Re: [PATCH v4] Bluetooth: fix UAF in l2cap_sock_cleanup_listen() vs l2cap_conn_del()

[Hillf Danton]

On Sat, 16 May 2026 21:15:04 +0300 Safa Karakus wrote:
> bt_accept_dequeue() unlinks a not-yet-accepted child from the parent
> accept queue and release_sock()s it before returning, so the returned
> sk has no caller reference and is unlocked.
> 
> l2cap_sock_cleanup_listen() walks these children on listening-socket
> close.  A concurrent HCI disconnect drives hci_rx_work ->
> l2cap_conn_del() which runs l2cap_chan_del() + l2cap_sock_kill() and
> frees the child sk and its l2cap_chan; cleanup_listen() then uses both:
> 
>   BUG: KASAN: slab-use-after-free in l2cap_sock_kill
>     l2cap_sock_kill / l2cap_sock_cleanup_listen / __x64_sys_close
>   Freed by: l2cap_conn_del -> l2cap_sock_close_cb -> l2cap_sock_kill
> 
Feel free to add the regular KASAN uaf calltrace to help understand your fix.