netdev - Re: neighbour netlink notifications delivered in wrong order

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Date:   Mon, 6 Jun 2022 20:19:10 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Andy Roulin <aroulin@...dia.com>
Cc:     fruggeri@...sta.com, netdev@...r.kernel.org
Subject: Re: neighbour netlink notifications delivered in wrong order

On Mon, 6 Jun 2022 19:07:04 -0700
Andy Roulin <aroulin@...dia.com> wrote:

> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index 54625287ee5b..a91dfcbfc01c 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c
> @@ -2531,23 +2531,19 @@ static int neigh_fill_info(struct sk_buff *skb, 
> struct neighbour *neigh,
>   	if (nla_put(skb, NDA_DST, neigh->tbl->key_len, neigh->primary_key))
>   		goto nla_put_failure;
> 
> -	read_lock_bh(&neigh->lock);
>   	ndm->ndm_state	 = neigh->nud_state;

Accessing neighbor state outside of lock is not safe.

But you should be able to use RCU here??