1 files changed, 244 insertions, 220 deletions

diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index bff4052b05e..cfe8466f7fe 100644
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -10,22 +10,24 @@
  *
  * ------------------------------------------------------------------------- */
 
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/sched.h>
 #include <linux/namei.h>
+#include <linux/slab.h>
 #include <linux/mount.h>
 #include <linux/tty.h>
 #include <linux/mutex.h>
+#include <linux/magic.h>
 #include <linux/idr.h>
 #include <linux/devpts_fs.h>
 #include <linux/parser.h>
 #include <linux/fsnotify.h>
 #include <linux/seq_file.h>
 
-#define DEVPTS_SUPER_MAGIC 0x1cd1
-
 #define DEVPTS_DEFAULT_MODE 0600
 /*
  * ptmx is a new node in /dev/pts and will be unused in legacy (single-
@@ -36,7 +38,61 @@
 #define DEVPTS_DEFAULT_PTMX_MODE 0000
 #define PTMX_MINOR	2
 
-extern int pty_limit;			/* Config limit on Unix98 ptys */
+/*
+ * sysctl support for setting limits on the number of Unix98 ptys allocated.
+ * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
+ */
+static int pty_limit = NR_UNIX98_PTY_DEFAULT;
+static int pty_reserve = NR_UNIX98_PTY_RESERVE;
+static int pty_limit_min;
+static int pty_limit_max = INT_MAX;
+static int pty_count;
+
+static struct ctl_table pty_table[] = {
+	{
+		.procname	= "max",
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.data		= &pty_limit,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &pty_limit_min,
+		.extra2		= &pty_limit_max,
+	}, {
+		.procname	= "reserve",
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.data		= &pty_reserve,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &pty_limit_min,
+		.extra2		= &pty_limit_max,
+	}, {
+		.procname	= "nr",
+		.maxlen		= sizeof(int),
+		.mode		= 0444,
+		.data		= &pty_count,
+		.proc_handler	= proc_dointvec,
+	},
+	{}
+};
+
+static struct ctl_table pty_kern_table[] = {
+	{
+		.procname	= "pty",
+		.mode		= 0555,
+		.child		= pty_table,
+	},
+	{}
+};
+
+static struct ctl_table pty_root_table[] = {
+	{
+		.procname	= "kernel",
+		.mode		= 0555,
+		.child		= pty_kern_table,
+	},
+	{}
+};
+
 static DEFINE_MUTEX(allocated_ptys_lock);
 
 static struct vfsmount *devpts_mnt;
@@ -44,15 +100,16 @@ static struct vfsmount *devpts_mnt;
 struct pts_mount_opts {
 	int setuid;
 	int setgid;
-	uid_t   uid;
-	gid_t   gid;
+	kuid_t   uid;
+	kgid_t   gid;
 	umode_t mode;
 	umode_t ptmxmode;
 	int newinstance;
+	int max;
 };
 
 enum {
-	Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance,
+	Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance,  Opt_max,
 	Opt_err
 };
 
@@ -63,6 +120,7 @@ static const match_table_t tokens = {
 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
 	{Opt_ptmxmode, "ptmxmode=%o"},
 	{Opt_newinstance, "newinstance"},
+	{Opt_max, "max=%d"},
 #endif
 	{Opt_err, NULL}
 };
@@ -90,16 +148,28 @@ static inline struct super_block *pts_sb_from_inode(struct inode *inode)
 #define PARSE_MOUNT	0
 #define PARSE_REMOUNT	1
 
+/*
+ * parse_mount_options():
+ *	Set @opts to mount options specified in @data. If an option is not
+ *	specified in @data, set it to its default value. The exception is
+ *	'newinstance' option which can only be set/cleared on a mount (i.e.
+ *	cannot be changed during remount).
+ *
+ * Note: @data may be NULL (in which case all options are set to default).
+ */
 static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
 {
 	char *p;
+	kuid_t uid;
+	kgid_t gid;
 
 	opts->setuid  = 0;
 	opts->setgid  = 0;
-	opts->uid     = 0;
-	opts->gid     = 0;
+	opts->uid     = GLOBAL_ROOT_UID;
+	opts->gid     = GLOBAL_ROOT_GID;
 	opts->mode    = DEVPTS_DEFAULT_MODE;
 	opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
+	opts->max     = NR_UNIX98_PTY_MAX;
 
