sunrpc: Const-ify all instances of struct rpc_xprt_ops

After transport instance creation, these function pointers never
change. Mark them as constant to prevent their use as an attack
vector for code injections.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

include/linux/sunrpc/xprt.h

@@ -174,7 +174,7 @@ enum xprt_transports {
 
 struct rpc_xprt {
 	struct kref		kref;		/* Reference count */
-	struct rpc_xprt_ops *	ops;		/* transport methods */
+	const struct rpc_xprt_ops *ops;		/* transport methods */
 
 	const struct rpc_timeout *timeout;	/* timeout parms */
 	struct sockaddr_storage	addr;		/* server address */

net/sunrpc/xprtrdma/svc_rdma_backchannel.c

@@ -266,7 +266,7 @@ xprt_rdma_bc_put(struct rpc_xprt *xprt)
 	module_put(THIS_MODULE);
 }
 
-static struct rpc_xprt_ops xprt_rdma_bc_procs = {
+static const struct rpc_xprt_ops xprt_rdma_bc_procs = {
 	.reserve_xprt		= xprt_reserve_xprt_cong,
 	.release_xprt		= xprt_release_xprt_cong,
 	.alloc_slot		= xprt_alloc_slot,

net/sunrpc/xprtrdma/transport.c

@@ -149,7 +149,7 @@ static struct ctl_table sunrpc_table[] = {
 
 #endif
 
-static struct rpc_xprt_ops xprt_rdma_procs;	/*forward reference */
+static const struct rpc_xprt_ops xprt_rdma_procs;
 
 static void
 xprt_rdma_format_addresses4(struct rpc_xprt *xprt, struct sockaddr *sap)
@@ -811,7 +811,7 @@ xprt_rdma_disable_swap(struct rpc_xprt *xprt)
  * Plumbing for rpc transport switch and kernel module
  */
 
-static struct rpc_xprt_ops xprt_rdma_procs = {
+static const struct rpc_xprt_ops xprt_rdma_procs = {
 	.reserve_xprt		= xprt_reserve_xprt_cong,
 	.release_xprt		= xprt_release_xprt_cong, /* sunrpc/xprt.c */
 	.alloc_slot		= xprt_alloc_slot,

net/sunrpc/xprtsock.c

@@ -2724,7 +2724,7 @@ static void bc_destroy(struct rpc_xprt *xprt)
 	module_put(THIS_MODULE);
 }
 
-static struct rpc_xprt_ops xs_local_ops = {
+static const struct rpc_xprt_ops xs_local_ops = {
 	.reserve_xprt		= xprt_reserve_xprt,
 	.release_xprt		= xs_tcp_release_xprt,
 	.alloc_slot		= xprt_alloc_slot,
@@ -2742,7 +2742,7 @@ static struct rpc_xprt_ops xs_local_ops = {
 	.disable_swap		= xs_disable_swap,
 };
 
-static struct rpc_xprt_ops xs_udp_ops = {
+static const struct rpc_xprt_ops xs_udp_ops = {
 	.set_buffer_size	= xs_udp_set_buffer_size,
 	.reserve_xprt		= xprt_reserve_xprt_cong,
 	.release_xprt		= xprt_release_xprt_cong,
@@ -2764,7 +2764,7 @@ static struct rpc_xprt_ops xs_udp_ops = {
 	.inject_disconnect	= xs_inject_disconnect,
 };
 
-static struct rpc_xprt_ops xs_tcp_ops = {
+static const struct rpc_xprt_ops xs_tcp_ops = {
 	.reserve_xprt		= xprt_reserve_xprt,
 	.release_xprt		= xs_tcp_release_xprt,
 	.alloc_slot		= xprt_lock_and_alloc_slot,
@@ -2795,7 +2795,7 @@ static struct rpc_xprt_ops xs_tcp_ops = {
  * The rpc_xprt_ops for the server backchannel
  */
 
-static struct rpc_xprt_ops bc_tcp_ops = {
+static const struct rpc_xprt_ops bc_tcp_ops = {
 	.reserve_xprt		= xprt_reserve_xprt,
 	.release_xprt		= xprt_release_xprt,
 	.alloc_slot		= xprt_alloc_slot,