selinux: initialize sock security class to default value

Initialize the security class of sock security structures
to the generic socket class.  This is similar to what is
already done in inode_alloc_security for files.  Generally
the sclass field will later by set by socket_post_create
or sk_clone or sock_graft, but for protocol implementations
that fail to call any of these for newly accepted sockets,
we want some sane default that will yield a legitimate
avc denied message with non-garbage values for class and
permission.
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <pmoore@redhat.com>

security/selinux/hooks.c

@@ -4559,6 +4559,7 @@ static int selinux_sk_alloc_security(struct sock *sk, int family, gfp_t priority
 
 	sksec->peer_sid = SECINITSID_UNLABELED;
 	sksec->sid = SECINITSID_UNLABELED;
+	sksec->sclass = SECCLASS_SOCKET;
 	selinux_netlbl_sk_security_reset(sksec);
 	sk->sk_security = sksec;