[mirror_ubuntu-zesty-kernel.git] / fs / devpts / inode.c

/* -*- linux-c -*- --------------------------------------------------------- *
 *
 * linux/fs/devpts/inode.c
 *
 *  Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
 *
 * This file is part of the Linux kernel and is made available under
 * the terms of the GNU General Public License, version 2, or at your
 * option, any later version, incorporated herein by reference.
 *
 * ------------------------------------------------------------------------- */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/tty.h>
#include <linux/mutex.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-
 * instance) mode. To prevent surprises in user space, set permissions of
 * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful
 * permissions.
 */
#define DEVPTS_DEFAULT_PTMX_MODE 0000
#define PTMX_MINOR	2

extern int pty_limit;			/* Config limit on Unix98 ptys */
static DEFINE_MUTEX(allocated_ptys_lock);

static struct vfsmount *devpts_mnt;

struct pts_mount_opts {
	int setuid;
	int setgid;
	uid_t   uid;
	gid_t   gid;
	umode_t mode;
	umode_t ptmxmode;
};

enum {
	Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode,
	Opt_err
};

static const match_table_t tokens = {
	{Opt_uid, "uid=%u"},
	{Opt_gid, "gid=%u"},
	{Opt_mode, "mode=%o"},
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	{Opt_ptmxmode, "ptmxmode=%o"},
#endif
	{Opt_err, NULL}
};

struct pts_fs_info {
	struct ida allocated_ptys;
	struct pts_mount_opts mount_opts;
	struct dentry *ptmx_dentry;
};

static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
{
	return sb->s_fs_info;
}

static inline struct super_block *pts_sb_from_inode(struct inode *inode)
{
	if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
		return inode->i_sb;

	return devpts_mnt->mnt_sb;
}

static int parse_mount_options(char *data, struct pts_mount_opts *opts)
{
	char *p;

	opts->setuid  = 0;
	opts->setgid  = 0;
	opts->uid     = 0;
	opts->gid     = 0;
	opts->mode    = DEVPTS_DEFAULT_MODE;
	opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;

	while ((p = strsep(&data, ",")) != NULL) {
		substring_t args[MAX_OPT_ARGS];
		int token;
		int option;

		if (!*p)
			continue;

		token = match_token(p, tokens, args);
		switch (token) {
		case Opt_uid:
			if (match_int(&args[0], &option))
				return -EINVAL;
			opts->uid = option;
			opts->setuid = 1;
			break;
		case Opt_gid:
			if (match_int(&args[0], &option))
				return -EINVAL;
			opts->gid = option;
			opts->setgid = 1;
			break;
		case Opt_mode:
			if (match_octal(&args[0], &option))
				return -EINVAL;
			opts->mode = option & S_IALLUGO;
			break;
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
		case Opt_ptmxmode:
			if (match_octal(&args[0], &option))
				return -EINVAL;
			opts->ptmxmode = option & S_IALLUGO;
			break;
#endif
		default:
			printk(KERN_ERR "devpts: called with bogus options\n");
			return -EINVAL;
		}
	}

	return 0;
}

#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
static int mknod_ptmx(struct super_block *sb)
{
	int mode;
	int rc = -ENOMEM;
	struct dentry *dentry;
	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;

	mutex_lock(&root->d_inode->i_mutex);

	/* If we have already created ptmx node, return */
	if (fsi->ptmx_dentry) {
		rc = 0;
		goto out;
	}

	dentry = d_alloc_name(root, "ptmx");
	if (!dentry) {
		printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
		goto out;
	}

	/*
	 * Create a new 'ptmx' node in this mount of devpts.
	 */
	inode = new_inode(sb);
	if (!inode) {
		printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
		dput(dentry);
		goto out;
	}

	inode->i_ino = 2;
	inode->i_uid = inode->i_gid = 0;
	inode->i_blocks = 0;
	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;

	mode = S_IFCHR|opts->ptmxmode;
	init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));

	d_add(dentry, inode);

	fsi->ptmx_dentry = dentry;
	rc = 0;

	printk(KERN_DEBUG "Created ptmx node in devpts ino %lu\n",
			inode->i_ino);
out:
	mutex_unlock(&root->d_inode->i_mutex);
	return rc;
}

static void update_ptmx_mode(struct pts_fs_info *fsi)
{
	struct inode *inode;
	if (fsi->ptmx_dentry) {
		inode = fsi->ptmx_dentry->d_inode;
		inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
	}
}
#else
static inline void update_ptmx_mode(struct pts_fs_info *fsi)
{
       return;
}
#endif

static int devpts_remount(struct super_block *sb, int *flags, char *data)
{
	int err;
	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	struct pts_mount_opts *opts = &fsi->mount_opts;

	err = parse_mount_options(data, opts);

