From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Wed, 5 Apr 2017 16:40:30 +0000 (+0100)
Subject: kexec: Disable at runtime if the kernel is locked down
X-Git-Tag: archive/raspbian/4.15.4-1+rpi1~1^2^2~65
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=b9ea179804b590603f2a4ad2cdb5fba99eded331;p=linux.git

kexec: Disable at runtime if the kernel is locked down

kexec permits the loading and execution of arbitrary code in ring 0, which
is something that lock-down is meant to prevent. It makes sense to disable
kexec in this situation.

This does not affect kexec_file_load() which can check for a signature on the
image to be booted.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>

Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0044-kexec-Disable-at-runtime-if-the-kernel-is-locked-dow.patch
---

diff --git a/kernel/kexec.c b/kernel/kexec.c
index e62ec4dc662..37f75d0b75d 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -201,6 +201,13 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 	if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
 		return -EPERM;
 
+	/*
+	 * kexec can be used to circumvent module loading restrictions, so
+	 * prevent loading in that case
+	 */
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	/*
 	 * Verify we have a legal set of flags
 	 * This leaves us room for future extensions.