Subject: Re: [PATCH iwl-net v3 4/6] ice: check ICE_VSI_DOWN under rtnl_lock when preparing for reset

From: Maciej Fijalkowski <[email-masked]>
Date: Thu, 22 Aug 2024 13:34:33 +0200

On Mon, Aug 19, 2024 at 12:05:41PM +0200, Larysa Zaremba wrote:
> Consider the following scenario:
> 
> .ndo_bpf()		| ice_prepare_for_reset()		|
> ________________________|_______________________________________|
> rtnl_lock()		|					|
> ice_down()		|					|
> 			| test_bit(ICE_VSI_DOWN) - true		|
> 			| ice_dis_vsi() returns			|
> ice_up()		|					|
> 			| proceeds to rebuild a running VSI	|
> 
> .ndo_bpf() is not the only rtnl-locked callback that toggles the interface
> to apply new configuration. Another example is .set_channels().
> 
> To avoid the race condition above, act only after reading ICE_VSI_DOWN
> under rtnl_lock.
> 
> Fixes: 0f9d5027a749 ("ice: Refactor VSI allocation, deletion and rebuild flow")
> Reviewed-by: Wojciech Drewek <[email-masked]>
> Reviewed-by: Jacob Keller <[email-masked]>
> Tested-by: Chandan Kumar Rout <[email-masked]>
> Signed-off-by: Larysa Zaremba <[email-masked]>
> ---
>  drivers/net/ethernet/intel/ice/ice_lib.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_lib.c b/drivers/net/ethernet/intel/ice/ice_lib.c
> index b72338974a60..94029e446b99 100644
> --- a/drivers/net/ethernet/intel/ice/ice_lib.c
> +++ b/drivers/net/ethernet/intel/ice/ice_lib.c
> @@ -2665,8 +2665,7 @@ int ice_ena_vsi(struct ice_vsi *vsi, bool locked)
>   */
>  void ice_dis_vsi(struct ice_vsi *vsi, bool locked)
>  {
> -	if (test_bit(ICE_VSI_DOWN, vsi->state))
> -		return;
> +	bool already_down = test_bit(ICE_VSI_DOWN, vsi->state);
>  
>  	set_bit(ICE_VSI_NEEDS_RESTART, vsi->state);
>  
> @@ -2674,15 +2673,16 @@ void ice_dis_vsi(struct ice_vsi *vsi, bool locked)
>  		if (netif_running(vsi->netdev)) {
>  			if (!locked)
>  				rtnl_lock();
> -
> -			ice_vsi_close(vsi);
> +			already_down = test_bit(ICE_VSI_DOWN, vsi->state);
> +			if (!already_down)
> +				ice_vsi_close(vsi);

ehh sorry for being sloppy reviewer. we still are testing ICE_VSI_DOWN in
ice_vsi_close(). wouldn't all of this be cleaner if we would bail out of
the called function when bit was already set?

>  
>  			if (!locked)
>  				rtnl_unlock();
> -		} else {
> +		} else if (!already_down) {
>  			ice_vsi_close(vsi);
>  		}
> -	} else if (vsi->type == ICE_VSI_CTRL) {
> +	} else if (vsi->type == ICE_VSI_CTRL && !already_down) {
>  		ice_vsi_close(vsi);
>  	}
>  }
> -- 
> 2.43.0
>