From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: [PATCH V32 04/27] kexec_load: Disable at runtime if the kernel is locked down Date: Wed, 3 Apr 2019 17:32:26 -0700 Message-ID: <20190404003249.14356-5-matthewgarrett@google.com> References: <20190404003249.14356-1-matthewgarrett@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20190404003249.14356-1-matthewgarrett@google.com> Sender: linux-kernel-owner@vger.kernel.org To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, dhowells@redhat.com, linux-api@vger.kernel.org, luto@kernel.org, Matthew Garrett , Matthew Garrett , Dave Young , kexec@lists.infradead.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: David Howells Signed-off-by: Matthew Garrett Acked-by: Dave Young cc: kexec@lists.infradead.org --- kernel/kexec.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/kexec.c b/kernel/kexec.c index 68559808fdfa..57047acc9a36 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -207,6 +207,14 @@ static inline int kexec_load_check(unsigned long nr_segments, if (result < 0) return result; + /* + * kexec can be used to circumvent module loading restrictions, so + * prevent loading in that case + */ + if (kernel_is_locked_down("kexec of unsigned images", + LOCKDOWN_INTEGRITY)) + return -EPERM; + /* * Verify we have a legal set of flags * This leaves us room for future extensions. -- 2.21.0.392.gf8f6787159e-goog