CVE-2026-31718

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger

When a durable file handle survives session disconnect (TCP close without

SMB2_LOGOFF), session_fd_check() sets fp->conn = NULL to preserve the

handle for later reconnection. However, it did not clean up the byte-range

locks on fp->lock_list.

Later, when the durable scavenger thread times out and calls

__ksmbd_close_fd(NULL, fp), the lock cleanup loop did:

spin_lock(&fp->conn->llist_lock);

This caused a slab use-after-free because fp->conn was NULL and the

original connection object had already been freed by

ksmbd_tcp_disconnect().

The root cause is asymmetric cleanup: lock entries (smb_lock->clist) were

left dangling on the freed conn->lock_list while fp->conn was nulled out.

To fix this issue properly, we need to handle the lifetime of

smb_lock->clist across three paths:

- Safely skip clist deletion when list is empty and fp->conn is NU

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References