> Now that SIT parameters and 6RD parameters are RCU-protected,
> and fwmark/encap are annotated with READ_ONCE()/WRITE_ONCE(),
> ipip6_fill_info() no longer requires RTNL to be held.
> 
> Wrap the attribute serialization in rcu_read_lock() and rcu_read_unlock().

Acked-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>

> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
>  net/ipv6/sit.c | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
> index c9049ab87e010eed5f53a342460ed10006083cd7..14ba3cfb304a83ee37e3be5b09a57c371f1977c3 100644
> --- a/net/ipv6/sit.c
> +++ b/net/ipv6/sit.c
> @@ -1846,11 +1846,18 @@ static size_t ipip6_get_size(const struct net_device *dev)
>  static int ipip6_fill_info(struct sk_buff *skb, const struct net_device *dev)
>  {
>  	struct ip_tunnel *tunnel = netdev_priv(dev);
> -	const struct ip_tunnel_parm_kern *parm = rtnl_dereference(tunnel->sit_parms);
> +	const struct ip_tunnel_parm_kern *parm;
>  #ifdef CONFIG_IPV6_SIT_6RD
>  	const struct ip_tunnel_6rd_parm *ip6rd;
>  #endif
>  
> +	rcu_read_lock();
> +	parm = rcu_dereference(tunnel->sit_parms);
> +	if (!parm) {
> +		rcu_read_unlock();
> +		return -ENODEV;
> +	}
> +
>  	if (nla_put_u32(skb, IFLA_IPTUN_LINK, parm->link) ||
>  	    nla_put_in_addr(skb, IFLA_IPTUN_LOCAL, parm->iph.saddr) ||
>  	    nla_put_in_addr(skb, IFLA_IPTUN_REMOTE, parm->iph.daddr) ||
> @@ -1865,7 +1872,7 @@ static int ipip6_fill_info(struct sk_buff *skb, const struct net_device *dev)
>  		goto nla_put_failure;
>  
>  #ifdef CONFIG_IPV6_SIT_6RD
> -	ip6rd = rcu_dereference_rtnl(tunnel->ip6rd);
> +	ip6rd = rcu_dereference(tunnel->ip6rd);
>  	if (ip6rd &&
>  	    (nla_put_in6_addr(skb, IFLA_IPTUN_6RD_PREFIX,
>  			      &ip6rd->prefix) ||
> @@ -1879,18 +1886,20 @@ static int ipip6_fill_info(struct sk_buff *skb, const struct net_device *dev)
>  #endif
>  
>  	if (nla_put_u16(skb, IFLA_IPTUN_ENCAP_TYPE,
> -			tunnel->encap.type) ||
> +			READ_ONCE(tunnel->encap.type)) ||
>  	    nla_put_be16(skb, IFLA_IPTUN_ENCAP_SPORT,
> -			tunnel->encap.sport) ||
> +			 READ_ONCE(tunnel->encap.sport)) ||
>  	    nla_put_be16(skb, IFLA_IPTUN_ENCAP_DPORT,
> -			tunnel->encap.dport) ||
> +			 READ_ONCE(tunnel->encap.dport)) ||
>  	    nla_put_u16(skb, IFLA_IPTUN_ENCAP_FLAGS,
> -			tunnel->encap.flags))
> +			READ_ONCE(tunnel->encap.flags)))
>  		goto nla_put_failure;
>  
> +	rcu_read_unlock();
>  	return 0;
>  
>  nla_put_failure:
> +	rcu_read_unlock();
>  	return -EMSGSIZE;
>  }
>  
> -- 
> 2.55.0.979.g7e5102b832-goog
>