netdev - Re: [Patch net] ipv6: fix double refcount of fib6

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Message-ID: <30bcd6d8-e1ec-2cc3-8b2f-8a21ad4a529a@gmail.com>
Date:   Sun, 12 Aug 2018 17:08:59 -0600
From:   David Ahern <dsahern@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org
Cc:     Sabrina Dubroca <sd@...asysnail.net>
Subject: Re: [Patch net] ipv6: fix double refcount of fib6_metrics

On 8/3/18 12:20 AM, Cong Wang wrote:
> All the callers of ip6_rt_copy_init()/rt6_set_from() hold refcnt
> of the "from" fib6_info, so there is no need to hold fib6_metrics
> refcnt again, because fib6_metrics refcnt is only released when
> fib6_info is gone, that is, they have the same life time, so the
> whole fib6_metrics refcnt can be removed actually.
> 
> This fixes a kmemleak warning reported by Sabrina.
> 
> Fixes: 93531c674315 ("net/ipv6: separate handling of FIB entries from dst based routes")
> Reported-by: Sabrina Dubroca <sd@...asysnail.net>
> Cc: Sabrina Dubroca <sd@...asysnail.net>
> Cc: David Ahern <dsahern@...il.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
> ---
>  net/ipv6/route.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index ec18b3ce8b6d..7208c16302f6 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -978,10 +978,6 @@ static void rt6_set_from(struct rt6_info *rt, struct fib6_info *from)
>  	rt->rt6i_flags &= ~RTF_EXPIRES;
>  	rcu_assign_pointer(rt->from, from);
>  	dst_init_metrics(&rt->dst, from->fib6_metrics->metrics, true);
> -	if (from->fib6_metrics != &dst_default_metrics) {
> -		rt->dst._metrics |= DST_METRICS_REFCOUNTED;
> -		refcount_inc(&from->fib6_metrics->refcnt);
> -	}
>  }
>  
>  /* Caller must already hold reference to @ort */
> 

This seems like a reasonable fix. Thanks for the patch.