audit: maintain an lsm_prop in audit_context

Replace the secid value stored in struct audit_context with a struct
lsm_prop. Change the code that uses this value to accommodate the
change. security_audit_rule_match() expects a lsm_prop, so existing
scaffolding can be removed. A call to security_secid_to_secctx()
is changed to security_lsmprop_to_secctx().  The call to
security_ipc_getsecid() is scaffolded.

A new function lsmprop_is_set() is introduced to identify whether
an lsm_prop contains a non-zero value.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
[PM: subject line tweak, fix lsmprop_is_set() typo]
Signed-off-by: Paul Moore <paul@paul-moore.com>

Author: cschaufler

include/linux/security.h

@@ -291,6 +291,19 @@ static inline const char *kernel_load_data_id_str(enum kernel_load_data_id id)
 
 #ifdef CONFIG_SECURITY
 
+/**
+ * lsmprop_is_set - report if there is a value in the lsm_prop
+ * @prop: Pointer to the exported LSM data
+ *
+ * Returns true if there is a value set, false otherwise
+ */
+static inline bool lsmprop_is_set(struct lsm_prop *prop)
+{
+	const struct lsm_prop empty = {};
+
+	return !!memcmp(prop, &empty, sizeof(*prop));
+}
+
 int call_blocking_lsm_notifier(enum lsm_event event, void *data);
 int register_blocking_lsm_notifier(struct notifier_block *nb);
 int unregister_blocking_lsm_notifier(struct notifier_block *nb);
@@ -552,6 +565,17 @@ int security_bdev_setintegrity(struct block_device *bdev,
 			       size_t size);
 #else /* CONFIG_SECURITY */
 
+/**
+ * lsmprop_is_set - report if there is a value in the lsm_prop
+ * @prop: Pointer to the exported LSM data
+ *
+ * Returns true if there is a value set, false otherwise
+ */
+static inline bool lsmprop_is_set(struct lsm_prop *prop)
+{
+	return false;
+}
+
 static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
 {
 	return 0;

kernel/audit.h

@@ -11,6 +11,7 @@
 
 #include <linux/fs.h>
 #include <linux/audit.h>
+#include <linux/security.h>
 #include <linux/skbuff.h>
 #include <uapi/linux/mqueue.h>
 #include <linux/tty.h>
@@ -160,7 +161,7 @@ struct audit_context {
 			kuid_t			uid;
 			kgid_t			gid;
 			umode_t			mode;
-			u32			osid;
+			struct lsm_prop		oprop;
 			int			has_perm;
 			uid_t			perm_uid;
 			gid_t			perm_gid;

kernel/auditsc.c

@@ -724,9 +724,7 @@ static int audit_filter_rules(struct task_struct *tsk,
 				/* Find ipc objects that match */
 				if (!ctx || ctx->type != AUDIT_IPC)
 					break;
-				/* scaffolding */
-				prop.scaffold.secid = ctx->ipc.osid;
-				if (security_audit_rule_match(&prop,
+				if (security_audit_rule_match(&ctx->ipc.oprop,
 							      f->type, f->op,
 							      f->lsm_rule))
 					++result;
@@ -1394,19 +1392,17 @@ static void show_special(struct audit_context *context, int *call_panic)
 			audit_log_format(ab, " a%d=%lx", i,
 				context->socketcall.args[i]);
 		break; }
-	case AUDIT_IPC: {
-		u32 osid = context->ipc.osid;
-
+	case AUDIT_IPC:
 		audit_log_format(ab, "ouid=%u ogid=%u mode=%#ho",
 				 from_kuid(&init_user_ns, context->ipc.uid),
 				 from_kgid(&init_user_ns, context->ipc.gid),
 				 context->ipc.mode);
-		if (osid) {
+		if (lsmprop_is_set(&context->ipc.oprop)) {
 			char *ctx = NULL;
 			u32 len;
 
-			if (security_secid_to_secctx(osid, &ctx, &len)) {
-				audit_log_format(ab, " osid=%u", osid);
+			if (security_lsmprop_to_secctx(&context->ipc.oprop,
+						       &ctx, &len)) {
 				*call_panic = 1;
 			} else {
 				audit_log_format(ab, " obj=%s", ctx);
@@ -1426,7 +1422,7 @@ static void show_special(struct audit_context *context, int *call_panic)
 				context->ipc.perm_gid,
 				context->ipc.perm_mode);
 		}
-		break; }
+		break;
 	case AUDIT_MQ_OPEN:
 		audit_log_format(ab,
 			"oflag=0x%x mode=%#ho mq_flags=0x%lx mq_maxmsg=%ld "
@@ -2642,7 +2638,8 @@ void __audit_ipc_obj(struct kern_ipc_perm *ipcp)
 	context->ipc.gid = ipcp->gid;
 	context->ipc.mode = ipcp->mode;
 	context->ipc.has_perm = 0;
-	security_ipc_getsecid(ipcp, &context->ipc.osid);
+	/* scaffolding */
+	security_ipc_getsecid(ipcp, &context->ipc.oprop.scaffold.secid);
 	context->type = AUDIT_IPC;
 }