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Date: Wed, 6 Mar 2019 15:58:51 -0800 From: Matthew Garrett <matthewgarrett@...gle.com> To: jmorris@...ei.org Cc: linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org, dhowells@...hat.com Subject: [PATCH 05/27] kexec_load: Disable at runtime if the kernel is locked down From: Matthew Garrett <mjg59@...f.ucam.org> 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 <mjg59@...f.ucam.org> Signed-off-by: David Howells <dhowells@...hat.com> Acked-by: Dave Young <dyoung@...hat.com> Reviewed-by: "Lee, Chun-Yi" <jlee@...e.com> Reviewed-by: James Morris <james.l.morris@...cle.com> cc: kexec@...ts.infradead.org Signed-off-by: Matthew Garrett <matthewgarrett@...gle.com> --- kernel/kexec.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/kexec.c b/kernel/kexec.c index 68559808fdfa..8ea0ce31271f 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -207,6 +207,13 @@ 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")) + return -EPERM; + /* * Verify we have a legal set of flags * This leaves us room for future extensions. -- 2.21.0.352.gf09ad66450-goog
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