CVE-2023-53794

What it actually does

The flaw permits collection of an exiting CIFS session in smb2_reconnect_server(), creating a window for use-after-free when the session is later released after cifs_free_ipc() and logoff().

Why it matters to the business

Unpatched systems risk kernel instability or crashes during network filesystem reconnects, potentially disrupting file sharing services and requiring emergency reboots with possible data loss in active transfers.

How an attack unfolds

An attacker triggers repeated CIFS session reconnect events while a session is exiting the smb_ses_list, racing the release path to access freed memory structures.

How to fix it

Upgrade the Linux kernel to a version containing the referenced cifs reconnect fix; apply the exact package update for affected distributions once available.

How to confirm the fix worked

Confirm kernel version includes the cifs session state check change; review smb2_reconnect_server() source to verify exiting sessions are skipped; test reconnect behavior under session exit conditions.

Typical attack path

1. Establish CIFS mount to target server
2. Force network interruption or server-side session termination to initiate reconnect
3. Time concurrent session exit to overlap with reconnect collection logic
4. Trigger use-after-free dereference leading to crash or memory corruption

How to detect it

Search kernel logs for CIFS reconnect warnings around session teardown, oops reports referencing smb2_reconnect_server or cifs_free_ipc, and any use-after-free stack traces involving smb_ses_list.

What your security team should do

• Prioritize kernel updates on all systems using CIFS/SMB mounts
• Monitor for unusual CIFS reconnect logs and kernel oops
• Temporarily disable automatic reconnect if feasible until patched