diff --git a/frameworks/native/backup_ext/src/tar_file.cpp b/frameworks/native/backup_ext/src/tar_file.cpp
index 4aa61f8504f6d16f59cfb6d9fe68781a32a7bd2e..e0123782037d8dba2f6cfaf1c2e301b5502f573e 100644
--- a/frameworks/native/backup_ext/src/tar_file.cpp
+++ b/frameworks/native/backup_ext/src/tar_file.cpp
@@ -419,8 +419,12 @@ int TarFile::WriteTarHeader(TarHeader &header)
 int TarFile::WriteAll(const vector<uint8_t> &buf, size_t len)
 {
     size_t count = 0;
-    while (count < len) {
-        auto i = fwrite(&buf[0] + count, sizeof(char), len - count, currentTarFile_);
+    size_t endLen = buf.size();
+    if (endLen > len) {
+        endLen = len;
+    }
+    while (count < endLen) {
+        auto i = fwrite(&buf[0] + count, sizeof(char), endLen - count, currentTarFile_);
         if (i < 1) {
             HILOGE("Failed to fwrite tar file, err = %{public}d", errno);
             return count;