Re: [PATCH net] net/smc: cancel event worker during device removal

[Leon Romanovsky <leon@kernel.org>]

On Fri, Mar 06, 2020 at 02:45:18PM +0100, Karsten Graul wrote:
> During IB device removal, cancel the event worker before the device
> structure is freed. In the worker, check if the device is being
> terminated and do not proceed with the event work in that case.
>
> Fixes: a4cf0443c414 ("smc: introduce SMC as an IB-client")
> Reported-by: syzbot+b297c6825752e7a07272@syzkaller.appspotmail.com
> Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
> Reviewed-by: Ursula Braun <ubraun@linux.ibm.com>
> ---
>  net/smc/smc_ib.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/net/smc/smc_ib.c b/net/smc/smc_ib.c
> index d6ba186f67e2..5e4e64a9aa4b 100644
> --- a/net/smc/smc_ib.c
> +++ b/net/smc/smc_ib.c
> @@ -240,6 +240,9 @@ static void smc_ib_port_event_work(struct work_struct *work)
>  		work, struct smc_ib_device, port_event_work);
>  	u8 port_idx;
>
> +	if (list_empty(&smcibdev->list))
> +		return;
> +

How can it be true if you are not holding "smc_ib_devices.lock" during
execution of smc_ib_port_event_work()?

>  	for_each_set_bit(port_idx, &smcibdev->port_event_mask, SMC_MAX_PORTS) {
>  		smc_ib_remember_port_attr(smcibdev, port_idx + 1);
>  		clear_bit(port_idx, &smcibdev->port_event_mask);
> @@ -582,6 +585,7 @@ static void smc_ib_remove_dev(struct ib_device *ibdev, void *client_data)
>  	smc_smcr_terminate_all(smcibdev);
>  	smc_ib_cleanup_per_ibdev(smcibdev);
>  	ib_unregister_event_handler(&smcibdev->event_handler);
> +	cancel_work_sync(&smcibdev->port_event_work);
>  	kfree(smcibdev);
>  }
>
> --
> 2.17.1
>