From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 381EEF8A146 for ; Thu, 16 Apr 2026 09:04:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 745CD6B0005; Thu, 16 Apr 2026 05:04:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 71D4C6B0089; Thu, 16 Apr 2026 05:04:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 633706B008A; Thu, 16 Apr 2026 05:04:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 527746B0005 for ; Thu, 16 Apr 2026 05:04:03 -0400 (EDT) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id ED10C8C41C for ; Thu, 16 Apr 2026 09:04:02 +0000 (UTC) X-FDA: 84663831924.16.053AFDC Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf02.hostedemail.com (Postfix) with ESMTP id 0C4A980010 for ; Thu, 16 Apr 2026 09:04:00 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=S61q3Dom; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1776330241; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=AJ1bXvUCaR6FNT2bXJB89I5iul0FtzrqOg6QCrgwCa0=; b=4uS2tjee1RubcfD+om+5Vlxc5knXrBSO/A0JJ+hiscJ0ClN/LcfQwyxkCP+b0S6VOesUo0 6GtdKaZRiq4KnoGf2eLjCMhhIzcaPI6C21eFuIjlcuX8azkNVlluq48baWzFt2jZcLCtSN BbZpRaj1coQkr7dxTS5GahgxeowjqXQ= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=S61q3Dom; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1776330241; a=rsa-sha256; cv=none; b=E1QndfRZ+WtFxDrI44I4Cc14MfRlPW/MaM2Dh2IqhNIOA5Qut6vAe2R9cI0mtwLpIPSAC8 Rfu9GjbKvGgPzCY6KZNkWGVhTOX9atYLqP+ljYIOwVWdxr2lJr6lZBd1oikSEqkzhCEdYP NG3k3ebjpBinRHbgarfEJ8crgdc1os8= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 05F4C4327B; Thu, 16 Apr 2026 09:04:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4DFF2C2BCAF; Thu, 16 Apr 2026 09:03:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776330239; bh=+NW/hoYJakiYKrdIWB886RGoTFd6AjYRobF/ZlT3V+Q=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=S61q3DomMTBSegKBAfkWX841vogBSQ2csr9NBAWLZlxrxS27oHm4+s7vtALk/YtQJ x0sNbDQy/NrV2UP1f6uMMRy6hCxohcyLDU1ZNG4Tzhs/jyr78OU8fWNs3O0B1m9179 aioU/65pLld1Ivx0Lrpfp/UhvmT7VwxKjFFwhKgQTfv6fOVbEEFOkIB5wFVhXI7XpJ UDRD2XEtEDlHPTb00EI1ivDqjRgLF4gGBAG8j3MIDORLcavi1gZ+sXhgb5nWJcZrBa QSw3dvK3vdIdvkPFiLevFozGZuhLd5b2pcWiX/AUhrMb+AWO90euPit4+LBB3mjghI Kdk+HoL7o1WGA== Message-ID: Date: Thu, 16 Apr 2026 11:03:46 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/3] kasan: skip HW tagging for all kernel thread stacks To: Catalin Marinas , Muhammad Usama Anjum Cc: Arnd Bergmann , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Kees Cook , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Uladzislau Rezki , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrey Konovalov , Marco Elver , Vincenzo Frascino , Peter Collingbourne , Will Deacon , Ryan.Roberts@arm.com, david.hildenbrand@arm.com References: <20260324132631.482520-1-usama.anjum@arm.com> <20260324132631.482520-3-usama.anjum@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: ntmym97jcd8kze7cuyxs8m4oqrqw91xp X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 0C4A980010 X-HE-Tag: 1776330240-496545 X-HE-Meta: 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 5G+hviD9 A7jIaFfdPyz0R6B7RzCw4w8ps3ZprIxbEDG9e1au54ttWWLY6h7jqwzpojGE/DIyPXqKYw3M8sG/9i3ldD83tjpihb+R6JuHYtA9YGSSV1oQfMq14Z03bVPVD+RQJQjPeFFU4yoaa8T0JnTrLLnbo/2YDcmI14Vy5Kwga6+PRKrqQZYUpqUAYlNpYuTrNxGS3KMROmYMfq/wuIsIz6wbE4NDidsq/9f6EaVNEhChZV5Eo4dk7FLYoOs0Rq4N2anlfMenp4wFTHVgquRQFEEAgxbvSG77J7ytxC2l7 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/10/26 20:36, Catalin Marinas wrote: > On Fri, Apr 10, 2026 at 07:32:23PM +0100, Catalin Marinas wrote: >> What the original approach might help with is use-after-realloc in case >> we had a tagged pointer in a past life of a page and it still works now. >> Oh well, that's I guess for other types of hardening to address like >> delayed reallocation. > > Another thought (for a separate series) - we could try to map the stack > as Untagged (unless stack tagging is enabled; needs compiler > instrumentation) and enable canonical tag checking (newer addition to > MTE). This way, any stray tagged pointer won't work on the stack since > it needs a 0xf tag (canonical). Do you mean mapping it as Untagged in the vmap for CONFIG_VMAP_STACK or also as Untagged in the directmap? The latter brings in the set of problems with direct map fragmentation. -- Cheers, David