sunrpc: Const-ify struct sv_serv_ops

Close an attack vector by moving the arrays of per-server methods to
read-only memory.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/lockd/svc.c

@@ -396,7 +396,7 @@ out_rqst:
 	return error;
 }
 
-static struct svc_serv_ops lockd_sv_ops = {
+static const struct svc_serv_ops lockd_sv_ops = {
 	.svo_shutdown		= svc_rpcb_cleanup,
 	.svo_enqueue_xprt	= svc_xprt_do_enqueue,
 };

fs/nfs/callback.c

@@ -226,26 +226,26 @@ err_bind:
 	return ret;
 }
 
-static struct svc_serv_ops nfs40_cb_sv_ops = {
+static const struct svc_serv_ops nfs40_cb_sv_ops = {
 	.svo_function		= nfs4_callback_svc,
 	.svo_enqueue_xprt	= svc_xprt_do_enqueue,
 	.svo_setup		= svc_set_num_threads_sync,
 	.svo_module		= THIS_MODULE,
 };
 #if defined(CONFIG_NFS_V4_1)
-static struct svc_serv_ops nfs41_cb_sv_ops = {
+static const struct svc_serv_ops nfs41_cb_sv_ops = {
 	.svo_function		= nfs41_callback_svc,
 	.svo_enqueue_xprt	= svc_xprt_do_enqueue,
 	.svo_setup		= svc_set_num_threads_sync,
 	.svo_module		= THIS_MODULE,
 };
 
-static struct svc_serv_ops *nfs4_cb_sv_ops[] = {
+static const struct svc_serv_ops *nfs4_cb_sv_ops[] = {
 	[0] = &nfs40_cb_sv_ops,
 	[1] = &nfs41_cb_sv_ops,
 };
 #else
-static struct svc_serv_ops *nfs4_cb_sv_ops[] = {
+static const struct svc_serv_ops *nfs4_cb_sv_ops[] = {
 	[0] = &nfs40_cb_sv_ops,
 	[1] = NULL,
 };
@@ -254,8 +254,8 @@ static struct svc_serv_ops *nfs4_cb_sv_ops[] = {
 static struct svc_serv *nfs_callback_create_svc(int minorversion)
 {
 	struct nfs_callback_data *cb_info = &nfs_callback_info[minorversion];
+	const struct svc_serv_ops *sv_ops;
 	struct svc_serv *serv;
-	struct svc_serv_ops *sv_ops;
 
 	/*
 	 * Check whether we're already up and running.

fs/nfsd/nfssvc.c

@@ -475,7 +475,7 @@ static int nfsd_get_default_max_blksize(void)
 	return ret;
 }
 
-static struct svc_serv_ops nfsd_thread_sv_ops = {
+static const struct svc_serv_ops nfsd_thread_sv_ops = {
 	.svo_shutdown		= nfsd_last_thread,
 	.svo_function		= nfsd,
 	.svo_enqueue_xprt	= svc_xprt_do_enqueue,

include/linux/sunrpc/svc.h

@@ -99,7 +99,7 @@ struct svc_serv {
 
 	unsigned int		sv_nrpools;	/* number of thread pools */
 	struct svc_pool *	sv_pools;	/* array of thread pools */
-	struct svc_serv_ops	*sv_ops;	/* server operations */
+	const struct svc_serv_ops *sv_ops;	/* server operations */
 #if defined(CONFIG_SUNRPC_BACKCHANNEL)
 	struct list_head	sv_cb_list;	/* queue for callback requests
 						 * that arrive over the same
@@ -465,7 +465,7 @@ int svc_rpcb_setup(struct svc_serv *serv, struct net *net);
 void svc_rpcb_cleanup(struct svc_serv *serv, struct net *net);
 int svc_bind(struct svc_serv *serv, struct net *net);
 struct svc_serv *svc_create(struct svc_program *, unsigned int,
-			    struct svc_serv_ops *);
+			    const struct svc_serv_ops *);
 struct svc_rqst *svc_rqst_alloc(struct svc_serv *serv,
 					struct svc_pool *pool, int node);
 struct svc_rqst *svc_prepare_thread(struct svc_serv *serv,
@@ -475,7 +475,7 @@ void		   svc_exit_thread(struct svc_rqst *);
 unsigned int	   svc_pool_map_get(void);
 void		   svc_pool_map_put(void);
 struct svc_serv *  svc_create_pooled(struct svc_program *, unsigned int,
-			struct svc_serv_ops *);
+			const struct svc_serv_ops *);
 int		   svc_set_num_threads(struct svc_serv *, struct svc_pool *, int);
 int		   svc_set_num_threads_sync(struct svc_serv *, struct svc_pool *, int);
 int		   svc_pool_stats_open(struct svc_serv *serv, struct file *file);

net/sunrpc/svc.c

@@ -421,7 +421,7 @@ __svc_init_bc(struct svc_serv *serv)
  */
 static struct svc_serv *
 __svc_create(struct svc_program *prog, unsigned int bufsize, int npools,
-	     struct svc_serv_ops *ops)
+	     const struct svc_serv_ops *ops)
 {
 	struct svc_serv	*serv;
 	unsigned int vers;
@@ -486,7 +486,7 @@ __svc_create(struct svc_program *prog, unsigned int bufsize, int npools,
 
 struct svc_serv *
 svc_create(struct svc_program *prog, unsigned int bufsize,
-	   struct svc_serv_ops *ops)
+	   const struct svc_serv_ops *ops)
 {
 	return __svc_create(prog, bufsize, /*npools*/1, ops);
 }
@@ -494,7 +494,7 @@ EXPORT_SYMBOL_GPL(svc_create);
 
 struct svc_serv *
 svc_create_pooled(struct svc_program *prog, unsigned int bufsize,
-		  struct svc_serv_ops *ops)
+		  const struct svc_serv_ops *ops)
 {
 	struct svc_serv *serv;
 	unsigned int npools = svc_pool_map_get();