CVE-2025-40039

/// Technical description

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

ksmbd: Fix race condition in RPC handle list access

The 'sess->rpc_handle_list' XArray manages RPC handles within a ksmbd

session. Access to this list is intended to be protected by

'sess->rpc_lock' (an rw_semaphore). However, the locking implementation was

flawed, leading to potential race conditions.

In ksmbd_session_rpc_open(), the code incorrectly acquired only a read lock

before calling xa_store() and xa_erase(). Since these operations modify

the XArray structure, a write lock is required to ensure exclusive access

and prevent data corruption from concurrent modifications.

Furthermore, ksmbd_session_rpc_method() accessed the list using xa_load()

without holding any lock at all. This could lead to reading inconsistent

data or a potential use-after-free if an entry is concurrently removed and

the pointer is dereferenced.

Fix these issues by:

1. Using down_write() and up_write() in ksmbd_session_rpc_open()

to

/// 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