[PATCH] selinux: Reduce memory use by avtab

This patch improves memory use by SELinux by both reducing the avtab node
size and reducing the number of avtab nodes.  The memory savings are
substantial, e.g.  on a 64-bit system after boot, James Morris reported the
following data for the targeted and strict policies:

            #objs  objsize   kernmem
Targeted:
  Before:  237888       40     9.1MB
  After:    19968       24     468KB

Strict:
  Before:  571680       40   21.81MB
  After:   221052       24    5.06MB

The improvement in memory use comes at a cost in the speed of security
server computations of access vectors, but these computations are only
required on AVC cache misses, and performance measurements by James Morris
using a number of benchmarks have shown that the change does not cause any
significant degradation.

Note that a rebuilt policy via an updated policy toolchain
(libsepol/checkpolicy) is required in order to gain the full benefits of
this patch, although some memory savings benefits are immediately applied
even to older policies (in particular, the reduction in avtab node size).
Sources for the updated toolchain are presently available from the
sourceforge CVS tree (http://sourceforge.net/cvs/?group_id=21266), and
tarballs are available from http://www.flux.utah.edu/~sds.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 18 insertions, 19 deletions

diff --git a/security/selinux/ss/avtab.h b/security/selinux/ss/avtab.h
index 519d4f6dc655..0a90d939af93 100644
--- a/security/selinux/ss/avtab.h
+++ b/security/selinux/ss/avtab.h
@@ -21,12 +21,9 @@
 #define _SS_AVTAB_H_
 
 struct avtab_key {
-        u32 source_type;        /* source type */
-        u32 target_type;        /* target type */
-        u32 target_class;       /* target object class */
-};
-
-struct avtab_datum {
+        u16 source_type;        /* source type */
+        u16 target_type;        /* target type */
+        u16 target_class;       /* target object class */
 #define AVTAB_ALLOWED     1
 #define AVTAB_AUDITALLOW  2
 #define AVTAB_AUDITDENY   4
@@ -35,15 +32,13 @@ struct avtab_datum {
 #define AVTAB_MEMBER     32
 #define AVTAB_CHANGE     64
 #define AVTAB_TYPE       (AVTAB_TRANSITION | AVTAB_MEMBER | AVTAB_CHANGE)
-#define AVTAB_ENABLED    0x80000000 /* reserved for used in cond_avtab */
-        u32 specified;  /* what fields are specified */
-        u32 data[3];    /* access vectors or types */
-#define avtab_allowed(x) (x)->data[0]
-#define avtab_auditdeny(x) (x)->data[1]
-#define avtab_auditallow(x) (x)->data[2]
-#define avtab_transition(x) (x)->data[0]
-#define avtab_change(x) (x)->data[1]
-#define avtab_member(x) (x)->data[2]
+#define AVTAB_ENABLED_OLD    0x80000000 /* reserved for used in cond_avtab */
+#define AVTAB_ENABLED    0x8000 /* reserved for used in cond_avtab */
+        u16 specified;  /* what field is specified */
+};
+
+struct avtab_datum {
+        u32 data; /* access vector or type value */
 };
 
 struct avtab_node {
@@ -58,17 +53,21 @@ struct avtab {
 };
 
 int avtab_init(struct avtab *);
-struct avtab_datum *avtab_search(struct avtab *h, struct avtab_key *k, int specified);
+struct avtab_datum *avtab_search(struct avtab *h, struct avtab_key *k);
 void avtab_destroy(struct avtab *h);
 void avtab_hash_eval(struct avtab *h, char *tag);
 
-int avtab_read_item(void *fp, struct avtab_datum *avdatum, struct avtab_key *avkey);
-int avtab_read(struct avtab *a, void *fp, u32 config);
+int avtab_read_item(void *fp, uint32_t vers, struct avtab *a,
+                    int (*insert)(struct avtab *a, struct avtab_key *k,
+                                  struct avtab_datum *d, void *p),
+                    void *p);
+
+int avtab_read(struct avtab *a, void *fp, u32 vers);
 
 struct avtab_node *avtab_insert_nonunique(struct avtab *h, struct avtab_key *key,
                                           struct avtab_datum *datum);
 
-struct avtab_node *avtab_search_node(struct avtab *h, struct avtab_key *key, int specified);
+struct avtab_node *avtab_search_node(struct avtab *h, struct avtab_key *key);
 
 struct avtab_node *avtab_search_node_next(struct avtab_node *node, int specified);