Missing deferred cleanup in `Exec()` function causes resource leaks on execution failure

[shivansh-source]

Description

The Exec() function in pkg/unikontainers/unikontainers.go performs multiple setup operations in sequence:

1. Network setup (TAP device creation)
2. Rootfs preparation (preSetup)
3. Monitor rootfs preparation (mount creation)
4. Rootfs post-setup
5. Shared filesystem setup (virtiofs/9pfs)
6. Many other operations...

Currently, if any step fails after network setup (line 405), TAP devices are never cleaned up. Similar issues exist for rootfs and shared filesystem mounts.

• Line 405: Network setup, no defer cleanup
• Line 507-530: Rootfs setup, no rollback on failure
• Line 522: prepareMonRootfs, no cleanup
• Line 570: prepareVSockEnvironment, no cleanup

all setup steps should register cleanup functions that execute in reverse order if any error occurs.

Testing

• Add tests that verify cleanup occurs when Exec fails at each setup stage
• Verify TAP devices are cleaned up
• Verify mounts are unmounted

[shivansh-source]

/cc @cmainas

[cmainas]

Hello @shivansh-source , we want to perform a major refactor in the Exec function. During this refactor we will also handle better errors and cleanup.

[shivansh-source]

got it @cmainas is the issue up for refactoring ? and if no one assiggned can i work on it ?

[cmainas]

I am already working on it. The refactor should be in accordance with some other features we plan to add in urunc (e.g. cgroups), so it would be better if the maintainers handle it.