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Date:   Wed, 18 Aug 2021 14:58:19 +0300
From:   Ido Schimmel <idosch@idosch.org>
To:     13145886936@163.com
Cc:     davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, gushengxian <gushengxian@yulong.com>
Subject: Re: [PATCH] flow_offload: action should not be NULL when it is
 referenced
Message-ID: <YRz1297sFSjG7/Cc@shredder>
References: <20210626115606.1243151-1-13145886936@163.com>
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On Sat, Jun 26, 2021 at 04:56:06AM -0700, 13145886936@163.com wrote:
> From: gushengxian <gushengxian@yulong.com>
> 
> "action" should not be NULL when it is referenced.
> 
> Signed-off-by: gushengxian <13145886936@163.com>
> Signed-off-by: gushengxian <gushengxian@yulong.com>
> ---
>  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
> 
>