netdev - Re: [PATCH net-next] rds: cancel send/recv work before queuing connection shutdown

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Message-Id: <20170716.190746.619711541077075506.davem@davemloft.net>
Date:   Sun, 16 Jul 2017 19:07:46 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     sowmini.varadhan@...cle.com
Cc:     netdev@...r.kernel.org, rds-devel@....oracle.com,
        santosh.shilimkar@...cle.com
Subject: Re: [PATCH net-next] rds: cancel send/recv work before queuing
 connection shutdown

From: Sowmini Varadhan <sowmini.varadhan@...cle.com>
Date: Sun, 16 Jul 2017 16:43:46 -0700

> We could end up executing rds_conn_shutdown before the rds_recv_worker
> thread, then rds_conn_shutdown -> rds_tcp_conn_shutdown can do a
> sock_release and set sock->sk to null, which may interleave in bad
> ways with rds_recv_worker, e.g., it could result in:
> 
> "BUG: unable to handle kernel NULL pointer dereference at 0000000000000078"
>     [ffff881769f6fd70] release_sock at ffffffff815f337b
>     [ffff881769f6fd90] rds_tcp_recv at ffffffffa043c888 [rds_tcp]
>     [ffff881769f6fdb0] rds_recv_worker at ffffffffa04a4810 [rds]
>     [ffff881769f6fde0] process_one_work at ffffffff810a14c1
>     [ffff881769f6fe40] worker_thread at ffffffff810a1940
>     [ffff881769f6fec0] kthread at ffffffff810a6b1e
> 
> Also, do not enqueue any new shutdown workq items when the connection is
> shutting down (this may happen for rds-tcp in softirq mode, if a FIN
> or CLOSE is received while the modules is in the middle of an unload)
> 
> Signed-off-by: Sowmini Varadhan <sowmini.varadhan@...cle.com>

Applied, thank you.