From 8a8f32699b71957b9421020794f4608f1ee2369d Mon Sep 17 00:00:00 2001
From: Marin Doetterer <marin@auterion.com>
Date: Thu, 13 Aug 2026 18:56:55 +0200
Subject: [PATCH] fix(nshterm): went out of stack fix(mavlink_shell): no echo
 of commands

---
 src/modules/mavlink/mavlink_shell.cpp | 11 +++++++++--
 src/systemcmds/nshterm/CMakeLists.txt |  1 +
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/modules/mavlink/mavlink_shell.cpp b/src/modules/mavlink/mavlink_shell.cpp
index 723c5357811..e211d7b94cc 100644
--- a/src/modules/mavlink/mavlink_shell.cpp
+++ b/src/modules/mavlink/mavlink_shell.cpp
@@ -70,6 +70,10 @@ MavlinkShell::~MavlinkShell()
 	if (_from_shell_fd >= 0) {
 		close(_from_shell_fd);
 	}
+
+	if (_shell_fds[1] >= 0) {
+		close(_shell_fds[1]);
+	}
 }
 
 int MavlinkShell::start()
@@ -170,9 +174,8 @@ int MavlinkShell::start()
 
 #endif
 
-	//close unused pipe fd's
+	//close unused pipe fd's; _shell_fds[1] is kept open, write() reuses it to echo input
 	close(_shell_fds[0]);
-	close(_shell_fds[1]);
 
 #ifdef __PX4_NUTTX
 	sched_unlock();
@@ -214,6 +217,10 @@ int MavlinkShell::shell_start_thread(int argc, char *argv[])
 
 size_t MavlinkShell::write(uint8_t *buffer, size_t len)
 {
+	if (::write(_shell_fds[1], buffer, len) < 0) {
+		PX4_WARN("echo failed");
+	}
+
 	return ::write(_to_shell_fd, buffer, len);
 }
 
diff --git a/src/systemcmds/nshterm/CMakeLists.txt b/src/systemcmds/nshterm/CMakeLists.txt
index 757ade30630..08963fe09ed 100644
--- a/src/systemcmds/nshterm/CMakeLists.txt
+++ b/src/systemcmds/nshterm/CMakeLists.txt
@@ -34,6 +34,7 @@ px4_add_module(
 	MODULE systemcmds__nshterm
 	MAIN nshterm
 	PRIORITY "SCHED_PRIORITY_DEFAULT-30"
+	STACK_MAIN 4096
 	COMPILE_FLAGS
 	SRCS
 		nshterm.cpp