path: root/security/integrity/ima/ima.h
diff options
authorEric Paris <eparis@redhat.com>2010-10-25 14:41:18 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2010-10-26 11:37:17 -0700
commit8549164143a5431f9d9ea846acaa35a862410d9c (patch)
tree79b0d2aeb2674f221854866cb067947dc47f2203 /security/integrity/ima/ima.h
parentf6f94e2ab1b33f0082ac22d71f66385a60d8157f (diff)
IMA: use rbtree instead of radix tree for inode information cache
The IMA code needs to store the number of tasks which have an open fd granting permission to write a file even when IMA is not in use. It needs this information in order to be enabled at a later point in time without losing it's integrity garantees. At the moment that means we store a little bit of data about every inode in a cache. We use a radix tree key'd on the inode's memory address. Dave Chinner pointed out that a radix tree is a terrible data structure for such a sparse key space. This patch switches to using an rbtree which should be more efficient. Bug report from Dave: "I just noticed that slabtop was reporting an awfully high usage of radix tree nodes: OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME 4200331 2778082 66% 0.55K 144839 29 2317424K radix_tree_node 2321500 2060290 88% 1.00K 72581 32 2322592K xfs_inode 2235648 2069791 92% 0.12K 69864 32 279456K iint_cache That is, 2.7M radix tree nodes are allocated, and the cache itself is consuming 2.3GB of RAM. I know that the XFS inodei caches are indexed by radix tree node, but for 2 million cached inodes that would mean a density of 1 inode per radix tree node, which for a system with 16M inodes in the filsystems is an impossibly low density. The worst I've seen in a production system like kernel.org is about 20-25% density, which would mean about 150-200k radix tree nodes for that many inodes. So it's not the inode cache. So I looked up what the iint_cache was. It appears to used for storing per-inode IMA information, and uses a radix tree for indexing. It uses the *address* of the struct inode as the indexing key. That means the key space is extremely sparse - for XFS the struct inode addresses are approximately 1000 bytes apart, which means the closest the radix tree index keys get is ~1000. Which means that there is a single entry per radix tree leaf node, so the radix tree is using roughly 550 bytes for every 120byte structure being cached. For the above example, it's probably wasting close to 1GB of RAM...." Reported-by: Dave Chinner <david@fromorbit.com> Signed-off-by: Eric Paris <eparis@redhat.com> Acked-by: Mimi Zohar <zohar@linux.vnet.ibm.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'security/integrity/ima/ima.h')
1 files changed, 3 insertions, 3 deletions
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 3fbcd1dda0e..7557791e954 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -100,6 +100,8 @@ static inline unsigned long ima_hash_key(u8 *digest)
/* integrity data associated with an inode */
struct ima_iint_cache {
+ struct rb_node rb_node; /* rooted in ima_iint_tree */
+ struct inode *inode; /* back pointer to inode in question */
u64 version; /* track inode changes */
unsigned long flags;
u8 digest[IMA_DIGEST_SIZE];
@@ -108,7 +110,6 @@ struct ima_iint_cache {
long writecount; /* measured files writecount */
long opencount; /* opens reference count */
struct kref refcount; /* ima_iint_cache reference count */
- struct rcu_head rcu;
/* LIM API function definitions */
@@ -122,13 +123,12 @@ int ima_store_template(struct ima_template_entry *entry, int violation,
void ima_template_show(struct seq_file *m, void *e,
enum ima_show_type show);
-/* radix tree calls to lookup, insert, delete
+/* rbtree tree calls to lookup, insert, delete
* integrity data associated with an inode.
struct ima_iint_cache *ima_iint_insert(struct inode *inode);
struct ima_iint_cache *ima_iint_find_get(struct inode *inode);
void iint_free(struct kref *kref);
-void iint_rcu_free(struct rcu_head *rcu);
/* IMA policy related functions */
enum ima_hooks { FILE_CHECK = 1, FILE_MMAP, BPRM_CHECK };