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Date: Wed, 3 Apr 2019 17:32:26 -0700 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, linux-api@...r.kernel.org, luto@...nel.org, Matthew Garrett <mjg59@...f.ucam.org>, Matthew Garrett <mjg59@...gle.com>, Dave Young <dyoung@...hat.com>, kexec@...ts.infradead.org Subject: [PATCH V32 04/27] 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: David Howells <dhowells@...hat.com> Signed-off-by: Matthew Garrett <mjg59@...gle.com> Acked-by: Dave Young <dyoung@...hat.com> cc: kexec@...ts.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
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