Entreprise française de cybersécurité depuis 2004
☎ 03 60 47 09 81 - info@securiteinfo.com
☎ 03 60 47 09 81 - info@securiteinfo.com
In the Linux kernel, the following vulnerability has been resolved:ksmbd: fix use-after-free in SMB request handlingA race condition exists between SMB request handling in`ksmbd_conn_handler_loop()` and the freeing of `ksmbd_conn` in theworkqueue 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_lockedThis 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 forsyzkaller's support for SMB requests.
No PoCs from references.
- https://github.com/cku-heise/euvd-api-doc