Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753418AbbFODvC (ORCPT ); Sun, 14 Jun 2015 23:51:02 -0400 Received: from imap.thunk.org ([74.207.234.97]:35148 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751993AbbFODu4 (ORCPT ); Sun, 14 Jun 2015 23:50:56 -0400 Date: Sun, 14 Jun 2015 23:50:51 -0400 From: "Theodore Ts'o" To: Eric Biederman , dhowells@redhat.com Cc: kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: kexec_load(2) bypasses signature verification Message-ID: <20150615035051.GA2634@thunk.org> Mail-Followup-To: Theodore Ts'o , Eric Biederman , dhowells@redhat.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.23 (2014-03-12) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on imap.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1399 Lines: 31 >From experimentation and from looking at the sources, it appears that the signature checking is only done in the kexec_file_load(2) system all, and not in the kexec_load(2) system call. And I understand why -- the signature is not sent from userspace to the kernel in the older kexec_load(2) system call. The problem is that if you use an old version of kexec, it will use the old kexec_load(2) system call, and even though CONFIG_KEXEC_VERIFY_SIG is enabled, kexec_load(2) will happily load an unsigned kernel, and then "kexec -e" will happily boot into it. Correct me if I am wrong, but this appears to be a hole in Secure Boot you could drive a Mack Truck through. (I noticed this because Debian is still using a kexec-tools from the stone ages, version 2.0.7, and I was wondering **why** I was able to kexec boot completely unsigned kernels.) It would appear to me that if CONFIG_KEXEC_VERIFY_SIG is enabled, the old kexec_load(2) system call should be disabled (and a warning be placed in the Kconfig help that the user should have at least verision 2.X of kexec-tools if they enable this kernel option). Am I missing something? - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/