libsepol: do not pass NULL to memcpy

For the first iteration `mod->perm_map[sclassi]` is NULL, thus do not
use it as source of a memcpy(3).
Use a realloc + memset instead of a calloc and free to increase the size
of `mod->perm_map[sclassi]`.

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>

Author: cgzones

libsepol/src/link.c

@@ -185,14 +185,12 @@ static int permission_copy_callback(hashtab_key_t key, hashtab_datum_t datum,
 	 * may have originated from the class -or- it could be from
 	 * the class's common parent.*/
 	if (perm->s.value > mod->perm_map_len[sclassi]) {
-		uint32_t *newmap = calloc(perm->s.value, sizeof(*newmap));
+		uint32_t *newmap = realloc(mod->perm_map[sclassi], perm->s.value * sizeof(*newmap));
 		if (newmap == NULL) {
 			ERR(state->handle, "Out of memory!");
 			return -1;
 		}
-		memcpy(newmap, mod->perm_map[sclassi],
-		       mod->perm_map_len[sclassi] * sizeof(*newmap));
-		free(mod->perm_map[sclassi]);
+		memset(newmap + mod->perm_map_len[sclassi], '\0', perm->s.value - mod->perm_map_len[sclassi]);
 		mod->perm_map[sclassi] = newmap;
 		mod->perm_map_len[sclassi] = perm->s.value;
 	}