From: David Howells <dhowells@redhat.com>
References: fate#314486
Acked-by: Jiri Bohac <jbohac@suse.cz>
Patch-mainline: Not yet, submitted https://lkml.org/lkml/2018/2/22/439
Subject: kexec_file: Restrict at runtime if the kernel is locked down

When KEXEC_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.

[Modified by David Howells to fit with modifications to the previous patch
 and to return -EPERM if the kernel is locked down for consistency with
 other lockdowns]

Signed-off-by: Jiri Bohac <jbohac@suse.cz>
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
cc: Chun-Yi Lee <jlee@suse.com>
cc: kexec@lists.infradead.org

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index d5931e392050..c47c4de604cd 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -167,6 +167,13 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 		}
 
 		ret = 0;
+
+		if (kernel_is_locked_down()) {
+			pr_notice("%s rejected, kernel is locked down\n", reason);
+			ret = -EPERM;
+			goto out;
+		}
+
 		break;
 
 		/* All other errors are fatal, including nomem, unparseable