[PATCH security-next v5 09/30] LSM: Provide init debugging infrastructure

[Kees Cook]

Booting with "lsm.debug" will report future details on how LSM ordering
decisions are being made.

Signed-off-by: Kees Cook <keescook at chromium.org>
Reviewed-by: Casey Schaufler <casey at schaufler-ca.com>
Reviewed-by: John Johansen <john.johansen at canonical.com>
Reviewed-by: James Morris <james.morris at microsoft.com>
---
 .../admin-guide/kernel-parameters.txt          |  2 ++
 security/security.c                            | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9871e649ffef..32d323ee9218 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2274,6 +2274,8 @@
 	ltpc=		[NET]
 			Format: <io>,<irq>,<dma>
 
+	lsm.debug	[SECURITY] Enable LSM initialization debugging output.
+
 	machvec=	[IA-64] Force the use of a particular machine-vector
 			(machvec) in a generic kernel.
 			Example: machvec=hpzx1_swiotlb
diff --git a/security/security.c b/security/security.c
index e74f46fba591..395f804f6a91 100644
--- a/security/security.c
+++ b/security/security.c
@@ -12,6 +12,8 @@
  *	(at your option) any later version.
  */
 
+#define pr_fmt(fmt) "LSM: " fmt
+
 #include <linux/bpf.h>
 #include <linux/capability.h>
 #include <linux/dcache.h>
@@ -43,11 +45,19 @@ char *lsm_names;
 static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
 	CONFIG_DEFAULT_SECURITY;
 
+static __initdata bool debug;
+#define init_debug(...)						\
+	do {							\
+		if (debug)					\
+			pr_info(__VA_ARGS__);			\
+	} while (0)
+
 static void __init major_lsm_init(void)
 {
 	struct lsm_info *lsm;
 
 	for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
+		init_debug("initializing %s\n", lsm->name);
 		lsm->init();
 	}
 }
@@ -91,6 +101,14 @@ static int __init choose_lsm(char *str)
 }
 __setup("security=", choose_lsm);
 
+/* Enable LSM order debugging. */
+static int __init enable_debug(char *str)
+{
+	debug = true;
+	return 1;
+}
+__setup("lsm.debug", enable_debug);
+
 static bool match_last_lsm(const char *list, const char *lsm)
 {
 	const char *last;
-- 
2.17.1