Re: [PATCH nf] netfilter: nft_fib_ipv6: bail out of sibling walk if rt got unlinked

[Jiayuan Chen <jiayuan.chen@linux.dev>]

On 5/26/26 10:17 PM, Florian Westphal wrote:
>> diff --git a/net/ipv6/netfilter/nft_fib_ipv6.c b/net/ipv6/netfilter/nft_fib_ipv6.c
>> index c0a0075e2590..2dbe44715df3 100644
>> --- a/net/ipv6/netfilter/nft_fib_ipv6.c
>> +++ b/net/ipv6/netfilter/nft_fib_ipv6.c
>> @@ -191,6 +191,9 @@ static bool nft_fib6_info_nh_uses_dev(struct fib6_info *rt,
>>   
>>   		if (nft_fib6_info_nh_dev_match(nh_dev, dev))
>>   			return true;
>> +
>> +		if (!READ_ONCE(rt->fib6_nsiblings))
>> +			return false;
>>   	}
> This time sashiko points to same bug pattern in rt6_fill_node:
>
> This is a pre-existing issue, but does rt6_fill_node() also need this
> detach check to prevent the same infinite loop?
>
> https://sashiko.dev/#/patchset/20260526020227.4857-1-jiayuan.chen%40linux.dev
>
> (No need to resend this patch, but maybe you have cycles to fix the
>   other spot too)



Hi Florian,

Thanks for the heads-up. After auditing the rest of net/ipv6/route.c
I noticed fib6_select_path() seems to have the same pattern as well
(walks &first->fib6_siblings under RCU with no inside-loop bail-out).

I'll send fixes for both spots directly against net.

Thanks,
Jiayuan