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Subject[RFC PATCH v3 2/3] ima: Add ns_status for storing namespaced iint data
Date
From: Mehmet Kayaalp <mkayaalp@linux.vnet.ibm.com>

This patch adds an rbtree to the IMA namespace structure that stores a
namespaced version of iint->flags in ns_status struct. Similar to the
integrity_iint_cache, both the iint ns_struct are looked up using the
inode pointer value. The lookup, allocate, and insertion code is also
similar, except ns_struct is not free'd when the inode is free'd.
Instead, the lookup verifies the i_ino and i_generation fields are also a
match. This could be replaced by a lazy clean up of the rbtree.

Signed-off-by: Mehmet Kayaalp <mkayaalp@linux.vnet.ibm.com>

Changelog:
v2:
* fixed tree traversal in __ima_ns_status_find()
---
include/linux/ima.h | 3 +
security/integrity/ima/ima.h | 19 +++++
security/integrity/ima/ima_init_ima_ns.c | 6 ++
security/integrity/ima/ima_ns.c | 117 +++++++++++++++++++++++++++++++
4 files changed, 145 insertions(+)

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 8bca67df0ad3..734934261011 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -110,6 +110,9 @@ static inline int ima_inode_removexattr(struct dentry *dentry,
struct ima_namespace {
struct kref kref;
struct ima_namespace *parent;
+ struct rb_root ns_status_tree;
+ rwlock_t ns_status_lock;
+ struct kmem_cache *ns_status_cache;
};

extern struct ima_namespace init_ima_ns;
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index e98c11c7cf75..e51a39ff75ff 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -128,6 +128,14 @@ static inline void ima_load_kexec_buffer(void) {}
*/
extern bool ima_canonical_fmt;

+struct ns_status {
+ struct rb_node rb_node;
+ struct inode *inode;
+ ino_t i_ino;
+ u32 i_generation;
+ unsigned long flags;
+};
+
/* Internal IMA function definitions */
int ima_init(void);
int ima_fs_init(void);
@@ -295,6 +303,17 @@ int ima_ns_init(void);
struct ima_namespace;
int ima_init_namespace(struct ima_namespace *ns);

+#ifdef CONFIG_IMA_NS
+struct ns_status *ima_get_ns_status(struct ima_namespace *ns,
+ struct inode *inode);
+#else
+static inline struct ns_status *ima_get_ns_status(struct ima_namespace *ns,
+ struct inode *inode)
+{
+ return NULL;
+}
+#endif /* CONFIG_IMA_NS */
+
/* LSM based policy rules require audit */
#ifdef CONFIG_IMA_LSM_RULES

diff --git a/security/integrity/ima/ima_init_ima_ns.c b/security/integrity/ima/ima_init_ima_ns.c
index 52cb94b1d392..66b681c1c722 100644
--- a/security/integrity/ima/ima_init_ima_ns.c
+++ b/security/integrity/ima/ima_init_ima_ns.c
@@ -12,9 +12,15 @@
#include <linux/export.h>
#include <linux/user_namespace.h>
#include <linux/ima.h>
+#include <linux/slab.h>
+
+#include "ima.h"

int ima_init_namespace(struct ima_namespace *ns)
{
+ ns->ns_status_tree = RB_ROOT;
+ rwlock_init(&ns->ns_status_lock);
+ ns->ns_status_cache = KMEM_CACHE(ns_status, SLAB_PANIC);
return 0;
}

diff --git a/security/integrity/ima/ima_ns.c b/security/integrity/ima/ima_ns.c
index 62148908015a..ef70fd1e25c6 100644
--- a/security/integrity/ima/ima_ns.c
+++ b/security/integrity/ima/ima_ns.c
@@ -69,9 +69,23 @@ struct ima_namespace *copy_ima(struct ima_namespace *old_ns)
return new_ns;
}

