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

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

commit 91751e2
Author: Stefano Garzarella <sgarzare@redhat.com>
Date:   Fri Jan 10 09:35:11 2025 +0100

    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>

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

Author: CKI Backport Bot

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);