nss_mcdb - register atexit() to cleanup open nss mcdb if -D_FORTIFY_S…

…OURCE

mcdb.c

@@ -160,8 +160,10 @@ mcdb_mmap_free(struct mcdb_mmap * const restrict map)
 {
     mcdb_mmap_unmap(map);
     if (map->fn_free) {
-        if (map->fname != NULL && map->fname != map->fnamebuf)
+        if (map->fname != NULL && map->fname != map->fnamebuf) {
             map->fn_free(map->fname);
+            map->fname = NULL;
+        }
         map->fn_free(map);
     }
 }

nss_mcdb.c

@@ -77,6 +77,21 @@ static struct mcdb_mmap *_nss_mcdb_mmap[_nss_num_dbs];
 
 static __thread struct mcdb _nss_mcdb_st[_nss_num_dbs];
 
+#ifdef _FORTIFY_SOURCE
+static void _nss_mcdb_atexit(void)
+{
+    struct mcdb_mmap * restrict map;
+    for (uintptr_t i = 0; i < _nss_num_dbs; ++i) {
+        map = &_nss_mcdb_mmap_st[i];
+        if (   _nss_mcdb_mmap_st[i].ptr != NULL
+            || _nss_mcdb_mmap_st[i].fname != NULL  ) {
+            mcdb_mmap_destroy(&_nss_mcdb_mmap_st[i]);
+            _nss_mcdb_mmap_st[i].ptr = NULL;
+            _nss_mcdb_mmap_st[i].fname = NULL;
+        }
+    }
+}
+#endif
 
 /* custom free for mcdb_mmap_* routines to not free initial static storage */
 static void
@@ -111,6 +126,11 @@ _nss_mcdb_db_openshared(const enum nss_dbtype dbtype)
         return true;
     }
 
+  #ifdef _FORTIFY_SOURCE
+    {   static bool atexit_once = true;
+        if (atexit_once) { atexit_once = false; atexit(_nss_mcdb_atexit); }   }
+  #endif
+
     /* pass full path in fname instead of separate dirname and basename
      * (not using openat(), fstatat() where someone might close dfd on us)
      * use static storage for initial struct mcdb_mmap for each dbtype