From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from YT5PR01CU002.outbound.protection.outlook.com (mail-canadacentralazon11021103.outbound.protection.outlook.com [40.107.192.103]) (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 C51CF2E7F3E; Fri, 8 May 2026 16:18:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.192.103 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778257116; cv=fail; b=Ztljb8HFXpVRvWtLTPfpTIeOZkMkvSOt/CznVD5yKbo86QAXlbCfP0mYJNstXugpy1aUmdRPxiB5HBqC8fqmHpFWMLRN+cpkpB2z052EuFeqrd7pgpueQuxa8y8S7cgDtkMdJnLHCpdcXNt/sasPYdfPMURaPWE2dRR3fb+ilhw= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778257116; c=relaxed/simple; bh=D27K9LqSYFGLIZvgXiYS81SxQcGmTFhNUviP2A3I5Ik=; h=Message-ID:Date:Subject:To:Cc:References:From:In-Reply-To: Content-Type:MIME-Version; b=gecDYpBS1CAq1xW+Qk5pO9JlAQjp4X//ICV8Z2sgn6wmQz0u4q0Y0ByTCMHYM8Sa2hgNvzo/vo2KvnVSjp08sAD8o2DLh7oEk3dUssYPczosVoLw70CppkKsWY8+rwmIq4DkVxO4JOlvzY+JGtKtS98Fle5RddefauyNKOZwU2E= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com; spf=pass smtp.mailfrom=efficios.com; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b=euu1j0wg; arc=fail smtp.client-ip=40.107.192.103 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=efficios.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="euu1j0wg" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=ten7zlkJdbRgzHL4sDPUcglYmjqYU+NIf5KqZYslUmm75fTD+xxPbsAktPhrPrzAjS7kmewkNGngP2X5aJ4CvyouQPIo2Zfn7kIX4o4NWp4XSFrt4qgTtGJ2EJ8muX6ICjezAy8mRO+W0jNQPDMOFoYX+XOP3keVf+OH7YHSNiE+G7HHP/Nskx8JPE25QpoXv1QrJSr3GM9wbspL9pzoZvpwU3bT1B3Rha3ZUNt0LE4TvckqfyQED2NdVafkLXhxq9b6HJ8mYTD1rk9o55KMzDOY/OLeZLKskZwVB4vTTl1o5w0qVJm/A4I4u757P55efNhYwRRoOm7pJgnF+dRqOg== 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=1UZ0k4Xal7fH5VxvEQyuYBP7vn742YyiQ2VvPczS8BM=; b=SpRyvQoTSIJBQk4tvXwdX9exeBFscSjkUnl20O+X+WqnbQtI4LQgwoqixE+H9ShNZnDuEZPLojvHyU8oVKFr6wDHvjNvq+c2k+nkWn9ySM0EBLi2xGiMDxlA00fA2wHs8Ai8gp6FXIrjNbhf01iAs0EJ6BSSAb1qcehUxtg/9y6n3514ivSrk9H0/2S7bVO/bLjQ5GSO+i+/orlGo4G/+8gqjtqQzciCWInx5v6xX5WpuABe/bXX/9AsyVCquw1MBkfZ0QW77X3J1VkaXQZtEXgwE+oZyWR0W2kaHBeN61XDOzqGJ0qkSA9RTBfxpKGg0Mv/p9UsKjtbdrWud7b4oQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=efficios.com; dmarc=pass action=none header.from=efficios.com; dkim=pass header.d=efficios.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=1UZ0k4Xal7fH5VxvEQyuYBP7vn742YyiQ2VvPczS8BM=; b=euu1j0wghyXed0Dy2ZbP9Sg3OZMnTYXr5AW4LbSVpztnNMPso98LVbz3s+HtE88UEsW9bDWprqmHzr5odVOAcgShbqCMrPgGyx/PQqGyShYl5GD1D9meDZXtyoumftT6III2U4+lZ3x7doXPTLIGa7UMRh3k8LpYKipt5WP94wDMx2r6bqPZiVim3OO/Shw/Prxh3yCvf+bpBD2iZZ9Ji5lruJD5T7I5dLr22LKR0EQ6+Kincaq2DOWXv7uTNyIW/2MYj2+w3aPOkEmqwhJ+7UqcWpQI/u9NLDNuJGkkoOx90KwCGOCPuStJ2vzudZTYsT2zdkqIUQsC68FVBrqJCg== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=efficios.com; Received: from YT2PR01MB9175.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:be::5) by YQBPR0101MB8397.