netdev - Re: [PATCH net 06/10] iavf: prevent accidental free of filter structure

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Date:   Tue, 16 Nov 2021 08:24:21 +0100
From:   Stefan Assmann <sassmann@...hat.com>
To:     Tony Nguyen <anthony.l.nguyen@...el.com>
Cc:     davem@...emloft.net, kuba@...nel.org,
        Jacob Keller <jacob.e.keller@...el.com>,
        netdev@...r.kernel.org, Tony Brelinski <tony.brelinski@...el.com>
Subject: Re: [PATCH net 06/10] iavf: prevent accidental free of filter
 structure

On 2021-11-15 15:59, Tony Nguyen wrote:
> From: Jacob Keller <jacob.e.keller@...el.com>
> 
> In iavf_config_clsflower, the filter structure could be accidentally
> released at the end, if iavf_parse_cls_flower or iavf_handle_tclass ever
> return a non-zero but positive value.
> 
> In this case, the function continues through to the end, and will call
> kfree() on the filter structure even though it has been added to the
> linked list.
> 
> This can actually happen because iavf_parse_cls_flower will return
> a positive IAVF_ERR_CONFIG value instead of the traditional negative
> error codes.

Hi Jacob,

where exactly does this happen?
Looking at iavf_parse_cls_flower() I see all returns of IAVF_ERR_CONFIG
as "return IAVF_ERR_CONFIG;" while IAVF_ERR_CONFIG is defined as
        IAVF_ERR_CONFIG                         = -4,

I'm not opposed to this change, just wondering what's going on.

  Stefan

> Fix this by ensuring that the kfree() check and error checks are
> similar. Use the more idiomatic "if (err)" to catch all non-zero error
> codes.
> 
> Fixes: 0075fa0fadd0 ("i40evf: Add support to apply cloud filters")
> Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
> Tested-by: Tony Brelinski <tony.brelinski@...el.com>
> Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
> ---
>  drivers/net/ethernet/intel/iavf/iavf_main.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/iavf/iavf_main.c b/drivers/net/ethernet/intel/iavf/iavf_main.c
> index 76c4ca0f055e..9c68c8628512 100644
> --- a/drivers/net/ethernet/intel/iavf/iavf_main.c
> +++ b/drivers/net/ethernet/intel/iavf/iavf_main.c
> @@ -3108,11 +3108,11 @@ static int iavf_configure_clsflower(struct iavf_adapter *adapter,
>  	/* start out with flow type and eth type IPv4 to begin with */
>  	filter->f.flow_type = VIRTCHNL_TCP_V4_FLOW;
>  	err = iavf_parse_cls_flower(adapter, cls_flower, filter);
> -	if (err < 0)
> +	if (err)
>  		goto err;
>  
>  	err = iavf_handle_tclass(adapter, tc, filter);
> -	if (err < 0)
> +	if (err)
>  		goto err;
>  
>  	/* add filter to the list */
> -- 
> 2.31.1
>