From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Howells Subject: [PATCH 06/24] kexec_load: Disable at runtime if the kernel is locked down Date: Wed, 11 Apr 2018 17:25:18 +0100 Message-ID: <152346391877.4030.6270466586590461223.stgit@warthog.procyon.org.uk> References: <152346387861.4030.4408662483445703127.stgit@warthog.procyon.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <152346387861.4030.4408662483445703127.stgit@warthog.procyon.org.uk> Sender: linux-kernel-owner@vger.kernel.org To: torvalds@linux-foundation.org Cc: linux-man@vger.kernel.org, linux-api@vger.kernel.org, jmorris@namei.org, linux-kernel@vger.kernel.org, dhowells@redhat.com, linux-security-module@vger.kernel.org List-Id: linux-api@vger.kernel.org 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. Signed-off-by: Matthew Garrett Signed-off-by: David Howells Acked-by: Dave Young Reviewed-by: "Lee, Chun-Yi" Reviewed-by: James Morris cc: kexec@lists.infradead.org --- kernel/kexec.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/kexec.c b/kernel/kexec.c index aed8fb2564b3..1553ac765e73 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -199,6 +199,13 @@ static inline int kexec_load_check(unsigned long nr_segments, if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) return -EPERM; + /* + * kexec can be used to circumvent module loading restrictions, so + * prevent loading in that case + */ + if (kernel_is_locked_down("kexec of unsigned images")) + return -EPERM; + /* * Verify we have a legal set of flags * This leaves us room for future extensions.