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 B8517C43458 for ; Mon, 13 Jul 2026 16:37:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DCAE96B0141; Mon, 13 Jul 2026 12:37:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D7B7B6B0143; Mon, 13 Jul 2026 12:37:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C443E6B0144; Mon, 13 Jul 2026 12:37:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id A2BA46B0141 for ; Mon, 13 Jul 2026 12:37:40 -0400 (EDT) Received: from smtpin22.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 6FE48168BB7 for ; Mon, 13 Jul 2026 14:08:32 +0000 (UTC) X-FDA: 84983933664.22.5036330 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf08.hostedemail.com (Postfix) with ESMTP id D6B1516000D for ; Mon, 13 Jul 2026 14:08:30 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=IEcGRUQm; spf=pass (imf08.hostedemail.com: domain of rppt@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=rppt@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=1783951710; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=5D70PgPOpXCYze4+Z72DPv3iGsJRzVh17hn0cbIFj6E=; b=qssz6lBpHnzWB3QF19mnN1d94ob9TsS3nuwkKP3Ekt2uxx1qPUYVJ+iZRUs1hSXngTQsY4 8JySpUMUgNSZR0TpZFU8vu2mECD4LFY4VVDWr646euTTdW2Ikzzg7m0TccL9HGKoO1QuOp YEshH8oEYD+jgISrqovwv/vleLDeqJE= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1783951710; b=biR9u36xQ+WVZS3nxg9lXPg1zf92aV5ZvzrmAgyDUZPO7RLS6iZ7ejqjUNQjMY+JowOfdq PXqYhLdeH7fA6oA3RV1ajjKw8HFebzXxHdwAubM9lHPT9SdaORPojwM/7TnKKYqkj9fvQQ 4+v4enaYDxiRUgziMVyw6dmTNrreXU8= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=IEcGRUQm; spf=pass (imf08.hostedemail.com: domain of rppt@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 659076013A; Mon, 13 Jul 2026 14:08:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 04F931F00A3A; Mon, 13 Jul 2026 14:08:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783951710; bh=5D70PgPOpXCYze4+Z72DPv3iGsJRzVh17hn0cbIFj6E=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=IEcGRUQmq/j2oZwL8Kf6eWI82YyVPYbNH14/2FzJeoTFePEit3iAhoG4ugytrOWrR ezVl9VkrgoNuCquhjp2caRSyWFKyvEA4Avoby4m52bd/FgGA7ty7D9RJhdpUUyPzTF 1X9WJm/iSqoa3qwgcFma1zhTzZJ4XR2pSNCFH/uGOlr4rgClyC4tp/iEiGbxNBIqXj bbbRBKZZ8Cr2oXnnM8Pr6nAKVuv2FQuQ72Mi+/qjRLearyyBnI4huUQdyifm5sNC78 i8TBAdjsJQ3WQef2klxC2+c+KcDEgROBsMslT0iy3f5f1+TUc59vzSF7QS+j4XoiFY NFVQrR8/FtVEQ== Date: Mon, 13 Jul 2026 17:08:19 +0300 From: Mike Rapoport To: Will Deacon Cc: Lorenzo Stoakes , Dev Jain , Andrew Morton , Suren Baghdasaryan , "Liam R. Howlett" , Vlastimil Babka , Shakeel Butt , David Hildenbrand , Michal Hocko , Uladzislau Rezki , Toshi Kani , Catalin Marinas , David Carlier , Ryan Roberts , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org, syzbot+fd95a72470f5a44e464c@syzkaller.appspotmail.com Subject: Re: [PATCH 0/2] mm: fix UAF caused by race between ptdump and vmap pgtable freeing Message-ID: References: <20260710-series-vmap-race-fix-v1-0-5b3794c113fe@kernel.org> <8e320b30-9658-4e9f-ac4c-f99dcf855944@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: D6B1516000D X-Stat-Signature: 3cbsmt3djhs1pksoq6f3ct3b6ajby4wb X-HE-Tag: 1783951710-748905 X-HE-Meta: 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 lsEyYJ9J rdzI7ktBHTX6s+Z+Ekg2pOT5l84aallfASMa1ZgbvWYHGoCfphH2WDcDNc1TbGzsFyag9PGyOlQcL7tX3GPnHmJsGDolxnPq2QwCU/9X9Q0cSLeqKJoIiRbeMCZOfV0qVG8uwPe9L5uGpq+luJ/kPHleEqrAmNY8iOr5NuLiPrQtWEkjFUzERk4k5ftnQpCJbz7gyl8XRhueeD4UbAGt1QPrF9nKLtWqpN7aUcRyybuRFo18K7D7L05lWVajIDhWwtjpcL/lxezp6T4ZJtpMIRXBW/xcXjq77GzEdDTpQPDg7BuZ5pfpayEtOb4sidcSivD4nq/UcwZGzk5vH9hWvyec4yqgAWrbvSRUMFy476RMCSqXLGVUQS4tECL2Cx6QIMHcKEYwnVHGqDFIs3egIbMCp9EcQoOGS0J3rOmH94M66psZPKulRc7ZTu6CCeHFS1+6Jj3cDNifnrxZUALHYt55vYw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Jul 13, 2026 at 12:37:46PM +0100, Will Deacon wrote: > On Sun, Jul 12, 2026 at 09:46:46AM +0100, Lorenzo Stoakes wrote: > > On Sun, Jul 12, 2026 at 12:50:08PM +0530, Dev Jain wrote: > > > Will Deacon had pushed back on a similar approach: > > > https://lore.kernel.org/all/20250530123527.GA30463@willie-the-truck/ > > > > > > Although now when I read back that thread, it feels more so like my > > > incompetency to convince :) because: > > > > No haha not so, I think more like this stuff is fiddly. > > Yup, not disputing that this is hard to get right. > > Conceptually, adding locking purely to deal with a vanishingly rare, > debug reader does turn my head but I'm _far_ less concerned about it if > it's done in the core code, as is the case here. x86 needs it and we're > recently running into related locking issues with the set_memory_*() > APIs if we want to collapse the page-table on arm64 [1]. If the overhead > is flagged as an issue, we can see if it's worth generalising the static > key trick that the second patch reverts but I definitely wouldn't start > from that position. I'd say it's worth generalizing the set_memory APIs ;-) Since it's de-facto machinery for manipulation of the kernel page tables it makes sense to have a common code for page table walks with hooks to architectures for checking/setting/clearing protection bits. Coincidentally, I'm working on a POC that lifts x86's CPA into mm/ with the intention to later use it on other architectures. > Will > > [1] https://lore.kernel.org/linux-arm-kernel/799181c3-a1a1-4de7-bc6a-576d3282efb0@arm.com/ -- Sincerely yours, Mike.