From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from SJ2PR03CU001.outbound.protection.outlook.com (mail-westusazon11012053.outbound.protection.outlook.com [52.101.43.53]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 899C62957CD; Sat, 8 Nov 2025 02:40:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.43.53 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762569605; cv=fail; b=C0aOlkJVZy7yX8Lm7BFQGBDmHcHvjcdKRG6u4Y9H5sfiqzylT73We7um3Pjr/FOqjTObVq34ktftI87f/jHsxvFouVtUUMd+6cs4fig42ezPp1+6312L4v3WkX4FIsKBRz9y5JE48yjw+o/ey3eXSmu5VlH+OqPhu14xuz3Ipk4= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762569605; c=relaxed/simple; bh=pTKbPlZKJasDDqKlh5+zuTihMtqixzVev85cj6UHhcU=; h=Message-ID:Date:Subject:To:Cc:References:From:In-Reply-To: Content-Type:MIME-Version; b=UV2Spl+UDMNlfiMl0DCZWZ6dQ/bfq+/WAB6JJ4qcnhqC/b4NSlmZdoRKMIObSYVIPqRrCOmZqCxAu1xJrBiEkPU5jyYkYA28Cfcq0YVVcudp15EH4o7w/hooXS3njZqOtntfrRl21atLEYuHWe8oqt3q1tgWoISImnsHMp/e99I= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com; spf=fail smtp.mailfrom=nvidia.com; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b=jSP5APgZ; arc=fail smtp.client-ip=52.101.43.53 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nvidia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b="jSP5APgZ" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=nQN5x3mAv5UuQkkyGW1MsgJHYviIWAh/k6CE1XtdfMf5p6ZCy39Mb+YXNXQyiWyPh0GNFkngEM4x3yGN2rNMp1vMfhkZLAvj3g7M6hUfWzLm+dcPhPrDTorkIgF3twzRpcJzO46uLsVNddV4RFWPU+et2mKDbYndSsBYyTDKLQNZhq6ow5DYGZeF8FK0Q43J6z0HjWJv6u4O1BvtUSfWcz/p62ysWI4WqmsSAbszFeonfaobjzC0HWYvEev7luztNY4RTOT2cLxo7J+/oq6+mdhjzoAsl/RD6ckSSeu7GthVaMqvQ5VLTF+wQDu/lKpUXhLuNnDOAPRUF0auI8LFXw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=IDkTjdjSm8Po1hq7peLxFx5fEGu8QvdP9C2dukiZRbc=; b=o9sbvrDDJDQj4zHBGFl22lCQ9ZsZiqdISL5A/YvUm4QjQVyYo3qeBK2C94NCsvoMbwgguyObOie2fGbtUbEoWggIbTT9F6F3uVjXZQqWQyHa/aDEUcht6L6EMSrU2/EDAp+g76h5jjELyusvQ9SO1OxmgPSMiEpNpXza0aGZclyUodjJnLiLrhWKp9arpJdJfZAlRctwDY/xTBEUYpyFhwT6r2OlX7pXl9EgvtJKzN1I9bt80W8EwTR88iEDh+Y/xKR9gWPbfAkbQZgjw32dfp9y7bmJp81bWvhcv3806w/1LwU9F2kp8lzRwTg/qwsboZbvzqwaK9u9VyMNK44sHQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=IDkTjdjSm8Po1hq7peLxFx5fEGu8QvdP9C2dukiZRbc=; b=jSP5APgZoo7of6k8Y2lJzwwPacIolqMdeknDPeYg