[mirror_ubuntu-bionic-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.
 *
 * ------------------------------------------------------------------------- */

#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_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

/*
 * 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);

struct pts_mount_opts {
	int setuid;
	int setgid;
	kuid_t   uid;
	kgid_t   gid;
	umode_t mode;
	umode_t ptmxmode;
	int reserve;
	int max;
};

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

static const match_table_t tokens = {
	{Opt_uid, "uid=%u"},
	{Opt_gid, "gid=%u"},
	{Opt_mode, "mode=%o"},
	{Opt_ptmxmode, "ptmxmode=%o"},
	{Opt_newinstance, "newinstance"},
	{Opt_max, "max=%d"},
	{Opt_err, NULL}
};

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

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

struct pts_fs_info *devpts_acquire(struct file *filp)
{
	struct pts_fs_info *result;
	struct path path;
	struct super_block *sb;
	int err;

	path = filp->f_path;
	path_get(&path);

	/* Has the devpts filesystem already been found? */
	sb = path.mnt->mnt_sb;
	if (sb->s_magic != DEVPTS_SUPER_MAGIC) {
		/* Is a devpts filesystem at "pts" in the same directory? */
		err = path_pts(&path);
		if (err) {
			result = ERR_PTR(err);
			goto out;
		}

		/* Is the path the root of a devpts filesystem? */
		result = ERR_PTR(-ENODEV);
		sb = path.mnt->mnt_sb;
		if ((sb->s_magic != DEVPTS_SUPER_MAGIC) ||
		    (path.mnt->mnt_root != sb->s_root))
			goto out;
	}

	/*
	 * pty code needs to hold extra references in case of last /dev/tty close
	 */
	atomic_inc(&sb->s_active);
	result = DEVPTS_SB(sb);

out:
	path_put(&path);
	return result;
}

void devpts_release(struct pts_fs_info *fsi)
{
	deactivate_super(fsi->sb);
}

#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.
 *
 * 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     = 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;

	/* Only allow instances mounted from the initial mount
	 * namespace to tap the reserve pool of ptys.
	 */
	if (op == PARSE_MOUNT)
		opts->reserve =
			(current->nsproxy->mnt_ns == init_task.nsproxy->mnt_ns);

	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;
			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;
			gid = make_kgid(current_user_ns(), option);
			if (!gid_valid(gid))
				return -EINVAL;
			opts->gid = gid;
			opts->setgid = 1;
			break;
		case Opt_mode:
			if (match_octal(&args[0], &option))
				return -EINVAL;
			opts->mode = option & S_IALLUGO;
			break;
		case Opt_ptmxmode:
			if (match_octal(&args[0], &option))
				return -EINVAL;
			opts->ptmxmode = option & S_IALLUGO;
			break;
		case Opt_newinstance:
			break;
		case Opt_max:
			if (match_int(&args[0], &option) ||
			    option < 0 || option > NR_UNIX98_PTY_MAX)
				return -EINVAL;
			opts->max = option;
			break;
		default:
			pr_err("called with bogus options\n");
			return -EINVAL;
		}
	}

	return 0;
}

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;
	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;

	inode_lock(d_inode(root));

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

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

	inode->i_ino = 2;
	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));
	inode->i_uid = root_uid;
	inode->i_gid = root_gid;

	d_add(dentry, inode);

	fsi->ptmx_dentry = dentry;
	rc = 0;
out:
	inode_unlock(d_inode(root));
	return rc;
}

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

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;

	sync_filesystem(sb);
	err = parse_mount_options(data, PARSE_REMOUNT, 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 dentry *root)
{
	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",
			   from_kuid_munged(&init_user_ns, opts->uid));
	if (opts->setgid)
		seq_printf(seq, ",gid=%u",
			   from_kgid_munged(&init_user_ns, opts->gid));
	seq_printf(seq, ",mode=%03o", opts->mode);
	seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
	if (opts->max < NR_UNIX98_PTY_MAX)
		seq_printf(seq, ",max=%d", opts->max);

