Re: [PATCH] netfilter: nft_socket: socket expressions for GID & UID

[Topi Miettinen <toiwoton@gmail.com>]

On 26.4.2022 1.34, Florian Westphal wrote:
> Topi Miettinen <toiwoton@gmail.com> wrote:
>> On 20.4.2022 21.54, Topi Miettinen wrote:
>>> Add socket expressions for checking GID or UID of the originating
>>> socket. These work also on input side, unlike meta skuid/skgid.
>>
>> Unfortunately, there's a reproducible kernel BUG when closing a local
>> connection:
>>
>> Apr 25 21:18:13 kernel:
>> ==================================================================
>> Apr 25 21:18:13 kernel: BUG: KASAN: null-ptr-deref in
>> nf_sk_lookup_slow_v6+0x45b/0x590 [nf_socket_ipv6]
> 
> You can pass this to scripts/faddr2line to get the location of the null deref.

Didn't work, but with grep and gdb I think I located the error to 
net/ipv6/netfilter/nf_socket_ipv6.c:

static struct sock *
nf_socket_get_sock_v6(struct net *net, struct sk_buff *skb, int doff,
                       const u8 protocol,
                       const struct in6_addr *saddr, const struct 
in6_addr *daddr,
                       const __be16 sport, const __be16 dport,
                       const struct net_device *in)
{
         switch (protocol) {
         case IPPROTO_TCP:
                 return inet6_lookup(net, &tcp_hashinfo, skb, doff,
                                     saddr, sport, daddr, dport,
                                     in->ifindex);
                                     ^^^^^^^^^^^
where in->ifindex would be a NULL deref.

-Topi