3KFVdoQTQDMBzbj3WTzdHlmqPaWu1GOUckH2pPVZGbiYGQt4Fr/kcD8k5pKeFkUL9IUzXn477ZrksIexlrUCHMmLOUA7jlLBgIYY2dtZktu8t1lRBo3/kKEC97wofnb9QryOgKsHOPNDtxOUG+5LsA8b1kSg61Ubrdlr7V0DPdvTBg8erex2u1hzv6LGXoIFQz9QZt2NYtlr/ICbkSS7o7sJEVxscgwYlQ27Fz7/mfhhio1Z6RkncQuBkfdD6uglalKDXx9TQawM4Fyxp+ir4qw2tD0Y8z1pKr+QHdYZcjNMcw== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from PH8PR12MB7277.namprd12.prod.outlook.com (2603:10b6:510:223::13) by DM4PR12MB7669.namprd12.prod.outlook.com (2603:10b6:8:106::22) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9298.13; Sat, 8 Nov 2025 02:40:01 +0000 Received: from PH8PR12MB7277.namprd12.prod.outlook.com ([fe80::3a4:70ea:ff05:1251]) by PH8PR12MB7277.namprd12.prod.outlook.com ([fe80::3a4:70ea:ff05:1251%7]) with mapi id 15.20.9298.012; Sat, 8 Nov 2025 02:40:00 +0000 Message-ID: Date: Sat, 8 Nov 2025 13:39:54 +1100 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/kaslr: P2PDMA is one of a class of ZONE_DEVICE-KASLR collisions To: Dan Williams , dave.hansen@linux.intel.com, peterz@infradead.org Cc: linux-mm@kvack.org, linux-cxl@vger.kernel.org, linux-pci@vger.kernel.org, Ingo Molnar , Kees Cook , Bjorn Helgaas , Andy Lutomirski , Logan Gunthorpe , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "Yasunori Gotou (Fujitsu)" References: <20251108023215.2984031-1-dan.j.williams@intel.com> Content-Language: en-US From: Balbir Singh In-Reply-To: <20251108023215.2984031-1-dan.j.williams@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BY3PR05CA0008.namprd05.prod.outlook.com (2603:10b6:a03:254::13) To PH8PR12MB7277.namprd12.prod.outlook.com (2603:10b6:510:223::13) Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH8PR12MB7277:EE_|DM4PR12MB7669:EE_ X-MS-Office365-Filtering-Correlation-Id: d90039ec-6e7c-4c0e-0173-08de1e701ce7 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|7416014|376014|10070799003|1800799024|7053199007; X-Microsoft-Antispam-Message-Info: =?utf-8?B?QkxLYWM4NjZ1Z3NSTWt6MTdpNlRLZ3pmcjBFdCtOSGlGZjBmOHk0ZEl4MG94?= =?utf-8?B?dGdIaUx1RXJ1VEJjWU5IWnhGdXh2cndpNXdwL1d6SERlTjF3WnFsMXUrMTJW?= =?utf-8?B?djZKQ0ZOZmtINXpGVmxkRDNKQ05nMEJuRFNQMlorZE5UWnBJZlFKRExPZ09U?= =?utf-8?B?dDE4Vk1IWWdTTVQrTTcyZmlPa29zVzlUWUhBSWVVVVJOaldzNWp6TzhYWW5H?= =?utf-8?B?dWxJWm92Z2M4cVVQbEQyTktYMlRUQUhJV2x0QjVRQ0ZiRk44Q3MxN2l1ckEx?