fix: avoid shell injection in training helper

[tianleiwu]

Description

Fix the command-injection risk in the training helper by removing shell-based execution and validating the safe subprocess path with regression tests.

Summary of Changes

Security fix: replace shell execution with argument-list execution

File	Change
orttraining/tools/scripts/train.py	Replace os.system(...) with subprocess.run([...], check=True) and add a small main(argv=None) entry point for safe argument forwarding.
orttraining/orttraining/test/python/test_train_script.py	Add regression tests to confirm the helper does not execute shell commands on import and uses an argument list when invoking the training binary.

Motivation

The previous implementation built a single shell string from sys.argv[1:] and executed it with os.system(). That allowed shell metacharacters in user-supplied arguments to be interpreted by the shell. The updated path passes the command and arguments directly to subprocess.run, which avoids shell interpretation and preserves the original argument boundaries.

Testing

• pytest orttraining/orttraining/test/python/test_train_script.py -q

Checklist

• Security fix implemented
• Regression tests added
• No shell-based command execution remains in the helper path

[Copilot]

Pull request overview

This PR mitigates command-injection risk in the ORT training helper script by removing shell-based command construction/execution and replacing it with safe argument-list subprocess invocation, plus adding regression tests.

Changes:

• Replace os.system() shell execution in train.py with subprocess.run([...], check=True) behind a main(argv=None) entry point.
• Add pytest coverage to ensure importing the script does not execute a command and that subprocess.run is called with an argument list.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
pr_description.md	Documents the security motivation, implementation summary, and test command for the change.
orttraining/tools/scripts/train.py	Switches from shell-string execution to subprocess.run with an argv list via a main() entry point.
orttraining/orttraining/test/python/test_train_script.py	Adds regression tests for import-time behavior and argv-list subprocess invocation.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.