	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(struct super_block *sb)
{
	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;
	fsi->sb = sb;

	return fsi;
}

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

	s->s_iflags &= ~SB_I_NODEV;
	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;

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

	error = parse_mount_options(data, PARSE_MOUNT, &DEVPTS_SB(s)->mount_opts);
	if (error)
		goto fail;

	error = -ENOMEM;
	inode = new_inode(s);
	if (!inode)
		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;
	set_nlink(inode, 2);

	s->s_root = d_make_root(inode);
	if (!s->s_root) {
		pr_err("get root dentry failed\n");
		goto fail;
	}

	error = mknod_ptmx(s);
	if (error)
		goto fail_dput;

	return 0;
fail_dput:
	dput(s->s_root);
	s->s_root = NULL;
fail:
	return error;
}

/*
 * devpts_mount()
 *
 *     Mount a new (private) instance of devpts.  PTYs created in this
 *     instance are independent of the PTYs in other devpts instances.
 */
static struct dentry *devpts_mount(struct file_system_type *fs_type,
	int flags, const char *dev_name, void *data)
{
	return mount_nodev(fs_type, flags, data, devpts_fill_super);
}

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 = {
	.name		= "devpts",
	.mount		= devpts_mount,
	.kill_sb	= devpts_kill_sb,
	.fs_flags	= FS_USERNS_MOUNT,
};

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

int devpts_new_index(struct pts_fs_info *fsi)
{
	int index;
	int ida_ret;

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

	mutex_lock(&allocated_ptys_lock);
	if (pty_count >= (pty_limit -
			  (fsi->mount_opts.reserve ? 0 : pty_reserve))) {
		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);
		if (ida_ret == -EAGAIN)
			goto retry;
		return -EIO;
	}

	if (index >= fsi->mount_opts.max) {
		ida_remove(&fsi->allocated_ptys, index);
		mutex_unlock(&allocated_ptys_lock);
		return -ENOSPC;
	}
	pty_count++;
	mutex_unlock(&allocated_ptys_lock);
	return index;
}

void devpts_kill_index(struct pts_fs_info *fsi, int idx)
{
	mutex_lock(&allocated_ptys_lock);
	ida_remove(&fsi->allocated_ptys, idx);
	pty_count--;
	mutex_unlock(&allocated_ptys_lock);
}

/**
 * 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 dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv)
{
	struct dentry *dentry;
	struct super_block *sb = fsi->sb;
	struct inode *inode;
	struct dentry *root;
	struct pts_mount_opts *opts;
	char s[12];

	root = sb->s_root;
	opts = &fsi->mount_opts;

	inode = new_inode(sb);
	if (!inode)
		return ERR_PTR(-ENOMEM);

	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, MKDEV(UNIX98_PTY_SLAVE_MAJOR, index));

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

	dentry = d_alloc_name(root, s);
	if (dentry) {
		dentry->d_fsdata = priv;
		d_add(dentry, inode);
		fsnotify_create(d_inode(root), dentry);
	} else {
		iput(inode);
		dentry = ERR_PTR(-ENOMEM);
	}

	return dentry;
}

/**
 * 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 dentry *dentry)
{
	if (dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC)
		return NULL;
	return dentry->d_fsdata;
}

/**
 * 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 dentry *dentry)
{
	WARN_ON_ONCE(dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC);

	dentry->d_fsdata = NULL;
	drop_nlink(dentry->d_inode);
	d_delete(dentry);
	dput(dentry);	/* d_alloc_name() in devpts_pty_new() */
}