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:c01:51::17) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9891.16; Fri, 8 May 2026 16:18:30 +0000 Received: from YT2PR01MB9175.CANPRD01.PROD.OUTLOOK.COM ([fe80::6004:a862:d45d:90c1]) by YT2PR01MB9175.CANPRD01.PROD.OUTLOOK.COM ([fe80::6004:a862:d45d:90c1%3]) with mapi id 15.20.9891.015; Fri, 8 May 2026 16:18:29 +0000 Message-ID: Date: Fri, 8 May 2026 12:18:28 -0400 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] killswitch: add per-function short-circuit mitigation primitive To: Sasha Levin Cc: Joshua Peisach , corbet@lwn.net, akpm@linux-foundation.org, skhan@linuxfoundation.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, gregkh@linuxfoundation.org References: <20260507070547.2268452-1-sashal@kernel.org> From: Mathieu Desnoyers Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: YQBPR0101CA0040.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:c00:1::17) To YT2PR01MB9175.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:be::5) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: YT2PR01MB9175:EE_|YQBPR0101MB8397:EE_ X-MS-Office365-Filtering-Correlation-Id: ec7c9be5-4cbf-4d72-f153-08dead1d7111 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|1800799024|18002099003|22082099003|56012099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:YT2PR01MB9175.CANPRD01.PROD.OUTLOOK.COM;PTR:;CAT:NONE;SFS:(13230040)(366016)(376014)(1800799024)(18002099003)(22082099003)(56012099003);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?Um1YN1NLK2tNcmxIR283U1k1cDU0OEJ2R1FqbVZib0JNWWJvTitteWxtT2Nv?= =?utf-8?B?MDMveUlpa2xsTEowdEZoNk9TNmZXU3UyNmZKSUprYzJjYkJTRktET2JjR1pH?= =?utf-8?B?RHBhdkUyckhGRnNFRXNTSWluSGVyQ1lqVWgvSFNVNmI4OXdlalExaERvM2hl?= =?utf-8?B?WmxOMkNGZXdBbnpvc0I1alNWTFVFZDlvTGFpZzNjK2ZKWjR4akdXRGFZaWp4?= =?utf-8?B?dkdsVjVxeldCR2JqU3NkRjdKUGoxOHJJS0grd1I5V1hRYXlXTVdvWTZrdHhZ?= =?utf-8?B?RjdWbmhDcWZxNDFTRFhGUkp5aU9NR1B1TXNMNjk1UW9USnpJOS8zUzlVbVEx?= =?utf-8?B?b1Jub3IzOHNHNHU3NkJ5SHpDcUlvVmpGRVQ2QlFuY1NYY3c0S2lsSWIwV29X?= =?utf-8?B?K3pMQmJyK25FT0Y0Ri9xaUtQV3JROXhFOWppZTN4Snk2eXlmb3UzL3h5bnBk?= =?utf-8?B?cE1PU2NrTVhwamlpWWFlT0FjNkVsSExQTGhNL0M1NmpHYXc3eDdyL2NGbDQ3?= =?utf-8?B?MjkwQlUwYVdjUEFVeitpTXlsUWd0a1JEMURIa1pFd0FZcG9OOG9TaFkxamYr?= =?utf-8?B?WFlXYVVjMCtERmxRK3VsT1hDdnA4RWJwZ24xVkgzYW82RDZ2SUpSNUlScm9B?= =?utf-8?B?UXAzL1NFb1R0cW5HeTRxdmZrTzBuZG9MTmVFWXJaRytGc2ZxcE1tQ3lkekxJ?= =?utf-8?B?RFgwTURoOHNSTjZsdWVOVXhMWVpwdWoxM003WjVwbU9MczNBUUtiKzQ4N2lu?= =?utf-8?B?blNTNElLT0hvQlcyR213Ym1IMWhJaXN3VnJEcGcra09YcTZPNGpvZjk2L0M0?= =?utf-8?B?U3A3V1ZzS1Vqc0phaU5lRnpRWHBjUDAwWHRzSFp5N0RiRUlzcUFvRVRBZGJ6?= =?utf-8?B?TWI4a2tvR2pvUFA5Um50cGZmWTJCR3N5OWtMSW1iVkNBVEhWRU9VT3pTQTNL?= =?utf-8?B?ckhrN3BSLzBZKzZObktURFA4aVhiaEE0TG5JOHg0UWRJZ0dsOU5xVkF5YWRZ?= =?utf-8?B?KzBWN0F0ZHh1eVFYNHBScHBNRmxHejlKbkgvYWdmdFhxMmdvSkNaVEUycEd6?= =?utf-8?B?aE5HN0VHeU9hNE0rb0VQcjAxck90SmRHV0FkQUFLVGhWSHhvbEFLMVlPaEd2?= =?utf-8?B?T08wNGt5RXQ4anRIYVA1bDBFZjdRbUdXeWFIcUI0c2hTbVkwdlg3R3RoeXRi?= =?utf-8?B?NGtsWDZjOUc0V3dLL0s1akpXUHBvTzJDT2d4SzNUbWZlcWdYbjU4YnhZQ2FP?= =?utf-8?B?L0RwZWloMFU5dWt2eXpZd3c2aXVaTEM2NC9hbnBmQTlCRnRjenFTWTJWNnJI?= =?utf-8?B?UzBFbHUxMzR2TFJ3cUtDNEtTWE1Wa09PMnZDaW13T3hUL3U5OGF3YnA0cXpN?= =?utf-8?B?R1hQVUtFdndTUDBpZ09HYXh1cXU0L293ZlgreWxNV3R2SERLR1QyTWkwYmRM?