[PATCH v10 17/27] ima: Add functions for creating and freeing of an ima_namespace

[Stefan Berger <stefanb@xxxxxxxxxxxxx>]

Implement create_ima_ns() to create an empty ima_namespace. Defer its
initialization to a later point outside this function. Implement
free_ima_ns() to free it.

Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
Acked-by: Christian Brauner <brauner@xxxxxxxxxx>

---
v9:
 - Set user_ns->ims_ns = NULL in free_ima_ns()
 - Refactored create_ima_ns() to defer initialization
 - Removed pr_debug functions
---
 include/linux/ima.h                      | 13 ++++++
 security/integrity/ima/Makefile          |  1 +
 security/integrity/ima/ima.h             | 15 +++++++
 security/integrity/ima/ima_init_ima_ns.c |  2 +-
 security/integrity/ima/ima_ns.c          | 53 ++++++++++++++++++++++++
 5 files changed, 83 insertions(+), 1 deletion(-)
 create mode 100644 security/integrity/ima/ima_ns.c

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 0cf2a80c8b35..964a08702573 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -220,4 +220,17 @@ static inline bool ima_appraise_signature(enum kernel_read_file_id func)
 	return false;
 }
 #endif /* CONFIG_IMA_APPRAISE && CONFIG_INTEGRITY_TRUSTED_KEYRING */
+
+#ifdef CONFIG_IMA_NS
+
+void free_ima_ns(struct user_namespace *ns);
+
+#else
+
+static inline void free_ima_ns(struct user_namespace *user_ns)
+{
+}
+
+#endif /* CONFIG_IMA_NS */
+
 #endif /* _LINUX_IMA_H */
diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
index f8a5e5f3975d..b86a35fbed60 100644
--- a/security/integrity/ima/Makefile
+++ b/security/integrity/ima/Makefile
@@ -14,6 +14,7 @@ ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
 ima-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
 ima-$(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) += ima_asymmetric_keys.o
 ima-$(CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS) += ima_queue_keys.o
+ima-$(CONFIG_IMA_NS) += ima_ns.o
 
 ifeq ($(CONFIG_EFI),y)
 ima-$(CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT) += ima_efi.o
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 8c757223d549..751e936a6311 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -167,6 +167,7 @@ extern bool ima_canonical_fmt;
 int ima_init(void);
 int ima_fs_init(void);
 int ima_ns_init(void);
+int ima_init_namespace(struct ima_namespace *ns);
 int ima_add_template_entry(struct ima_namespace *ns,
 			   struct ima_template_entry *entry, int violation,
 			   const char *op, struct inode *inode,
@@ -502,4 +503,18 @@ static inline struct ima_namespace
 	return NULL;
 }
 
+#ifdef CONFIG_IMA_NS
+
+struct ima_namespace *create_ima_ns(void);
+
+#else
+
+static inline struct ima_namespace *create_ima_ns(void)
+{
+	WARN(1, "Cannot create an IMA namespace\n");
+	return ERR_PTR(-EFAULT);
+}
+
+#endif /* CONFIG_IMA_NS */
+
 #endif /* __LINUX_IMA_H */
diff --git a/security/integrity/ima/ima_init_ima_ns.c b/security/integrity/ima/ima_init_ima_ns.c
index 1cba545ae477..166dab4a3126 100644
--- a/security/integrity/ima/ima_init_ima_ns.c
+++ b/security/integrity/ima/ima_init_ima_ns.c
@@ -8,7 +8,7 @@
 
 #include "ima.h"
 
-static int ima_init_namespace(struct ima_namespace *ns)
+int ima_init_namespace(struct ima_namespace *ns)
 {
 	int rc;
 
diff --git a/security/integrity/ima/ima_ns.c b/security/integrity/ima/ima_ns.c
new file mode 100644
index 000000000000..b3b81a1e313e
--- /dev/null
+++ b/security/integrity/ima/ima_ns.c
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2016-2021 IBM Corporation
+ * Author:
+ *  Yuqiong Sun <suny@xxxxxxxxxx>
+ *  Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx>
+ */
+
+#include <linux/ima.h>
+
+#include "ima.h"
+
+static struct kmem_cache *imans_cachep;
+
+struct ima_namespace *create_ima_ns(void)
+{
+	struct ima_namespace *ns;
+
+	ns = kmem_cache_zalloc(imans_cachep, GFP_KERNEL);
+	if (!ns)
+		return ERR_PTR(-ENOMEM);
+
+	return ns;
+}
+
+/* destroy_ima_ns() must only be called after ima_init_namespace() was called */
+static void destroy_ima_ns(struct ima_namespace *ns)
+{
+	unregister_blocking_lsm_notifier(&ns->ima_lsm_policy_notifier);
+	kfree(ns->arch_policy_entry);
+	ima_free_policy_rules(ns);
+}
+
+void free_ima_ns(struct user_namespace *user_ns)
+{
+	struct ima_namespace *ns = user_ns->ima_ns;
+
+	if (!ns || WARN_ON(ns == &init_ima_ns))
+		return;
+
+	destroy_ima_ns(ns);
+
+	kmem_cache_free(imans_cachep, ns);
+
+	user_ns->ima_ns = NULL;
+}
+
+static int __init imans_cache_init(void)
+{
+	imans_cachep = KMEM_CACHE(ima_namespace, SLAB_PANIC);
+	return 0;
+}
+subsys_initcall(imans_cache_init)
-- 
2.31.1