CVE-2026-64396ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation

Official description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation When a blocking byte-range lock request is deferred in the FILE_LOCK_DEFERRED path, ksmbd registers the asynchronous work into the connection's async_requests list via setup_async_work(). The cancel callback smb2_remove_blocked_lock() holds a reference to the flock. If the lock waiter is subsequently woken up but the work state is no longer KSMBD_WORK_ACTIVE (e.g., due to a concurrent cancellation), the cleanup path calls locks_free_lock(flock) without dequeuing the work from the async_requests list. Concurrently, smb2_cancel() walks the list under conn->request_lock and invokes the cancel callback, which then dereferences the already freed 'flock'. This leads to a slab-use-after-free inside __wake_up_common. Fix this by restructuring the cleanup logic after the worker returns from ksmbd_vfs_posix_lock_wait(). Move list_del(&smb_lock->llist) and release_async_work(work) to the top of the cleanup block. This guarantees that the async work is completely dequeued and serialized under conn->request_lock before locks_free_lock(flock) is called, rendering the flock unreachable for any concurrent smb2_cancel().

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/367c42a611fe488b7b03f1f6737f4dee0e8b20a2
• https://git.kernel.org/stable/c/7703fd9aba1f2483c8e55f9ff73b7663e0761ed9
• https://git.kernel.org/stable/c/463bbd79698513af4dad50fe1c573825f297ca2e
• https://git.kernel.org/stable/c/5aa1cb01155f96824003baf7997cdf1f150caba3
• https://git.kernel.org/stable/c/5c75275c0fc9a2deb0d8f5604edcb16f288171c8
• https://git.kernel.org/stable/c/d20d1c8ba5765d1d12eefc0aee6385ab3f240e1e