= =?utf-8?B?R0RHOStVa3JTMWhrOTBSTlhIV053MmR6MWhxbzEzTUxkUlNPYmVaTTV0QmdE?= =?utf-8?B?K2Y0aUVDT3l6SlhXdkpUdWtjUE1kN3BPNXNucHdmWlpQTHF6Qzh6cXlSaEFa?= =?utf-8?B?YnA2b0pGbG1nRW1IOXYzZFNsay91SWwvcWJZUXcxUy9mUStXcUVSOWtXek5k?= =?utf-8?B?UE5XWC9rdkM3ekxYeDJ1Vllua3FSUTFQOGhsalRKakprYkhiMm96RzlISW83?= =?utf-8?B?allBbE1RY2Z4ZnFFQ1lWdVNFb2NHT2EzNlE2ZXVTVE4wN3ZVWkRub2dPOVRR?= =?utf-8?B?MHJ3T1F1UDVsNXR0aHJWaXNqWlpWRXVacmNFTkd4YmhWTmRuMTA0bWo5cjZ3?= =?utf-8?B?SmIxUGVTYzRqcjZySGVKZVBDc0NNT1k0azFzMlBYbWVJanllV2RuQjhXQ2FX?= =?utf-8?B?WGViZHBpU1pkcTJJeFdwNmpvT2ZqWVBEL25SSWEzZmFtWXpvbmdjeVAxMTVn?= =?utf-8?B?KzdTOVluZndMdnBYR2dWdERoMmI2d0FyN1F5MDFVUElSQUtlcG9zZWU5WjMw?= =?utf-8?B?clRvY0pVWGdTTFR0T1pjbytuWmxpR0lTS0Jnc2dhVEV1N2V3eHBLUVNpTE9s?= =?utf-8?B?L2c1UW84clZyS2xVMlgrcnBKeFhQVDRXK3krYXpWdWtCTXFqQXZ5YjhFcEVy?= =?utf-8?B?NTZ0SjBwL2ZkZGJjRVQxaDMwY0dxODF3U29PVXZaVFgxQ0ZvSUVYOGJMeWJk?= =?utf-8?B?aDk0anlHSFlaOEtsRFk1UXZVRytCTVd4SnJnc0xpelBPYzZNNGszZUpCK2dp?= =?utf-8?B?MmxJYWdSdkF3R3JxMUEwRm5kWFd2NUw0YXFyTUp5NEhEYkd0ZUwyYjhhVDc2?= =?utf-8?B?T2hQTW4vcll4ZnNtN1c1a2QrMzNSNm9xejZoU0xnTUVqNTB3TS9KanZoUnZa?= =?utf-8?Q?m6xlmuk+aG53Ct7AEtJW6y3ihjP9a6u1X0H2h?= X-OriginatorOrg: efficios.com X-MS-Exchange-CrossTenant-Network-Message-Id: ec7c9be5-4cbf-4d72-f153-08dead1d7111 X-MS-Exchange-CrossTenant-AuthSource: YT2PR01MB9175.CANPRD01.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 May 2026 16:18:29.7623 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4f278736-4ab6-415c-957e-1f55336bd31e X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 2+yOmr02T155TweteFLnijr1ypK9M/8vtoKDsmI/VhbeTT/2aXSwey7bAI0z5gctSWt4covqQCUvB2o9vats8KpRy3nntWS8bcQI0Uq1ozE= X-MS-Exchange-Transport-CrossTenantHeadersStamped: YQBPR0101MB8397 On 2026-05-08 12:13, Sasha Levin wrote: [...] >> One possible approach to prevent "footgun" type of killswitch use would >> be to first apply a statistics collection killswitch handler that does >> not change the behavior: it checks whether the target function is >> invoked at all on the system for a given period of time. Then it applies >> the killswitch if it was not invoked during that period. Overall >> sequence: >> >> - pre-soak killswitch for e.g. 30s, checking whether the function is >>  invoked at all. (period would be user-configurable) >> - if no calls were detected, engage killswitch, else report failure to >>  the user. >> >> This should prevent footguns such as trying to killswitch fork, malloc >> or other core functions which are inherently required. > > Why not just use our good old tracing infra? Set tracepoints where ever you > want, collect any data you might need, and engage the killswitch when > you're > happy with the data you have? > > It feels a bit weird adding something like this into killswitch. It really depends on whether you want to include some basic safety nets directly within killswitch, or leave that entirely to the end user. I don't have a strong opinion either way. I was just pointing out the feasibility of a pre-soak sanity check before applying the killswitch. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com