check pointer received from sane_control_option()

backend/hp.c

@@ -43,9 +43,12 @@
    HP Scanner Control Language (SCL).
 */
 
-static char *hp_backend_version = "1.02";
+static char *hp_backend_version = "1.03";
 /* Changes:
 
+   V 1.03, 14-Apr-2003, PK (peter@kirchgessner.net)
+      - check valp in call of sane_control_option()
+
    V 1.02, 02-Feb-2003, PK (peter@kirchgessner.net)
       - add OS/2-support by Franz Bakan
 
@@ -880,6 +883,29 @@ sane_control_option (SANE_Handle handle, SANE_Int optnum,
 
   DBG(10, "sane_control_option called\n");
 
+  status = SANE_STATUS_GOOD;
+  switch (action)
+  {
+    case SANE_ACTION_GET_VALUE:
+    case SANE_ACTION_SET_VALUE:
+           if (!valp)
+           {
+             DBG (1,"sane_control_option: valp is NULL\n");
+             status = SANE_STATUS_INVAL;
+           }
+           break;
+
+    case SANE_ACTION_SET_AUTO:
+           break;
+
+    default:
+           DBG (1,"sane_control_option: action unknown\n");
+           status = SANE_STATUS_INVAL;
+           break;
+  }
+
+  if (status != SANE_STATUS_GOOD) return status;
+
   status = sanei_hp_handle_control(h, optnum, action, valp, info);
 
   DBG(10, "sane_control_option will finish with %s\n",