 	/* newinstance makes sense only on initial mount */
 	if (op == PARSE_MOUNT)
@@ -118,13 +188,19 @@ static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
 		case Opt_uid:
 			if (match_int(&args[0], &option))
 				return -EINVAL;
-			opts->uid = option;
+			uid = make_kuid(current_user_ns(), option);
+			if (!uid_valid(uid))
+				return -EINVAL;
+			opts->uid = uid;
 			opts->setuid = 1;
 			break;
 		case Opt_gid:
 			if (match_int(&args[0], &option))
 				return -EINVAL;
-			opts->gid = option;
+			gid = make_kgid(current_user_ns(), option);
+			if (!gid_valid(gid))
+				return -EINVAL;
+			opts->gid = gid;
 			opts->setgid = 1;
 			break;
 		case Opt_mode:
@@ -143,9 +219,15 @@ static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
 			if (op == PARSE_MOUNT)
 				opts->newinstance = 1;
 			break;
+		case Opt_max:
+			if (match_int(&args[0], &option) ||
+			    option < 0 || option > NR_UNIX98_PTY_MAX)
+				return -EINVAL;
+			opts->max = option;
+			break;
 #endif
 		default:
-			printk(KERN_ERR "devpts: called with bogus options\n");
+			pr_err("called with bogus options\n");
 			return -EINVAL;
 		}
 	}
@@ -163,6 +245,13 @@ static int mknod_ptmx(struct super_block *sb)
 	struct dentry *root = sb->s_root;
 	struct pts_fs_info *fsi = DEVPTS_SB(sb);
 	struct pts_mount_opts *opts = &fsi->mount_opts;
+	kuid_t root_uid;
+	kgid_t root_gid;
+
+	root_uid = make_kuid(current_user_ns(), 0);
+	root_gid = make_kgid(current_user_ns(), 0);
+	if (!uid_valid(root_uid) || !gid_valid(root_gid))
+		return -EINVAL;
 
 	mutex_lock(&root->d_inode->i_mutex);
 
@@ -174,7 +263,7 @@ static int mknod_ptmx(struct super_block *sb)
 
 	dentry = d_alloc_name(root, "ptmx");
 	if (!dentry) {
-		printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
+		pr_err("Unable to alloc dentry for ptmx node\n");
 		goto out;
 	}
 
@@ -183,7 +272,7 @@ static int mknod_ptmx(struct super_block *sb)
 	 */
 	inode = new_inode(sb);
 	if (!inode) {
-		printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
+		pr_err("Unable to alloc inode for ptmx node\n");
 		dput(dentry);
 		goto out;
 	}
@@ -193,6 +282,8 @@ static int mknod_ptmx(struct super_block *sb)
 
 	mode = S_IFCHR|opts->ptmxmode;
 	init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
+	inode->i_uid = root_uid;
+	inode->i_gid = root_gid;
 
 	d_add(dentry, inode);
 
@@ -214,7 +305,7 @@ static void update_ptmx_mode(struct pts_fs_info *fsi)
 #else
 static inline void update_ptmx_mode(struct pts_fs_info *fsi)
 {
-       return;
+	return;
 }
 #endif
 
@@ -224,6 +315,7 @@ static int devpts_remount(struct super_block *sb, int *flags, char *data)
 	struct pts_fs_info *fsi = DEVPTS_SB(sb);
 	struct pts_mount_opts *opts = &fsi->mount_opts;
 
+	sync_filesystem(sb);
 	err = parse_mount_options(data, PARSE_REMOUNT, opts);
 
 	/*
@@ -237,18 +329,22 @@ static int devpts_remount(struct super_block *sb, int *flags, char *data)
 	return err;
 }
 
