From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 5C11D339719; Wed, 14 Jan 2026 21:09:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768424941; cv=none; b=MVHB7I3uvYe1TflcsHK1yWB04CyfkfbPHhbeRtdpuJBiAqHrWKjmNISFC3ql3M8aUSeCbN516OkQk0HvUPS/se8MFShpvheu2zVOJJci9NrgRIs4wp2cLVbRoRGM1jKjC+/18o4TUmPI5+z+KmlEAF4qhaYfBrH09oQ2phHD/q4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768424941; c=relaxed/simple; bh=WY2v7TTkVAMIoJ6VgjyCIHMaXfZc57Ip7xvQxHTv4p8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZPhFG7z9Q+9m0ETSIpB1nhevmUgxZRinPdWix40eXGx46fHqDWB/SOv3VftD8vDybl0alI1DeYxG1bHAx5WCXum6JK8oRYQWXXSKTWn1ETGr129vkBxQCBtfKZarmcoKJIKrjOEEv/AnxnyEEmv2rISFUto/KsJ6DLxYem5bcOo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MQlP4ogz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MQlP4ogz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F8A1C4CEF7; Wed, 14 Jan 2026 21:09:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768424940; bh=WY2v7TTkVAMIoJ6VgjyCIHMaXfZc57Ip7xvQxHTv4p8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=MQlP4ogzmIg+JA/pCvyHUUO5wvv/C5zQHlnBqXHSLlASijL8pmOpQxN6Mp9g8yjZF JSbWr/fkUFCssMc/dFWx53WUUKe4zHJ6ZYkSjNd6r1yX3mp12SLuUxgl9ozv63ZnlZ jl3raBW0MaXvD6R6YWE58deFr8RmXTmk8TGzXsH0Sdi35Ya/1ZFr2ubX1tizPnxouv dvucGK7xwkmHYbzM9vwJrQRTq/Y/S9jRrITCBXqvHPHWZJixTXbAVxA08Spk1KIgSe lOZgKwHm4frxFppMK3Q/ZKKdz7ijGrqpXG3ah1bIYM6EXceqoiApHVgyMomBL50l0S HZqj6PBTuoFBQ== Date: Wed, 14 Jan 2026 15:08:59 -0600 From: Rob Herring To: Coiby Xu Cc: kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Arnaud Lefebvre , Baoquan he , Dave Young , Kairui Song , Pingfan Liu , Andrew Morton , Catalin Marinas , Will Deacon , Saravana Kannan , open list , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE" Subject: Re: [PATCH] arm64/kdump: pass dm-crypt keys to kdump kernel Message-ID: <20260114210859.GA3197242-robh@kernel.org> References: <20251226141116.1379601-1-coxu@redhat.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=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, Jan 07, 2026 at 07:39:24PM +0800, Coiby Xu wrote: > On Tue, Jan 06, 2026 at 09:44:37AM -0600, Rob Herring wrote: > > On Fri, Dec 26, 2025 at 8:11 AM Coiby Xu wrote: > > > > > > Based on the CONFIG_CRASH_DM_CRYPT feature, this patch adds > > > LUKS-encrypted device dump target support to ARM64 by addressing two > > > challenges [1], > > > - Kdump kernel may not be able to decrypt the LUKS partition. For some > > > machines, a system administrator may not have a chance to enter the > > > password to decrypt the device in kdump initramfs after the 1st kernel > > > crashes > > > > > > - LUKS2 by default use the memory-hard Argon2 key derivation function > > > which is quite memory-consuming compared to the limited memory reserved > > > for kdump. > > > > > > 1st kernel will add device tree property dmcryptkeys as similar to > > > elfcorehdr to pass the memory address of the stored info of dm-crypt > > > keys to the kdump kernel. > > > > Is there not any security issue with putting the key into the DT? The > > DT is provided to userspace. There's provisions already to not expose > > "security-*" properties to userspace (see __of_add_property_sysfs). > > Though I think that has a hole in that the FDT is also provided as-is. > > However, I don't even know who or what uses these properties. > > > > Rob > > Hi Rob, > > Thanks for raising the concern! If I understand DT correctly, this > property is only accessible to the kexec'ed kdump kernel. A new DT is > allocated and set up by of_kexec_alloc_and_setup_fdt. Btw, to be > precise, it's putting the memory address where the key is stored but > not the key itself into DT. The key is stored in the memory exclusively > reserved for kdump. For more info on by who and how this property will > used, I've created a dt-schema pull request as suggested by Krzysztof, > https://github.com/devicetree-org/dt-schema/pull/181 Okay, that's a bit less sensitive. That still could expose a memory address to user space which has generally been locked down in recent years. Though I'm not sure we'd consider addresses of blobs passed by kexec sensitive or secure. > > And yes, there is no need for even userspace of the kdump kernel to > access it. So this idea of "security-*" properties/__of_add_property_sysfs > seems desirable. Thanks for bringing it up! I'll give it a try. Since it is just the memory address, kdump just moving the key would be sufficient. Or the property can be removed early on. I think we do that with kaslr seed IIRC. Rob