fix: prevent SU2 Python runner stderr deadlock and harden config path copies

- SU2_PY: use subprocess.communicate() to reliably drain stderr while keeping stdout streamed,
  avoiding potential hangs when stderr output is large.
- SU2_PY: fix incorrect path reporting in error messages (abspath(".") instead of abspath(",")).
- C++ entrypoints: guard/limit copies into fixed-size config filename buffers to prevent
  potential overflow on long paths.

Signed-off-by: shbhmexe <shubhushukla586@gmail.com>

Author: shbhmexe

SU2_CFD/src/SU2_CFD.cpp

@@ -27,6 +27,8 @@
 
 #include "../include/SU2_CFD.hpp"
 
+#include <cstring>
+
 /* Include file, needed for the runtime NaN catching. You also have to include feenableexcept(...) below. */
 //#include <fenv.h>
 
@@ -78,7 +80,11 @@ int main(int argc, char *argv[]) {
 
   /*--- Load in the number of zones and spatial dimensions in the mesh file (If no config
    file is specified, default.cfg is used) ---*/
-  strcpy(config_file_name, filename.c_str());
+  if (filename.size() >= MAX_STRING_SIZE) {
+    SU2_MPI::Error("Config file path too long (exceeds MAX_STRING_SIZE).", CURRENT_FUNCTION);
+  }
+  strncpy(config_file_name, filename.c_str(), MAX_STRING_SIZE - 1);
+  config_file_name[MAX_STRING_SIZE - 1] = '\0';
 
   /*--- Read the name and format of the input mesh file to get from the mesh
    file the number of zones and dimensions from the numerical grid (required

SU2_DEF/src/SU2_DEF.cpp

@@ -27,6 +27,8 @@
 
 #include "../include/drivers/CDeformationDriver.hpp"
 
+#include <cstring>
+
 int main(int argc, char* argv[]) {
   char config_file_name[MAX_STRING_SIZE];
 
@@ -44,7 +46,11 @@ int main(int argc, char* argv[]) {
    (if no config file is specified, default.cfg is used). ---*/
 
   if (argc == 2) {
-    strcpy(config_file_name, argv[1]);
+    if (strlen(argv[1]) >= MAX_STRING_SIZE) {
+      SU2_MPI::Error("Config file path too long (exceeds MAX_STRING_SIZE).", CURRENT_FUNCTION);
+    }
+    strncpy(config_file_name, argv[1], MAX_STRING_SIZE - 1);
+    config_file_name[MAX_STRING_SIZE - 1] = '\0';
   } else {
     strcpy(config_file_name, "default.cfg");
   }

SU2_DOT/src/SU2_DOT.cpp

@@ -27,6 +27,8 @@
 
 #include "../../SU2_DEF/include/drivers/CDiscAdjDeformationDriver.hpp"
 
+#include <cstring>
+
 int main(int argc, char* argv[]) {
   char config_file_name[MAX_STRING_SIZE];
 
@@ -47,7 +49,11 @@ int main(int argc, char* argv[]) {
    (if no config file is specified, default.cfg is used). ---*/
 
   if (argc == 2) {
-    strcpy(config_file_name, argv[1]);
+    if (strlen(argv[1]) >= MAX_STRING_SIZE) {
+      SU2_MPI::Error("Config file path too long (exceeds MAX_STRING_SIZE).", CURRENT_FUNCTION);
+    }
+    strncpy(config_file_name, argv[1], MAX_STRING_SIZE - 1);
+    config_file_name[MAX_STRING_SIZE - 1] = '\0';
   } else {
     strcpy(config_file_name, "default.cfg");
   }

