libsepol: Improve writing CIL category rules

Improves writing of CIL category rules when converting MLS kernel
policy to CIL. No changes to functionality, but eliminate useless
checks for category aliases when using the p_cat_val_to_name array,
find the actual number of aliases before allocating memory, and
skip the category alias rules if there are no aliases.

Signed-off-by: James Carter <jwcart2@gmail.com>
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>

libsepol/src/kernel_to_cil.c

@@ -886,6 +886,17 @@ static int write_sensitivity_rules_to_cil(FILE *out, struct policydb *pdb)
 	return rc;
 }
 
+static int map_count_category_aliases(__attribute__((unused)) char *key, void *data, void *args)
+{
+	cat_datum_t *cat = data;
+	unsigned *count = args;
+
+	if (cat->isalias)
+		(*count)++;
+
+	return SEPOL_OK;
+}
+
 static int map_category_aliases_to_strs(char *key, void *data, void *args)
 {
 	cat_datum_t *cat = data;
@@ -903,26 +914,13 @@ static int write_category_rules_to_cil(FILE *out, struct policydb *pdb)
 {
 	cat_datum_t *cat;
 	char *prev, *name, *actual;
-	struct strs *strs;
-	unsigned i, num;
+	struct strs *strs = NULL;
+	unsigned i, num = 0;
 	int rc = 0;
 
-	rc = strs_init(&strs, pdb->p_levels.nprim);
-	if (rc != 0) {
-		goto exit;
-	}
-
 	/* categories */
 	for (i=0; i < pdb->p_cats.nprim; i++) {
 		name = pdb->p_cat_val_to_name[i];
-		if (!name) continue;
-		cat = hashtab_search(pdb->p_cats.table, name);
-		if (!cat) {
-			rc = -1;
-			goto exit;
-		}
-		if (cat->isalias) continue;
-
 		sepol_printf(out, "(category %s)\n", name);
 	}
 
@@ -931,14 +929,6 @@ static int write_category_rules_to_cil(FILE *out, struct policydb *pdb)
 	prev = NULL;
 	for (i=0; i < pdb->p_cats.nprim; i++) {
 		name = pdb->p_cat_val_to_name[i];
-		if (!name) continue;
-		cat = hashtab_search(pdb->p_cats.table, name);
-		if (!cat) {
-			rc = -1;
-			goto exit;
-		}
-		if (cat->isalias) continue;
-
 		if (prev) {
 			sepol_printf(out, "%s ", prev);
 		}
@@ -949,23 +939,32 @@ static int write_category_rules_to_cil(FILE *out, struct policydb *pdb)
 	}
 	sepol_printf(out, "))\n");
 
+	rc = hashtab_map(pdb->p_cats.table, map_count_category_aliases, &num);
+	if (rc != 0) {
+		goto exit;
+	}
+
+	if (num == 0) {
+		/* No aliases, so skip category alias rules */
+		rc = 0;
+		goto exit;
+	}
+
+	rc = strs_init(&strs, num);
+	if (rc != 0) {
+		goto exit;
+	}
+
 	rc = hashtab_map(pdb->p_cats.table, map_category_aliases_to_strs, strs);
 	if (rc != 0) {
 		goto exit;
 	}
 
 	strs_sort(strs);
 
-	num = strs_num_items(strs);
-
 	/* category aliases */
 	for (i=0; i < num; i++) {
 		name = strs_read_at_index(strs, i);
-		cat = hashtab_search(pdb->p_cats.table, name);
-		if (!cat) {
-			rc = -1;
-			goto exit;
-		}
 		sepol_printf(out, "(categoryalias %s)\n", name);
 	}