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Mon, 9 Feb 2026 22:46:26 -0800 From: Gal Pressman To: Sean Christopherson , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , , "H. Peter Anvin" , Naveen N Rao , , CC: Gal Pressman , Dragos Tatulea Subject: [PATCH 2/2] KVM: x86/mmu: Fix UBSAN warning when reading nx_huge_pages parameter Date: Tue, 10 Feb 2026 08:46:21 +0200 Message-ID: <20260210064621.1902269-3-gal@nvidia.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260210064621.1902269-1-gal@nvidia.com> References: <20260210064621.1902269-1-gal@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH2PEPF00000147:EE_|MW6PR12MB8867:EE_ X-MS-Office365-Filtering-Correlation-Id: 98824655-f9d3-4fa1-f7fe-08de6870291c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|376014|7416014|1800799024|36860700013|921020; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?ICe/+cmB4UFL/Sif3iuTQx8SrfX84+u28QpIdFwmmcaiEEyZ20xrFg6Jmy95?= =?us-ascii?Q?hMST8RIGXyHOAY9YANYUcLADpMxsThhIhu1MYK/ZR5uRwVfyrM3nFSEUv9wq?= =?us-ascii?Q?x4PxwfMWmr/1Q2f/dHI9MBFgmMAc47DwU9cE1QKSYNePvNmrtAK2boMSzFG1?= =?us-ascii?Q?uzcA93wW5/QWdyNZM/jPLnDVBfjwJZHkYU4OtR9brHv75uQ2jWeuiz9yuMn4?= =?us-ascii?Q?OScwywshjn2yDNr9zNUoOVx4ETx5Had0hIWM9TcN3QaG/pR2ffKfy0bHSTkG?= =?us-ascii?Q?rsF3R6JRFAL8cP9lAwn+GKpsDJV6qfuXooFmE9M1/h2Mct8V68CvY7IJqpn3?= =?us-ascii?Q?Pc/gs8nYp7VFSnQ4LP2AxV45JwObGJzgyAYRyg5uvC5M969hm85tTw1A9un9?= =?us-ascii?Q?YYJhItND0rZQTVFegj69FmQHgahoW8is7FCVaLgSjMKG4LlTEadFyMj+OWm8?= =?us-ascii?Q?7+UdhobSP/0XZtvtAb018bHz/IKaJv7WrUlVYmxD99YgCbLaJwH5T//N8Bqh?= =?us-ascii?Q?1TMkqOoNsjc5h/aZbU11GUuIzsV8HP4fDTax+4MFOuODj0KErfPeFTpufjNw?= =?us-ascii?Q?G8R0V6bF6zC0tDfoZBpBRGNwe7w4f5h5xLMGgkg0dYa3/wqOaBXUyCivaSLu?= =?us-ascii?Q?WZab6d7GTM9OYkVmhGnriqtjs7QBxyQIsCzhY/R2cCimvH4WpvLk4JLNH78o?= =?us-ascii?Q?hIeNqYGskQ6/Fl31QyToGIib3M+FnX5YrFbSj7+jo8G+KnWQxWNTKbC56KPA?= =?us-ascii?Q?ifgiJKlR5J/YeV5gzIw2YwtQGXMb1o0JA93qsNsjQU6X/jKv/zO0nTh/swF2?= =?us-ascii?Q?FLN+CG7yzyModAVCDUUe+22AZPtEHa0XqQqgVxJ4pXleAt/DDaTGszMCNdip?= =?us-ascii?Q?g1XVBOj9pbdhoa835LZd0JLbJ9c1xpOY2FqFzUAZCzebJ+oTvVM+rXRTZ4Rq?= =?us-ascii?Q?RhaPB1FScSsAdbhowGwh85mbza5+TW5hCfHbVkrazAaruVHky6tSeiaY3XJ7?= =?us-ascii?Q?HkYDDBff+r2jDbYuguYf+3ewC8g8d7Y6fKNJ/6MrxxAnizgzJjI8kXSLpwtG?= =?us-ascii?Q?WQHo483TtvPOadK+Bbh8Cu5B9P1lLjvZSsLUf2PB4X/KtryWHfDFiyWDTa6K?= =?us-ascii?Q?9kvK6CKAwVHmRci6Bp9hNzAsewM2ZWAXNbOv2OCA9l/yBmUpel/JMAB2Ha5S?= =?us-ascii?Q?Ymeegb26PSil6e23wkQm04wpqL/JuIkVBSVTLhpMOWjwTVYlLEWGHTfZjFap?= =?us-ascii?Q?VcuGuuUCZW1x0x2UYSe4Fv7Lo8bQXNeLYUSH1lZe0Ed+H+aBzbVX9eAQZmBA?= =?us-ascii?Q?2dV/YGc5i8J5oFP08RpNhxiXwKoof2+IuojLdxxKQml3nALKkXIN0gWW7yNw?= =?us-ascii?Q?uwW5P8cCqtJH/Wo4KUyqZr6496H11SIKQNvctvw3cGSpJnq9DNFkW0jabE+j?= =?us-ascii?Q?IPIa6xQyrup7Pv92yJcj7nd6okdu3+ZyJn3PJttX5ticciOcGJERC0HSC7L8?= =?us-ascii?Q?mJ5W3iSy5ZuczmmJhVQPSWczRG4dRzUyW5goFwWiaSd0zvZ0Zw0ZOtCWLlvq?