kexec_load: Disable at runtime if the kernel is locked down

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@srcf.ucam.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Dave Young <dyoung@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
cc: kexec@lists.infradead.org

Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0006-kexec_load-Disable-at-runtime-if-the-kernel-is-locke.patch

diff --git a/kernel/kexec.c b/kernel/kexec.c
index 1b018f1a6e0d85647e4cc5e6646cacc15e5a2bee..fc87f152c2298e82273ce9569fabfecc163cd05e 100644 (file)
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -205,6 +205,13 @@ 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.