	/*
	 * parse_mount_options() restores options to default values
	 * before parsing and may have changed ptmxmode. So, update the
	 * mode in the inode too. Bogus options don't fail the remount,
	 * so do this even on error return.
	 */
	update_ptmx_mode(fsi);

	return err;
}

static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
	struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
	struct pts_mount_opts *opts = &fsi->mount_opts;

	if (opts->setuid)
		seq_printf(seq, ",uid=%u", opts->uid);
	if (opts->setgid)
		seq_printf(seq, ",gid=%u", opts->gid);
	seq_printf(seq, ",mode=%03o", opts->mode);
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
#endif

	return 0;
}

static const struct super_operations devpts_sops = {
	.statfs		= simple_statfs,
	.remount_fs	= devpts_remount,
	.show_options	= devpts_show_options,
};

static void *new_pts_fs_info(void)
{
	struct pts_fs_info *fsi;

	fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
	if (!fsi)
		return NULL;

	ida_init(&fsi->allocated_ptys);
	fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
	fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;

	return fsi;
}

static int
devpts_fill_super(struct super_block *s, void *data, int silent)
{
	struct inode *inode;

	s->s_blocksize = 1024;
	s->s_blocksize_bits = 10;
	s->s_magic = DEVPTS_SUPER_MAGIC;
	s->s_op = &devpts_sops;
	s->s_time_gran = 1;

	s->s_fs_info = new_pts_fs_info();
	if (!s->s_fs_info)
		goto fail;

	inode = new_inode(s);
	if (!inode)
		goto free_fsi;
	inode->i_ino = 1;
	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	inode->i_blocks = 0;
	inode->i_uid = inode->i_gid = 0;
	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;

	s->s_root = d_alloc_root(inode);
	if (s->s_root)
		return 0;

	printk("devpts: get root dentry failed\n");
	iput(inode);

free_fsi:
	kfree(s->s_fs_info);
fail:
	return -ENOMEM;
}

static int compare_init_pts_sb(struct super_block *s, void *p)
{
	if (devpts_mnt)
		return devpts_mnt->mnt_sb == s;

	return 0;
}

/*
 * get_init_pts_sb()
 *
 *     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.
 *
 *     But for single-mount semantics, devpts cannot use get_sb_single(),
 *     because get_sb_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
 *     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)
{
        struct super_block *s;
        int error;

        s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
        if (IS_ERR(s))
                return PTR_ERR(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;
                }
                s->s_flags |= MS_ACTIVE;
        }
        do_remount_sb(s, flags, data, 0);
        return simple_set_mnt(mnt, s);
}

static int devpts_get_sb(struct file_system_type *fs_type,
	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
	return get_init_pts_sb(fs_type, flags, data, mnt);
}

static void devpts_kill_sb(struct super_block *sb)
{
	struct pts_fs_info *fsi = DEVPTS_SB(sb);

	kfree(fsi);
	kill_litter_super(sb);
}

static struct file_system_type devpts_fs_type = {
	.owner		= THIS_MODULE,
	.name		= "devpts",
	.get_sb		= devpts_get_sb,
	.kill_sb	= devpts_kill_sb,
};

/*
 * The normal naming convention is simply /dev/pts/<number>; this conforms
 * to the System V naming convention
 */

int devpts_new_index(struct inode *ptmx_inode)
{
	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	int index;
	int ida_ret;

retry:
	if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) {
		return -ENOMEM;
	}

	mutex_lock(&allocated_ptys_lock);
	ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
	if (ida_ret < 0) {
		mutex_unlock(&allocated_ptys_lock);
		if (ida_ret == -EAGAIN)
			goto retry;
		return -EIO;
	}

	if (index >= pty_limit) {
		ida_remove(&fsi->allocated_ptys, index);
		mutex_unlock(&allocated_ptys_lock);
		return -EIO;
	}
	mutex_unlock(&allocated_ptys_lock);
	return index;
}

void devpts_kill_index(struct inode *ptmx_inode, int idx)
{
	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	struct pts_fs_info *fsi = DEVPTS_SB(sb);

