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client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by MWH0EPF000A6731.mail.protection.outlook.com (10.167.249.23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.9052.8 via Frontend Transport; Tue, 19 Aug 2025 19:22:19 +0000 Received: from tiny.amd.com (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Tue, 19 Aug 2025 14:22:18 -0500 From: David Kaplan To: Thomas Gleixner , Borislav Petkov , Peter Zijlstra , Josh Poimboeuf , Pawan Gupta , Ingo Molnar , Dave Hansen , , "H . Peter Anvin" CC: Subject: [PATCH v2 4/5] x86/bugs: Add attack vector controls for SSB Date: Tue, 19 Aug 2025 14:21:59 -0500 Message-ID: <20250819192200.2003074-5-david.kaplan@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250819192200.2003074-1-david.kaplan@amd.com> References: <20250819192200.2003074-1-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: SATLEXMB03.amd.com (10.181.40.144) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MWH0EPF000A6731:EE_|MN2PR12MB4094:EE_ X-MS-Office365-Filtering-Correlation-Id: ab3973f0-f132-44fd-8b7f-08dddf55b712 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|82310400026|1800799024|376014|7416014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?EwjxU9QWZ1u+tCmrrbhirk/lHXtEa1y8NVmbUyS5NK75Fcyx19ZUc1vCZKHO?= =?us-ascii?Q?xyOHzQnVaD2j9xmCXLwU3PjlIOKnUY7QDWrS7DNRV5gsU9w3PXhfygklFUrt?= =?us-ascii?Q?P6z7aJBXTNhje/NcVKPyA1rfpUt3Mt/eDdWftZZxcxgkoy4vmWAVmxQvzRVs?= =?us-ascii?Q?ol9gB9x488Re3U4xup6J0VpApIdAjWzhzJaJJMY6mU7TEYYc57MMRBgjJE2W?= =?us-ascii?Q?0FBh1MmAx1tnvtQBp3/JW1okyhGajotHJGjGAxJD1bHpR8wYfXnipnI0W7Wk?= =?us-ascii?Q?eNvx4pncKfuXq9xdiz5ZtnX393vF+jxS7YV/4QcBxz1dO5Dg77avTHSNrOn5?= =?us-ascii?Q?ZFA/lVl8FkeDoHevqujwKBmvBlfW66HN7INLngULx1IpENQdkF+Jh8sWa6+2?= =?us-ascii?Q?Jvp0MhcYKMd5KboCG3N7FlsoMdQ714ocge+NlomM5R11qOLe8GJrZkBeuOWk?= =?us-ascii?Q?a2dUJdCALKB0x9QJIkH7RRP+LNG7O9XPaDTgN3Qu5mPl1uGoFMLF24ZE9WFt?= =?us-ascii?Q?U4SQbkDIYRb9OkAF3ULqxlZUTjksbNGL4Y9QZxKMz0q36HJ0qGnVh55ckiOK?= =?us-ascii?Q?119jJRlFC1sLF2JXBqEMyJ6/xyYhocrJJslRufgJUC8IQ1L1VJdkR+I0fs8w?= =?us-ascii?Q?hMvAbtO9dbhNciPuICMw2+x149oYMx9lhhXvFtzGuUsp3Fyxwv4BAZmtTzmD?= =?us-ascii?Q?CxdATf+SLMZXx7msft6vQx7HktINLbrZ5qcN8Sd9hu7bktBeuLeD+YywASut?= =?us-ascii?Q?T2nYf9w8vrQ9gD959oSRPcDAQ/qT59InWz5blmXdNeleCuv5/1q4Y/thNyS6?= =?us-ascii?Q?1Ng/JrlEGhnQlAwcS6pSfVOtUChBSmomWfKaFmS+3io1+K0D+W+0Nr/3C5eU?= =?us-ascii?Q?tQTymeNAwOIVRQ3Hjx8bKv1ezdsyps4yyaMf3ivln72DLdTPW2W/W3xPtrho?= =?us-ascii?Q?C1nFcaPcV07mN/xdY6KjhJ0vlH4wh0cSrd3mqrA2NL/6BYwdTM33cH3gjvhh?= =?us-ascii?Q?uO+Ips9mI7+s8vXxMs1CnBsxtwe5AhGAreddcxGQebXXxSMILKo0uOW2CnrF?= =?us-ascii?Q?bABDZpJu5IFmPdh7wJTLpR1vJeCrDuBomzVL75UlK5R8yTFhPXAe+XO3krs6?= =?us-ascii?Q?gIy097Yid8BUYJ+N3AJ9J8XTFdla2d3helHeZM8qT292UFhpJpAY2MC2B+RV?= =?us-ascii?Q?UOSh7tQo/bqIA9NK0w2j6oMU1YqCFOrRVBc4WOFZVDPv+S23vmcHZMMxy9oh?= =?us-ascii?Q?jZawIn03O14Et22lTfmcUKnwM6a1VWlC9yecnAK7E4WqrP/E3cxwcACWGjFq?= =?us-ascii?Q?xYtf5Oc/0f8+bYPrlDVjbofRuELsA+K990LISKi1Lx69wpXYkHRi+KsvypJs?= =?us-ascii?Q?xBINv1O8gfBIz9K/PbwRrhLuwVZIXVv4VVnQiCDdzLWDLJQWTNN2ckRr8R4Y?= =?us-ascii?Q?fMK4ednRaikrdkgtR5jnLJ8bn3FqK18z5sH1RAfD4mrXc4PdWS/ieggrnVh1?= =?us-ascii?Q?zz7VacQr6SSV0zpMqXAnBZlJ8qZha06kpAgc?= 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)(36860700013)(82310400026)(1800799024)(376014)(7416014);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Aug 2025 19:22:19.1799 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: ab3973f0-f132-44fd-8b7f-08dddf55b712 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: MWH0EPF000A6731.