From: Chun-Yi Lee <joeyli.kernel@gmail.com>
Date: Wed, 8 Nov 2017 15:11:33 +0000 (+0000)
Subject: kexec_file: Restrict at runtime if the kernel is locked down
X-Git-Tag: archive/raspbian/4.15.11-1+rpi1^2~40
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=d2c8614f1b8579ff2bdc7027ab2751d4abfc7960;p=linux.git

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 e5bcd94c1ef..5691e192002 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 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;