On 8/9/23 1:33 AM, Lorenz Bauer wrote:
Kumar reported a KASAN splat in tcp_v6_rcv: bash-5.2# ./test_progs -t btf_skc_cls_ingress ... [ 51.810085] BUG: KASAN: slab-out-of-bounds in tcp_v6_rcv+0x2d7d/0x3440 [ 51.810458] Read of size 2 at addr ffff8881053f038c by task test_progs/226 The problem is that inet[6]_steal_sock accesses sk->sk_protocol without accounting for request sockets. I added the check to ensure that we only every try to perform a reuseport lookup on a supported socket. It turns out that this isn't necessary at all. struct sock_common contains a skc_reuseport flag which indicates whether a socket is part of a
Does it go back to the earlier discussion (https://lore.kernel.org/bpf/7188429a-c380-14c8-57bb-9d05d3ba4e5e@xxxxxxxxx/) that the sk->sk_reuseport is 1 from sk_clone for TCP_ESTABLISHED? It works because there is sk->sk_reuseport"_cb" check going deeper into reuseport_select_sock() but there is an extra inet6_ehashfn for all TCP_ESTABLISHED.
reuseport group. inet[6]_lookup_reuseport already check this flag, so we can't execute an erroneous reuseport lookup by definition. Remove the unnecessary assertions to fix the out of bounds access. Fixes: 9c02bec95954 ("bpf, net: Support SO_REUSEPORT sockets with bpf_sk_assign") Reported-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx> Signed-off-by: Lorenz Bauer <lmb@xxxxxxxxxxxxx> --- include/net/inet6_hashtables.h | 10 ---------- include/net/inet_hashtables.h | 10 ---------- 2 files changed, 20 deletions(-) diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h index 284b5ce7205d..f9907ed36d54 100644 --- a/include/net/inet6_hashtables.h +++ b/include/net/inet6_hashtables.h @@ -119,16 +119,6 @@ struct sock *inet6_steal_sock(struct net *net, struct sk_buff *skb, int doff, if (!prefetched) return sk;- if (sk->sk_protocol == IPPROTO_TCP) {- if (sk->sk_state != TCP_LISTEN) - return sk; - } else if (sk->sk_protocol == IPPROTO_UDP) { - if (sk->sk_state != TCP_CLOSE) - return sk; - } else { - return sk; - } - reuse_sk = inet6_lookup_reuseport(net, sk, skb, doff, saddr, sport, daddr, ntohs(dport), ehashfn); diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h index 1177effabed3..57a46993383a 100644 --- a/include/net/inet_hashtables.h +++ b/include/net/inet_hashtables.h @@ -465,16 +465,6 @@ struct sock *inet_steal_sock(struct net *net, struct sk_buff *skb, int doff, if (!prefetched) return sk;- if (sk->sk_protocol == IPPROTO_TCP) {- if (sk->sk_state != TCP_LISTEN) - return sk; - } else if (sk->sk_protocol == IPPROTO_UDP) { - if (sk->sk_state != TCP_CLOSE) - return sk; - } else { - return sk; - } - reuse_sk = inet_lookup_reuseport(net, sk, skb, doff, saddr, sport, daddr, ntohs(dport), ehashfn); --- base-commit: eb62e6aef940fcb1879100130068369d4638088f change-id: 20230808-bpf-next-a442a095562b Best regards,
