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 handleksmbdwork - KASAN: slab-use-after-free in rtlockslowlocklocked 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.