= =?us-ascii?Q?WtGN8Mmex67vRqGX2pTzDaq/83vFJf2kbz0Sdmlvq9bksKQhhNc26k2jPNAe?= =?us-ascii?Q?CIqQxPX3WZac1DoGCYWpBFViQn5zUupTIJUrf834q4J0cy7FAV/XErDUeuUZ?= =?us-ascii?Q?833m7pj7W/ueRCR3IMCiVcdpa8k=3D?= X-Forefront-Antispam-Report: CIP:216.228.117.160;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge1.nvidia.com;CAT:NONE;SFS:(13230040)(82310400026)(376014)(7416014)(1800799024)(36860700013)(921020);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: pVTao3qzfGl2pz4YU/3b5WeF/TxBboCjQmaqO7BEtxi5TSJNxhQCuZgDyBtbVYd0tt3nI26rfSlCGMJTbZo5H613qzaEqUv+hYk5mlA3gQdw6NSlJOWdsLgirdhUA3KcW/dY0V3e8Nnf0i8addwwEYW4FTv0sQTqf7ZslATKbpsPjShMyDlvidjyDPwYMuahOSiB3eYGsvd/Ogan7Q5Tw77QkbPM/HSoUnzHlBwjF/WNwpO7AqtpH72Hz/kE+E7zAE7km2UonTNdNaZrrCbXYH8zwXC93WznWsYwR+lKIBkL8353nFj4BQ0gLnBqqCSLyEm3I6ymGZ3dCtlGAY/B4VZjb087j7o7B4SwC0x0/frmvEVJyNn4CMciNYRm69gJx7EydGd5KHNo2lWqdDanQkhyV5sOS0EbzeELKzDg9PE+/QZ3uDdhfI7qMbAUU43S X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Feb 2026 06:46:46.6977 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 98824655-f9d3-4fa1-f7fe-08de6870291c X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CH2PEPF00000147.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW6PR12MB8867 The nx_huge_pages parameter is stored as an int (initialized to -1 to indicate auto mode), but get_nx_huge_pages() calls param_get_bool() which expects a bool pointer. This causes UBSAN to report "load of value 255 is not a valid value for type '_Bool'" when the parameter is read via sysfs during a narrow time window. The issue occurs during module load: the module parameter is registered and its sysfs file becomes readable before the kvm_mmu_x86_module_init() function runs: 1. Module load begins, static variable initialized to -1 2. mod_sysfs_setup() creates /sys/module/kvm/parameters/nx_huge_pages 3. (Parameter readable, value = -1) 4. do_init_module() runs kvm_x86_init() 5. kvm_mmu_x86_module_init() resolves -1 to bool If userspace (e.g., sos report) reads the parameter during step 3, param_get_bool() dereferences the int as a bool, triggering the UBSAN warning. Fix that by properly reading and converting the -1 value into an 'auto' string. Fixes: b8e8c8303ff2 ("kvm: mmu: ITLB_MULTIHIT mitigation") Reviewed-by: Dragos Tatulea Signed-off-by: Gal Pressman --- arch/x86/kvm/mmu/mmu.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 02c450686b4a..3644d1db8be1 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -7488,9 +7488,14 @@ static void kvm_wake_nx_recovery_thread(struct kvm *kvm) static int get_nx_huge_pages(char *buffer, const struct kernel_param *kp) { + int val = *(int *)kp->arg; + if (nx_hugepage_mitigation_hard_disabled) return sysfs_emit(buffer, "never\n"); + if (val == -1) + return sysfs_emit(buffer, "auto\n"); + return param_get_bool(buffer, kp); } -- 2.52.0