Subject: Re: [PATCH net 2/2] sit: check if IPv6 enabled before call ip6_err_gen_icmpv6_unreach()

From: Stefano Brivio <[email-masked]>
Date: Wed, 6 Feb 2019 16:00:30 +0100

On Wed,  6 Feb 2019 20:51:11 +0800
Hangbin Liu <[email-masked]> wrote:

> If we disabled IPv6 from kernel boot up cmd(ipv6.disable=1), we should not
> call ip6_err_gen_icmpv6_unreach().
> 
> Reproducer:
> ip link add sit1 type sit local 10.10.0.1 remote 10.10.1.1 ttl 1
> ip link set sit1 up
> ip addr add 192.168.0.1/24 dev sit1
> ping 192.168.0.2
> 
> Reported-by: Jianlin Shi <[email-masked]>
> Signed-off-by: Hangbin Liu <[email-masked]>
> ---
>  net/ipv6/sit.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
> index 1e03305c0549..e43fbac0fd1a 100644
> --- a/net/ipv6/sit.c
> +++ b/net/ipv6/sit.c
> @@ -493,6 +493,7 @@ static int ipip6_err(struct sk_buff *skb, u32 info)
>  	const int type = icmp_hdr(skb)->type;
>  	const int code = icmp_hdr(skb)->code;
>  	unsigned int data_len = 0;
> +	struct inet6_dev *idev;
>  	struct ip_tunnel *t;
>  	int sifindex;
>  	int err;
> @@ -546,8 +547,13 @@ static int ipip6_err(struct sk_buff *skb, u32 info)
>  	}
>  
>  	err = 0;
> -	if (!ip6_err_gen_icmpv6_unreach(skb, iph->ihl * 4, type, data_len))
> +
> +	idev = in6_dev_get(skb->dev);
> +	if (idev &&
> +	    !ip6_err_gen_icmpv6_unreach(skb, iph->ihl * 4, type, data_len)) {
> +		in6_dev_put(idev);
>  		goto out;
> +	}

You are leaking a reference if idev && ip6_err_gen_icmpv6_unreach(...).
You should call in6_dev_put(idev) whenever idev is not NULL instead.

-- 
Stefano