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 329C53D8100 for ; Tue, 1 Sep 2026 15:27:43 +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=1788276464; cv=none; b=pRtXZpSbkKQrAOP49uZfWcgM9D43mn46xGymn1/UKOmcCCmeK5sLMaX6vJzvxO+YIbW59l2mSHt+Prl5zgdWHeSlKrNn0RqMPrWhG21ddGuifrafkW3Hpyl/HYMmu3JFwTZfOglUFPdtl+Xq00lJqaKMYr95VebZSIEErm63B5M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788276464; c=relaxed/simple; bh=oUjwv2smWe0xFHylp188LMnL3s3sI4RXp84y/JQaByA=; h=MIME-Version:Date:From:To:Cc:Message-Id:In-Reply-To:References: Subject:Content-Type; b=XfOkwJqagqCDmATiBE2fvE/ZEAcYjzW7a5y3DbXXv/KhTkhW0PROioAOG9qaM8p2tDBzK1FkIb3F8qNP+jz8sas/VB6noimsxlFdIZ0H3VmyksDfM+ZsHRK876Ino1eJtT6TZg+eZ/k7K0wlqiBVp/YEWL3hpoRpgWn70z0tNhU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YGjBIESb; 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="YGjBIESb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 214131F00A3D; Tue, 1 Sep 2026 15:27:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788276462; bh=WyEqG2EDFAv8L3v16RuFJGJjVfEcYFvYeKnOELESY/Q=; h=Date:From:To:Cc:In-Reply-To:References:Subject; b=YGjBIESb0kPhDR3x6K+5zvA56QDewqOX15CYgCBzBPMMuJmzktwQKVdQV3tZFt1Qd vampDfQK4hYZJ0YyviLO9ITENNSPE5DkK/erKPVSu5LMTIYxd0mCmvHhnRDX6tikC/ 1Tgz7csqXW4AbNSlgipsWPnng0AKp70ErN+lMZ0fg9nB0MgL+nwu3RHXmQu+eWMsiN E0pItI8I9YlJTHzAipJnkCIDY2VoCc95l+DJlHBC4LheqHVM9pdKGL5UVjiAciuDim oTyUvHSG7jtgjtylizBIz9Gm2AW6zc+6iss5nlKQwhNJUL5x6M/THE8A5PLbg/g+k1 mHK9g1/WqldNw== Received: from ams-compute-02.internal (ams-compute-02.internal [10.64.2.62]) by mailfauth.ams.internal (Postfix) with ESMTP id C48981980054; Tue, 1 Sep 2026 11:27:40 -0400 (EDT) Received: from ams-imap-11 ([10.64.2.31]) by ams-compute-02.internal (MEProxy); Tue, 01 Sep 2026 11:27:40 -0400 X-ME-Sender: X-ME-Proxy-Cause: dmFkZTGW+Ifzafl7YaMspyuBctpPC/RThvsqfhP8KkNKucJauF3YPEHcu/NY+tnA4tfIOa AsI9YXyR2o/PfrqQn5AzfDwULoj6yxYxqT8H88MJO2Vf1R4oS/QQPXE6lDswShxcssEJa/ lLEPJ6NLdd8ynBpJZWdvuFD2wjVIaLk/76vUOgCWHpFtlMKWYbGAi70vDXiQbCVOtRnt/d SOctprH2hIEQtYoDSNmxcENcHRUyLsHlidGm5DINwV/cTK7n+Jydfl4L4i5zG6zQD+3mCV yigVFCmLpqBF0rDa7W9P6uhi/mJ93RKg6aB4ybD5uxuFVhQ5w/K3ilhLnDWQU3KSQ3+rFY gDR/u/N74vDciYZyHSBalKtpTSL1mNH8C1SvWxrJAX1a/X9tG5APjQ2jEQuOoVjbkA8qIn SUsXq0gC64XojjeCiGdyBDPExQ9Ixc46gEzKnVF5Bh6IuraqtDgs72ex46tkdH1dOKWtO5 07HpVjmsbmD2XvaN3z8RlSBAM7Xz185beDIQVqC7a7JAhadXsvIqdmeAbNNdMTaSnjJghJ 6qseeSq0ISD9kWorVdgsXc5KyQBO/t2lzwGUV8xdZB2LeidnAsD8+iLUQL+k/OdYaJh5yT /JVos41tmWEWk0o0q7yNd0NTROko2Nqa87+7RMKpPJ9WpzmqVvgEXq0ePZJw X-ME-Proxy: Feedback-ID: ice86485a:Fastmail Received: by mailuser.ams.internal (Postfix, from userid 501) id BE3EBF8007D; Tue, 1 Sep 2026 11:27:38 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Tue, 01 Sep 2026 17:27:18 +0200 From: "Ard Biesheuvel" To: "Kevin Brodsky" , "Ard Biesheuvel" , linux-kernel@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, "Ryan Roberts" , "Anshuman Khandual" , "Liz Prucka" , "Seth Jenkins" , "Kees Cook" , "Jann Horn" , linux-hardening@vger.kernel.org Message-Id: <3df447dc-ccdd-457d-aad3-ede116ce552c@app.fastmail.com> In-Reply-To: <16f40b06-e871-4921-bbc6-42637c63e6bd@arm.com> References: <20260827164409.3421848-6-ardb+git@google.com> <16f40b06-e871-4921-bbc6-42637c63e6bd@arm.com> Subject: Re: [RFC PATCH v2 0/4] arm64: mm: Map fixmap page tables read-only Content-Type: text/plain Content-Transfer-Encoding: 7bit On Tue, 1 Sep 2026, at 11:21, Kevin Brodsky wrote: > On 27/08/2026 18:44, Ard Biesheuvel wrote: >> From: Ard Biesheuvel >> >> This v2 now covers intermediate level page tables as well as the PTE >> level page table for the fixmap. The latter is a special case, as it >> >> a) is only accessed via the kernel image's mapping, and never via the >> linear map (except for ptdump etc) >> >> b) must be accessible via a read-write mapping, as all manipulation of >> read-only page table descriptors relies on the fixmap itself >> >> and so it is treated separately. The intermediate page tables may be >> shared with other mappings in the upper kernel/vmalloc region, so they >> must be updatable using the ordinary APIs. >> >> Build tested and boot tested on a Lenovo Yoga C630 using 16k pages. >> >> v1: https://lore.kernel.org/all/20260805104042.1107678-2-ardb+git@google.com/ >> >> Cc: Ryan Roberts >> Cc: Anshuman Khandual >> Cc: Kevin Brodsky >> Cc: Liz Prucka >> Cc: Seth Jenkins >> Cc: Kees Cook >> Cc: Jann Horn >> Cc: linux-hardening@vger.kernel.org > > Looks like the Cc's didn't propagate to the actual patches, fortunately > my lei filters did catch this series ;) > Ugh I must have forgotten to put --cc-cover > Either way I quite like this series, it's an elegant approach and it > should increase security without overhead, what's not to like! > > I also considered it from the perspective of kpkeys protection [1] and I > think they should work together fine. The kpkeys series still allows > page table setters to write to all page tables, so if we get a fault > there it must be because the target is read only, and not because of a > pkey fault. > Excellent, thanks for confirming.