util/grub-mkrescue: Check existence of option arguments

As reported by Victoriia Egorova in bug 65880, grub-mkrescue does not
verify that the expected argument of an option like -d or -k does really
exist in argv. So, check the loop counter before incrementing it inside
the loop which copies argv to argp_argv. Issue an error message similar
to what older versions of grub-mkrescue did with a missing argument,
e.g. 2.02.

Fixes: https://savannah.gnu.org/bugs/index.php?65880

Signed-off-by: Thomas Schmitt <[email protected]>
Reviewed-by: Daniel Kiper <[email protected]>

Author: scdbackup

util/grub-mkrescue.c

@@ -477,6 +477,8 @@ main (int argc, char *argv[])
     for (i = 1; i < argc; i++)
       {
 	if (strcmp (argv[i], "-output") == 0) {
+	  if (i + 1 >= argc)
+	    grub_util_error ("%s -- '%s'", _("option requires an argument"), argv[i]);
 	  argp_argv[argp_argc++] = (char *) "--output";
 	  i++;
 	  argp_argv[argp_argc++] = argv[i];
@@ -485,6 +487,8 @@ main (int argc, char *argv[])
 	switch (args_to_eat (argv[i]))
 	  {
 	  case 2:
+	    if (i + 1 >= argc)
+	      grub_util_error ("%s -- '%s'", _("option requires an argument"), argv[i]);
 	    argp_argv[argp_argc++] = argv[i++];
 	    /* Fallthrough  */
 	  case 1: