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Peter Anvin" CC: Subject: [PATCH v6 04/21] x86/bugs: Define attack vectors relevant for each bug Date: Mon, 7 Jul 2025 13:32:59 -0500 Message-ID: <20250707183316.1349127-5-david.kaplan@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250707183316.1349127-1-david.kaplan@amd.com> References: <20250707183316.1349127-1-david.kaplan@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: SATLEXMB04.amd.com (10.181.40.145) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MWH0EPF000989E8:EE_|MN0PR12MB5739:EE_ X-MS-Office365-Filtering-Correlation-Id: a69d3de9-39c4-4232-337e-08ddbd84c7b5 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|36860700013|7416014|376014|82310400026; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?eq+suB+uSSmspch/90Dlu7G3KIngJd4HCLHnsp6MHyTjciEHvPuLZz/NotEQ?= =?us-ascii?Q?sdX5wqmtolvCu2meeamL+3tLeyMSiFOLqhpIOqJ1Hnjy9xITh6xoXTdBsekD?= =?us-ascii?Q?i+FlxgD9Y7/Pqaqm8qwVEi/sSC1No0pzZpTifWswTK9NbQ+xoTf0YqUUhQ7V?= =?us-ascii?Q?R21QkEmrJ2bYV2fJEhPVME+NXYIgp9GNYoXFNj2vX+6sA2wJmSTqnlEp5cyp?= =?us-ascii?Q?qEmvfgWASXXrOtSWYLhzsuL0IK2OqQgfHHyyzolAo6pmfZrYZ3W1pdqWXx57?= =?us-ascii?Q?Mzi10IAnUZKVz7vGJV/CoS6DMWwgbj2U431vbG69Ei+xMbmlpDI5FM2DSor2?= =?us-ascii?Q?qQ9lEd7K17oevNmPuk+c56+Os+cwqCD9/6kNKmbc39I6EfQ6iBI+TPQDmbvX?= =?us-ascii?Q?Ypb8poqLPKq2qrSAEa6tlVUAmnhALWs9CikrzDokkOc7XE8Ea7H32THOB+yp?= =?us-ascii?Q?5LEgj8elQuk1T6i1X1duDh8QsxaIAPHbu02fX6vJqs9ilP1eiMVnmlUt0TZU?= =?us-ascii?Q?leaMTvg7/baJwijAo5uqceNi4vOWEp4x/sidl8jOC9NYdg2Yam+9ejXPSkQ2?= =?us-ascii?Q?Kh9n5iXma3wplZCDv4lS4aFSeaM028bo4b2rzXqxEfhW9vkocCT8Ie/8g/Ee?= =?us-ascii?Q?JTAJY7dT92DiJD9Qs891wAwXhHWZjtftYAvK1UmvLyxNPl00CXFkPjuooTfo?= =?us-ascii?Q?mq34+/6PSaIDmz0z7Y8LTh1mkn5h+/sXIStuw6Vxm+Cs+KFFpdHkx5ybng7v?= =?us-ascii?Q?A/qNBj/5wh1UFfDsWj564HyjkpBw9YPUL5tELaFXJY8gL+iXt4YHIbHKip7V?= =?us-ascii?Q?dnl4um1or8+e/9PSaDHi8nY7CfnKKfBKMIG7L9vQrVNfKeQvo4ivvvhxwUx/?= =?us-ascii?Q?1LSuY+t8eYL+QnPUE5Q3F7sPCIDXeBgOTZYXpTpIprkWRdFwEYGrfnWWf56f?= =?us-ascii?Q?4vXMx4GjoztD0mrn5nsb3FnVnxCJe9hpprswacEhsiYDI4qiJS9QoiyNDTxj?= =?us-ascii?Q?Ppxo12pfyuGggpi9MWgBED6z/8U57KlbXp4lDR5KCmp8s8AcAauuULh1tNjS?= =?us-ascii?Q?Pgf5M3WLydxoXl4fC0n2t0OD0NglSI2k7FA5PV1i+5ztT6fAOfsQIsMwyt86?= =?us-ascii?Q?gsar+chVNrRgacV8ru8N8la12ypZ51rEFRfBsFkWdjfC0cPI6pxM8MlD0Pwa?= =?us-ascii?Q?veQNm9F9Qifkp1DXjF3I0Kj80kytLDK8B7dgndT52iq9KNKNzv+m/BsXPCed?= =?us-ascii?Q?b0QG9jt2+Qxznb55rtrrlmy9nTmExT5c4T+QHYvRTq1+alAz/4lm7MD5zIEK?= =?us-ascii?Q?yn8MSQp2EqAWILouMgOxsRyL8psKaQ5ghIrvj8BhbhqUa6X+ei6dvSw962gY?= =?us-ascii?Q?M8drexi7BqlVu9D4xV6PWlfT6RlKsSLqmp4nz+fVdRzlJG+m32nE0ViRsMOF?= =?us-ascii?Q?5gnGMPlQW5hxDc3x0QdxHB8r2fx8nhb5jd+wTBbHs9IL6i+4RkkksHPVm+iB?= =?us-ascii?Q?Q1RBqqVxSxSEbf66YoRPd1Es+NHdopR5wZ6k?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(1800799024)(36860700013)(7416014)(376014)(82310400026);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Jul 2025 18:33:33.9002 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a69d3de9-39c4-4232-337e-08ddbd84c7b5 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: MWH0EPF000989E8.