linux-kernel - Re: [PATCH linux-next] xfrm: Remove redundant fields

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Date:   Wed, 20 Oct 2021 11:07:29 +0200
From:   Simon Horman <horms@...nel.org>
To:     luo penghao <cgel.zte@...il.com>
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, penghao luo <luo.penghao@....com.cn>,
        Zeal Robot <zealci@....com.cn>
Subject: Re: [PATCH linux-next] xfrm: Remove redundant fields

On Mon, Oct 18, 2021 at 09:17:58AM +0000, luo penghao wrote:
> From: penghao luo <luo.penghao@....com.cn>
> 
> the variable err is not necessary in such places. It should be revmoved
> for the simplicity of the code.
> 
> The clang_analyzer complains as follows:
> 
> net/xfrm/xfrm_input.c:530: warning:
> 
> Although the value stored to 'err' is used in the enclosing expression,
> the value is never actually read from 'err'.
> 
> Reported-by: Zeal Robot <zealci@....com.cn>
> Signed-off-by: penghao luo <luo.penghao@....com.cn>
> ---
>  net/xfrm/xfrm_input.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c
> index 3df0861..ff34667 100644
> --- a/net/xfrm/xfrm_input.c
> +++ b/net/xfrm/xfrm_input.c
> @@ -530,7 +530,7 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
>  				goto drop;
>  			}
>  
> -			if ((err = xfrm_parse_spi(skb, nexthdr, &spi, &seq)) != 0) {
> +			if ((xfrm_parse_spi(skb, nexthdr, &spi, &seq)) != 0) {

I agree that assigning the value to err is not needed.
But you may also wish to consider:

1. Dropping the () around the call to xfrm_parse_spi, which seem out of
   place now.
2. Dropping the explicit check against zero

Which would leave you with:

			if (xfrm_parse_spi(skb, nexthdr, &spi, &seq)) {

>  				XFRM_INC_STATS(net, LINUX_MIB_XFRMINHDRERROR);
>  				goto drop;
>  			}
> @@ -560,7 +560,7 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
>  	}
>  
>  	seq = 0;
> -	if (!spi && (err = xfrm_parse_spi(skb, nexthdr, &spi, &seq)) != 0) {
> +	if (!spi && (xfrm_parse_spi(skb, nexthdr, &spi, &seq)) != 0) {
>  		secpath_reset(skb);
>  		XFRM_INC_STATS(net, LINUX_MIB_XFRMINHDRERROR);
>  		goto drop;
> -- 
> 2.15.2
> 
>