	mutex_lock(&allocated_ptys_lock);
	ida_remove(&fsi->allocated_ptys, idx);
	mutex_unlock(&allocated_ptys_lock);
}

int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
{
	int number = tty->index; /* tty layer puts index from devpts_new_index() in here */
	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 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);

	if (!inode)
		return -ENOMEM;

	inode->i_ino = number+2;
	inode->i_uid = config.setuid ? config.uid : current_fsuid();
	inode->i_gid = config.setgid ? config.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;

	sprintf(s, "%d", number);

	mutex_lock(&root->d_inode->i_mutex);

	dentry = d_alloc_name(root, s);
	if (!IS_ERR(dentry)) {
		d_add(dentry, inode);
		fsnotify_create(root->d_inode, dentry);
	}

	mutex_unlock(&root->d_inode->i_mutex);

	return 0;
}

struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
{
	BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));

	if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
		return (struct tty_struct *)pts_inode->i_private;
	return NULL;
}

void devpts_pty_kill(struct tty_struct *tty)
{
	struct inode *inode = tty->driver_data;
	struct super_block *sb = pts_sb_from_inode(inode);
	struct dentry *root = sb->s_root;
	struct dentry *dentry;

	BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));

	mutex_lock(&root->d_inode->i_mutex);

	dentry = d_find_alias(inode);
	if (dentry && !IS_ERR(dentry)) {
		inode->i_nlink--;
		d_delete(dentry);
		dput(dentry);
	}

