From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mimi Zohar Subject: Re: [PATCH 06/24] kexec_load: Disable at runtime if the kernel is locked down Date: Wed, 11 Apr 2018 16:09:35 -0400 Message-ID: <1523477375.5268.78.camel@linux.vnet.ibm.com> References: <152346387861.4030.4408662483445703127.stgit@warthog.procyon.org.uk> <152346391877.4030.6270466586590461223.stgit@warthog.procyon.org.uk> <87po35k1q6.fsf@xmission.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <87po35k1q6.fsf@xmission.com> Sender: linux-kernel-owner@vger.kernel.org To: "Eric W. Biederman" , David Howells Cc: torvalds@linux-foundation.org, linux-man@vger.kernel.org, linux-api@vger.kernel.org, jmorris@namei.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org List-Id: linux-man@vger.kernel.org On Wed, 2018-04-11 at 14:00 -0500, Eric W. Biederman wrote: > David Howells writes: > > > From: Matthew Garrett > > > > The kexec_load() syscall permits the loading and execution of arbitrary > > code in ring 0, which is something that lock-down is meant to prevent. It > > makes sense to disable kexec_load() in this situation. > > > > This does not affect kexec_file_load() syscall which can check for a > > signature on the image to be booted. > > Maybing I am missing it but I am not seeing anything that would require > kexec_file_load be configured such that it checks the loaded kernel. > > Without that I don't see the point of disabling kexec_load. > > Nacked-by: "Eric W. Biederman" The IMA "secure boot" policy requires the kexec image to be signed.  This call to kernel_is_locked_down() could be replaced with a call to security_kernel_read_file(NULL, READING_KEXEC_IMAGE). It would be similar to the existing init_module syscall calling security_kernel_read_file(). Mimi