static int __init init_devpts_fs(void)
{
	int err = register_filesystem(&devpts_fs_type);
	if (!err) {
		register_sysctl_table(pty_root_table);
	}
	return err;
}
module_init(init_devpts_fs)
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
04541a2f FF	13	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
04541a2f FF	14
1da177e4 LT	15	#include <linux/module.h>
	16	#include <linux/init.h>
	17	#include <linux/fs.h>
	18	#include <linux/sched.h>
	19	#include <linux/namei.h>
5a0e3ad6	20	#include <linux/slab.h>
1da177e4 LT	21	#include <linux/mount.h>
1da177e4 LT	22	#include <linux/tty.h>
718a9163	23	#include <linux/mutex.h>
1fd7317d	24	#include <linux/magic.h>
718a9163	25	#include <linux/idr.h>
1da177e4	26	#include <linux/devpts_fs.h>
7a673c6b	27	#include <linux/parser.h>
3972b7f6	28	#include <linux/fsnotify.h>
b87a267e	29	#include <linux/seq_file.h>
1da177e4	30
b87a267e	31	#define DEVPTS_DEFAULT_MODE 0600
1f8f1e29 SB	32	/*
	33	* ptmx is a new node in /dev/pts and will be unused in legacy (single-
	34	* instance) mode. To prevent surprises in user space, set permissions of
	35	* ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful
	36	* permissions.
	37	*/
	38	#define DEVPTS_DEFAULT_PTMX_MODE 0000
527b3e47	39	#define PTMX_MINOR 2
b87a267e	40
a4834c10 KK	41	/*
	42	* sysctl support for setting limits on the number of Unix98 ptys allocated.
	43	* Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
	44	*/
	45	static int pty_limit = NR_UNIX98_PTY_DEFAULT;
e9aba515	46	static int pty_reserve = NR_UNIX98_PTY_RESERVE;
a4834c10	47	static int pty_limit_min;
e9aba515	48	static int pty_limit_max = INT_MAX;
a4834c10 KK	49	static int pty_count;
	50
	51	static struct ctl_table pty_table[] = {
	52	{
	53	.procname = "max",
	54	.maxlen = sizeof(int),
	55	.mode = 0644,
	56	.data = &pty_limit,
	57	.proc_handler = proc_dointvec_minmax,
	58	.extra1 = &pty_limit_min,
	59	.extra2 = &pty_limit_max,
e9aba515 KK	60	}, {
	61	.procname = "reserve",
	62	.maxlen = sizeof(int),
	63	.mode = 0644,
	64	.data = &pty_reserve,
	65	.proc_handler = proc_dointvec_minmax,
	66	.extra1 = &pty_limit_min,
	67	.extra2 = &pty_limit_max,
a4834c10 KK	68	}, {
	69	.procname = "nr",
	70	.maxlen = sizeof(int),
	71	.mode = 0444,
	72	.data = &pty_count,
	73	.proc_handler = proc_dointvec,
	74	},
	75	{}
	76	};
	77
	78	static struct ctl_table pty_kern_table[] = {
	79	{
	80	.procname = "pty",
	81	.mode = 0555,
	82	.child = pty_table,
	83	},
	84	{}
	85	};
	86
	87	static struct ctl_table pty_root_table[] = {
	88	{
	89	.procname = "kernel",
	90	.mode = 0555,
	91	.child = pty_kern_table,
	92	},
	93	{}
	94	};
	95
718a9163 SB	96	static DEFINE_MUTEX(allocated_ptys_lock);
718a9163 SB	97
31af0abb	98	struct pts_mount_opts {
1da177e4 LT	99	int setuid;
1da177e4 LT	100	int setgid;
f04c6ce2 EB	101	kuid_t uid;
f04c6ce2 EB	102	kgid_t gid;
1da177e4	103	umode_t mode;
1f8f1e29	104	umode_t ptmxmode;
eedf265a	105	int reserve;
e9aba515	106	int max;
31af0abb	107	};
1da177e4	108
7a673c6b	109	enum {
e9aba515	110	Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, Opt_max,
