SMACK: Add sk_clone_security LSM hook

Using smk_of_current() during sk_alloc_security hook leads in
rare cases to a faulty initialization of the security context
of the created socket.

By adding the LSM hook sk_clone_security to SMACK this initialization
fault is corrected by copying the security context of the old socket
pointer to the newly cloned one.

Co-authored-by: Martin Ostertag: <[email protected]>
Signed-off-by: Lontke Michael <[email protected]>
Signed-off-by: Casey Schaufler <[email protected]>

security/smack/smack_lsm.c

@@ -2278,6 +2278,21 @@ static void smack_sk_free_security(struct sock *sk)
 	kfree(sk->sk_security);
 }
 
+/**
+ * smack_sk_clone_security - Copy security context
+ * @sk: the old socket
+ * @newsk: the new socket
+ *
+ * Copy the security context of the old socket pointer to the cloned
+ */
+static void smack_sk_clone_security(const struct sock *sk, struct sock *newsk)
+{
+	struct socket_smack *ssp_old = sk->sk_security;
+	struct socket_smack *ssp_new = newsk->sk_security;
+
+	*ssp_new = *ssp_old;
+}
+
 /**
 * smack_ipv4host_label - check host based restrictions
 * @sip: the object end
@@ -4851,6 +4866,7 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(socket_getpeersec_dgram, smack_socket_getpeersec_dgram),
 	LSM_HOOK_INIT(sk_alloc_security, smack_sk_alloc_security),
 	LSM_HOOK_INIT(sk_free_security, smack_sk_free_security),
+	LSM_HOOK_INIT(sk_clone_security, smack_sk_clone_security),
 	LSM_HOOK_INIT(sock_graft, smack_sock_graft),
 	LSM_HOOK_INIT(inet_conn_request, smack_inet_conn_request),
 	LSM_HOOK_INIT(inet_csk_clone, smack_inet_csk_clone),