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Message-ID: <20230526014317.80715-1-kuniyu@amazon.com>
Date: Thu, 25 May 2023 18:43:17 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <martin.lau@...ux.dev>
CC: <andrii@...nel.org>, <ast@...nel.org>, <bpf@...r.kernel.org>,
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Subject: Re: [PATCH bpf-next 1/2] bpf, net: Support SO_REUSEPORT sockets with bpf_sk_assign
From: Martin KaFai Lau <martin.lau@...ux.dev>
Date: Thu, 25 May 2023 16:42:46 -0700
> On 5/25/23 1:19 AM, Lorenz Bauer wrote:
> > diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h
> > index 56f1286583d3..3ba4dc2703da 100644
> > --- a/include/net/inet6_hashtables.h
> > +++ b/include/net/inet6_hashtables.h
> > @@ -48,6 +48,13 @@ struct sock *__inet6_lookup_established(struct net *net,
> > const u16 hnum, const int dif,
> > const int sdif);
> >
> > +struct sock *inet6_lookup_reuseport(struct net *net, struct sock *sk,
> > + struct sk_buff *skb, int doff,
> > + const struct in6_addr *saddr,
> > + __be16 sport,
> > + const struct in6_addr *daddr,
> > + unsigned short hnum);
> > +
> > struct sock *inet6_lookup_listener(struct net *net,
> > struct inet_hashinfo *hashinfo,
> > struct sk_buff *skb, int doff,
> > @@ -85,14 +92,33 @@ static inline struct sock *__inet6_lookup_skb(struct inet_hashinfo *hashinfo,
> > int iif, int sdif,
> > bool *refcounted)
> > {
> > - struct sock *sk = skb_steal_sock(skb, refcounted);
> > -
> > + bool prefetched;
> > + struct sock *sk = skb_steal_sock(skb, refcounted, &prefetched);
> > + struct net *net = dev_net(skb_dst(skb)->dev);
> > + const struct ipv6hdr *ip6h = ipv6_hdr(skb);
> > +
> > + if (prefetched) {
> > + struct sock *reuse_sk = inet6_lookup_reuseport(net, sk, skb, doff,
>
> If sk is TCP_ESTABLISHED, I suspect sk->sk_reuseport is 1 (from sk_clone)?
Exactly, it will cause null-ptr-deref in reuseport_select_sock().
We may want to use rcu_access_pointer(sk->sk_reuseport_cb) in
each lookup_reuseport() instead of adding sk_state check ?
>
> If it is, it should still work other than an extra inet6_ehashfn. Does it worth
> an extra sk->sk_state check or it is overkill?
>
>
> > + &ip6h->saddr, sport,
> > + &ip6h->daddr, ntohs(dport));
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