7a673c6b DP	111	Opt_err
	112	};
	113
a447c093	114	static const match_table_t tokens = {
7a673c6b DP	115	{Opt_uid, "uid=%u"},
	116	{Opt_gid, "gid=%u"},
	117	{Opt_mode, "mode=%o"},
1f8f1e29	118	{Opt_ptmxmode, "ptmxmode=%o"},
2a1b2dc0	119	{Opt_newinstance, "newinstance"},
e9aba515	120	{Opt_max, "max=%d"},
7a673c6b DP	121	{Opt_err, NULL}
	122	};
	123
e76b7c01 SB	124	struct pts_fs_info {
e76b7c01 SB	125	struct ida allocated_ptys;
31af0abb	126	struct pts_mount_opts mount_opts;
67245ff3	127	struct super_block *sb;
1f8f1e29	128	struct dentry *ptmx_dentry;
e76b7c01 SB	129	};
	130
	131	static inline struct pts_fs_info DEVPTS_SB(struct super_block sb)
	132	{
	133	return sb->s_fs_info;
	134	}
	135
eedf265a	136	struct pts_fs_info devpts_acquire(struct file filp)
59e55e6c	137	{
eedf265a EB	138	struct pts_fs_info *result;
	139	struct path path;
	140	struct super_block *sb;
	141	int err;
	142
	143	path = filp->f_path;
	144	path_get(&path);
	145
	146	/* Has the devpts filesystem already been found? */
	147	sb = path.mnt->mnt_sb;
	148	if (sb->s_magic != DEVPTS_SUPER_MAGIC) {
	149	/* Is a devpts filesystem at "pts" in the same directory? */
	150	err = path_pts(&path);
	151	if (err) {
	152	result = ERR_PTR(err);
	153	goto out;
	154	}
	155
	156	/* Is the path the root of a devpts filesystem? */
	157	result = ERR_PTR(-ENODEV);
	158	sb = path.mnt->mnt_sb;
	159	if ((sb->s_magic != DEVPTS_SUPER_MAGIC) \|\|
	160	(path.mnt->mnt_root != sb->s_root))
	161	goto out;
	162	}
	163
	164	/*
	165	* pty code needs to hold extra references in case of last /dev/tty close
	166	*/
	167	atomic_inc(&sb->s_active);
	168	result = DEVPTS_SB(sb);
	169
	170	out:
	171	path_put(&path);
	172	return result;
	173	}
	174
	175	void devpts_release(struct pts_fs_info *fsi)
	176	{
	177	deactivate_super(fsi->sb);
59e55e6c SB	178	}
59e55e6c SB	179
2a1b2dc0 SB	180	#define PARSE_MOUNT 0
	181	#define PARSE_REMOUNT 1
	182
1f71ebed SB	183	/*
1f71ebed SB	184	* parse_mount_options():
04541a2f	185	* Set @opts to mount options specified in @data. If an option is not
eedf265a	186	* specified in @data, set it to its default value.
1f71ebed SB	187	*
	188	* Note: @data may be NULL (in which case all options are set to default).
	189	*/
2a1b2dc0	190	static int parse_mount_options(char data, int op, struct pts_mount_opts opts)
1da177e4	191	{
7a673c6b	192	char *p;
f04c6ce2 EB	193	kuid_t uid;
f04c6ce2 EB	194	kgid_t gid;
7a673c6b	195
31af0abb SB	196	opts->setuid = 0;
31af0abb SB	197	opts->setgid = 0;
f04c6ce2 EB	198	opts->uid = GLOBAL_ROOT_UID;
f04c6ce2 EB	199	opts->gid = GLOBAL_ROOT_GID;
31af0abb	200	opts->mode = DEVPTS_DEFAULT_MODE;
1f8f1e29	201	opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
e9aba515	202	opts->max = NR_UNIX98_PTY_MAX;
7a673c6b	203
eedf265a EB	204	/* Only allow instances mounted from the initial mount
	205	* namespace to tap the reserve pool of ptys.
	206	*/
2a1b2dc0	207	if (op == PARSE_MOUNT)
eedf265a EB	208	opts->reserve =
eedf265a EB	209	(current->nsproxy->mnt_ns == init_task.nsproxy->mnt_ns);
