[PATCH v6 10/17] ima: Implement hierarchical processing of file accesses

[Stefan Berger <stefanb@linux.ibm.com>]

Implement hierarchical processing of file accesses in IMA namespaces by
walking the list of IMA namespaces towards the init_ima_ns. This way
file accesses can be audited in an IMA namespace and also be evaluated
against the IMA policies of parent IMA namespaces.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 include/linux/ima.h               |  9 +++++++++
 security/integrity/ima/ima_main.c | 29 +++++++++++++++++++++++++----
 2 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 85903f40acfd..fda371cbde50 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -66,6 +66,15 @@ static inline const char * const *arch_get_ima_policy(void)
 }
 #endif
 
+static inline struct user_namespace *ima_user_ns(struct ima_namespace *ns)
+{
+	struct user_namespace *user_ns;
+
+	user_ns = current_user_ns();
+	WARN_ON(user_ns->ima_ns != ns);
+	return user_ns;
+}
+
 #else
 static inline enum hash_algo ima_get_current_hash_algo(void)
 {
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 2121a831f38a..6ebc57cd91d3 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -200,10 +200,10 @@ void ima_file_free(struct file *file)
 	ima_check_last_writer(iint, inode, file);
 }
 
-static int process_measurement(struct ima_namespace *ns,
-			       struct file *file, const struct cred *cred,
-			       u32 secid, char *buf, loff_t size, int mask,
-			       enum ima_hooks func)
+static int __process_measurement(struct ima_namespace *ns,
+				 struct file *file, const struct cred *cred,
+				 u32 secid, char *buf, loff_t size, int mask,
+				 enum ima_hooks func)
 {
 	struct inode *inode = file_inode(file);
 	struct integrity_iint_cache *iint = NULL;
@@ -405,6 +405,27 @@ static int process_measurement(struct ima_namespace *ns,
 	return 0;
 }
 
+static int process_measurement(struct ima_namespace *ns,
+			       struct file *file, const struct cred *cred,
+			       u32 secid, char *buf, loff_t size, int mask,
+			       enum ima_hooks func)
+{
+	struct user_namespace *user_ns = ima_user_ns(ns);
+	int ret = 0;
+
+	while (user_ns) {
+		ns = user_ns->ima_ns;
+
+		ret = __process_measurement(ns, file, cred, secid, buf, size, mask, func);
+		if (ret)
+			break;
+
+		user_ns = user_ns->parent;
+	};
+
+	return ret;
+}
+
 /**
  * ima_file_mmap - based on policy, collect/store measurement.
  * @file: pointer to the file to be measured (May be NULL)
-- 
2.31.1