Re: [PATCH net-next v8 03/13] net/rds: ib: refuse to attach a connection to a device being removed

[sashiko-bot@kernel.org]

> rds_ib_remove_one() drops every connection on the device's conn_list
> in rds_ib_dev_shutdown(), then clears the client data so that no new
> connect can find the device.  A connect that is already past
> rds_ib_get_client_data() when the walk runs is not covered by either:
> rds_ib_setup_qp() goes on to rds_ib_add_conn(), which moves the
> connection onto the conn_list the walk has just finished with, and
> builds a QP on a device that is on its way out.  Nothing drops that
> connection afterwards - the device's shutdown walk is over, and the
> connection never returns to ib_nodev_conns, which is the only list the
> transport exit sweeps - so it outlives the device, and the module.
> 
> Make rds_ib_dev_shutdown() mark the device as shutting down under
> rds_ibdev->spinlock before it walks conn_list, and have
> rds_ib_add_conn() refuse, under the same lock, to attach a connection
> to a device so marked.  Every connection is then either on the list
> when the walk drops it, or refused: the connect fails, the connection
> stays on ib_nodev_conns, and either its own drop or the exit sweep
> tears it down.  rds_ib_setup_qp() has not taken anything from the
> device at that point, so the failure needs no unwinding beyond the
> client-data reference it already releases.
> 
> This mirrors the UEK gate on the device removal flag in
> rds_ib_add_conn().
> 
> Fixes: fc19de38be92 ("RDS/IB: disconnect when IB devices are removed")
> Assisted-by: Claude-Code:claude-fable-5
> Signed-off-by: Allison Henderson <achender@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

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