lockd: create NSM handles per net namespace

Commit cb7323fffa85 ("lockd: create and use per-net NSM
RPC clients on MON/UNMON requests") introduced per-net
NSM RPC clients. Unfortunately this doesn't make any sense
without per-net nsm_handle.

E.g. the following scenario could happen
Two hosts (X and Y) in different namespaces (A and B) share
the same nsm struct.

1. nsm_monitor(host_X) called => NSM rpc client created,
nsm->sm_monitored bit set.
2. nsm_mointor(host-Y) called => nsm->sm_monitored already set,
we just exit. Thus in namespace B ln->nsm_clnt == NULL.
3. host X destroyed => nsm->sm_count decremented to 1
4. host Y destroyed => nsm_unmonitor() => nsm_mon_unmon() => NULL-ptr
dereference of *ln->nsm_clnt

So this could be fixed by making per-net nsm_handles list,
instead of global. Thus different net namespaces will not be able
share the same nsm_handle.

Signed-off-by: Andrey Ryabinin <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: J. Bruce Fields <[e-mail]>

fs/lockd/host.c

···
 		atomic_inc(&nsm->sm_count);
 	else {
 		host = NULL;
-		nsm = nsm_get_handle(ni->sap, ni->salen,
+		nsm = nsm_get_handle(ni->net, ni->sap, ni->salen,
 					ni->hostname, ni->hostname_len);
 		if (unlikely(nsm == NULL)) {
 			dprintk("lockd: %s failed; no nsm handle\n",
···
 
 /**
  * nlm_host_rebooted - Release all resources held by rebooted host
+ * @net:  network namespace
  * @info: pointer to decoded results of NLM_SM_NOTIFY call
  *
  * We were notified that the specified host has rebooted.  Release
  * all resources held by that peer.
  */
-void nlm_host_rebooted(const struct nlm_reboot *info)
+void nlm_host_rebooted(const struct net *net, const struct nlm_reboot *info)
 {
 	struct nsm_handle *nsm;
 	struct nlm_host	*host;
 
-	nsm = nsm_reboot_lookup(info);
+	nsm = nsm_reboot_lookup(net, info);
 	if (unlikely(nsm == NULL))
 		return;
 

fs/lockd/mon.c

···
 };
 
 static const struct rpc_program	nsm_program;
-static				LIST_HEAD(nsm_handles);
 static				DEFINE_SPINLOCK(nsm_lock);
 
 /*
···
 	}
 }
 
-static struct nsm_handle *nsm_lookup_hostname(const char *hostname,
-					      const size_t len)
+static struct nsm_handle *nsm_lookup_hostname(const struct list_head *nsm_handles,
+					const char *hostname, const size_t len)
 {
 	struct nsm_handle *nsm;
 
-	list_for_each_entry(nsm, &nsm_handles, sm_link)
+	list_for_each_entry(nsm, nsm_handles, sm_link)
 		if (strlen(nsm->sm_name) == len &&
 		    memcmp(nsm->sm_name, hostname, len) == 0)
 			return nsm;
 	return NULL;
 }
 
-static struct nsm_handle *nsm_lookup_addr(const struct sockaddr *sap)
+static struct nsm_handle *nsm_lookup_addr(const struct list_head *nsm_handles,
+					const struct sockaddr *sap)
 {
 	struct nsm_handle *nsm;
 
-	list_for_each_entry(nsm, &nsm_handles, sm_link)
+	list_for_each_entry(nsm, nsm_handles, sm_link)
 		if (rpc_cmp_addr(nsm_addr(nsm), sap))
 			return nsm;
 	return NULL;
 }
 
-static struct nsm_handle *nsm_lookup_priv(const struct nsm_private *priv)
+static struct nsm_handle *nsm_lookup_priv(const struct list_head *nsm_handles,
+					const struct nsm_private *priv)
 {
 	struct nsm_handle *nsm;
 
-	list_for_each_entry(nsm, &nsm_handles, sm_link)
+	list_for_each_entry(nsm, nsm_handles, sm_link)
 		if (memcmp(nsm->sm_priv.data, priv->data,
 					sizeof(priv->data)) == 0)
 			return nsm;
···
 
