Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752217AbdLFSho (ORCPT ); Wed, 6 Dec 2017 13:37:44 -0500 Received: from mail-wm0-f67.google.com ([74.125.82.67]:43351 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751630AbdLFShj (ORCPT ); Wed, 6 Dec 2017 13:37:39 -0500 X-Google-Smtp-Source: AGs4zMbkzTsebSLa19D3jOGTgnw3Ta/G8lBGQCAapwZEn1aB499qkmMtVBFFyd6vZDwY3f/ZhWgryg== Date: Wed, 6 Dec 2017 19:37:34 +0100 From: Ingo Molnar To: Gary Lin Cc: Josh Boyer , x86 , "Linux-Kernel@Vger. Kernel. Org" , "linux-efi@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "H. Peter Anvin" , Thomas Gleixner , Ard Biesheuvel , Ingo Molnar , Matt Fleming , Catalin Marinas , Will Deacon , Joey Lee Subject: Re: [RFC v3 PATCH 0/2] Introduce Security Version to EFI Stub Message-ID: <20171206183734.xmgecyrd5suiurm6@gmail.com> References: <20171205100148.5757-1-glin@suse.com> <20171206032437.pifxxcewgozlghfs@GaryWorkstation> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171206032437.pifxxcewgozlghfs@GaryWorkstation> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1664 Lines: 36 * Gary Lin wrote: > On Tue, Dec 05, 2017 at 04:14:26PM -0500, Josh Boyer wrote: > > On Tue, Dec 5, 2017 at 5:01 AM, Gary Lin wrote: > > > The series of patches introduce Security Version to EFI stub. > > > > > > Security Version is a monotonically increasing number and designed to > > > prevent the user from loading an insecure kernel accidentally. The > > > bootloader maintains a list of security versions corresponding to > > > different distributions. After fixing a critical vulnerability, the > > > distribution kernel maintainer bumps the "version", and the bootloader > > > updates the list automatically. When the user tries to load a kernel > > > with a lower security version, the bootloader shows a warning prompt > > > to notify the user the potential risk. > > > > If a distribution releases a kernel with a higher security version and > > that it automatically updated on boot, what happens if that kernel > > contains a different bug that causes it to fail to boot or break > > critical functionality? At that point, the user's machine would be in > > a state where the higher security version is enforced but the only > > kernel that provides that is broken. Wouldn't that make a bad > > situation even worse by now requiring manual acceptance of the older > > SV kernel boot physically at the machine? > > > > I feel like I'm missing a detail here or something. > > > If the new kernel fails to boot, then the user has to choose the kernel > manually anyway, and there will be an option in the warning prompt to > lower SV. And what if the firmware does not support a lowering of the SV? Thanks, Ingo