-static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
+static int devpts_show_options(struct seq_file *seq, struct dentry *root)
 {
-	struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
+	struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb);
 	struct pts_mount_opts *opts = &fsi->mount_opts;
 
 	if (opts->setuid)
-		seq_printf(seq, ",uid=%u", opts->uid);
+		seq_printf(seq, ",uid=%u",
+			   from_kuid_munged(&init_user_ns, opts->uid));
 	if (opts->setgid)
-		seq_printf(seq, ",gid=%u", opts->gid);
+		seq_printf(seq, ",gid=%u",
+			   from_kgid_munged(&init_user_ns, opts->gid));
 	seq_printf(seq, ",mode=%03o", opts->mode);
 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
 	seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
+	if (opts->max < NR_UNIX98_PTY_MAX)
+		seq_printf(seq, ",max=%d", opts->max);
 #endif
 
 	return 0;
@@ -292,23 +388,20 @@ devpts_fill_super(struct super_block *s, void *data, int silent)
 
 	inode = new_inode(s);
 	if (!inode)
-		goto free_fsi;
+		goto fail;
 	inode->i_ino = 1;
 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 	inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
 	inode->i_op = &simple_dir_inode_operations;
 	inode->i_fop = &simple_dir_operations;
-	inode->i_nlink = 2;
+	set_nlink(inode, 2);
 
-	s->s_root = d_alloc_root(inode);
+	s->s_root = d_make_root(inode);
 	if (s->s_root)
 		return 0;
 
-	printk(KERN_ERR "devpts: get root dentry failed\n");
-	iput(inode);
+	pr_err("get root dentry failed\n");
 
-free_fsi:
-	kfree(s->s_fs_info);
 fail:
 	return -ENOMEM;
 }
@@ -322,186 +415,87 @@ static int compare_init_pts_sb(struct super_block *s, void *p)
 }
 
