libsepol: Improve writing CIL sensitivity rules

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

Signed-off-by: James Carter <jwcart2@gmail.com>

libsepol/src/kernel_to_cil.c

@@ -782,6 +782,17 @@ static void write_default_mls_level(FILE *out)
 	sepol_printf(out, "(level %s (s0))\n", DEFAULT_LEVEL);
 }
 
+static int map_count_sensitivity_aliases(__attribute__((unused)) char *key, void *data, void *args)
+{
+	level_datum_t *sens = data;
+	unsigned *count = args;
+
+	if (sens->isalias)
+		(*count)++;
+
+	return SEPOL_OK;
+}
+
 static int map_sensitivity_aliases_to_strs(char *key, void *data, void *args)
 {
 	level_datum_t *sens = data;
@@ -799,26 +810,13 @@ static int write_sensitivity_rules_to_cil(FILE *out, struct policydb *pdb)
 {
 	level_datum_t *level;
 	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;
-	}
-
 	/* sensitivities */
 	for (i=0; i < pdb->p_levels.nprim; i++) {
 		name = pdb->p_sens_val_to_name[i];
-		if (!name) continue;
-		level = hashtab_search(pdb->p_levels.table, name);
-		if (!level) {
-			rc = -1;
-			goto exit;
-		}
-		if (level->isalias) continue;
-
 		sepol_printf(out, "(sensitivity %s)\n", name);
 	}
 
@@ -827,14 +825,6 @@ static int write_sensitivity_rules_to_cil(FILE *out, struct policydb *pdb)
 	prev = NULL;
 	for (i=0; i < pdb->p_levels.nprim; i++) {
 		name = pdb->p_sens_val_to_name[i];
-		if (!name) continue;
-		level = hashtab_search(pdb->p_levels.table, name);
-		if (!level) {
-			rc = -1;
-			goto exit;
-		}
-		if (level->isalias) continue;
-
 		if (prev) {
 			sepol_printf(out, "%s ", prev);
 		}
@@ -845,23 +835,32 @@ static int write_sensitivity_rules_to_cil(FILE *out, struct policydb *pdb)
 	}
 	sepol_printf(out, "))\n");
 
+	rc = hashtab_map(pdb->p_levels.table, map_count_sensitivity_aliases, &num);
+	if (rc != 0) {
+		goto exit;
+	}
+
+	if (num == 0) {
+		/* No aliases, so skip sensitivity alias rules */
+		rc = 0;
+		goto exit;
+	}
+
+	rc = strs_init(&strs, num);
+	if (rc != 0) {
+		goto exit;
+	}
+
 	rc = hashtab_map(pdb->p_levels.table, map_sensitivity_aliases_to_strs, strs);
 	if (rc != 0) {
 		goto exit;
 	}
 
 	strs_sort(strs);
 
-	num = strs_num_items(strs);
-
 	/* sensitivity aliases */
 	for (i=0; i < num; i++) {
 		name = strs_read_at_index(strs, i);
-		level = hashtab_search(pdb->p_levels.table, name);
-		if (!level) {
-			rc = -1;
-			goto exit;
-		}
 		sepol_printf(out, "(sensitivityalias %s)\n", name);
 	}