netdev - Re: [PATCH net-next] neigh: fix a possible leak issue of neigh entry

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Message-ID: <1431498048.566.131.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 12 May 2015 23:20:48 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ying Xue <ying.xue@...driver.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [PATCH net-next] neigh: fix a possible leak issue of neigh entry

On Wed, 2015-05-13 at 13:43 +0800, Ying Xue wrote:
> Once modifying a pending timer of a neighbour, it's insufficient to
> post a warning message. Instead we should not take the neighbour's
> reference count at the same time, otherwise, it causes an issue that
> the neighbour cannot be freed forever.
> 
> Signed-off-by: Ying Xue <ying.xue@...driver.com>
> ---
>  net/core/neighbour.c |    9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index 3de6542..5595db3 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c
> @@ -164,10 +164,11 @@ static int neigh_forced_gc(struct neigh_table *tbl)
>  
>  static void neigh_add_timer(struct neighbour *n, unsigned long when)
>  {
> -	neigh_hold(n);
> -	if (unlikely(mod_timer(&n->timer, when))) {
> -		printk("NEIGH: BUG, double timer add, state is %x\n",
> -		       n->nud_state);
> +	if (likely(!mod_timer(&n->timer, when))) {
> +		neigh_hold(n);
> +	} else {
> +		pr_warn("NEIGH: BUG, double timer add, state is %x\n",
> +			n->nud_state);
>  		dump_stack();
>  	}
>  }

Have you hit this condition ?

If yes, there is a bug elsewhere and we need to fix it, not trying to
recover.



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