In the Linux kernel, the following vulnerability has been resolved:
net/iucv: take a reference on the socket found in afiucv_hs_rcv()
afiucv_hs_rcv() looks up the destination socket under iucv_sk_list.lock, drops the lock, and then passes the socket to the afiucv_hs_callback_*() handlers without holding a reference. AF_IUCV sockets are not RCU-protected and are freed synchronously by iucv_sock_kill() -> sock_put(), so a concurrent close can free the socket in the window between read_unlock() and the handler, which then dereferences freed memory (for example sk->sk_data_ready() in afiucv_hs_callback_syn()).
Take a reference with sock_hold() while the socket is still on the list and release it with sock_put() once the handler has run.
References
- https://git.kernel.org/stable/c/1801cb20a5025a787d6853e19c38db138344b4b4
- https://git.kernel.org/stable/c/4dc0e63abf8bc7ba8892e617c1fb8b204361e022
- https://git.kernel.org/stable/c/4fa349156043dc119721d067329714179f501749
- https://git.kernel.org/stable/c/5595ea59cdf29182cf6a270cacc1426c57b603de
- https://git.kernel.org/stable/c/c75a950e77356e526672cba4584080c6c8b793b6