Re: [PATCH net] ipv4: igmp: fix refcnt uaf issue when receiving igmp query packet

[Hangbin Liu <liuhangbin@gmail.com>]

Hi Zhengchao,
On Tue, Nov 21, 2023 at 10:05:58AM +0800, Zhengchao Shao wrote:
> ---
>  net/ipv4/igmp.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
> index 76c3ea75b8dd..f217581904d6 100644
> --- a/net/ipv4/igmp.c
> +++ b/net/ipv4/igmp.c
> @@ -1044,6 +1044,8 @@ static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
>  	for_each_pmc_rcu(in_dev, im) {
>  		int changed;
>  
> +		if (!netif_running(im->interface->dev))
> +			continue;

I haven't checked this part for a long time. What's the difference of in_dev->dev
and im->interface->dev? I though they are the same, no?

If they are the same, should we stop processing the query earlier? e.g.

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 76c3ea75b8dd..f4e1d229c9aa 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -1082,6 +1082,9 @@ int igmp_rcv(struct sk_buff *skb)
                        goto drop;
        }

+       if (!netif_running(dev))
+               goto drop;
+
        in_dev = __in_dev_get_rcu(dev);
        if (!in_dev)
                goto drop;


BTW, does IPv6 MLD has this issue?

Thanks
Hangbin