= =?utf-8?B?Q0xSbWp2S01OSHNITnQ1VlZsNFdVK0t1RTVPN0IvZi85aHR3NHJRdW8zY2l1?= =?utf-8?B?TkdPTmNQUFJ4Nm1hSzgyVGZuRjB6RWJUNjZHcmRtdGxxWktON3FocUNQcHdJ?= =?utf-8?B?dXFwYnZ0cUcvbUJ6R25BUE9NVG4yTVF6VGthcE5xVEJUekU5VDVWSUNOL1JD?= =?utf-8?B?cnViVzdCMVFNK01UdDZRVnpienFYU2xwcVFxcElWa2FUUkpUaGR5TE5sT2dO?= =?utf-8?B?TzI5Y0pnQlNHOUQrb2NFTkVoaTEwRHg1VUVYeWo4SExYK3hwaXoxSW9MZElR?= =?utf-8?B?VndBRkkzTThOdDNaZ1hIcVNTN0EzRnBjMmJHSkJ1UDBkT1I2V1pudllOSXEx?= =?utf-8?B?Y3ptdldzTFErcUdIUzJCVmFBN1MyM2lzZDdLSHlub1ZMWURkTEVDOUxmUFB5?= =?utf-8?B?UldReGp6OHVOWE00Y3V5WkpLcDRxVXI5dE1YbGxYMHJDaDNBOXU5eVdIOVZ3?= =?utf-8?B?cll4a1Q3WUhIMlRHTTV3WkhScWgrdGltZFBXUG9hYUtLRXN2UG02M3NEZmdS?= =?utf-8?B?T1ZxdGw2b0hOV3Z3MERwem42MlU0RHpBZHVoci9MdHB3TWlkSFRIVzE1NG1X?= =?utf-8?B?c2p4ZkRjNGVYdVdkVTYzK2IwUzljMVpvdDhuMDJjL1ZHU0Vac05pWmwvSmVo?= =?utf-8?B?SlBlcFRPVnFsR29JVlZnSEpJd09sMnFWUGJJNEdpZkx5dVhENXAvN0V4Z0VR?= =?utf-8?B?K1RrdlJQMTM4Y1JoSXhRVm1jZktCZFE5WFpaazB2V2c2dkhpZ01kWnh1R1VO?= =?utf-8?B?UzZOYXZyYnpyY3VHeWRpRW16VTUvYUVJNDhtSC9ySngrYWFYQk03RW5Benlq?= =?utf-8?B?WUdOdzIzWXdYc0xFTnhRVlh5WHZncGZNR1F0TWdwS0laQnp5bjVUdHlFWkpu?= =?utf-8?B?TmtxWHpJL0p0eE14U0ZyMEdXS2ZOMTdGeE8xRGJ6dys1VE5adFloS08zRzVn?= =?utf-8?B?WDdkZUw3QVRiUkhNdlQxOXZBNHhVV0lNZ0YyY3hvVmpXaVZHU3Qva0szK0FO?= =?utf-8?B?WXJvRDRza1hoRmdzeDRFb0szUndlazVrZWNMRExjanhYVEQxeXo5VFpDZThG?= =?utf-8?B?K2hRYVZDdGRSTWpTenFQOFZLR2hkZUc5UmJWdENCNFhHT092N2dNUHBLbEQw?= =?utf-8?B?dHVsZWxXWTRObllsZUlZclc1STR4WnExcm56TDR1VHI2UzFzRnN0eHF6NUZO?= =?utf-8?B?V0dKVHJpVmdVRVJ4QllTbTdOYjFQbFM0ZlY1cTV6dWcrTUxib2hjZjZ6SDJD?= =?utf-8?B?a1BPQVorZ1UxbEp2THZRSS8wWk9EYWF4aXZubldyaEhTeS9TUFZMYUh3eXRE?= =?utf-8?B?TDd5OUF3UUNCbFhLb0ZaSURGSC9vbDVTTWFOT1dPQjZKdy8wZEVLM0hDTC9Q?= =?utf-8?B?YS9Vai83a3ppWGFYbThUZkl2OE9GVGNGQWovRWdLdkZOZUpwYVpqWW11aEc2?= =?utf-8?B?bWFESFJQck9uZFF2TmxDbVZJYUZGUXdFcC9GMlYrTXdzQklJNFVaL0Ireklh?= =?utf-8?B?aW9yZHVDQkJ4cWN4YXhmY2JuK2dXOUhwQlF3eFZlUkxBaGpTMEIrUXRkSlJJ?= =?utf-8?B?akRuU2l6ZmlCNnhtdjNMSzRObklLSDdVWjk4elNwTmZVcEhHSm9pSnFEaXRr?= =?utf-8?Q?jtajltok8+LQxg0Ts04FtjKmaSF3fJXC?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:PH8PR12MB7277.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(7416014)(376014)(10070799003)(1800799024)(7053199007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?eGF0bWREUkZIMGQyZ1FDNGdhMWFCenVmSnlKNTZicCtXVHdRTXQ2VXRGN2t5?