diff --git a/src/basic/user-util.c b/src/basic/user-util.c
index b8d1066929..4cf4c5a341 100644
--- a/src/basic/user-util.c
+++ b/src/basic/user-util.c
@@ -350,6 +350,9 @@ char* uid_to_name(uid_t uid) {
                         if (r != ERANGE)
                                 break;
 
+                        if (bufsize > LONG_MAX/2) /* overflow check */
+                                return NULL;
+
                         bufsize *= 2;
                 }
         }
@@ -391,6 +394,9 @@ char* gid_to_name(gid_t gid) {
                         if (r != ERANGE)
                                 break;
 
+                        if (bufsize > LONG_MAX/2) /* overflow check */
+                                return NULL;
+
                         bufsize *= 2;
                 }
         }