text: // SPDX-License-Identifier: GPL-2.0
  /*
   * linux/fs/nfs/callback.c
   *
   * Copyright (C) 2004 Trond Myklebust
   *
   * NFSv4 callback handling
   */
  
  #include <linux/completion.h>
  #include <linux/ip.h>
  #include <linux/module.h>
  #include <linux/sched/signal.h>
  #include <linux/sunrpc/svc.h>
  #include <linux/sunrpc/svcsock.h>
  #include <linux/nfs_fs.h>
  #include <linux/errno.h>
  #include <linux/mutex.h>
  #include <linux/freezer.h>
  #include <linux/kthread.h>
  #include <linux/sunrpc/svcauth_gss.h>
  #include <linux/sunrpc/bc_xprt.h>
  
  #include <net/inet_sock.h>
  
  #include "nfs4_fs.h"
  #include "callback.h"
  #include "internal.h"
  #include "netns.h"
  
  #define NFSDBG_FACILITY NFSDBG_CALLBACK
  
  struct nfs_callback_data {
  	unsigned int users;
  	struct svc_serv *serv;
  };
  
  static struct nfs_callback_data nfs_callback_info[NFS4_MAX_MINOR_VERSION + 1];
  static DEFINE_MUTEX(nfs_callback_mutex);
  static struct svc_program nfs4_callback_program;
  
  static int nfs4_callback_up_net(struct svc_serv *serv, struct net *net)
  {
  	int ret;
  	struct nfs_net *nn = net_generic(net, nfs_net_id);
  
  	ret = svc_create_xprt(serv, "tcp", net, PF_INET,
  				nfs_callback_set_tcpport, SVC_SOCK_ANONYMOUS);
  	if (ret <= 0)
  		goto out_err;
  	nn->nfs_callback_tcpport = ret;
  	dprintk("NFS: Callback listener port = %u (af %u, net %p)\n",
  			nn->nfs_callback_tcpport, PF_INET, net);
  
  	ret = svc_create_xprt(serv, "tcp", net, PF_INET6,
  				nfs_callback_set_tcpport, SVC_SOCK_ANONYMOUS);
  	if (ret > 0) {
  		nn->nfs_callback_tcpport6 = ret;
  		dprintk("NFS: Callback listener port = %u (af %u, net %p)\n",
  				nn->nfs_callback_tcpport6, PF_INET6, net);
  	} else if (ret != -EAFNOSUPPORT)
  		goto out_err;
  	return 0;
  
  out_err:
  	return (ret) ? ret : -ENOMEM;
  }
  
  /*
   * This is the NFSv4 callback kernel thread.
   */
  static int
  nfs4_callback_svc(void *vrqstp)
  {
  	int err;
  	struct svc_rqst *rqstp = vrqstp;
  
  	set_freezable();
  
  	while (!kthread_freezable_should_stop(NULL)) {
  
  		if (signal_pending(current))
  			flush_signals(current);
  		/*
  		 * Listen for a request on the socket
  		 */
  		err = svc_recv(rqstp, MAX_SCHEDULE_TIMEOUT);
  		if (err == -EAGAIN || err == -EINTR)
  			continue;
  		svc_process(rqstp);
  	}
  	svc_exit_thread(rqstp);
  	module_put_and_exit(0);
  	return 0;
  }
  
  #if defined(CONFIG_NFS_V4_1)
  /*
   * The callback service for NFSv4.1 callbacks
   */
  static int
  nfs41_callback_svc(void *vrqstp)
  {
  	struct svc_rqst *rqstp = vrqstp;
  	struct svc_serv *serv = rqstp->rq_server;
  	struct rpc_rqst *req;
  	int error;
  	DEFINE_WAIT(wq);
  
  	set_freezable();
  
  	while (!kthread_freezable_should_stop(NULL)) {
  
  		if (signal_pending(current))
  			flush_signals(current);
  
  		prepare_to_wait(&serv->sv_cb_waitq, &wq, TASK_INTERRUPTIBLE);
  		spin_lock_bh(&serv->sv_cb_lock);
  		if (!list_empty(&serv->sv_cb_list)) {
  			req = list_first_entry(&serv->sv_cb_list,
  					struct rpc_rqst, rq_bc_list);
  			list_del(&req->rq_bc_list);
  			spin_unlock_bh(&serv->sv_cb_lock);
  			finish_wait(&serv->sv_cb_waitq, &wq);
  			dprintk("Invoking bc_svc_process()\n");
  			error = bc_svc_process(serv, req, rqstp);
  			dprintk("bc_svc_process() returned w/ error code= %d\n",
  				error);
  		} else {
  			spin_unlock_bh(&serv->sv_cb_lock);
  			if (!kthread_should_stop())
  				schedule();
  			finish_wait(&serv->sv_cb_waitq, &wq);
  		}
  	}
  	svc_exit_thread(rqstp);
  	module_put_and_exit(0);
  	return 0;
  }
  