= =?utf-8?B?ejFyQk4yam9LMWhmMTR5UVJFUFViTmI2VEtJUmpqK09KbXl5K2FBNE13bEdq?= =?utf-8?B?WG5QS0dFMzlqZWNwT3ppVjlYUzArRjlqZk12Q1FaeHZCR3Y0Nzh3UENqaTJZ?= =?utf-8?B?K3ppaU5NSHo2UEFtNTI5azI2VHkyVHdoQUdpcERaM1lFRS9DMnpiSVlaeGlH?= =?utf-8?B?Z2w2QmhIbXVVTnowVGRQZnN3WURiZVVIRXVBeDYzcGhmSjEvZUREUWl4ZjBh?= =?utf-8?B?aU9KUmF4YWFxT2NPNUZxYjdYRHJOZmtNbkhsUkNLa1d6aXQ1SW1NODlMQmJx?= =?utf-8?B?STgwM2RpQUdrVEllblRWZ2haZHY2b3F0VUtMcHVzNVlTYStmVjh6Nm1Bajlu?= =?utf-8?B?WXdSKy9CbmI5RUl3ZXJWZjZXMEcyMU1pbjc0ZGx0TGs5SjJ0OXhpYXc2blZS?= =?utf-8?B?dDVjeXNIbURrYnhYdjRsQWhvNGVrOGRQK0NzZFNBbFVqN3lFUUF0QzBpY2hR?= =?utf-8?B?M2JockwvZ3NmR3JSQUZsSDFHMmlPWW0xYk03RDVKTjFjRy9lcU1oSlg5TVdx?= =?utf-8?B?cWp6UWJ1WEFRcmg5ODVCWkNVaEgrdDBsRVVWdFBtMituZ1JGY2NZSXZKMDRa?= =?utf-8?B?US9leDZ2OGIwbWI4Qkp0c1VsUnR0cmFYbEVGUVpKYUY3blYwb0gxL1pwUGJU?= =?utf-8?B?Y2ZodkppOWlCVGMwVVo1NW1RWk1zTG51UllZeVN2TmQ0YTk3SkxlSGhTQk5s?= =?utf-8?B?UGJmTUgvcDdZeFhFY0ZPV0RVNDFHQlRqK2FvK3R4UTRzYnBBV2czZGlLajhR?= =?utf-8?B?VDBybXhualUrQ3laSVhmSnMwYkZHWHVkWTlpbVpnS0NiNVVYVFNiZjJvUWd2?= =?utf-8?B?d2xkV2QyaCtSbXZweGZObzQyaGFxQ3NKa0poMERtSWR1bGYvWFExb2hRQXFu?= =?utf-8?B?d042UlA4RUdOY2RvRnBPeGtMSkJFcEJtbDhxS1dxRmJqY0hYWUJUUTdOV0xD?= =?utf-8?B?MEdkOXFuUm1BOWZVK2F0Vk5JM0d4elpXY1g4MWw1c0VmTFlmVndTSVZYV2N5?= =?utf-8?B?NDZwLzFHd29zM2ZITWcvd0krZUFSWjNOTXhGeHpwdjZGNjFyM0UvaDJyczFC?= =?utf-8?B?Y1dyRkJkeGUvVTd3ZFFSNXh4dG5sVXU5eVhVOUFPaGlnVUhvTUQzRW9BM3Z6?= =?utf-8?B?SnpXZ1pHRzVDcjJEYnorbDVOeU9NQXJGSDJuTzhGQk4wY2JhYzFMZ0h5NnF1?= =?utf-8?B?QlFmN2lZQ1pmVTZnOGROWGFJRSt1ZEpNUUVmY1d1WEkrWDVLL2RqQUREUDBq?= =?utf-8?B?VU5uamdIQmlKdXYwQ1RSNnRGVkYrTnNqU3YxTDlOSzF5RlRCaUgrZkZyQnFp?= =?utf-8?B?ejR3K2NKQVdlOXJCQjh4SS9vT0hoZ3pPWkFvVk42LzU3TWxSTDFvRVkydmJY?= =?utf-8?B?eEQya0pMVi9jcWNDSW1tNHZQbFpCbFcyZzVNL3FHcGhsRmtwcmlOQ3p5S0Jz?= =?utf-8?B?STdSK1NiMUphb3FGWk9WRmNtc25SRytLdXVFVE8wTnVhQWlKaTBJbmVyMndB?= =?utf-8?B?WXpTVFJxTWJsZjlJeVArcmFhd2JqSWJ4U3h6c0s3ZmJyaEhvL0lLV1g4Z090?= =?utf-8?B?YWI5R3ZtVEdHYVZLOCtIRkQyOU1LbUtxVCtIbkVkeWdXdXRNY01QOTZBMGhl?= =?utf-8?B?UnV4b2lENmlMUnhhYUd3U1pSZGtjWlNJbVlSSXBrbEtBVzROTGs2TzZObjlC?= =?utf-8?B?cWdkRnR2ZE92WjJjaTFiOGhIazVKQTdRNHpGemwyS09ZVzkybjlOejVCcHo4?= =?utf-8?B?R0RETUdBVmxJc0ZTSzNHT1d2UXorN1lGYW1FemNjZGk3Y1hsYUZndkRHdFU2?