISTORY_VMEXIT /* Put return value in AX */ mov %_ASM_BX, %_ASM_AX