[PATCH] kexec_file: The integrity must be checked when the kernel is locked down

[Lee, Chun-Yi]

When KEXEC_VERIFY_SIG and IMA appraise are not enabled, kernel should
not allow that the image to be loaded by kexec_file systemcall when the
kernel is locked down.

The original code was showed in Matthew's patch but not in the later
patch set:
    https://lkml.org/lkml/2015/3/13/778

Signed-off-by: "Lee, Chun-Yi" <jlee@xxxxxxxx>
---
 kernel/kexec_file.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 9f48f44..b6dc218 100644
--- 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 check the integrity 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;
-- 
2.6.2