kexec_file: Disable at runtime if securelevel has been set

When KEXEC_VERIFY_SIG is not enabled, kernel should not loads image
through kexec_file systemcall if securelevel has been set.

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: Lee, Chun-Yi <jlee@suse.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0046-kexec_file-Disable-at-runtime-if-securelevel-has-bee.patch

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index b118735fea9da471a15ba627c87af523b891bafa..f6937eecd1eb2eeddf3e193a4478c9e9b92ed4ed 100644 (file)
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -268,6 +268,12 @@ 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) && kernel_is_locked_down())
+               return -EPERM;
+
        /* Make sure we have a legal set of flags */
        if (flags != (flags & KEXEC_FILE_FLAGS))
                return -EINVAL;