Re: [PATCH 4/6] selinux: convert cond_av_list to array

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On 1/16/20 7:04 AM, Ondrej Mosnacek wrote:
Since it is fixed-size after allocation and we know the size beforehand,
using a plain old array is simpler and more efficient.

Signed-off-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>

Reviewed-by: Stephen Smalley <sds@xxxxxxxxxxxxx>

---
  security/selinux/ss/conditional.c | 125 ++++++++++++------------------
  security/selinux/ss/conditional.h |   8 +-
  2 files changed, 53 insertions(+), 80 deletions(-)

diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
index c8a02c9b23ee..b847fd2a6a51 100644
--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -87,8 +87,9 @@ static int cond_evaluate_expr(struct policydb *p, struct cond_expr *expr)
   */
  void evaluate_cond_node(struct policydb *p, struct cond_node *node)
  {
+	struct avtab_node *avnode;
  	int new_state;
-	struct cond_av_list *cur;
+	u32 i;
new_state = cond_evaluate_expr(p, node->expr);
  	if (new_state != node->cur_state) {
@@ -96,19 +97,21 @@ void evaluate_cond_node(struct policydb *p, struct cond_node *node)
  		if (new_state == -1)
  			pr_err("SELinux: expression result was undefined - disabling all rules.\n");
  		/* turn the rules on or off */
-		for (cur = node->true_list; cur; cur = cur->next) {
+		for (i = 0; i < node->true_list.len; i++) {
+			avnode = node->true_list.nodes[i];
  			if (new_state <= 0)
-				cur->node->key.specified &= ~AVTAB_ENABLED;
+				avnode->key.specified &= ~AVTAB_ENABLED;
  			else
-				cur->node->key.specified |= AVTAB_ENABLED;
+				avnode->key.specified |= AVTAB_ENABLED;
  		}
- for (cur = node->false_list; cur; cur = cur->next) {
+		for (i = 0; i < node->false_list.len; i++) {
+			avnode = node->false_list.nodes[i];
  			/* -1 or 1 */
  			if (new_state)
-				cur->node->key.specified &= ~AVTAB_ENABLED;
+				avnode->key.specified &= ~AVTAB_ENABLED;
  			else
-				cur->node->key.specified |= AVTAB_ENABLED;
+				avnode->key.specified |= AVTAB_ENABLED;
  		}
  	}
  }
@@ -128,16 +131,6 @@ int cond_policydb_init(struct policydb *p)
  	return 0;
  }
-static void cond_av_list_destroy(struct cond_av_list *list)
-{
-	struct cond_av_list *cur, *next;
-	for (cur = list; cur; cur = next) {
-		next = cur->next;
-		/* the avtab_ptr_t node is destroy by the avtab */
-		kfree(cur);
-	}
-}
-
  static void cond_node_destroy(struct cond_node *node)
  {
  	struct cond_expr *cur_expr, *next_expr;
@@ -146,8 +139,9 @@ static void cond_node_destroy(struct cond_node *node)
  		next_expr = cur_expr->next;
  		kfree(cur_expr);
  	}
-	cond_av_list_destroy(node->true_list);
-	cond_av_list_destroy(node->false_list);
+	/* the avtab_ptr_t nodes are destroyed by the avtab */
+	kfree(node->true_list.nodes);
+	kfree(node->false_list.nodes);
  }
static void cond_list_destroy(struct policydb *p)
@@ -255,19 +249,17 @@ err:
struct cond_insertf_data {
  	struct policydb *p;
+	struct avtab_node **dst;
  	struct cond_av_list *other;
-	struct cond_av_list *head;
-	struct cond_av_list *tail;
  };
static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum *d, void *ptr)
  {
  	struct cond_insertf_data *data = ptr;
  	struct policydb *p = data->p;
-	struct cond_av_list *other = data->other, *list, *cur;
  	struct avtab_node *node_ptr;
-	u8 found;
-	int rc = -EINVAL;
+	u32 i;
+	bool found;
/*
  	 * For type rules we have to make certain there aren't any
@@ -277,7 +269,7 @@ static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum
  	if (k->specified & AVTAB_TYPE) {
  		if (avtab_search(&p->te_avtab, k)) {
  			pr_err("SELinux: type rule already exists outside of a conditional.\n");
-			goto err;
+			return -EINVAL;
  		}
  		/*
  		 * If we are reading the false list other will be a pointer to
@@ -287,29 +279,29 @@ static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum
  		 * If we are reading the true list (other == NULL) there shouldn't
  		 * be any other entries.
  		 */
-		if (other) {
+		if (data->other) {
  			node_ptr = avtab_search_node(&p->te_cond_avtab, k);
  			if (node_ptr) {
  				if (avtab_search_node_next(node_ptr, k->specified)) {
  					pr_err("SELinux: too many conflicting type rules.\n");
-					goto err;
+					return -EINVAL;
  				}
-				found = 0;
-				for (cur = other; cur; cur = cur->next) {
-					if (cur->node == node_ptr) {