2a1b2dc0	210
7a673c6b DP	211	while ((p = strsep(&data, ",")) != NULL) {
	212	substring_t args[MAX_OPT_ARGS];
	213	int token;
	214	int option;
	215
	216	if (!*p)
1da177e4	217	continue;
7a673c6b DP	218
	219	token = match_token(p, tokens, args);
	220	switch (token) {
	221	case Opt_uid:
	222	if (match_int(&args[0], &option))
	223	return -EINVAL;
f04c6ce2 EB	224	uid = make_kuid(current_user_ns(), option);
	225	if (!uid_valid(uid))
	226	return -EINVAL;
	227	opts->uid = uid;
31af0abb	228	opts->setuid = 1;
7a673c6b DP	229	break;
	230	case Opt_gid:
	231	if (match_int(&args[0], &option))
	232	return -EINVAL;
f04c6ce2 EB	233	gid = make_kgid(current_user_ns(), option);
	234	if (!gid_valid(gid))
	235	return -EINVAL;
	236	opts->gid = gid;
31af0abb	237	opts->setgid = 1;
7a673c6b DP	238	break;
	239	case Opt_mode:
	240	if (match_octal(&args[0], &option))
	241	return -EINVAL;
31af0abb	242	opts->mode = option & S_IALLUGO;
7a673c6b	243	break;
1f8f1e29 SB	244	case Opt_ptmxmode:
	245	if (match_octal(&args[0], &option))
	246	return -EINVAL;
	247	opts->ptmxmode = option & S_IALLUGO;
	248	break;
2a1b2dc0	249	case Opt_newinstance:
2a1b2dc0	250	break;
e9aba515 KK	251	case Opt_max:
	252	if (match_int(&args[0], &option) \|\|
	253	option < 0 \|\| option > NR_UNIX98_PTY_MAX)
	254	return -EINVAL;
	255	opts->max = option;
	256	break;
7a673c6b	257	default:
04541a2f	258	pr_err("called with bogus options\n");
1da177e4 LT	259	return -EINVAL;
	260	}
	261	}
1da177e4 LT	262
	263	return 0;
	264	}
	265
1f8f1e29 SB	266	static int mknod_ptmx(struct super_block *sb)
	267	{
	268	int mode;
	269	int rc = -ENOMEM;
	270	struct dentry *dentry;
	271	struct inode *inode;
	272	struct dentry *root = sb->s_root;
	273	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	274	struct pts_mount_opts *opts = &fsi->mount_opts;
ec2aa8e8 EB	275	kuid_t root_uid;
	276	kgid_t root_gid;
	277
	278	root_uid = make_kuid(current_user_ns(), 0);
	279	root_gid = make_kgid(current_user_ns(), 0);
	280	if (!uid_valid(root_uid) \|\| !gid_valid(root_gid))
	281	return -EINVAL;
1f8f1e29	282
5955102c	283	inode_lock(d_inode(root));
1f8f1e29 SB	284
	285	/* If we have already created ptmx node, return */
	286	if (fsi->ptmx_dentry) {
	287	rc = 0;
	288	goto out;
	289	}
	290
	291	dentry = d_alloc_name(root, "ptmx");
	292	if (!dentry) {
04541a2f	293	pr_err("Unable to alloc dentry for ptmx node\n");
1f8f1e29 SB	294	goto out;
	295	}
	296
	297	/*
	298	* Create a new 'ptmx' node in this mount of devpts.
	299	*/
	300	inode = new_inode(sb);
	301	if (!inode) {
04541a2f	302	pr_err("Unable to alloc inode for ptmx node\n");
1f8f1e29 SB	303	dput(dentry);
	304	goto out;
	305	}
	306
	307	inode->i_ino = 2;
1f8f1e29 SB	308	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	309
	310	mode = S_IFCHR\|opts->ptmxmode;
	311	init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
ec2aa8e8 EB	312	inode->i_uid = root_uid;
ec2aa8e8 EB	313	inode->i_gid = root_gid;
1f8f1e29 SB	314
	315	d_add(dentry, inode);
	316
	317	fsi->ptmx_dentry = dentry;
