kexec_file: Restrict at runtime if the kernel is locked down

When KEXEC_VERIFY_SIG is not enabled, kernel should not load images through
kexec_file systemcall if the kernel is locked down unless IMA can be used
to validate the image.

This code was showed in Matthew's patch but not in git:
https://lkml.org/lkml/2015/3/13/778

Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: Chun-Yi Lee <jlee@suse.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
cc: kexec@lists.infradead.org

Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0008-kexec_file-Restrict-at-runtime-if-the-kernel-is-lock.patch

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index e5bcd94c1efb13db5daa12d7dd188279ea25c1a1..5691e192002ffa65b70b43632ca0253e82d46f0b 100644 (file)
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -255,6 +255,14 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
        if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
                return -EPERM;
 
+       /* Don't permit images to be loaded into trusted kernels if we're not
+        * going to verify the signature on them
+        */
+       if (!IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG) &&
+           !is_ima_appraise_enabled() &&
+           kernel_is_locked_down("kexec of unsigned images"))
+               return -EPERM;
+
        /* Make sure we have a legal set of flags */
        if (flags != (flags & KEXEC_FILE_FLAGS))
                return -EINVAL;