 /*
- * Safely parse the mount options in @data and update @opts.
+ * devpts_mount()
  *
- * devpts ends up parsing options two times during mount, due to the
- * two modes of operation it supports. The first parse occurs in
- * devpts_get_sb() when determining the mode (single-instance or
- * multi-instance mode). The second parse happens in devpts_remount()
- * or new_pts_mount() depending on the mode.
+ *     If the '-o newinstance' mount option was specified, mount a new
+ *     (private) instance of devpts.  PTYs created in this instance are
+ *     independent of the PTYs in other devpts instances.
  *
- * Parsing of options modifies the @data making subsequent parsing
- * incorrect. So make a local copy of @data and parse it.
+ *     If the '-o newinstance' option was not specified, mount/remount the
+ *     initial kernel mount of devpts.  This type of mount gives the
+ *     legacy, single-instance semantics.
  *
- * Return: 0 On success, -errno on error
- */
-static int safe_parse_mount_options(void *data, struct pts_mount_opts *opts)
-{
-	int rc;
-	void *datacp;
-
-	if (!data)
-		return 0;
-
-	/* Use kstrdup() ?  */
-	datacp = kmalloc(PAGE_SIZE, GFP_KERNEL);
-	if (!datacp)
-		return -ENOMEM;
-
-	memcpy(datacp, data, PAGE_SIZE);
-	rc = parse_mount_options((char *)datacp, PARSE_MOUNT, opts);
-	kfree(datacp);
-
-	return rc;
-}
-
-/*
- * Mount a new (private) instance of devpts.  PTYs created in this
- * instance are independent of the PTYs in other devpts instances.
- */
-static int new_pts_mount(struct file_system_type *fs_type, int flags,
-		void *data, struct vfsmount *mnt)
-{
-	int err;
-	struct pts_fs_info *fsi;
-	struct pts_mount_opts *opts;
-
-	err = get_sb_nodev(fs_type, flags, data, devpts_fill_super, mnt);
-	if (err)
-		return err;
-
-	fsi = DEVPTS_SB(mnt->mnt_sb);
-	opts = &fsi->mount_opts;
-
-	err = parse_mount_options(data, PARSE_MOUNT, opts);
-	if (err)
-		goto fail;
-
-	err = mknod_ptmx(mnt->mnt_sb);
-	if (err)
-		goto fail;
-
-	return 0;
-
-fail:
-	dput(mnt->mnt_sb->s_root);
-	deactivate_super(mnt->mnt_sb);
-	return err;
-}
-
-/*
- * Check if 'newinstance' mount option was specified in @data.
- *
- * Return: -errno  	on error (eg: invalid mount options specified)
- * 	 : 1 		if 'newinstance' mount option was specified
- * 	 : 0 		if 'newinstance' mount option was NOT specified
- */
-static int is_new_instance_mount(void *data)
-{
-	int rc;
-	struct pts_mount_opts opts;
-
-	if (!data)
-		return 0;
-
-	rc = safe_parse_mount_options(data, &opts);
-	if (!rc)
-		rc = opts.newinstance;
-
-	return rc;
-}
-
-/*
- * get_init_pts_sb()
+ *     The 'newinstance' option is needed to support multiple namespace
+ *     semantics in devpts while preserving backward compatibility of the
+ *     current 'single-namespace' semantics. i.e all mounts of devpts
+ *     without the 'newinstance' mount option should bind to the initial
+ *     kernel mount, like mount_single().
  *
- *     This interface is needed to support multiple namespace semantics in
- *     devpts while preserving backward compatibility of the current 'single-
- *     namespace' semantics. i.e all mounts of devpts without the 'newinstance'
- *     mount option should bind to the initial kernel mount, like
- *     get_sb_single().
+ *     Mounts with 'newinstance' option create a new, private namespace.
  *
- *     Mounts with 'newinstance' option create a new private namespace.
+ *     NOTE:
  *
- *     But for single-mount semantics, devpts cannot use get_sb_single(),
- *     because get_sb_single()/sget() find and use the super-block from
+ *     For single-mount semantics, devpts cannot use mount_single(),
+ *     because mount_single()/sget() find and use the super-block from
  *     the most recent mount of devpts. But that recent mount may be a
- *     'newinstance' mount and get_sb_single() would pick the newinstance
+ *     'newinstance' mount and mount_single() would pick the newinstance
  *     super-block instead of the initial super-block.
- *
- *     This interface is identical to get_sb_single() except that it
- *     consistently selects the 'single-namespace' superblock even in the
- *     presence of the private namespace (i.e 'newinstance') super-blocks.
  */
-static int get_init_pts_sb(struct file_system_type *fs_type, int flags,
-		void *data, struct vfsmount *mnt)
+static struct dentry *devpts_mount(struct file_system_type *fs_type,
+	int flags, const char *dev_name, void *data)
 {
-	struct super_block *s;
 	int error;
+	struct pts_mount_opts opts;
+	struct super_block *s;
+
+	error = parse_mount_options(data, PARSE_MOUNT, &opts);
+	if (error)
+		return ERR_PTR(error);
+
+	/* Require newinstance for all user namespace mounts to ensure
+	 * the mount options are not changed.
+	 */
+	if ((current_user_ns() != &init_user_ns) && !opts.newinstance)
+		return ERR_PTR(-EINVAL);
+
+	if (opts.newinstance)
+		s = sget(fs_type, NULL, set_anon_super, flags, NULL);
+	else
+		s = sget(fs_type, compare_init_pts_sb, set_anon_super, flags,
+			 NULL);
 
-	s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
 	if (IS_ERR(s))
-		return PTR_ERR(s);
+		return ERR_CAST(s);
 
 	if (!s->s_root) {
-		s->s_flags = flags;
 		error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
-		if (error) {
-			up_write(&s->s_umount);
-			deactivate_super(s);
-			return error;
-		}
+		if (error)
+			goto out_undo_sget;
 		s->s_flags |= MS_ACTIVE;
 	}
-	do_remount_sb(s, flags, data, 0);
-	return simple_set_mnt(mnt, s);
-}
 
-/*
- * Mount or remount the initial kernel mount of devpts. This type of
- * mount maintains the legacy, single-instance semantics, while the
- * kernel still allows multiple-instances.
- */
-static int init_pts_mount(struct file_system_type *fs_type, int flags,
-		void *data, struct vfsmount *mnt)
-{
-	int err;
+	memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
 
-	err = get_init_pts_sb(fs_type, flags, data, mnt);
-	if (err)
-		return err;
+	error = mknod_ptmx(s);
+	if (error)
+		goto out_undo_sget;
 
