util/grub-mkstandalone: Ensure deterministic tar file creation by sorting contents

The add_tar_files() function currently iterates through a directory's
content using readdir(), which doesn't guarantee a specific order. This
lack of deterministic behavior impacts reproducibility in the build process.

This commit resolves the issue by introducing sorting functionality.
The list retrieved by readdir() is now sorted alphabetically before
incorporation into the tar archive, ensuring consistent and predictable
file ordering within the archive.

On the occasion fix tfp memory leak.

Signed-off-by: Michael Chang <[email protected]>
Signed-off-by: Bernhard Wiedemann <[email protected]>
Reviewed-by: Daniel Kiper <[email protected]>

Author: WenhuaChang

util/grub-mkstandalone.c

@@ -205,22 +205,43 @@ add_tar_file (const char *from,
     {
       grub_util_fd_dir_t d;
       grub_util_fd_dirent_t de;
+      char **from_files;
+      grub_size_t alloc = 8, used = 0;
+      grub_size_t i;
 
       d = grub_util_fd_opendir (from);
 
+      from_files = xmalloc (alloc * sizeof (*from_files));
       while ((de = grub_util_fd_readdir (d)))
 	{
-	  char *fp, *tfp;
 	  if (strcmp (de->d_name, ".") == 0)
 	    continue;
 	  if (strcmp (de->d_name, "..") == 0)
 	    continue;
-	  fp = grub_util_path_concat (2, from, de->d_name);
-	  tfp = xasprintf ("%s/%s", to, de->d_name);
+	  if (alloc <= used)
+	    {
+	      alloc <<= 1;
+	      from_files = xrealloc (from_files, alloc * sizeof (*from_files));
+	    }
+	  from_files[used++] = xstrdup (de->d_name);
+	}
+
+      qsort (from_files, used, sizeof (*from_files), grub_qsort_strcmp);
+
+      for (i = 0; i < used; i++)
+	{
+	  char *fp, *tfp;
+
+	  fp = grub_util_path_concat (2, from, from_files[i]);
+	  tfp = xasprintf ("%s/%s", to, from_files[i]);
 	  add_tar_file (fp, tfp);
+	  free (tfp);
 	  free (fp);
+	  free (from_files[i]);
 	}
+
       grub_util_fd_closedir (d);
+      free (from_files);
       free (tcn);
       return;
     }