Re: [PATCH net] net/iucv: fix use-after-free of a severed iucv_path

[Alexandra Winter <wintera@linux.ibm.com>]

On 24.07.26 11:33, Bryam Vargas wrote:
> Alexandra,
> 
>> After iucv_sever_path it should not be possible to call
>> iucv_process_message_q() anymore.
> For the close path, yes -- iucv_sock_close() ends at IUCV_CLOSED/SOCK_ZAPPED
> and recvmsg() is out, so message_q just leaks. The peer-sever path is
> different: iucv_callback_connrej() severs and then sets IUCV_DISCONN, leaving
> the socket open. recvmsg()'s early return needs message_q.list empty; with a
> saved entry it falls through, and if a datagram is still on sk_receive_queue it
> reaches iucv_process_message_q() and hands the freed path to message_receive()
> -- pathid is the read.
> 

Thank you very much for the explanation. I overlooked that one. I think this
was a design bug in f0703c80e515 ("[AF_IUCV]: postpone receival of iucv-packets").
It doesn't make sense to check the message_q if IUCV_DISCONN.
I'm taking notes for future cleanups.

[...]
> 
> I'll fold the reachability point into the receive-path locking rework and send
> that RFC to netdev and linux-s390, as you asked.
> 

Looking forward to that, thank you.

> Thanks,
> Bryam