SU2_GEO/src/SU2_GEO.cpp

@@ -26,6 +26,9 @@
  */
 
 #include "../include/SU2_GEO.hpp"
+
+#include <cstring>
+
 using namespace std;
 
 int main(int argc, char* argv[]) {
@@ -92,7 +95,11 @@ int main(int argc, char* argv[]) {
    file is specified, default.cfg is used) ---*/
 
   if (argc == 2) {
-    strcpy(config_file_name, argv[1]);
+    if (strlen(argv[1]) >= MAX_STRING_SIZE) {
+      SU2_MPI::Error("Config file path too long (exceeds MAX_STRING_SIZE).", CURRENT_FUNCTION);
+    }
+    strncpy(config_file_name, argv[1], MAX_STRING_SIZE - 1);
+    config_file_name[MAX_STRING_SIZE - 1] = '\0';
   } else {
     strcpy(config_file_name, "default.cfg");
   }

SU2_PY/SU2/run/interface.py

@@ -38,7 +38,13 @@
 #  Setup
 # ------------------------------------------------------------
 
-SU2_RUN = os.environ["SU2_RUN"]
+try:
+    SU2_RUN = os.environ["SU2_RUN"]
+except KeyError as exc:
+    raise RuntimeError(
+        'Environment variable "SU2_RUN" is not set. Please set SU2_RUN to the SU2 installation bin directory.'
+    ) from exc
+
 sys.path.append(SU2_RUN)
 quote = '"' if sys.platform == "win32" else ""
 
@@ -263,11 +269,13 @@ def run_command(Command):
     """
     sys.stdout.flush()
 
-    proc = subprocess.Popen(
-        Command, shell=True, stdout=sys.stdout, stderr=subprocess.PIPE
-    )
-    return_code = proc.wait()
-    message = proc.stderr.read().decode()
+    # Avoid potential deadlocks when a child process writes heavily to stderr:
+    # read stderr via communicate() while streaming stdout to the console.
+    proc = subprocess.Popen(Command, shell=True, stdout=sys.stdout, stderr=subprocess.PIPE)
+    _, stderr = proc.communicate()
+
+    return_code = proc.returncode
+    message = (stderr or b"").decode(errors="replace")
 
     if return_code < 0:
         message = "SU2 process was terminated by signal '%s'\n%s" % (
@@ -277,7 +285,7 @@ def run_command(Command):
         raise SystemExit(message)
     elif return_code > 0:
         message = "Path = %s\nCommand = %s\nSU2 process returned error '%s'\n%s" % (
-            os.path.abspath(","),
+            os.path.abspath("."),
             Command,
             return_code,
             message,

SU2_SOL/src/SU2_SOL.cpp

@@ -27,6 +27,8 @@
 
 #include "../include/SU2_SOL.hpp"
 
+#include <cstring>
+
 using namespace std;
 
 int main(int argc, char* argv[]) {
@@ -56,7 +58,11 @@ int main(int argc, char* argv[]) {
    file is specified, default.cfg is used) ---*/
 
   if (argc == 2 || argc == 3) {
-    strcpy(config_file_name, argv[1]);
+    if (strlen(argv[1]) >= MAX_STRING_SIZE) {
+      SU2_MPI::Error("Config file path too long (exceeds MAX_STRING_SIZE).", CURRENT_FUNCTION);
+    }
+    strncpy(config_file_name, argv[1], MAX_STRING_SIZE - 1);
+    config_file_name[MAX_STRING_SIZE - 1] = '\0';
   } else {
     strcpy(config_file_name, "default.cfg");
   }
@@ -98,7 +104,12 @@ int main(int argc, char* argv[]) {
      read and stored. ---*/
 
     if (driver_config->GetnConfigFiles() > 0) {
-      strcpy(zone_file_name, driver_config->GetConfigFilename(iZone).c_str());
+      const auto& zone_filename = driver_config->GetConfigFilename(iZone);
+      if (zone_filename.size() >= MAX_STRING_SIZE) {
+        SU2_MPI::Error("Zone config file path too long (exceeds MAX_STRING_SIZE).", CURRENT_FUNCTION);
+      }
+      strncpy(zone_file_name, zone_filename.c_str(), MAX_STRING_SIZE - 1);
+      zone_file_name[MAX_STRING_SIZE - 1] = '\0';
       config_container[iZone] = new CConfig(driver_config, zone_file_name, SU2_COMPONENT::SU2_SOL, iZone, nZone, true);
     } else {
       config_container[iZone] =