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN0PR12MB5739 Content-Type: text/plain; charset="utf-8" Add a function which defines which vulnerabilities should be mitigated based on the selected attack vector controls. The selections here are based on the individual characteristics of each vulnerability. Signed-off-by: David Kaplan --- arch/x86/kernel/cpu/bugs.c | 56 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 56 insertions(+) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index e2a8a21efb10..1fa0704a8694 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -328,6 +328,62 @@ static void x86_amd_ssb_disable(void) #undef pr_fmt #define pr_fmt(fmt) "MDS: " fmt =20 +/* + * Returns true if vulnerability should be mitigated based on the + * selected attack vector controls. + * + * See Documentation/admin-guide/hw-vuln/attack_vector_controls.rst + */ +static bool __init should_mitigate_vuln(unsigned int bug) +{ + switch (bug) { + /* + * The only runtime-selected spectre_v1 mitigations in the kernel are + * related to SWAPGS protection on kernel entry. Therefore, protection + * is only required for the user->kernel attack vector. + */ + case X86_BUG_SPECTRE_V1: + return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL); + + case X86_BUG_SPECTRE_V2: + case X86_BUG_RETBLEED: + case X86_BUG_SRSO: + case X86_BUG_L1TF: + case X86_BUG_ITS: + return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL) || + cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST); + + case X86_BUG_SPECTRE_V2_USER: + return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER) || + cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST); + + /* + * All the vulnerabilities below allow potentially leaking data + * across address spaces. Therefore, mitigation is required for + * any of these 4 attack vectors. + */ + case X86_BUG_MDS: + case X86_BUG_TAA: + case X86_BUG_MMIO_STALE_DATA: + case X86_BUG_RFDS: + case X86_BUG_SRBDS: + return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL) || + cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST) || + cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER) || + cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST); + + case X86_BUG_GDS: + return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL) || + cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST) || + cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER) || + cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST) || + (smt_mitigations !=3D SMT_MITIGATIONS_OFF); + default: + WARN(1, "Unknown bug %x\n", bug); + return false; + } +} + /* Default mitigation for MDS-affected CPUs */ static enum mds_mitigations mds_mitigation __ro_after_init =3D IS_ENABLED(CONFIG_MITIGATION_MDS) ? MDS_MITIGATION_AUTO : MDS_MITIGATION_= OFF; --=20 2.34.1