CVE-2024-53186

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 syzkallers support for SMB requests.

Affected Software

References

• https://git.kernel.org/stable/c/96261adb998a3b513468b6ce17dbec76be5507d4
• https://git.kernel.org/stable/c/9a8c5d89d327ff58e9b2517f8a6afb4181d32c6e
• https://git.kernel.org/stable/c/a96f9eb7add30ba0fafcfe7b7aca090978196800
• https://git.kernel.org/stable/c/f20b77f7897e6aab9ce5527e6016ad2be5d70a33