ksmbd: fix use-after-free in SMB request handling

Summary

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in SMB request handling A race condition exists between SMB request handling in `ksmbd_conn_handler_loop()` and the freeing of `ksmbd_conn` in the workqueue handler `handle_ksmbd_work()`. This leads to a UAF. • KASAN: slab-use-after-free Read in handle_ksmbd_work • KASAN: slab-use-after-free in rtlock_slowlock_locked This race condition arises as follows: • `ksmbd_conn_handler_loop()` waits for `conn->r_count` to reach zero: `wait_event(conn->r_count_q, atomic_read(&conn->r_count) == 0);` • Meanwhile, `handle_ksmbd_work()` decrements `conn->r_count` using `atomic_dec_return(&conn->r_count)`, and if it reaches zero, calls `ksmbd_conn_free()`, which frees `conn`. • However, after `handle_ksmbd_work()` decrements `conn->r_count`, it may still access `conn->r_count_q` in the following line: `waitqueue_active(&conn->r_count_q)` or `wake_up(&conn->r_count_q)` This results in a UAF, as `conn` has already been freed. The discovery of this UAF can be referenced in the following PR for syzkaller's support for SMB requests.

Timeline

1. Dec 27, 2024, 1:49 PM UTCCVE published
2. Feb 10, 2025, 5:13 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Aug 5, 2026, 11:44 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 6.6.55 · fixed in 6.6.64; From 6.11.3 · fixed in 6.11.11; From 6.10.14 · fixed in 6.11

• Linux Linux

  6.12

References 4