	318	rc = 0;
1f8f1e29	319	out:
5955102c	320	inode_unlock(d_inode(root));
1f8f1e29 SB	321	return rc;
	322	}
	323
	324	static void update_ptmx_mode(struct pts_fs_info *fsi)
	325	{
	326	struct inode *inode;
	327	if (fsi->ptmx_dentry) {
2b0143b5	328	inode = d_inode(fsi->ptmx_dentry);
1f8f1e29 SB	329	inode->i_mode = S_IFCHR\|fsi->mount_opts.ptmxmode;
	330	}
	331	}
1f8f1e29	332
53af8ee4 SB	333	static int devpts_remount(struct super_block sb, int flags, char *data)
53af8ee4 SB	334	{
1f8f1e29	335	int err;
53af8ee4 SB	336	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	337	struct pts_mount_opts *opts = &fsi->mount_opts;
	338
02b9984d	339	sync_filesystem(sb);
2a1b2dc0	340	err = parse_mount_options(data, PARSE_REMOUNT, opts);
1f8f1e29 SB	341
	342	/*
	343	* parse_mount_options() restores options to default values
	344	* before parsing and may have changed ptmxmode. So, update the
	345	* mode in the inode too. Bogus options don't fail the remount,
	346	* so do this even on error return.
	347	*/
	348	update_ptmx_mode(fsi);
	349
	350	return err;
53af8ee4 SB	351	}
53af8ee4 SB	352
34c80b1d	353	static int devpts_show_options(struct seq_file seq, struct dentry root)
b87a267e	354	{
34c80b1d	355	struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb);
31af0abb SB	356	struct pts_mount_opts *opts = &fsi->mount_opts;
	357
	358	if (opts->setuid)
04541a2f FF	359	seq_printf(seq, ",uid=%u",
04541a2f FF	360	from_kuid_munged(&init_user_ns, opts->uid));
31af0abb	361	if (opts->setgid)
04541a2f FF	362	seq_printf(seq, ",gid=%u",
04541a2f FF	363	from_kgid_munged(&init_user_ns, opts->gid));
31af0abb	364	seq_printf(seq, ",mode=%03o", opts->mode);
1f8f1e29	365	seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
e9aba515 KK	366	if (opts->max < NR_UNIX98_PTY_MAX)
e9aba515 KK	367	seq_printf(seq, ",max=%d", opts->max);
b87a267e MS	368
	369	return 0;
	370	}
	371
ee9b6d61	372	static const struct super_operations devpts_sops = {
1da177e4 LT	373	.statfs = simple_statfs,
1da177e4 LT	374	.remount_fs = devpts_remount,
b87a267e	375	.show_options = devpts_show_options,
1da177e4 LT	376	};
1da177e4 LT	377
67245ff3	378	static void new_pts_fs_info(struct super_block sb)
e76b7c01 SB	379	{
	380	struct pts_fs_info *fsi;
	381
	382	fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
	383	if (!fsi)
	384	return NULL;
	385
	386	ida_init(&fsi->allocated_ptys);
31af0abb	387	fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
1f8f1e29	388	fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
67245ff3	389	fsi->sb = sb;
e76b7c01 SB	390
	391	return fsi;
	392	}
	393
1da177e4 LT	394	static int
	395	devpts_fill_super(struct super_block s, void data, int silent)
	396	{
1f8f1e29	397	struct inode *inode;
dee87d47	398	int error;
1da177e4	399
cc50a07a	400	s->s_iflags &= ~SB_I_NODEV;
1da177e4 LT	401	s->s_blocksize = 1024;
	402	s->s_blocksize_bits = 10;
	403	s->s_magic = DEVPTS_SUPER_MAGIC;
	404	s->s_op = &devpts_sops;
1da177e4 LT	405	s->s_time_gran = 1;
1da177e4 LT	406
dee87d47	407	error = -ENOMEM;
