[Patch net] ipv6: fix double refcount of fib6_metrics

[Patch net] ipv6: fix double refcount of fib6_metrics

[Cong Wang]

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@queasysnail.net>
Cc: Sabrina Dubroca <sd@queasysnail.net>
Cc: David Ahern <dsahern@gmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.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 */
-- 
2.14.4

Re: [Patch net] ipv6: fix double refcount of fib6_metrics

[David Miller]

From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Thu,  2 Aug 2018 23:20:38 -0700

> 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@queasysnail.net>
> Cc: Sabrina Dubroca <sd@queasysnail.net>
> Cc: David Ahern <dsahern@gmail.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>

Sabrina, please review!

Re: [Patch net] ipv6: fix double refcount of fib6_metrics

[David Miller]

From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Thu,  2 Aug 2018 23:20:38 -0700

> 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@queasysnail.net>
> Cc: Sabrina Dubroca <sd@queasysnail.net>
> Cc: David Ahern <dsahern@gmail.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>

Applied, thanks Cong.

Re: [Patch net] ipv6: fix double refcount of fib6_metrics

[David Ahern]

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@queasysnail.net>
> Cc: Sabrina Dubroca <sd@queasysnail.net>
> Cc: David Ahern <dsahern@gmail.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.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.