 /**
  * nsm_get_handle - Find or create a cached nsm_handle
+ * @net: network namespace
  * @sap: pointer to socket address of handle to find
  * @salen: length of socket address
  * @hostname: pointer to C string containing hostname to find
···
  * @hostname cannot be found in the handle cache.  Returns NULL if
  * an error occurs.
  */
-struct nsm_handle *nsm_get_handle(const struct sockaddr *sap,
+struct nsm_handle *nsm_get_handle(const struct net *net,
+				  const struct sockaddr *sap,
 				  const size_t salen, const char *hostname,
 				  const size_t hostname_len)
 {
 	struct nsm_handle *cached, *new = NULL;
+	struct lockd_net *ln = net_generic(net, lockd_net_id);
 
 	if (hostname && memchr(hostname, '/', hostname_len) != NULL) {
 		if (printk_ratelimit()) {
···
 	spin_lock(&nsm_lock);
 
 	if (nsm_use_hostnames && hostname != NULL)
-		cached = nsm_lookup_hostname(hostname, hostname_len);
+		cached = nsm_lookup_hostname(&ln->nsm_handles,
+					hostname, hostname_len);
 	else
-		cached = nsm_lookup_addr(sap);
+		cached = nsm_lookup_addr(&ln->nsm_handles, sap);
 
 	if (cached != NULL) {
 		atomic_inc(&cached->sm_count);
···
 	}
 
 	if (new != NULL) {
-		list_add(&new->sm_link, &nsm_handles);
+		list_add(&new->sm_link, &ln->nsm_handles);
 		spin_unlock(&nsm_lock);
 		dprintk("lockd: created nsm_handle for %s (%s)\n",
 				new->sm_name, new->sm_addrbuf);
···
 
 /**
  * nsm_reboot_lookup - match NLMPROC_SM_NOTIFY arguments to an nsm_handle
+ * @net:  network namespace
  * @info: pointer to NLMPROC_SM_NOTIFY arguments
  *
  * Returns a matching nsm_handle if found in the nsm cache. The returned
  * nsm_handle's reference count is bumped. Otherwise returns NULL if some
  * error occurred.
  */
-struct nsm_handle *nsm_reboot_lookup(const struct nlm_reboot *info)
+struct nsm_handle *nsm_reboot_lookup(const struct net *net,
+				const struct nlm_reboot *info)
 {
 	struct nsm_handle *cached;
+	struct lockd_net *ln = net_generic(net, lockd_net_id);
 
 	spin_lock(&nsm_lock);
 
-	cached = nsm_lookup_priv(&info->priv);
+	cached = nsm_lookup_priv(&ln->nsm_handles, &info->priv);
 	if (unlikely(cached == NULL)) {
 		spin_unlock(&nsm_lock);
 		dprintk("lockd: never saw rebooted peer '%.*s' before\n",

fs/lockd/netns.h

···
 	spinlock_t nsm_clnt_lock;
 	unsigned int nsm_users;
 	struct rpc_clnt *nsm_clnt;
+	struct list_head nsm_handles;
 };
 
 extern int lockd_net_id;

fs/lockd/svc.c

···
 	INIT_LIST_HEAD(&ln->lockd_manager.list);
 	ln->lockd_manager.block_opens = false;
 	spin_lock_init(&ln->nsm_clnt_lock);
+	INIT_LIST_HEAD(&ln->nsm_handles);
 	return 0;
 }
 

fs/lockd/svc4proc.c

···
 		return rpc_system_err;
 	}
 
-	nlm_host_rebooted(argp);
+	nlm_host_rebooted(SVC_NET(rqstp), argp);
 	return rpc_success;
 }
 

fs/lockd/svcproc.c

···
 		return rpc_system_err;
 	}
 
-	nlm_host_rebooted(argp);
+	nlm_host_rebooted(SVC_NET(rqstp), argp);
 	return rpc_success;
 }
 

include/linux/lockd/lockd.h

···
 struct nlm_host * nlm_get_host(struct nlm_host *);
 void		  nlm_shutdown_hosts(void);
 void		  nlm_shutdown_hosts_net(struct net *net);
-void		  nlm_host_rebooted(const struct nlm_reboot *);
+void		  nlm_host_rebooted(const struct net *net,
+					const struct nlm_reboot *);
 
 /*
  * Host monitoring
···
 int		  nsm_monitor(const struct nlm_host *host);
 void		  nsm_unmonitor(const struct nlm_host *host);
 
-struct nsm_handle *nsm_get_handle(const struct sockaddr *sap,
+struct nsm_handle *nsm_get_handle(const struct net *net,
+					const struct sockaddr *sap,
 					const size_t salen,
 					const char *hostname,
 					const size_t hostname_len);
-struct nsm_handle *nsm_reboot_lookup(const struct nlm_reboot *info);
+struct nsm_handle *nsm_reboot_lookup(const struct net *net,
+					const struct nlm_reboot *info);
 void		  nsm_release(struct nsm_handle *nsm);
 
 /*