= =?utf-8?B?a20rOVRNNVR5UWp2T2s1WTIyVnNNZWtxdVFleUtxSHVGVTFHK05GM0t0eGp3?= =?utf-8?B?RFFDYWFtYTNrck9GYWovMi80cmsxYnVhOHVGd2ZRaWYrNWNSblR1OGFBd0dE?= =?utf-8?B?ZkxvbHlROUl0V2NUVWhqUW5CRDBaMUtXYmE3YXp5RGo4OU9FR2JTVldIWGdV?= =?utf-8?B?YWpaWVlWUUFCVTBmUmJ6eUNRRUN1dEV3WE42SGoySXNVa3NaektMVEdQZThm?= =?utf-8?B?bVQzdG5veFRKM1pVaVpjUXg1THRXdDJVS0dBYzQyK2JNWVFNdlhpYjUwYW1H?= =?utf-8?Q?8ZzxOJBRLqVg+vr1yjhShVIygTEoEmgjR7bAB9c8B//3?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: d90039ec-6e7c-4c0e-0173-08de1e701ce7 X-MS-Exchange-CrossTenant-AuthSource: PH8PR12MB7277.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Nov 2025 02:40:00.5709 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: aaMiCGCT4FDYTOvBWJT0Uux6Kotn6mvpC7w8WnQICMuJt/oPV3PhPhs3Yda23Cm6dYEHaSpqCiNxpMCQoZpheA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB7669 On 11/8/25 13:32, Dan Williams wrote: > Commit 7ffb791423c7 ("x86/kaslr: Reduce KASLR entropy on most x86 systems") > is too narrow. ZONE_DEVICE, in general, lets any physical address be added > to the direct-map. I.e. not only ACPI hotplug ranges, CXL Memory Windows, > or EFI Specific Purpose Memory, but also any PCI MMIO range for the > CONFIG_DEVICE_PRIVATE and CONFIG_PCI_P2PDMA cases. > > A potential path to recover entropy would be to walk ACPI and determine the > limits for hotplug and PCI MMIO before kernel_randomize_memory(). On > smaller systems that could yield some KASLR address bits. This needs > additional investigation to determine if some limited ACPI table scanning > can happen this early without an open coded solution like > arch/x86/boot/compressed/acpi.c needs to deploy. > > Cc: Balbir Singh > Cc: Ingo Molnar > Cc: Kees Cook > Cc: Bjorn Helgaas > Cc: Peter Zijlstra > Cc: Andy Lutomirski > Cc: Logan Gunthorpe > Cc: Andrew Morton > Cc: David Hildenbrand > Cc: Lorenzo Stoakes > Cc: "Liam R. Howlett" > Cc: Vlastimil Babka > Cc: Mike Rapoport > Cc: Suren Baghdasaryan > Cc: Michal Hocko > Cc: "Yasunori Gotou (Fujitsu)" > Fixes: 7ffb791423c7 ("x86/kaslr: Reduce KASLR entropy on most x86 systems") > Signed-off-by: Dan Williams P2PDMA requires ZONE_DEVICE, Most distros have P2PDMA enabled, you mention smaller devices - are you referring to kernels/distros where P2PDMA is not enabled and only ZONE_DEVICE is? Balbir