-	err = mknod_ptmx(mnt->mnt_sb);
-	if (err) {
-		dput(mnt->mnt_sb->s_root);
-		deactivate_super(mnt->mnt_sb);
-	}
+	return dget(s->s_root);
 
-	return err;
+out_undo_sget:
+	deactivate_locked_super(s);
+	return ERR_PTR(error);
 }
 
-static int devpts_get_sb(struct file_system_type *fs_type,
-	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
-{
-	int new;
-
-	new = is_new_instance_mount(data);
-	if (new < 0)
-		return new;
-
-	if (new)
-		return new_pts_mount(fs_type, flags, data, mnt);
-
-	return init_pts_mount(fs_type, flags, data, mnt);
-}
 #else
 /*
  * This supports only the legacy single-instance semantics (no
  * multiple-instance semantics)
  */
-static int devpts_get_sb(struct file_system_type *fs_type, int flags,
-		const char *dev_name, void *data, struct vfsmount *mnt)
+static struct dentry *devpts_mount(struct file_system_type *fs_type, int flags,
+		const char *dev_name, void *data)
 {
-	return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
+	return mount_single(fs_type, flags, data, devpts_fill_super);
 }
 #endif
 
@@ -509,15 +503,18 @@ static void devpts_kill_sb(struct super_block *sb)
 {
 	struct pts_fs_info *fsi = DEVPTS_SB(sb);
 
+	ida_destroy(&fsi->allocated_ptys);
 	kfree(fsi);
 	kill_litter_super(sb);
 }
 
 static struct file_system_type devpts_fs_type = {
-	.owner		= THIS_MODULE,
 	.name		= "devpts",
-	.get_sb		= devpts_get_sb,
+	.mount		= devpts_mount,
 	.kill_sb	= devpts_kill_sb,
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+	.fs_flags	= FS_USERNS_MOUNT | FS_USERNS_DEV_MOUNT,
+#endif
 };
 
 /*
@@ -537,6 +534,12 @@ retry:
 		return -ENOMEM;
 
 	mutex_lock(&allocated_ptys_lock);
+	if (pty_count >= pty_limit -
+			(fsi->mount_opts.newinstance ? pty_reserve : 0)) {
+		mutex_unlock(&allocated_ptys_lock);
+		return -ENOSPC;
+	}
+
 	ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
 	if (ida_ret < 0) {
 		mutex_unlock(&allocated_ptys_lock);
@@ -545,11 +548,12 @@ retry:
 		return -EIO;
 	}
 
-	if (index >= pty_limit) {
+	if (index >= fsi->mount_opts.max) {
 		ida_remove(&fsi->allocated_ptys, index);
 		mutex_unlock(&allocated_ptys_lock);
-		return -EIO;
+		return -ENOSPC;
 	}
+	pty_count++;
 	mutex_unlock(&allocated_ptys_lock);
 	return index;
 }
@@ -561,65 +565,93 @@ void devpts_kill_index(struct inode *ptmx_inode, int idx)
 
 	mutex_lock(&allocated_ptys_lock);
 	ida_remove(&fsi->allocated_ptys, idx);
+	pty_count--;
 	mutex_unlock(&allocated_ptys_lock);
 }
 
-int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
+/**
+ * devpts_pty_new -- create a new inode in /dev/pts/
+ * @ptmx_inode: inode of the master
+ * @device: major+minor of the node to be created
+ * @index: used as a name of the node
+ * @priv: what's given back by devpts_get_priv
+ *
+ * The created inode is returned. Remove it from /dev/pts/ by devpts_pty_kill.
+ */
+struct inode *devpts_pty_new(struct inode *ptmx_inode, dev_t device, int index,
+		void *priv)
 {
-	/* tty layer puts index from devpts_new_index() in here */
-	int number = tty->index;
-	struct tty_driver *driver = tty->driver;
-	dev_t device = MKDEV(driver->major, driver->minor_start+number);
 	struct dentry *dentry;
 	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
-	struct inode *inode = new_inode(sb);
+	struct inode *inode;
 	struct dentry *root = sb->s_root;
 	struct pts_fs_info *fsi = DEVPTS_SB(sb);
 	struct pts_mount_opts *opts = &fsi->mount_opts;
 	char s[12];
 