  static inline void nfs_callback_bc_serv(u32 minorversion, struct rpc_xprt *xprt,
  		struct svc_serv *serv)
  {
  	if (minorversion)
  		/*
  		 * Save the svc_serv in the transport so that it can
  		 * be referenced when the session backchannel is initialized
  		 */
  		xprt->bc_serv = serv;
  }
  #else
  static inline void nfs_callback_bc_serv(u32 minorversion, struct rpc_xprt *xprt,
  		struct svc_serv *serv)
  {
  }
  #endif /* CONFIG_NFS_V4_1 */
  
  static int nfs_callback_start_svc(int minorversion, struct rpc_xprt *xprt,
  				  struct svc_serv *serv)
  {
  	int nrservs = nfs_callback_nr_threads;
  	int ret;
  
  	nfs_callback_bc_serv(minorversion, xprt, serv);
  
  	if (nrservs < NFS4_MIN_NR_CALLBACK_THREADS)
  		nrservs = NFS4_MIN_NR_CALLBACK_THREADS;
  
  	if (serv->sv_nrthreads-1 == nrservs)
  		return 0;
  
  	ret = serv->sv_ops->svo_setup(serv, NULL, nrservs);
  	if (ret) {
  		serv->sv_ops->svo_setup(serv, NULL, 0);
  		return ret;
  	}
  	dprintk("nfs_callback_up: service started\n");
  	return 0;
  }
  
  static void nfs_callback_down_net(u32 minorversion, struct svc_serv *serv, struct net *net)
  {
  	struct nfs_net *nn = net_generic(net, nfs_net_id);
  
  	if (--nn->cb_users[minorversion])
  		return;
  
  	dprintk("NFS: destroy per-net callback data; net=%p\n", net);
  	svc_shutdown_net(serv, net);
  }
  
  static int nfs_callback_up_net(int minorversion, struct svc_serv *serv,
  			       struct net *net, struct rpc_xprt *xprt)
  {
  	struct nfs_net *nn = net_generic(net, nfs_net_id);
  	int ret;
  
  	if (nn->cb_users[minorversion]++)
  		return 0;
  
  	dprintk("NFS: create per-net callback data; net=%p\n", net);
  
  	ret = svc_bind(serv, net);
  	if (ret < 0) {
  		printk(KERN_WARNING "NFS: bind callback service failed\n");
  		goto err_bind;
  	}
  
  	ret = -EPROTONOSUPPORT;
  	if (!IS_ENABLED(CONFIG_NFS_V4_1) || minorversion == 0)
  		ret = nfs4_callback_up_net(serv, net);
  	else if (xprt->ops->bc_up)
  		ret = xprt->ops->bc_up(serv, net);
  
  	if (ret < 0) {
  		printk(KERN_ERR "NFS: callback service start failed\n");
  		goto err_socks;
  	}
  	return 0;
  
  err_socks:
  	svc_rpcb_cleanup(serv, net);
  err_bind:
  	nn->cb_users[minorversion]--;
  	dprintk("NFS: Couldn't create callback socket: err = %d; "
  			"net = %p\n", ret, net);
  	return ret;
  }
  
  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 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 const struct svc_serv_ops *nfs4_cb_sv_ops[] = {
  	[0] = &nfs40_cb_sv_ops,
  	[1] = &nfs41_cb_sv_ops,
  };
  #else
  static const struct svc_serv_ops *nfs4_cb_sv_ops[] = {
  	[0] = &nfs40_cb_sv_ops,
  	[1] = NULL,
  };
  #endif
  
  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;
  
  	/*
  	 * Check whether we're already up and running.
  	 */
  	if (cb_info->serv) {
  		/*
  		 * Note: increase service usage, because later in case of error
  		 * svc_destroy() will be called.
  		 */
  		svc_get(cb_info->serv);
  		return cb_info->serv;
  	}
  
  	switch (minorversion) {
  	case 0:
  		sv_ops = nfs4_cb_sv_ops[0];
  		break;
  	default:
  		sv_ops = nfs4_cb_sv_ops[1];
  	}
  
  	if (sv_ops == NULL)
  		return ERR_PTR(-ENOTSUPP);
  
  	/*
  	 * Sanity check: if there's no task,
  	 * we should be the first user ...
  	 */
  	if (cb_info->users)
  		printk(KERN_WARNING "nfs_callback_create_svc: no kthread, %d users??\n",
  			cb_info->users);
  
  	serv = svc_create_pooled(&nfs4_callback_program, NFS4_CALLBACK_BUFSIZE, sv_ops);
  	if (!serv) {
  		printk(KERN_ERR "nfs_callback_create_svc: create service failed\n");
  		return ERR_PTR(-ENOMEM);
  	}
  	cb_info->serv = serv;
  	/* As there is only one thread we need to over-ride the
  	 * default maximum of 80 connections
  	 */
  	serv->sv_maxconn = 1024;
  	dprintk("nfs_callback_create_svc: service created\n");
  	return serv;
  }
  
