Subject: Re: [PATCH] flow_offload: action should not be NULL when it is referenced

From: Ido Schimmel <[email-masked]>
Date: Wed, 18 Aug 2021 14:58:19 +0300

On Sat, Jun 26, 2021 at 04:56:06AM -0700, [email-masked] wrote:
> From: gushengxian <[email-masked]>
> 
> "action" should not be NULL when it is referenced.
> 
> Signed-off-by: gushengxian <[email-masked]>
> Signed-off-by: gushengxian <[email-masked]>
> ---
>  include/net/flow_offload.h | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/include/net/flow_offload.h b/include/net/flow_offload.h
> index dc5c1e69cd9f..69c9eabf8325 100644
> --- a/include/net/flow_offload.h
> +++ b/include/net/flow_offload.h
> @@ -319,12 +319,14 @@ flow_action_mixed_hw_stats_check(const struct flow_action *action,
>  	if (flow_offload_has_one_action(action))
>  		return true;
>  
> -	flow_action_for_each(i, action_entry, action) {
> -		if (i && action_entry->hw_stats != last_hw_stats) {
> -			NL_SET_ERR_MSG_MOD(extack, "Mixing HW stats types for actions is not supported");
> -			return false;
> +	if (action) {

This patch generates a smatch warning:

include/net/flow_offload.h:322 flow_action_mixed_hw_stats_check() warn: variable dereferenced before check 'action' (see line 319)

Why the patch is needed? 'action' is already dereferenced in
flow_offload_has_one_action()

> +		flow_action_for_each(i, action_entry, action) {
> +			if (i && action_entry->hw_stats != last_hw_stats) {
> +				NL_SET_ERR_MSG_MOD(extack, "Mixing HW stats types for actions is not supported");
> +				return false;
> +			}
> +			last_hw_stats = action_entry->hw_stats;
>  		}
> -		last_hw_stats = action_entry->hw_stats;
>  	}
>  	return true;
>  }
> -- 
> 2.25.1
> 
>