sunrpc: Const-ify instances of struct svc_xprt_ops

Close an attack vector by moving the arrays of server-side transport
methods to read-only memory.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

include/linux/sunrpc/svc_xprt.h

@@ -31,7 +31,7 @@ struct svc_xprt_ops {
 struct svc_xprt_class {
 	const char		*xcl_name;
 	struct module		*xcl_owner;
-	struct svc_xprt_ops	*xcl_ops;
+	const struct svc_xprt_ops *xcl_ops;
 	struct list_head	xcl_list;
 	u32			xcl_max_payload;
 	int			xcl_ident;
@@ -49,7 +49,7 @@ struct svc_xpt_user {
 
 struct svc_xprt {
 	struct svc_xprt_class	*xpt_class;
-	struct svc_xprt_ops	*xpt_ops;
+	const struct svc_xprt_ops *xpt_ops;
 	struct kref		xpt_ref;
 	struct list_head	xpt_list;
 	struct list_head	xpt_ready;

net/sunrpc/svcsock.c

@@ -687,7 +687,7 @@ static struct svc_xprt *svc_udp_create(struct svc_serv *serv,
 	return svc_create_socket(serv, IPPROTO_UDP, net, sa, salen, flags);
 }
 
-static struct svc_xprt_ops svc_udp_ops = {
+static const struct svc_xprt_ops svc_udp_ops = {
 	.xpo_create = svc_udp_create,
 	.xpo_recvfrom = svc_udp_recvfrom,
 	.xpo_sendto = svc_udp_sendto,
@@ -1229,7 +1229,7 @@ static void svc_bc_tcp_sock_detach(struct svc_xprt *xprt)
 {
 }
 
-static struct svc_xprt_ops svc_tcp_bc_ops = {
+static const struct svc_xprt_ops svc_tcp_bc_ops = {
 	.xpo_create = svc_bc_tcp_create,
 	.xpo_detach = svc_bc_tcp_sock_detach,
 	.xpo_free = svc_bc_sock_free,
@@ -1263,7 +1263,7 @@ static void svc_cleanup_bc_xprt_sock(void)
 }
 #endif /* CONFIG_SUNRPC_BACKCHANNEL */
 
-static struct svc_xprt_ops svc_tcp_ops = {
+static const struct svc_xprt_ops svc_tcp_ops = {
 	.xpo_create = svc_tcp_create,
 	.xpo_recvfrom = svc_tcp_recvfrom,
 	.xpo_sendto = svc_tcp_sendto,

net/sunrpc/xprtrdma/svc_rdma_transport.c

@@ -70,7 +70,7 @@ static int svc_rdma_has_wspace(struct svc_xprt *xprt);
 static int svc_rdma_secure_port(struct svc_rqst *);
 static void svc_rdma_kill_temp_xprt(struct svc_xprt *);
 
-static struct svc_xprt_ops svc_rdma_ops = {
+static const struct svc_xprt_ops svc_rdma_ops = {
 	.xpo_create = svc_rdma_create,
 	.xpo_recvfrom = svc_rdma_recvfrom,
 	.xpo_sendto = svc_rdma_sendto,
@@ -98,7 +98,7 @@ static struct svc_xprt *svc_rdma_bc_create(struct svc_serv *, struct net *,
 static void svc_rdma_bc_detach(struct svc_xprt *);
 static void svc_rdma_bc_free(struct svc_xprt *);
 
-static struct svc_xprt_ops svc_rdma_bc_ops = {
+static const struct svc_xprt_ops svc_rdma_bc_ops = {
 	.xpo_create = svc_rdma_bc_create,
 	.xpo_detach = svc_rdma_bc_detach,
 	.xpo_free = svc_rdma_bc_free,