	mutex_unlock(&root->d_inode->i_mutex);
}

static int __init init_devpts_fs(void)
{
	int err = register_filesystem(&devpts_fs_type);
	if (!err) {
		devpts_mnt = kern_mount(&devpts_fs_type);
		if (IS_ERR(devpts_mnt))
			err = PTR_ERR(devpts_mnt);
	}
	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");
Commit	Line	Data
1da177e4 LT	1	/* -- linux-c -- --------------------------------------------------------- *
	2	*
	3	* linux/fs/devpts/inode.c
	4	*
	5	* Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
	6	*
	7	* This file is part of the Linux kernel and is made available under
	8	* the terms of the GNU General Public License, version 2, or at your
	9	* option, any later version, incorporated herein by reference.
	10	*
	11	* ------------------------------------------------------------------------- */
	12
	13	#include <linux/module.h>
	14	#include <linux/init.h>
	15	#include <linux/fs.h>
	16	#include <linux/sched.h>
	17	#include <linux/namei.h>
	18	#include <linux/mount.h>
	19	#include <linux/tty.h>
718a9163 SB	20	#include <linux/mutex.h>
718a9163 SB	21	#include <linux/idr.h>
1da177e4	22	#include <linux/devpts_fs.h>
7a673c6b	23	#include <linux/parser.h>
3972b7f6	24	#include <linux/fsnotify.h>
b87a267e	25	#include <linux/seq_file.h>
1da177e4 LT	26
	27	#define DEVPTS_SUPER_MAGIC 0x1cd1
	28
b87a267e	29	#define DEVPTS_DEFAULT_MODE 0600
1f8f1e29 SB	30	/*
	31	* ptmx is a new node in /dev/pts and will be unused in legacy (single-
	32	* instance) mode. To prevent surprises in user space, set permissions of
	33	* ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful
	34	* permissions.
	35	*/
	36	#define DEVPTS_DEFAULT_PTMX_MODE 0000
527b3e47	37	#define PTMX_MINOR 2
b87a267e	38
718a9163	39	extern int pty_limit; /* Config limit on Unix98 ptys */
718a9163 SB	40	static DEFINE_MUTEX(allocated_ptys_lock);
718a9163 SB	41
1da177e4	42	static struct vfsmount *devpts_mnt;
1da177e4	43
31af0abb	44	struct pts_mount_opts {
1da177e4 LT	45	int setuid;
	46	int setgid;
	47	uid_t uid;
	48	gid_t gid;
	49	umode_t mode;
1f8f1e29	50	umode_t ptmxmode;
31af0abb	51	};
1da177e4	52
7a673c6b	53	enum {
1f8f1e29	54	Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode,
7a673c6b DP	55	Opt_err
	56	};
	57
a447c093	58	static const match_table_t tokens = {
7a673c6b DP	59	{Opt_uid, "uid=%u"},
	60	{Opt_gid, "gid=%u"},
	61	{Opt_mode, "mode=%o"},
1f8f1e29 SB	62	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	63	{Opt_ptmxmode, "ptmxmode=%o"},
	64	#endif
7a673c6b DP	65	{Opt_err, NULL}
	66	};
	67
e76b7c01 SB	68	struct pts_fs_info {
e76b7c01 SB	69	struct ida allocated_ptys;
31af0abb	70	struct pts_mount_opts mount_opts;
1f8f1e29	71	struct dentry *ptmx_dentry;
e76b7c01 SB	72	};
	73
	74	static inline struct pts_fs_info DEVPTS_SB(struct super_block sb)
	75	{
	76	return sb->s_fs_info;
	77	}
	78
59e55e6c SB	79	static inline struct super_block pts_sb_from_inode(struct inode inode)
	80	{
	81	if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
	82	return inode->i_sb;
	83
	84	return devpts_mnt->mnt_sb;
	85	}
	86
53af8ee4	87	static int parse_mount_options(char data, struct pts_mount_opts opts)
1da177e4	88	{
7a673c6b DP	89	char *p;
7a673c6b DP	90
31af0abb SB	91	opts->setuid = 0;
	92	opts->setgid = 0;
	93	opts->uid = 0;
	94	opts->gid = 0;
	95	opts->mode = DEVPTS_DEFAULT_MODE;
1f8f1e29	96	opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
7a673c6b DP	97
	98	while ((p = strsep(&data, ",")) != NULL) {
	99	substring_t args[MAX_OPT_ARGS];
	100	int token;
	101	int option;
	102
	103	if (!*p)
1da177e4	104	continue;
7a673c6b DP	105
	106	token = match_token(p, tokens, args);
	107	switch (token) {
	108	case Opt_uid:
	109	if (match_int(&args[0], &option))
	110	return -EINVAL;
31af0abb SB	111	opts->uid = option;
31af0abb SB	112	opts->setuid = 1;
7a673c6b DP	113	break;
	114	case Opt_gid:
	115	if (match_int(&args[0], &option))
	116	return -EINVAL;
31af0abb SB	117	opts->gid = option;
31af0abb SB	118	opts->setgid = 1;
7a673c6b DP	119	break;
	120	case Opt_mode:
	121	if (match_octal(&args[0], &option))
	122	return -EINVAL;
31af0abb	123	opts->mode = option & S_IALLUGO;
7a673c6b	124	break;
1f8f1e29 SB	125	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	126	case Opt_ptmxmode:
	127	if (match_octal(&args[0], &option))
	128	return -EINVAL;
	129	opts->ptmxmode = option & S_IALLUGO;
	130	break;
	131	#endif
7a673c6b DP	132	default:
7a673c6b DP	133	printk(KERN_ERR "devpts: called with bogus options\n");
1da177e4 LT	134	return -EINVAL;
	135	}
	136	}
1da177e4 LT	137
	138	return 0;
	139	}
	140
1f8f1e29 SB	141	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	142	static int mknod_ptmx(struct super_block *sb)
	143	{
	144	int mode;
	145	int rc = -ENOMEM;
	146	struct dentry *dentry;
	147	struct inode *inode;
	148	struct dentry *root = sb->s_root;
	149	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	150	struct pts_mount_opts *opts = &fsi->mount_opts;
	151
	152	mutex_lock(&root->d_inode->i_mutex);
	153
	154	/* If we have already created ptmx node, return */
	155	if (fsi->ptmx_dentry) {
	156	rc = 0;
	157	goto out;
	158	}
	159
	160	dentry = d_alloc_name(root, "ptmx");
	161	if (!dentry) {
	162	printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
	163	goto out;
	164	}
	165
	166	/*
	167	* Create a new 'ptmx' node in this mount of devpts.
	168	*/
	169	inode = new_inode(sb);
	170	if (!inode) {
	171	printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
	172	dput(dentry);
	173	goto out;
	174	}
	175
	176	inode->i_ino = 2;
	177	inode->i_uid = inode->i_gid = 0;
	178	inode->i_blocks = 0;
	179	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	180
	181	mode = S_IFCHR\|opts->ptmxmode;
	182	init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
	183
	184	d_add(dentry, inode);
	185
	186	fsi->ptmx_dentry = dentry;
	187	rc = 0;
	188
	189	printk(KERN_DEBUG "Created ptmx node in devpts ino %lu\n",
	190	inode->i_ino);
	191	out:
	192	mutex_unlock(&root->d_inode->i_mutex);
	193	return rc;
	194	}
	195
	196	static void update_ptmx_mode(struct pts_fs_info *fsi)
	197	{
	198	struct inode *inode;
	199	if (fsi->ptmx_dentry) {
	200	inode = fsi->ptmx_dentry->d_inode;
	201	inode->i_mode = S_IFCHR\|fsi->mount_opts.ptmxmode;
	202	}
	203	}
	204	#else
205	static inline void update_ptmx_mode(struct pts_fs_info *fsi)
206	{
207	return;
208	}
209	#endif
210
53af8ee4 SB	211	static int devpts_remount(struct super_block sb, int flags, char *data)
53af8ee4 SB	212	{
1f8f1e29	213	int err;
53af8ee4 SB	214	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	215	struct pts_mount_opts *opts = &fsi->mount_opts;
	216
1f8f1e29 SB	217	err = parse_mount_options(data, opts);
	218
	219	/*
	220	* parse_mount_options() restores options to default values
	221	* before parsing and may have changed ptmxmode. So, update the
	222	* mode in the inode too. Bogus options don't fail the remount,
	223	* so do this even on error return.
	224	*/
	225	update_ptmx_mode(fsi);
	226
	227	return err;
53af8ee4 SB	228	}
53af8ee4 SB	229
b87a267e MS	230	static int devpts_show_options(struct seq_file seq, struct vfsmount vfs)
b87a267e MS	231	{
31af0abb SB	232	struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
	233	struct pts_mount_opts *opts = &fsi->mount_opts;
	234
	235	if (opts->setuid)
	236	seq_printf(seq, ",uid=%u", opts->uid);
	237	if (opts->setgid)
	238	seq_printf(seq, ",gid=%u", opts->gid);
	239	seq_printf(seq, ",mode=%03o", opts->mode);
1f8f1e29 SB	240	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	241	seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
	242	#endif
b87a267e MS	243
	244	return 0;
	245	}
	246
ee9b6d61	247	static const struct super_operations devpts_sops = {
1da177e4 LT	248	.statfs = simple_statfs,
1da177e4 LT	249	.remount_fs = devpts_remount,
b87a267e	250	.show_options = devpts_show_options,
1da177e4 LT	251	};
1da177e4 LT	252
e76b7c01 SB	253	static void *new_pts_fs_info(void)
	254	{
	255	struct pts_fs_info *fsi;
	256
	257	fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
	258	if (!fsi)
	259	return NULL;
	260
	261	ida_init(&fsi->allocated_ptys);
31af0abb	262	fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
1f8f1e29	263	fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
e76b7c01 SB	264
	265	return fsi;
	266	}
	267
1da177e4 LT	268	static int
	269	devpts_fill_super(struct super_block s, void data, int silent)
	270	{
