netdev - Re: [PATCH net 3/4] sfc: null out channel->rps_flow

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Date:   Tue, 18 Aug 2020 11:58:57 -0700
From:   Jesse Brandeburg <jesse.brandeburg@...el.com>
To:     Edward Cree <ecree@...arflare.com>
Cc:     <linux-net-drivers@...arflare.com>, <davem@...emloft.net>,
        <netdev@...r.kernel.org>
Subject: Re: [PATCH net 3/4] sfc: null out channel->rps_flow_id after
 freeing it

Edward Cree wrote:

> If an ef100_net_open() fails, ef100_net_stop() may be called without
>  channel->rps_flow_id having been written; thus it may hold the address
>  freed by a previous ef100_net_stop()'s call to efx_remove_filters().
>  This then causes a double-free when efx_remove_filters() is called
>  again, leading to a panic.
> To prevent this, after freeing it, overwrite it with NULL.
> 
> Fixes: a9dc3d5612ce ("sfc_ef100: RX filter table management and related gubbins")
> Signed-off-by: Edward Cree <ecree@...arflare.com>
> ---
>  drivers/net/ethernet/sfc/rx_common.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/ethernet/sfc/rx_common.c b/drivers/net/ethernet/sfc/rx_common.c
> index ef9bca92b0b7..5e29284c89c9 100644
> --- a/drivers/net/ethernet/sfc/rx_common.c
> +++ b/drivers/net/ethernet/sfc/rx_common.c
> @@ -849,6 +849,7 @@ void efx_remove_filters(struct efx_nic *efx)
>  	efx_for_each_channel(channel, efx) {
>  		cancel_delayed_work_sync(&channel->filter_work);
>  		kfree(channel->rps_flow_id);
> +		channel->rps_flow_id = NULL;
>  	}
>  #endif
>  	down_write(&efx->filter_sem);
>