Re: [PATCH iwl-net v2 4/6] ice: check ICE_VSI_DOWN under rtnl_lock when preparing for reset

[Jacob Keller <jacob.e.keller@intel.com>]

On 7/24/2024 9:48 AM, 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 <wojciech.drewek@intel.com>
> Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
> ---
>  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 f9852f1a136e..b773078ad81a 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);
>  

Do we need to initialize already_down? I guess its because the other
initialization happens inside the conditional which may not be executed
in every flow. Ok.

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>

>  	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);
>  
>  			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);
>  	}
>  }