From: Matthew Garrett <mjg59@srcf.ucam.org>
Date: Mon, 19 Aug 2019 17:17:42 -0700
Subject: kexec_load: Disable at runtime if the kernel is locked down
Patch-mainline: v5.4-rc1
Git-commit: 7d31f4602f8d366072471ca138e4ea7b8edf9be0
References: jsc#SLE-9870
The kexec_load() syscall 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_load() in this situation.
This does not affect kexec_file_load() syscall which can check for a
signature on the image to be booted.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Acked-by: Dave Young <dyoung@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
cc: kexec@lists.infradead.org
Signed-off-by: James Morris <jmorris@namei.org>
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
include/linux/security.h | 1 +
kernel/kexec.c | 8 ++++++++
security/lockdown/lockdown.c | 1 +
3 files changed, 10 insertions(+)
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -105,6 +105,7 @@ enum lockdown_reason {
LOCKDOWN_NONE,
LOCKDOWN_MODULE_SIGNATURE,
LOCKDOWN_DEV_MEM,
+ LOCKDOWN_KEXEC,
LOCKDOWN_INTEGRITY_MAX,
LOCKDOWN_CONFIDENTIALITY_MAX,
};
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -206,6 +206,14 @@ static inline int kexec_load_check(unsig
return result;
/*
+ * kexec can be used to circumvent module loading restrictions, so
+ * prevent loading in that case
+ */
+ result = security_locked_down(LOCKDOWN_KEXEC);
+ if (result)
+ return result;
+
+ /*
* Verify we have a legal set of flags
* This leaves us room for future extensions.
*/
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -20,6 +20,7 @@ static char *lockdown_reasons[LOCKDOWN_C
[LOCKDOWN_NONE] = "none",
[LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading",
[LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port",
+ [LOCKDOWN_KEXEC] = "kexec of unsigned images",
[LOCKDOWN_INTEGRITY_MAX] = "integrity",
[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
};