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR12MB4094 Content-Type: text/plain; charset="utf-8" Attack vector controls for SSB were missed in the initial attack vector series. The default mitigation for SSB requires user-space opt-in so it is only relevant for user->user attacks. Add an AUTO mitigation for SSB and use this attack vector control to select the SSB mitigation. Signed-off-by: David Kaplan Reviewed-by: Pawan Gupta --- .../hw-vuln/attack_vector_controls.rst | 5 +---- arch/x86/include/asm/nospec-branch.h | 1 + arch/x86/kernel/cpu/bugs.c | 18 +++++++++++++++--- 3 files changed, 17 insertions(+), 7 deletions(-) diff --git a/Documentation/admin-guide/hw-vuln/attack_vector_controls.rst b= /Documentation/admin-guide/hw-vuln/attack_vector_controls.rst index 6dd0800146f6..5964901d66e3 100644 --- a/Documentation/admin-guide/hw-vuln/attack_vector_controls.rst +++ b/Documentation/admin-guide/hw-vuln/attack_vector_controls.rst @@ -215,7 +215,7 @@ Spectre_v2 X X Spectre_v2_user X X = * (Note 1) SRBDS X X X X SRSO X X X X -SSB = (Note 4) +SSB X TAA X X X X = * (Note 2) TSA X X X X =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D @@ -229,9 +229,6 @@ Notes: 3 -- Disables SMT if cross-thread mitigations are fully enabled, the C= PU is vulnerable, and STIBP is not supported =20 - 4 -- Speculative store bypass is always enabled by default (no kernel - mitigation applied) unless overridden with spec_store_bypass_disable op= tion - When an attack-vector is disabled, all mitigations for the vulnerabilities listed in the above table are disabled, unless mitigation is required for a different enabled attack-vector or a mitigation is explicitly selected via= a diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/no= spec-branch.h index 10f261678749..e263c126723a 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -514,6 +514,7 @@ enum spectre_v2_user_mitigation { /* The Speculative Store Bypass disable variants */ enum ssb_mitigation { SPEC_STORE_BYPASS_NONE, + SPEC_STORE_BYPASS_AUTO, SPEC_STORE_BYPASS_DISABLE, SPEC_STORE_BYPASS_PRCTL, SPEC_STORE_BYPASS_SECCOMP, diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 8dc654ccdbb9..059269f3f56f 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -416,6 +416,10 @@ static bool __init should_mitigate_vuln(unsigned int b= ug) cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER) || cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST) || (smt_mitigations !=3D SMT_MITIGATIONS_OFF); + + case X86_BUG_SPEC_STORE_BYPASS: + return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER); + default: WARN(1, "Unknown bug %x\n", bug); return false; @@ -2595,7 +2599,7 @@ void cpu_bugs_smt_update(void) #define pr_fmt(fmt) "Speculative Store Bypass: " fmt =20 static enum ssb_mitigation ssb_mode __ro_after_init =3D - IS_ENABLED(CONFIG_MITIGATION_SSB) ? SPEC_STORE_BYPASS_PRCTL : SPEC_STORE_= BYPASS_NONE; + IS_ENABLED(CONFIG_MITIGATION_SSB) ? SPEC_STORE_BYPASS_AUTO : SPEC_STORE_B= YPASS_NONE; =20 static const char * const ssb_strings[] =3D { [SPEC_STORE_BYPASS_NONE] =3D "Vulnerable", @@ -2626,7 +2630,7 @@ static int __init ssb_parse_cmdline(char *str) return 0; =20 if (!strcmp(str, "auto")) - ssb_mode =3D SPEC_STORE_BYPASS_PRCTL; + ssb_mode =3D SPEC_STORE_BYPASS_AUTO; else if (!strcmp(str, "on")) ssb_mode =3D SPEC_STORE_BYPASS_DISABLE; else if (!strcmp(str, "off")) @@ -2646,11 +2650,18 @@ early_param("spec_store_bypass_disable", ssb_parse_= cmdline); =20 static void __init ssb_select_mitigation(void) { - if (!boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS) || cpu_mitigations_off()= ) { + if (!boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS)) { ssb_mode =3D SPEC_STORE_BYPASS_NONE; return; } =20 + if (ssb_mode =3D=3D SPEC_STORE_BYPASS_AUTO) { + if (should_mitigate_vuln(X86_BUG_SPEC_STORE_BYPASS)) + ssb_mode =3D SPEC_STORE_BYPASS_PRCTL; + else + ssb_mode =3D SPEC_STORE_BYPASS_NONE; + } + if (!boot_cpu_has(X86_FEATURE_SSBD)) ssb_mode =3D SPEC_STORE_BYPASS_NONE; =20 @@ -2870,6 +2881,7 @@ static int ssb_prctl_get(struct task_struct *task) return PR_SPEC_DISABLE; case SPEC_STORE_BYPASS_SECCOMP: case SPEC_STORE_BYPASS_PRCTL: + case SPEC_STORE_BYPASS_AUTO: if (task_spec_ssb_force_disable(task)) return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE; if (task_spec_ssb_noexec(task)) --=20 2.34.1