Re: [PATCH net 2/4] vsock/bpf: Warn on socket without transport

[Stefano Garzarella <sgarzare@xxxxxxxxxx>]

On Thu, Feb 13, 2025 at 12:58:50PM +0100, Michal Luczaj wrote:
> In the spirit of commit 91751e248256 ("vsock: prevent null-ptr-deref in
> vsock_*[has_data|has_space]"), armorize the "impossible" cases with a
> warning.
>
> Fixes: 634f1a7110b4 ("vsock: support sockmap")
> Signed-off-by: Michal Luczaj <mhal@xxxxxxx>
> ---
> net/vmw_vsock/af_vsock.c  | 3 +++
> net/vmw_vsock/vsock_bpf.c | 2 +-
> 2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> index 53a081d49d28ac1c04e7f8057c8a55e7b73cc131..7e3db87ae4333cf63327ec105ca99253569bb9fe 100644
> --- a/net/vmw_vsock/af_vsock.c
> +++ b/net/vmw_vsock/af_vsock.c
> @@ -1189,6 +1189,9 @@ static int vsock_read_skb(struct sock *sk, skb_read_actor_t read_actor)
> {
> 	struct vsock_sock *vsk = vsock_sk(sk);
>
> +	if (WARN_ON_ONCE(!vsk->transport))
> +		return -ENODEV;
> +
> 	return vsk->transport->read_skb(vsk, read_actor);
> }
>
> diff --git a/net/vmw_vsock/vsock_bpf.c b/net/vmw_vsock/vsock_bpf.c
> index f201d9eca1df2f8143638cf7a4d08671e8368c11..07b96d56f3a577af71021b1b8132743554996c4f 100644
> --- a/net/vmw_vsock/vsock_bpf.c
> +++ b/net/vmw_vsock/vsock_bpf.c
> @@ -87,7 +87,7 @@ static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
> 	lock_sock(sk);
> 	vsk = vsock_sk(sk);
>
> -	if (!vsk->transport) {
> +	if (WARN_ON_ONCE(!vsk->transport)) {
> 		copied = -ENODEV;
> 		goto out;
> 	}

I'm not a sockmap expert, so I don't understand why here print an
error.

Since there was already a check, I expected it to be a case that can 
happen, but instead calling `rcvmsg()` on a socket not yet connected is 
impossible?

Thanks,
Stefano