From 81eccb99fe404b04a34b898bba63644a2fa08c03 Mon Sep 17 00:00:00 2001
From: stefanrueger <stefan.rueger@urclocks.com>
Date: Sun, 16 Aug 2026 07:38:32 +0200
Subject: [PATCH] Harden jtag3_command_tpi()

---
 src/jtag3.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/src/jtag3.c b/src/jtag3.c
index 5ddc11d2..eae8e7aa 100644
--- a/src/jtag3.c
+++ b/src/jtag3.c
@@ -2889,22 +2889,18 @@ int jtag3_recv_tpi(const PROGRAMMER *pgm, unsigned char **msg) {
 int jtag3_command_tpi(const PROGRAMMER *pgm, unsigned char *cmd, unsigned int cmdlen,
   unsigned char **resp, const char *descr) {
 
-  int status;
-  unsigned char c;
-
   jtag3_send_tpi(pgm, cmd, cmdlen);
 
-  status = jtag3_recv_tpi(pgm, resp);
+  *resp = NULL;
+  int status = jtag3_recv_tpi(pgm, resp);
   if(status <= 0) {
     msg_notice2("\n");
     pmsg_notice2("TPI %s command: timeout/error communicating with programmer (status %d)\n", descr, status);
     return LIBAVRDUDE_GENERAL_FAILURE;
   }
 
-  c = (*resp)[1];
-  if(c != XPRG_ERR_OK) {
-    pmsg_error("[TPI] command %s FAILED! Status: 0x%02x\n", descr, c);
-    status = (*resp)[3];
+  if(status < 2 || !*resp || (*resp)[1] != XPRG_ERR_OK) {
+    pmsg_error("[TPI] command %s failed (status 0x%02x)\n", descr, *resp? (*resp)[1]: -1);
     mmt_free(*resp);
     *resp = NULL;
     return LIBAVRDUDE_GENERAL_FAILURE;