linux-kernel - Re: [PATCH net-next v2] net/ipv6: silence 'passing zero to ERR

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Message-ID: <7e98e085-a167-f69d-5fcd-358157e1741e@intel.com>
Date:   Thu, 13 Apr 2023 15:50:16 -0700
From:   Jacob Keller <jacob.e.keller@...el.com>
To:     Haoyi Liu <iccccc@...t.edu.cn>,
        "David S. Miller" <davem@...emloft.net>,
        David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "Jakub Kicinski" <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
CC:     <hust-os-kernel-patches@...glegroups.com>, <yalongz@...t.edu.cn>,
        <error27@...il.com>, Dongliang Mu <dzm91@...t.edu.cn>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v2] net/ipv6: silence 'passing zero to ERR_PTR()'
 warning



On 4/13/2023 3:10 AM, Haoyi Liu wrote:
> Smatch complains that if xfrm_lookup() returns NULL then this does a
> weird thing with "err":
> 
>     net/ ipv6/ icmp.c:411 icmpv6_route_lookup()
>     warn: passing zero to ERR_PTR()
> 
> Merge conditional paths and remove unnecessary 'else'. No functional
> change.
> 
> Signed-off-by: Haoyi Liu <iccccc@...t.edu.cn>
> Reviewed-by: Dongliang Mu <dzm91@...t.edu.cn>
> ---
> v1->v2: Remove unnecessary 'else'.
> The issue is found by static analysis, and the patch is remains untested.
> ---
>  net/ipv6/icmp.c | 17 ++++++-----------
>  1 file changed, 6 insertions(+), 11 deletions(-)
> 
> diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
> index 1f53f2a74480..a12eef11c7ee 100644
> --- a/net/ipv6/icmp.c
> +++ b/net/ipv6/icmp.c
> @@ -393,17 +393,12 @@ static struct dst_entry *icmpv6_route_lookup(struct net *net,
>  		goto relookup_failed;
>  
>  	dst2 = xfrm_lookup(net, dst2, flowi6_to_flowi(&fl2), sk, XFRM_LOOKUP_ICMP);
> -	if (!IS_ERR(dst2)) {
> -		dst_release(dst);
> -		dst = dst2;
> -	} else {
> -		err = PTR_ERR(dst2);
> -		if (err == -EPERM) {
> -			dst_release(dst);
> -			return dst2;
> -		} else
> -			goto relookup_failed;
> -	}
> +	err = PTR_ERR_OR_ZERO(dst2);
> +	if (err && err != -EPERM)
> +		goto relookup_failed;
> +
> +	dst_release(dst);
> +	return dst2;	/* returns success or ERR_PTR(-EPERM) */
>  

This result looks much cleaner!

Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>

Thanks,
Jake

>  relookup_failed:
>  	if (dst)