NFSv4: Fix a use-after-free issue with the nfs server.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/client.c

@@ -164,6 +164,26 @@ static struct nfs_client *nfs_alloc_client(const char *hostname,
 	return NULL;
 }
 
+static void nfs4_shutdown_client(struct nfs_client *clp)
+{
+#ifdef CONFIG_NFS_V4
+	if (__test_and_clear_bit(NFS_CS_RENEWD, &clp->cl_res_state))
+		nfs4_kill_renewd(clp);
+	while (!list_empty(&clp->cl_unused)) {
+		struct nfs4_state_owner *sp;
+
+		sp = list_entry(clp->cl_unused.next,
+				struct nfs4_state_owner,
+				so_list);
+		list_del(&sp->so_list);
+		kfree(sp);
+	}
+	BUG_ON(!list_empty(&clp->cl_state_owners));
+	if (__test_and_clear_bit(NFS_CS_IDMAP, &clp->cl_res_state))
+		nfs_idmap_delete(clp);
+#endif
+}
+
 /*
  * Destroy a shared client record
  */
@@ -171,21 +191,7 @@ static void nfs_free_client(struct nfs_client *clp)
 {
 	dprintk("--> nfs_free_client(%d)\n", clp->cl_nfsversion);
 
-#ifdef CONFIG_NFS_V4
-	if (__test_and_clear_bit(NFS_CS_IDMAP, &clp->cl_res_state)) {
-		while (!list_empty(&clp->cl_unused)) {
-			struct nfs4_state_owner *sp;
-
-			sp = list_entry(clp->cl_unused.next,
-					struct nfs4_state_owner,
-					so_list);
-			list_del(&sp->so_list);
-			kfree(sp);
-		}
-		BUG_ON(!list_empty(&clp->cl_state_owners));
-		nfs_idmap_delete(clp);
-	}
-#endif
+	nfs4_shutdown_client(clp);
 
 	/* -EIO all pending I/O */
 	if (!IS_ERR(clp->cl_rpcclient))

fs/nfs/nfs4renewd.c

@@ -121,6 +121,7 @@ nfs4_schedule_state_renewal(struct nfs_client *clp)
 			__FUNCTION__, (timeout + HZ - 1) / HZ);
 	cancel_delayed_work(&clp->cl_renewd);
 	schedule_delayed_work(&clp->cl_renewd, timeout);
+	set_bit(NFS_CS_RENEWD, &clp->cl_res_state);
 	spin_unlock(&clp->cl_lock);
 }
 

fs/nfs/super.c

@@ -883,13 +883,15 @@ static int nfs4_get_sb(struct file_system_type *fs_type,
 		goto out_free;
 	}
 
+	if (s->s_fs_info != server) {
+		nfs_free_server(server);
+		server = NULL;
+	}
+
 	if (!s->s_root) {
 		/* initial superblock/root creation */
 		s->s_flags = flags;
-
 		nfs4_fill_super(s);
-	} else {
-		nfs_free_server(server);
 	}
 
 	mntroot = nfs4_get_root(s, &mntfh);

include/linux/nfs_fs_sb.h

@@ -19,6 +19,7 @@ struct nfs_client {
 #define NFS_CS_RPCIOD		0		/* - rpciod started */
 #define NFS_CS_CALLBACK		1		/* - callback started */
 #define NFS_CS_IDMAP		2		/* - idmap started */
+#define NFS_CS_RENEWD		3		/* - renewd started */
 	struct sockaddr_in	cl_addr;	/* server identifier */
 	char *			cl_hostname;	/* hostname of server */
 	struct list_head	cl_share_link;	/* link in global client list */