linux-kernel - [PATCH 09/24] kexec_file: Disable at runtime if securelevel has been set

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Message-ID: <149141228170.31282.6899985667525868658.stgit@warthog.procyon.org.uk>
Date:   Wed, 05 Apr 2017 18:11:21 +0100
From:   David Howells <dhowells@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Matthew Garrett <mjg59@...f.ucam.org>, dhowells@...hat.com,
        linux-efi@...r.kernel.org, gnomes@...rguk.ukuu.org.uk,
        gregkh@...uxfoundation.org, Chun-Yi Lee <jlee@...e.com>,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        matthew.garrett@...ula.com
Subject: [PATCH 09/24] kexec_file: Disable at runtime if securelevel has
 been set

From: Chun-Yi Lee <joeyli.kernel@...il.com>

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@...f.ucam.org>
Signed-off-by: Chun-Yi Lee <jlee@...e.com>
Signed-off-by: David Howells <dhowells@...hat.com>
---

 kernel/kexec_file.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index b118735fea9d..f6937eecd1eb 100644
--- 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;