+static void free_ns_status_cache(struct ima_namespace *ns)
+{
+ struct ns_status *status, *next;
+
+ write_lock(&ns->ns_status_lock);
+ rbtree_postorder_for_each_entry_safe(status, next,
+ &ns->ns_status_tree, rb_node)
+ kmem_cache_free(ns->ns_status_cache, status);
+ ns->ns_status_tree = RB_ROOT;
+ write_unlock(&ns->ns_status_lock);
+ kmem_cache_destroy(ns->ns_status_cache);
+}
+
static void destroy_ima_ns(struct ima_namespace *ns)
{
put_ima_ns(ns->parent);
+ free_ns_status_cache(ns);
kfree(ns);
}

@@ -84,3 +98,106 @@ void free_ima_ns(struct kref *kref)

destroy_ima_ns(ns);
}
+
+/*
+ * __ima_ns_status_find - return the ns_status associated with an inode
+ */
+static struct ns_status *__ima_ns_status_find(struct ima_namespace *ns,
+ struct inode *inode)
+{
+ struct ns_status *status;
+ struct rb_node *n = ns->ns_status_tree.rb_node;
+
+ while (n) {
+ status = rb_entry(n, struct ns_status, rb_node);
+
+ if (inode < status->inode)
+ n = n->rb_left;
+ else if (inode > status->inode)
+ n = n->rb_right;
+ else
+ break;
+ }
+ if (!n)
+ return NULL;
+
+ return status;
+}
+
+/*
+ * ima_ns_status_find - return the ns_status associated with an inode
+ */
+static struct ns_status *ima_ns_status_find(struct ima_namespace *ns,
+ struct inode *inode)
+{
+ struct ns_status *status;
+
+ read_lock(&ns->ns_status_lock);
+ status = __ima_ns_status_find(ns, inode);
+ read_unlock(&ns->ns_status_lock);
+
+ return status;
+}
+
+void insert_ns_status(struct ima_namespace *ns, struct inode *inode,
+ struct ns_status *status)
+{
+ struct rb_node **p;
+ struct rb_node *node, *parent = NULL;
+ struct ns_status *test_status;
+
+ p = &ns->ns_status_tree.rb_node;
+ while (*p) {
+ parent = *p;
+ test_status = rb_entry(parent, struct ns_status, rb_node);
+ if (inode < test_status->inode)
+ p = &(*p)->rb_left;
+ else
+ p = &(*p)->rb_right;
+ }
+ node = &status->rb_node;
+ rb_link_node(node, parent, p);
+ rb_insert_color(node, &ns->ns_status_tree);
+}
+
+struct ns_status *ima_get_ns_status(struct ima_namespace *ns,
+ struct inode *inode)
+{
+ struct ns_status *status;
+ int skip_insert = 0;
+
+ status = ima_ns_status_find(ns, inode);
+ if (status) {
+ /*
+ * Unlike integrity_iint_cache we are not free'ing the
+ * ns_status data when the inode is free'd. So, in addition to
+ * checking the inode pointer, we need to make sure the
+ * (i_generation, i_ino) pair matches as well. In the future
+ * we might want to add support for lazily walking the rbtree
+ * to clean it up.
+ */
+ if (inode->i_ino == status->i_ino &&
+ inode->i_generation == status->i_generation)
+ return status;
+
+ /* Same inode number is reused, overwrite the ns_status */
+ skip_insert = 1;
+ } else {
+ status = kmem_cache_alloc(ns->ns_status_cache, GFP_NOFS);
+ if (!status)
+ return ERR_PTR(-ENOMEM);
+ }
+
+ write_lock(&ns->ns_status_lock);
+
+ if (!skip_insert)
+ insert_ns_status(ns, inode, status);
+
+ status->inode = inode;
+ status->i_ino = inode->i_ino;
+ status->i_generation = inode->i_generation;
+ status->flags = 0UL;
+ write_unlock(&ns->ns_status_lock);
+
+ return status;
+}
--
2.14.3
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