Merge: CVE-2025-21666: vsock: prevent null-ptr-deref in vsock_*has_data|has_space]

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/6315

JIRA: https://issues.redhat.com/browse/RHEL-77211
CVE: CVE-2025-21666

```
vsock: prevent null-ptr-deref in vsock_*[has_data|has_space]

Recent reports have shown how we sometimes call vsock_*_has_data()
when a vsock socket has been de-assigned from a transport (see attached
links), but we shouldn't.

Previous commits should have solved the real problems, but we may have
more in the future, so to avoid null-ptr-deref, we can return 0
(no space, no data available) but with a warning.

This way the code should continue to run in a nearly consistent state
and have a warning that allows us to debug future problems.

Fixes: c0cfa2d ("vsock: add multi-transports support")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/netdev/Z2K%2FI4nlHdfMRTZC@v4bel-B760M-AORUS-ELITE-AX/
Link: https://lore.kernel.org/netdev/5ca20d4c-1017-49c2-9516-f6f75fd331e9@rbox.co/
Link: https://lore.kernel.org/netdev/677f84a8.050a0220.25a300.01b3.GAE@google.com/
Co-developed-by: Hyunwoo Kim <v4bel@theori.io>
Signed-off-by: Hyunwoo Kim <v4bel@theori.io>
Co-developed-by: Wongi Lee <qwerty@theori.io>
Signed-off-by: Wongi Lee <qwerty@theori.io>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Luigi Leonardi <leonardi@redhat.com>
Reviewed-by: Hyunwoo Kim <v4bel@theori.io>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

(cherry picked from commit 91751e2)
```

Signed-off-by: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>

---

<small>Created 2025-01-31 18:32 UTC by backporter - [KWF FAQ](https://red.ht/kernel_workflow_doc) - [Slack #team-kernel-workflow](https://redhat-internal.slack.com/archives/C04LRUPMJQ5) - [Source](https://gitlab.com/cki-project/kernel-workflow/-/blob/main/webhook/utils/backporter.py) - [Documentation](https://gitlab.com/cki-project/kernel-workflow/-/blob/main/docs/README.backporter.md) - [Report an issue](https://gitlab.com/cki-project/kernel-workflow/-/issues/new?issue%5Btitle%5D=backporter%20webhook%20issue)</small>

Approved-by: Jon Maloy <jmaloy@redhat.com>
Approved-by: Stefano Garzarella <sgarzare@redhat.com>
Approved-by: Stefan Hajnoczi <stefanha@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Patrick Talbert <ptalbert@redhat.com>

Author: ptalbert

net/vmw_vsock/af_vsock.c

@@ -870,6 +870,9 @@ EXPORT_SYMBOL_GPL(vsock_create_connected);
 
 s64 vsock_stream_has_data(struct vsock_sock *vsk)
 {
+	if (WARN_ON(!vsk->transport))
+		return 0;
+
 	return vsk->transport->stream_has_data(vsk);
 }
 EXPORT_SYMBOL_GPL(vsock_stream_has_data);
@@ -878,6 +881,9 @@ s64 vsock_connectible_has_data(struct vsock_sock *vsk)
 {
 	struct sock *sk = sk_vsock(vsk);
 
+	if (WARN_ON(!vsk->transport))
+		return 0;
+
 	if (sk->sk_type == SOCK_SEQPACKET)
 		return vsk->transport->seqpacket_has_data(vsk);
 	else
@@ -887,6 +893,9 @@ EXPORT_SYMBOL_GPL(vsock_connectible_has_data);
 
 s64 vsock_stream_has_space(struct vsock_sock *vsk)
 {
+	if (WARN_ON(!vsk->transport))
+		return 0;
+
 	return vsk->transport->stream_has_space(vsk);
 }
 EXPORT_SYMBOL_GPL(vsock_stream_has_space);