The Linux kernel liveupdate subsystem did not validate the session type before dispatching ioctl operations. Specifically, PRESERVE_FD is only valid for outgoing sessions, while RETRIEVE_FD and FINISH are only valid for incoming sessions. Calling an incoming ioctl on an outgoing session causes the memfd retrieve handler to execute improperly, triggering internal errors and kernel warnings due to unexpected context. The fix involves associating each ioctl operation with a session type and validating this in luo_session_ioctl() before dispatching handlers to prevent invalid calls.

Improper ioctl calls on the wrong session type cause internal kernel errors and warnings, which may lead to unexpected behavior in kernel memory handling. While this does not appear to allow privilege escalation or code execution, it can cause instability or error conditions in the liveupdate subsystem.

A fix has been implemented in the Linux kernel to validate session types before ioctl operations are performed, preventing invalid ioctl calls. Users should apply the official kernel update that includes this fix. Patch status is not explicitly stated here; check the Linux kernel vendor advisory for the current remediation guidance.