[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, 23 insertions, 19 deletions

diff --git a/security/selinux/ss/mls.c b/security/selinux/ss/mls.c
index d4c32c39ccc..aaefac2921f 100644
--- a/security/selinux/ss/mls.c
+++ b/security/selinux/ss/mls.c
@@ -27,6 +27,7 @@
 int mls_compute_context_len(struct context * context)
 {
 	int i, l, len, range;
+	struct ebitmap_node *node;
 
 	if (!selinux_mls_enabled)
 		return 0;
@@ -36,24 +37,24 @@ int mls_compute_context_len(struct context * context)
 		range = 0;
 		len += strlen(policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
 
-		for (i = 1; i <= ebitmap_length(&context->range.level[l].cat); i++) {
-			if (ebitmap_get_bit(&context->range.level[l].cat, i - 1)) {
+		ebitmap_for_each_bit(&context->range.level[l].cat, node, i) {
+			if (ebitmap_node_get_bit(node, i)) {
 				if (range) {
 					range++;
 					continue;
 				}
 
-				len += strlen(policydb.p_cat_val_to_name[i - 1]) + 1;
+				len += strlen(policydb.p_cat_val_to_name[i]) + 1;
 				range++;
 			} else {
 				if (range > 1)
-					len += strlen(policydb.p_cat_val_to_name[i - 2]) + 1;
+					len += strlen(policydb.p_cat_val_to_name[i - 1]) + 1;
 				range = 0;
 			}
 		}
 		/* Handle case where last category is the end of range */
 		if (range > 1)
-			len += strlen(policydb.p_cat_val_to_name[i - 2]) + 1;
+			len += strlen(policydb.p_cat_val_to_name[i - 1]) + 1;
 
 		if (l == 0) {
 			if (mls_level_eq(&context->range.level[0],
@@ -77,6 +78,7 @@ void mls_sid_to_context(struct context *context,
 {
 	char *scontextp;
 	int i, l, range, wrote_sep;
+	struct ebitmap_node *node;
 
 	if (!selinux_mls_enabled)
 		return;
@@ -94,8 +96,8 @@ void mls_sid_to_context(struct context *context,
 		scontextp += strlen(policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
 
 		/* categories */
-		for (i = 1; i <= ebitmap_length(&context->range.level[l].cat); i++) {
-			if (ebitmap_get_bit(&context->range.level[l].cat, i - 1)) {
+		ebitmap_for_each_bit(&context->range.level[l].cat, node, i) {
+			if (ebitmap_node_get_bit(node, i)) {
 				if (range) {
 					range++;
 					continue;
@@ -106,8 +108,8 @@ void mls_sid_to_context(struct context *context,
 					wrote_sep = 1;
 				} else
 					*scontextp++ = ',';
-				strcpy(scontextp, policydb.p_cat_val_to_name[i - 1]);
-				scontextp += strlen(policydb.p_cat_val_to_name[i - 1]);
+				strcpy(scontextp, policydb.p_cat_val_to_name[i]);
+				scontextp += strlen(policydb.p_cat_val_to_name[i]);
 				range++;
 			} else {
 				if (range > 1) {
@@ -116,8 +118,8 @@ void mls_sid_to_context(struct context *context,
 					else
 						*scontextp++ = ',';
 
-					strcpy(scontextp, policydb.p_cat_val_to_name[i - 2]);
-					scontextp += strlen(policydb.p_cat_val_to_name[i - 2]);
+					strcpy(scontextp, policydb.p_cat_val_to_name[i - 1]);
+					scontextp += strlen(policydb.p_cat_val_to_name[i - 1]);
 				}
 				range = 0;
 			}
@@ -130,8 +132,8 @@ void mls_sid_to_context(struct context *context,
 			else
 				*scontextp++ = ',';
 
-			strcpy(scontextp, policydb.p_cat_val_to_name[i - 2]);
-			scontextp += strlen(policydb.p_cat_val_to_name[i - 2]);
+			strcpy(scontextp, policydb.p_cat_val_to_name[i - 1]);
+			scontextp += strlen(policydb.p_cat_val_to_name[i - 1]);
 		}
 
 		if (l == 0) {
@@ -157,6 +159,7 @@ int mls_context_isvalid(struct policydb *p, struct context *c)
 {
 	struct level_datum *levdatum;
 	struct user_datum *usrdatum;
+	struct ebitmap_node *node;
 	int i, l;
 
 	if (!selinux_mls_enabled)
@@ -179,11 +182,11 @@ int mls_context_isvalid(struct policydb *p, struct context *c)
 		if (!levdatum)
 			return 0;
 
-		for (i = 1; i <= ebitmap_length(&c->range.level[l].cat); i++) {
-			if (ebitmap_get_bit(&c->range.level[l].cat, i - 1)) {
+		ebitmap_for_each_bit(&c->range.level[l].cat, node, i) {
+			if (ebitmap_node_get_bit(node, i)) {
 				if (i > p->p_cats.nprim)
 					return 0;
-				if (!ebitmap_get_bit(&levdatum->level->cat, i - 1))
+				if (!ebitmap_get_bit(&levdatum->level->cat, i))
 					/*
 					 * Category may not be associated with
 					 * sensitivity in low level.
@@ -468,6 +471,7 @@ int mls_convert_context(struct policydb *oldp,
 	struct level_datum *levdatum;
 	struct cat_datum *catdatum;
 	struct ebitmap bitmap;
+	struct ebitmap_node *node;
 	int l, i;
 
 	if (!selinux_mls_enabled)
@@ -482,12 +486,12 @@ int mls_convert_context(struct policydb *oldp,
 		c->range.level[l].sens = levdatum->level->sens;
 
 		ebitmap_init(&bitmap);
-		for (i = 1; i <= ebitmap_length(&c->range.level[l].cat); i++) {
-			if (ebitmap_get_bit(&c->range.level[l].cat, i - 1)) {
+		ebitmap_for_each_bit(&c->range.level[l].cat, node, i) {
+			if (ebitmap_node_get_bit(node, i)) {
 				int rc;
 
 				catdatum = hashtab_search(newp->p_cats.table,
-				         	oldp->p_cat_val_to_name[i - 1]);
+				         	oldp->p_cat_val_to_name[i]);
 				if (!catdatum)
 					return -EINVAL;
 				rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);