1f8f1e29	271	struct inode *inode;
1da177e4 LT	272
	273	s->s_blocksize = 1024;
	274	s->s_blocksize_bits = 10;
	275	s->s_magic = DEVPTS_SUPER_MAGIC;
	276	s->s_op = &devpts_sops;
1da177e4 LT	277	s->s_time_gran = 1;
1da177e4 LT	278
e76b7c01 SB	279	s->s_fs_info = new_pts_fs_info();
	280	if (!s->s_fs_info)
	281	goto fail;
	282
1da177e4 LT	283	inode = new_inode(s);
1da177e4 LT	284	if (!inode)
e76b7c01	285	goto free_fsi;
1da177e4 LT	286	inode->i_ino = 1;
	287	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	288	inode->i_blocks = 0;
1da177e4 LT	289	inode->i_uid = inode->i_gid = 0;
	290	inode->i_mode = S_IFDIR \| S_IRUGO \| S_IXUGO \| S_IWUSR;
	291	inode->i_op = &simple_dir_inode_operations;
	292	inode->i_fop = &simple_dir_operations;
	293	inode->i_nlink = 2;
	294
59e55e6c	295	s->s_root = d_alloc_root(inode);
1da177e4 LT	296	if (s->s_root)
1da177e4 LT	297	return 0;
1f8f1e29	298
1da177e4 LT	299	printk("devpts: get root dentry failed\n");
1da177e4 LT	300	iput(inode);
e76b7c01 SB	301
	302	free_fsi:
	303	kfree(s->s_fs_info);
1da177e4 LT	304	fail:
	305	return -ENOMEM;
	306	}
	307
d4076ac5 SB	308	static int compare_init_pts_sb(struct super_block s, void p)
	309	{
	310	if (devpts_mnt)
	311	return devpts_mnt->mnt_sb == s;
	312
	313	return 0;
	314	}
	315
	316	/*
	317	* get_init_pts_sb()
	318	*
	319	* This interface is needed to support multiple namespace semantics in
	320	* devpts while preserving backward compatibility of the current 'single-
	321	* namespace' semantics. i.e all mounts of devpts without the 'newinstance'
	322	* mount option should bind to the initial kernel mount, like
	323	* get_sb_single().
	324	*
	325	* Mounts with 'newinstance' option create a new private namespace.
	326	*
	327	* But for single-mount semantics, devpts cannot use get_sb_single(),
	328	* because get_sb_single()/sget() find and use the super-block from
	329	* the most recent mount of devpts. But that recent mount may be a
	330	* 'newinstance' mount and get_sb_single() would pick the newinstance
	331	* super-block instead of the initial super-block.
	332	*
	333	* This interface is identical to get_sb_single() except that it
	334	* consistently selects the 'single-namespace' superblock even in the
	335	* presence of the private namespace (i.e 'newinstance') super-blocks.
	336	*/
	337	static int get_init_pts_sb(struct file_system_type *fs_type, int flags,
	338	void data, struct vfsmount mnt)
	339	{
	340	struct super_block *s;
	341	int error;
	342
	343	s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
	344	if (IS_ERR(s))
	345	return PTR_ERR(s);
	346
	347	if (!s->s_root) {
	348	s->s_flags = flags;
	349	error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
	350	if (error) {
	351	up_write(&s->s_umount);
	352	deactivate_super(s);
	353	return error;
	354	}
	355	s->s_flags \|= MS_ACTIVE;
	356	}
	357	do_remount_sb(s, flags, data, 0);
	358	return simple_set_mnt(mnt, s);
	359	}
	360
454e2398 DH	361	static int devpts_get_sb(struct file_system_type *fs_type,
454e2398 DH	362	int flags, const char dev_name, void data, struct vfsmount *mnt)
1da177e4	363	{
d4076ac5	364	return get_init_pts_sb(fs_type, flags, data, mnt);
1da177e4 LT	365	}
1da177e4 LT	366
e76b7c01 SB	367	static void devpts_kill_sb(struct super_block *sb)
	368	{
	369	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	370
	371	kfree(fsi);
1f8f1e29	372	kill_litter_super(sb);
e76b7c01 SB	373	}
e76b7c01 SB	374
1da177e4 LT	375	static struct file_system_type devpts_fs_type = {
	376	.owner = THIS_MODULE,
	377	.name = "devpts",
	378	.get_sb = devpts_get_sb,
e76b7c01	379	.kill_sb = devpts_kill_sb,
1da177e4 LT	380	};
	381
	382	/*
	383	* The normal naming convention is simply /dev/pts/<number>; this conforms
	384	* to the System V naming convention
	385	*/
	386
15f1a633	387	int devpts_new_index(struct inode *ptmx_inode)
718a9163	388	{
e76b7c01 SB	389	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
e76b7c01 SB	390	struct pts_fs_info *fsi = DEVPTS_SB(sb);
718a9163	391	int index;
7ee7c12b	392	int ida_ret;
718a9163 SB	393
718a9163 SB	394	retry:
e76b7c01	395	if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) {
718a9163 SB	396	return -ENOMEM;
	397	}
	398