-	/* We're supposed to be given the slave end of a pty */
-	BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
-	BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
-
+	inode = new_inode(sb);
 	if (!inode)
-		return -ENOMEM;
+		return ERR_PTR(-ENOMEM);
 
-	inode->i_ino = number + 3;
+	inode->i_ino = index + 3;
 	inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
 	inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 	init_special_inode(inode, S_IFCHR|opts->mode, device);
-	inode->i_private = tty;
-	tty->driver_data = inode;
+	inode->i_private = priv;
 
-	sprintf(s, "%d", number);
+	sprintf(s, "%d", index);
 
 	mutex_lock(&root->d_inode->i_mutex);
 
 	dentry = d_alloc_name(root, s);
-	if (!IS_ERR(dentry)) {
+	if (dentry) {
 		d_add(dentry, inode);
 		fsnotify_create(root->d_inode, dentry);
+	} else {
+		iput(inode);
+		inode = ERR_PTR(-ENOMEM);
 	}
 
 	mutex_unlock(&root->d_inode->i_mutex);
 
-	return 0;
+	return inode;
 }
 
-struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
+/**
+ * devpts_get_priv -- get private data for a slave
+ * @pts_inode: inode of the slave
+ *
+ * Returns whatever was passed as priv in devpts_pty_new for a given inode.
+ */
+void *devpts_get_priv(struct inode *pts_inode)
 {
+	struct dentry *dentry;
+	void *priv = NULL;
+
 	BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
 
+	/* Ensure dentry has not been deleted by devpts_pty_kill() */
+	dentry = d_find_alias(pts_inode);
+	if (!dentry)
+		return NULL;
+
 	if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
-		return (struct tty_struct *)pts_inode->i_private;
-	return NULL;
+		priv = pts_inode->i_private;
+
+	dput(dentry);
+
+	return priv;
 }
 
-void devpts_pty_kill(struct tty_struct *tty)
+/**
+ * devpts_pty_kill -- remove inode form /dev/pts/
+ * @inode: inode of the slave to be removed
+ *
+ * This is an inverse operation of devpts_pty_new.
+ */
+void devpts_pty_kill(struct inode *inode)
 {
-	struct inode *inode = tty->driver_data;
 	struct super_block *sb = pts_sb_from_inode(inode);
 	struct dentry *root = sb->s_root;
 	struct dentry *dentry;
@@ -629,37 +661,29 @@ void devpts_pty_kill(struct tty_struct *tty)
 	mutex_lock(&root->d_inode->i_mutex);
 
 	dentry = d_find_alias(inode);
-	if (IS_ERR(dentry))
-		goto out;
-
-	if (dentry) {
-		inode->i_nlink--;
-		d_delete(dentry);
-		dput(dentry);	/* d_alloc_name() in devpts_pty_new() */
-	}
 
+	drop_nlink(inode);
+	d_delete(dentry);
+	dput(dentry);	/* d_alloc_name() in devpts_pty_new() */
 	dput(dentry);		/* d_find_alias above */
-out:
+
 	mutex_unlock(&root->d_inode->i_mutex);
 }
 
 static int __init init_devpts_fs(void)
 {
 	int err = register_filesystem(&devpts_fs_type);
+	struct ctl_table_header *table;
+
 	if (!err) {
+		table = register_sysctl_table(pty_root_table);
 		devpts_mnt = kern_mount(&devpts_fs_type);
-		if (IS_ERR(devpts_mnt))
+		if (IS_ERR(devpts_mnt)) {
 			err = PTR_ERR(devpts_mnt);
+			unregister_filesystem(&devpts_fs_type);
+			unregister_sysctl_table(table);
+		}
 	}
 	return err;
 }
-
-static void __exit exit_devpts_fs(void)
-{
-	unregister_filesystem(&devpts_fs_type);
-	mntput(devpts_mnt);
-}
-
 module_init(init_devpts_fs)
-module_exit(exit_devpts_fs)
-MODULE_LICENSE("GPL");