  /*
   * Bring up the callback thread if it is not already up.
   */
  int nfs_callback_up(u32 minorversion, struct rpc_xprt *xprt)
  {
  	struct svc_serv *serv;
  	struct nfs_callback_data *cb_info = &nfs_callback_info[minorversion];
  	int ret;
  	struct net *net = xprt->xprt_net;
  
  	mutex_lock(&nfs_callback_mutex);
  
  	serv = nfs_callback_create_svc(minorversion);
  	if (IS_ERR(serv)) {
  		ret = PTR_ERR(serv);
  		goto err_create;
  	}
  
  	ret = nfs_callback_up_net(minorversion, serv, net, xprt);
  	if (ret < 0)
  		goto err_net;
  
  	ret = nfs_callback_start_svc(minorversion, xprt, serv);
  	if (ret < 0)
  		goto err_start;
  
  	cb_info->users++;
  	/*
  	 * svc_create creates the svc_serv with sv_nrthreads == 1, and then
  	 * svc_prepare_thread increments that. So we need to call svc_destroy
  	 * on both success and failure so that the refcount is 1 when the
  	 * thread exits.
  	 */
  err_net:
  	if (!cb_info->users)
  		cb_info->serv = NULL;
  	svc_destroy(serv);
  err_create:
  	mutex_unlock(&nfs_callback_mutex);
  	return ret;
  
  err_start:
  	nfs_callback_down_net(minorversion, serv, net);
  	dprintk("NFS: Couldn't create server thread; err = %d\n", ret);
  	goto err_net;
  }
  
  /*
   * Kill the callback thread if it's no longer being used.
   */
  void nfs_callback_down(int minorversion, struct net *net)
  {
  	struct nfs_callback_data *cb_info = &nfs_callback_info[minorversion];
  	struct svc_serv *serv;
  
  	mutex_lock(&nfs_callback_mutex);
  	serv = cb_info->serv;
  	nfs_callback_down_net(minorversion, serv, net);
  	cb_info->users--;
  	if (cb_info->users == 0) {
  		svc_get(serv);
  		serv->sv_ops->svo_setup(serv, NULL, 0);
  		svc_destroy(serv);
  		dprintk("nfs_callback_down: service destroyed\n");
  		cb_info->serv = NULL;
  	}
  	mutex_unlock(&nfs_callback_mutex);
  }
  
  /* Boolean check of RPC_AUTH_GSS principal */
  int
  check_gss_callback_principal(struct nfs_client *clp, struct svc_rqst *rqstp)
  {
  	char *p = rqstp->rq_cred.cr_principal;
  
  	if (rqstp->rq_authop->flavour != RPC_AUTH_GSS)
  		return 1;
  
  	/* No RPC_AUTH_GSS on NFSv4.1 back channel yet */
  	if (clp->cl_minorversion != 0)
  		return 0;
  	/*
  	 * It might just be a normal user principal, in which case
  	 * userspace won't bother to tell us the name at all.
  	 */
  	if (p == NULL)
  		return 0;
  
  	/*
  	 * Did we get the acceptor from userland during the SETCLIENID
  	 * negotiation?
  	 */
  	if (clp->cl_acceptor)
  		return !strcmp(p, clp->cl_acceptor);
  
  	/*
  	 * Otherwise try to verify it using the cl_hostname. Note that this
  	 * doesn't work if a non-canonical hostname was used in the devname.
  	 */
  
  	/* Expect a GSS_C_NT_HOSTBASED_NAME like "nfs@serverhostname" */
  
  	if (memcmp(p, "nfs@", 4) != 0)
  		return 0;
  	p += 4;
  	if (strcmp(p, clp->cl_hostname) != 0)
  		return 0;
  	return 1;
  }
  
  /*
   * pg_authenticate method for nfsv4 callback threads.
   *
   * The authflavor has been negotiated, so an incorrect flavor is a server
   * bug. Deny packets with incorrect authflavor.
   *
   * All other checking done after NFS decoding where the nfs_client can be
   * found in nfs4_callback_compound
   */
  static int nfs_callback_authenticate(struct svc_rqst *rqstp)
  {
  	switch (rqstp->rq_authop->flavour) {
  	case RPC_AUTH_NULL:
  		if (rqstp->rq_proc != CB_NULL)
  			return SVC_DENIED;
  		break;
  	case RPC_AUTH_GSS:
  		/* No RPC_AUTH_GSS support yet in NFSv4.1 */
  		 if (svc_is_backchannel(rqstp))
  			return SVC_DENIED;
  	}
  	return SVC_OK;
  }
  
  /*
   * Define NFS4 callback program
   */
  static const struct svc_version *nfs4_callback_version[] = {
  	[1] = &nfs4_callback_version1,
  	[4] = &nfs4_callback_version4,
  };
  
  static struct svc_stat nfs4_callback_stats;
  
  static struct svc_program nfs4_callback_program = {
  	.pg_prog = NFS4_CALLBACK,			/* RPC service number */
  	.pg_nvers = ARRAY_SIZE(nfs4_callback_version),	/* Number of entries */
  	.pg_vers = nfs4_callback_version,		/* version table */
  	.pg_name = "NFSv4 callback",			/* service name */
  	.pg_class = "nfs",				/* authentication class */
  	.pg_stats = &nfs4_callback_stats,
  	.pg_authenticate = nfs_callback_authenticate,
  };
  