Subject: Re: [PATCH iwl-net v4] ice: Fix memory management in ice_ethtool_fdir.c

From: Leon Romanovsky <[email-masked]>
Date: Wed, 12 Jul 2023 09:29:58 +0300

On Tue, Jul 11, 2023 at 12:04:50PM +0200, Jedrzej Jagielski wrote:
> Fix ethtool FDIR logic to not use memory after its release.
> In the ice_ethtool_fdir.c file there are 2 spots where code can
> refer to pointers which may be missing.
> 
> In the ice_cfg_fdir_xtrct_seq() function seg may be freed but
> even then may be still used by memcpy(&tun_seg[1], seg, sizeof(*seg)).
> 
> In the ice_add_fdir_ethtool() function struct ice_fdir_fltr *input
> may first fail to be added via ice_fdir_update_list_entry() but then
> may be deleted by ice_fdir_update_list_entry.
> 
> Terminate in both cases when the returned value of the previous
> operation is other than 0, free memory and don't use it anymore.
> 
> Reported-by: Michal Schmidt <[email-masked]>
> Link: https://bugzilla.redhat.com/show_bug.cgi?id=2208423
> Fixes: cac2a27cd9ab ("ice: Support IPv4 Flow Director filters")
> Reviewed-by: Przemek Kitszel <[email-masked]>
> Signed-off-by: Jedrzej Jagielski <[email-masked]>
> ---
> v2: extend CC list, fix freeing memory before return
> v3: correct typos in the commit msg
> v4: restore devm() approach
> ---
>  .../net/ethernet/intel/ice/ice_ethtool_fdir.c | 30 +++++++++++--------
>  1 file changed, 18 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_ethtool_fdir.c b/drivers/net/ethernet/intel/ice/ice_ethtool_fdir.c
> index ead6d50fc0ad..b6308780362b 100644
> --- a/drivers/net/ethernet/intel/ice/ice_ethtool_fdir.c
> +++ b/drivers/net/ethernet/intel/ice/ice_ethtool_fdir.c
> @@ -1281,16 +1281,25 @@ ice_cfg_fdir_xtrct_seq(struct ice_pf *pf, struct ethtool_rx_flow_spec *fsp,
>  				     ICE_FLOW_FLD_OFF_INVAL);
>  	}
>  
> -	/* add filter for outer headers */
>  	fltr_idx = ice_ethtool_flow_to_fltr(fsp->flow_type & ~FLOW_EXT);
> +
> +	if (perfect_filter)
> +		set_bit(fltr_idx, hw->fdir_perfect_fltr);
> +	else
> +		clear_bit(fltr_idx, hw->fdir_perfect_fltr);
> +

The code above is assign_bit(fltr_idx, hw->fdir_perfect_fltr, perfect_filter);

> +	/* add filter for outer headers */
>  	ret = ice_fdir_set_hw_fltr_rule(pf, seg, fltr_idx,
>  					ICE_FD_HW_SEG_NON_TUN);
> -	if (ret == -EEXIST)
> -		/* Rule already exists, free memory and continue */
> -		devm_kfree(dev, seg);
> -	else if (ret)
> +	if (ret == -EEXIST) {
> +		/* Rule already exists, free memory and count as success */
> +		ret = 0;
> +		goto err_exit;
> +	} else if (ret) {
>  		/* could not write filter, free memory */
> +		ret = -EOPNOTSUPP;

I see that original code returned -EOPNOTSUPP, but why?
Why do you rewrite return value? Why can't you return "ret" as is?

Thanks

>  		goto err_exit;
> +	}
>  
>  	/* make tunneled filter HW entries if possible */
>  	memcpy(&tun_seg[1], seg, sizeof(*seg));
> @@ -1305,18 +1314,13 @@ ice_cfg_fdir_xtrct_seq(struct ice_pf *pf, struct ethtool_rx_flow_spec *fsp,
>  		devm_kfree(dev, tun_seg);
>  	}
>  
> -	if (perfect_filter)
> -		set_bit(fltr_idx, hw->fdir_perfect_fltr);
> -	else
> -		clear_bit(fltr_idx, hw->fdir_perfect_fltr);
> -
>  	return ret;
>  
>  err_exit:
>  	devm_kfree(dev, tun_seg);
>  	devm_kfree(dev, seg);
>  
> -	return -EOPNOTSUPP;
> +	return ret;
>  }
>  
>  /**
> @@ -1914,7 +1918,9 @@ int ice_add_fdir_ethtool(struct ice_vsi *vsi, struct ethtool_rxnfc *cmd)
>  	input->comp_report = ICE_FXD_FLTR_QW0_COMP_REPORT_SW_FAIL;
>  
>  	/* input struct is added to the HW filter list */
> -	ice_fdir_update_list_entry(pf, input, fsp->location);
> +	ret = ice_fdir_update_list_entry(pf, input, fsp->location);
> +	if (ret)
> +		goto release_lock;
>  
>  	ret = ice_fdir_write_all_fltr(pf, input, true);
>  	if (ret)
> -- 
> 2.31.1
> 
>