From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 EC0713E866B; Mon, 13 Jul 2026 11:37:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783942674; cv=none; b=H9zsGQvXZghr0Jx6LM1w5vDbRPOfm43MDpqqCmzrkjhDBGSIwrnrATgcx95ZMBK6Ku5b3nqOy5I9NAFlWRHGjcg5pa0tDbg0A1ZVjdciN4ZJOEsZFE9aY4WAc2pkiWwJdREXpxTWcvhgEp4BFQo0urQqQ9fqxnmyRoFbyilJIAs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783942674; c=relaxed/simple; bh=T9I9LggSZGnd+opeAplGGNQctxNzn/jhs9k9J87eSGg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=b1MhnXsx/MXEN9FG+xPazoEZij0FKTIu2rnbdS9kP/tJ5V2xHIm7MMsR0cVrsNi961wCvKsTMib78bSDcb/I5/uJ3Jc8NX9KHA8XQLfdF2HZAzwkkKSBbnvMFLf5wIiZsDQpGBU6cjinVmN46GBhCTlrEks+SHN6wVBnoF4lx2c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lwsqz1Ru; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lwsqz1Ru" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 126A51F000E9; Mon, 13 Jul 2026 11:37:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783942673; bh=/BjtT2J2J6zXKuxGY/oNhYmRT76YRdnfRvP+EVhF3Q0=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=lwsqz1RuU3/1+c0OVzE60Yb3p9ZEdRyv87rOvJQj2jHlLDEJ9FJh3edRHAabzd8wG camah820QByAwHgAARZVVejvD11aO+S9Ik8ny9LouWcULNkE1aQXCemywImUs6WKfe GDEVgH7ZgoNJI7HcE1g7bcNYXDtt8CrQ/eWnGg2fEWMwktPX7Fww8DmwHln3sdp12T D3uAw0aHU9doRMgRKZY8ITJ7+5ZQAQtLaK2rBS+h//zPXpg/FDXOpqa8jixTrT3CLp 7T5xptgnEXNSjzGBE9uqCjgtRrEMT7yXfCEDCtOh+IFFSelv4KHvpqcfasikBCvYr5 LvZXZRZnbq1mQ== Date: Mon, 13 Jul 2026 12:37:46 +0100 From: Will Deacon To: Lorenzo Stoakes Cc: Dev Jain , Andrew Morton , Suren Baghdasaryan , "Liam R. Howlett" , Vlastimil Babka , Shakeel Butt , David Hildenbrand , Mike Rapoport , 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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. Will [1] https://lore.kernel.org/linux-arm-kernel/799181c3-a1a1-4de7-bc6a-576d3282efb0@arm.com/