	399	mutex_lock(&allocated_ptys_lock);
e76b7c01	400	ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
7ee7c12b	401	if (ida_ret < 0) {
718a9163	402	mutex_unlock(&allocated_ptys_lock);
7ee7c12b	403	if (ida_ret == -EAGAIN)
718a9163 SB	404	goto retry;
	405	return -EIO;
	406	}
	407
	408	if (index >= pty_limit) {
e76b7c01	409	ida_remove(&fsi->allocated_ptys, index);
718a9163 SB	410	mutex_unlock(&allocated_ptys_lock);
	411	return -EIO;
	412	}
	413	mutex_unlock(&allocated_ptys_lock);
	414	return index;
	415	}
	416
15f1a633	417	void devpts_kill_index(struct inode *ptmx_inode, int idx)
718a9163	418	{
e76b7c01 SB	419	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	420	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	421
718a9163	422	mutex_lock(&allocated_ptys_lock);
e76b7c01	423	ida_remove(&fsi->allocated_ptys, idx);
718a9163 SB	424	mutex_unlock(&allocated_ptys_lock);
	425	}
	426
15f1a633	427	int devpts_pty_new(struct inode ptmx_inode, struct tty_struct tty)
1da177e4	428	{
718a9163	429	int number = tty->index; /* tty layer puts index from devpts_new_index() in here */
1da177e4 LT	430	struct tty_driver *driver = tty->driver;
	431	dev_t device = MKDEV(driver->major, driver->minor_start+number);
	432	struct dentry *dentry;
59e55e6c SB	433	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	434	struct inode *inode = new_inode(sb);
	435	struct dentry *root = sb->s_root;
31af0abb SB	436	struct pts_fs_info *fsi = DEVPTS_SB(sb);
31af0abb SB	437	struct pts_mount_opts *opts = &fsi->mount_opts;
89a52e10	438	char s[12];
1da177e4 LT	439
	440	/* We're supposed to be given the slave end of a pty */
	441	BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
	442	BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
	443
	444	if (!inode)
	445	return -ENOMEM;
	446
	447	inode->i_ino = number+2;
ec4c2aac DH	448	inode->i_uid = config.setuid ? config.uid : current_fsuid();
ec4c2aac DH	449	inode->i_gid = config.setgid ? config.gid : current_fsgid();
1da177e4	450	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
31af0abb	451	init_special_inode(inode, S_IFCHR\|opts->mode, device);
8e18e294	452	inode->i_private = tty;
a6f37daa	453	tty->driver_data = inode;
1da177e4	454
89a52e10 SB	455	sprintf(s, "%d", number);
89a52e10 SB	456
59e55e6c	457	mutex_lock(&root->d_inode->i_mutex);
89a52e10	458
59e55e6c	459	dentry = d_alloc_name(root, s);
89a52e10 SB	460	if (!IS_ERR(dentry)) {
89a52e10 SB	461	d_add(dentry, inode);
59e55e6c	462	fsnotify_create(root->d_inode, dentry);
3972b7f6	463	}
1da177e4	464
59e55e6c	465	mutex_unlock(&root->d_inode->i_mutex);
1da177e4 LT	466
	467	return 0;
	468	}
	469
15f1a633	470	struct tty_struct devpts_get_tty(struct inode pts_inode, int number)
1da177e4	471	{
527b3e47	472	BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
1da177e4	473
527b3e47 SB	474	if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
	475	return (struct tty_struct *)pts_inode->i_private;
	476	return NULL;
1da177e4 LT	477	}
1da177e4 LT	478
15f1a633	479	void devpts_pty_kill(struct tty_struct *tty)
1da177e4	480	{
a6f37daa	481	struct inode *inode = tty->driver_data;
59e55e6c SB	482	struct super_block *sb = pts_sb_from_inode(inode);
59e55e6c SB	483	struct dentry *root = sb->s_root;
a6f37daa	484	struct dentry *dentry;
1da177e4	485
a6f37daa SB	486	BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
a6f37daa SB	487
59e55e6c	488	mutex_lock(&root->d_inode->i_mutex);
a6f37daa SB	489
	490	dentry = d_find_alias(inode);
	491	if (dentry && !IS_ERR(dentry)) {
	492	inode->i_nlink--;
	493	d_delete(dentry);
1da177e4 LT	494	dput(dentry);
1da177e4 LT	495	}
a6f37daa	496
59e55e6c	497	mutex_unlock(&root->d_inode->i_mutex);
1da177e4 LT	498	}
	499
	500	static int __init init_devpts_fs(void)
	501	{
	502	int err = register_filesystem(&devpts_fs_type);
	503	if (!err) {
	504	devpts_mnt = kern_mount(&devpts_fs_type);
	505	if (IS_ERR(devpts_mnt))
	506	err = PTR_ERR(devpts_mnt);
	507	}
	508	return err;
	509	}
	510
	511	static void __exit exit_devpts_fs(void)
	512	{
	513	unregister_filesystem(&devpts_fs_type);
	514	mntput(devpts_mnt);
	515	}
	516
	517	module_init(init_devpts_fs)
	518	module_exit(exit_devpts_fs)
	519	MODULE_LICENSE("GPL");