Subject: Re: [PATCH bpf 1/4] bpf, sockmap: SK_DROP on attempted redirects of unsupported af_vsock

From: Martin KaFai Lau <[email-masked]>
Date: Thu, 10 Oct 2024 11:54:12 -0700

On 10/9/24 2:20 PM, Michal Luczaj wrote:
> Don't mislead the callers of bpf_{sk,msg}_redirect_{map,hash}(): make sure
> to immediately and visibly fail the forwarding of unsupported af_vsock
> packets.
> 
> Fixes: 634f1a7110b4 ("vsock: support sockmap")
> Signed-off-by: Michal Luczaj <[email-masked]>
> ---
>   include/net/sock.h  | 5 +++++
>   net/core/sock_map.c | 8 ++++++++
>   2 files changed, 13 insertions(+)
> 
> diff --git a/include/net/sock.h b/include/net/sock.h
> index c58ca8dd561b7312ffc0836585c04d9fe917a124..c87295f3476db23934d4fcbeabc7851c61ad2bc4 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -2715,6 +2715,11 @@ static inline bool sk_is_stream_unix(const struct sock *sk)
>   	return sk->sk_family == AF_UNIX && sk->sk_type == SOCK_STREAM;
>   }
>   
> +static inline bool sk_is_vsock(const struct sock *sk)
> +{
> +	return sk->sk_family == AF_VSOCK;
> +}
> +
>   /**
>    * sk_eat_skb - Release a skb if it is no longer needed
>    * @sk: socket to eat this skb from
> diff --git a/net/core/sock_map.c b/net/core/sock_map.c
> index 242c91a6e3d3870ec6da6fa095d180a933d1d3d4..07d6aa4e39ef606aab33bd0d95711ecf156596b9 100644
> --- a/net/core/sock_map.c
> +++ b/net/core/sock_map.c
> @@ -647,6 +647,8 @@ BPF_CALL_4(bpf_sk_redirect_map, struct sk_buff *, skb,
>   	sk = __sock_map_lookup_elem(map, key);
>   	if (unlikely(!sk || !sock_map_redirect_allowed(sk)))
>   		return SK_DROP;
> +	if ((flags & BPF_F_INGRESS) && sk_is_vsock(sk))
> +		return SK_DROP;
>   
>   	skb_bpf_set_redir(skb, sk, flags & BPF_F_INGRESS);
>   	return SK_PASS;
> @@ -675,6 +677,8 @@ BPF_CALL_4(bpf_msg_redirect_map, struct sk_msg *, msg,
>   		return SK_DROP;
>   	if (!(flags & BPF_F_INGRESS) && !sk_is_tcp(sk))
>   		return SK_DROP;
> +	if (sk_is_vsock(sk))
> +		return SK_DROP;
>   
>   	msg->flags = flags;
>   	msg->sk_redir = sk;
> @@ -1249,6 +1253,8 @@ BPF_CALL_4(bpf_sk_redirect_hash, struct sk_buff *, skb,
>   	sk = __sock_hash_lookup_elem(map, key);
>   	if (unlikely(!sk || !sock_map_redirect_allowed(sk)))
>   		return SK_DROP;
> +	if ((flags & BPF_F_INGRESS) && sk_is_vsock(sk))
> +		return SK_DROP;
>   
>   	skb_bpf_set_redir(skb, sk, flags & BPF_F_INGRESS);
>   	return SK_PASS;
> @@ -1277,6 +1283,8 @@ BPF_CALL_4(bpf_msg_redirect_hash, struct sk_msg *, msg,
>   		return SK_DROP;
>   	if (!(flags & BPF_F_INGRESS) && !sk_is_tcp(sk))
>   		return SK_DROP;
> +	if (sk_is_vsock(sk))
> +		return SK_DROP;

Jakub Sitnicki, I think you have been on another thread about this change. 
Please help to take a look and ack if it looks good. Thanks.

>   	msg->flags = flags;
>   	msg->sk_redir = sk;