-						found = 1;
+				found = false;
+				for (i = 0; i < data->other->len; i++) {
+					if (data->other->nodes[i] == node_ptr) {
+						found = true;
  						break;
  					}
  				}
  				if (!found) {
  					pr_err("SELinux: conflicting type rules.\n");
-					goto err;
+					return -EINVAL;
  				}
  			}
  		} else {
  			if (avtab_search(&p->te_cond_avtab, k)) {
  				pr_err("SELinux: conflicting type rules when adding type rule for true.\n");
-				goto err;
+				return -EINVAL;
  			}
  		}
  	}
@@ -317,39 +309,22 @@ static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum
  	node_ptr = avtab_insert_nonunique(&p->te_cond_avtab, k, d);
  	if (!node_ptr) {
  		pr_err("SELinux: could not insert rule.\n");
-		rc = -ENOMEM;
-		goto err;
-	}
-
-	list = kzalloc(sizeof(*list), GFP_KERNEL);
-	if (!list) {
-		rc = -ENOMEM;
-		goto err;
+		return -ENOMEM;
  	}
- list->node = node_ptr;
-	if (!data->head)
-		data->head = list;
-	else
-		data->tail->next = list;
-	data->tail = list;
+	*data->dst = node_ptr;
  	return 0;
-
-err:
-	cond_av_list_destroy(data->head);
-	data->head = NULL;
-	return rc;
  }
-static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list **ret_list, struct cond_av_list *other)
+static int cond_read_av_list(struct policydb *p, void *fp,
+			     struct cond_av_list *list,
+			     struct cond_av_list *other)
  {
-	int i, rc;
+	int rc;
  	__le32 buf[1];
-	u32 len;
+	u32 i, len;
  	struct cond_insertf_data data;
- *ret_list = NULL;
-
  	rc = next_entry(buf, fp, sizeof(u32));
  	if (rc)
  		return rc;
@@ -358,18 +333,24 @@ static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list *
  	if (len == 0)
  		return 0;
+ list->nodes = kcalloc(len, sizeof(*list->nodes), GFP_KERNEL);
+	if (!list->nodes)
+		return -ENOMEM;
+
  	data.p = p;
  	data.other = other;
-	data.head = NULL;
-	data.tail = NULL;
  	for (i = 0; i < len; i++) {
+		data.dst = &list->nodes[i];
  		rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf,
  				     &data);
-		if (rc)
+		if (rc) {
+			kfree(list->nodes);
+			list->nodes = NULL;
  			return rc;
+		}
  	}
- *ret_list = data.head;
+	list->len = len;
  	return 0;
  }
@@ -432,7 +413,7 @@ static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
  	rc = cond_read_av_list(p, fp, &node->true_list, NULL);
  	if (rc)
  		goto err;
-	rc = cond_read_av_list(p, fp, &node->false_list, node->true_list);
+	rc = cond_read_av_list(p, fp, &node->false_list, &node->true_list);
  	if (rc)
  		goto err;
  	return 0;
@@ -511,24 +492,16 @@ static int cond_write_av_list(struct policydb *p,
  			      struct cond_av_list *list, struct policy_file *fp)
  {
  	__le32 buf[1];
-	struct cond_av_list *cur_list;
-	u32 len;
+	u32 i;
  	int rc;
- len = 0;
-	for (cur_list = list; cur_list != NULL; cur_list = cur_list->next)
-		len++;
-
-	buf[0] = cpu_to_le32(len);
+	buf[0] = cpu_to_le32(list->len);
  	rc = put_entry(buf, sizeof(u32), 1, fp);
  	if (rc)
  		return rc;
- if (len == 0)
-		return 0;
-
-	for (cur_list = list; cur_list != NULL; cur_list = cur_list->next) {
-		rc = avtab_write_item(p, cur_list->node, fp);
+	for (i = 0; i < list->len; i++) {
+		rc = avtab_write_item(p, list->nodes[i], fp);
  		if (rc)
  			return rc;
  	}
@@ -565,10 +538,10 @@ static int cond_write_node(struct policydb *p, struct cond_node *node,
  			return rc;
  	}
- rc = cond_write_av_list(p, node->true_list, fp);
+	rc = cond_write_av_list(p, &node->true_list, fp);
  	if (rc)
  		return rc;
-	rc = cond_write_av_list(p, node->false_list, fp);
+	rc = cond_write_av_list(p, &node->false_list, fp);
  	if (rc)
  		return rc;
diff --git a/security/selinux/ss/conditional.h b/security/selinux/ss/conditional.h
index e474bdd3a0ed..5f97f678440e 100644
--- a/security/selinux/ss/conditional.h
+++ b/security/selinux/ss/conditional.h
@@ -39,8 +39,8 @@ struct cond_expr {
   * struct is for that list.
   */
  struct cond_av_list {
-	struct avtab_node *node;
-	struct cond_av_list *next;
+	struct avtab_node **nodes;
+	u32 len;
  };
/*
@@ -53,8 +53,8 @@ struct cond_av_list {
  struct cond_node {
  	int cur_state;
  	struct cond_expr *expr;
-	struct cond_av_list *true_list;
-	struct cond_av_list *false_list;
+	struct cond_av_list true_list;
+	struct cond_av_list false_list;
  };
int cond_policydb_init(struct policydb *p);





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