67245ff3	408	s->s_fs_info = new_pts_fs_info(s);
e76b7c01 SB	409	if (!s->s_fs_info)
	410	goto fail;
	411
dee87d47 EB	412	error = parse_mount_options(data, PARSE_MOUNT, &DEVPTS_SB(s)->mount_opts);
	413	if (error)
	414	goto fail;
	415
	416	error = -ENOMEM;
1da177e4 LT	417	inode = new_inode(s);
1da177e4 LT	418	if (!inode)
3850aba7	419	goto fail;
1da177e4 LT	420	inode->i_ino = 1;
1da177e4 LT	421	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
1da177e4 LT	422	inode->i_mode = S_IFDIR \| S_IRUGO \| S_IXUGO \| S_IWUSR;
	423	inode->i_op = &simple_dir_inode_operations;
	424	inode->i_fop = &simple_dir_operations;
bfe86848	425	set_nlink(inode, 2);
1da177e4	426
48fde701	427	s->s_root = d_make_root(inode);
180d9044 EB	428	if (!s->s_root) {
	429	pr_err("get root dentry failed\n");
	430	goto fail;
	431	}
1f8f1e29	432
180d9044 EB	433	error = mknod_ptmx(s);
	434	if (error)
	435	goto fail_dput;
e76b7c01	436
180d9044 EB	437	return 0;
	438	fail_dput:
	439	dput(s->s_root);
	440	s->s_root = NULL;
1da177e4	441	fail:
dee87d47	442	return error;
1da177e4 LT	443	}
1da177e4 LT	444
2a1b2dc0	445	/*
fc14f2fe	446	* devpts_mount()
1bd79035	447	*
eedf265a EB	448	* Mount a new (private) instance of devpts. PTYs created in this
eedf265a EB	449	* instance are independent of the PTYs in other devpts instances.
d4076ac5	450	*/
fc14f2fe AV	451	static struct dentry devpts_mount(struct file_system_type fs_type,
fc14f2fe AV	452	int flags, const char dev_name, void data)
1da177e4	453	{
c1b241f0	454	return mount_nodev(fs_type, flags, data, devpts_fill_super);
1da177e4	455	}
482984f0	456
e76b7c01 SB	457	static void devpts_kill_sb(struct super_block *sb)
	458	{
	459	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	460
66da0e1f	461	ida_destroy(&fsi->allocated_ptys);
e76b7c01	462	kfree(fsi);
1f8f1e29	463	kill_litter_super(sb);
e76b7c01 SB	464	}
e76b7c01 SB	465
1da177e4	466	static struct file_system_type devpts_fs_type = {
1da177e4	467	.name = "devpts",
fc14f2fe	468	.mount = devpts_mount,
e76b7c01	469	.kill_sb = devpts_kill_sb,
cc50a07a	470	.fs_flags = FS_USERNS_MOUNT,
1da177e4 LT	471	};
	472
	473	/*
	474	* The normal naming convention is simply /dev/pts/<number>; this conforms
	475	* to the System V naming convention
	476	*/
	477
67245ff3	478	int devpts_new_index(struct pts_fs_info *fsi)
718a9163 SB	479	{
718a9163 SB	480	int index;
7ee7c12b	481	int ida_ret;
718a9163 SB	482
718a9163 SB	483	retry:
835aa440	484	if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
718a9163	485	return -ENOMEM;
718a9163 SB	486
718a9163 SB	487	mutex_lock(&allocated_ptys_lock);
eedf265a EB	488	if (pty_count >= (pty_limit -
eedf265a EB	489	(fsi->mount_opts.reserve ? 0 : pty_reserve))) {
e9aba515 KK	490	mutex_unlock(&allocated_ptys_lock);
	491	return -ENOSPC;
	492	}
	493
e76b7c01	494	ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
7ee7c12b	495	if (ida_ret < 0) {
718a9163	496	mutex_unlock(&allocated_ptys_lock);
7ee7c12b	497	if (ida_ret == -EAGAIN)
718a9163 SB	498	goto retry;
	499	return -EIO;
	500	}
	501
e9aba515	502	if (index >= fsi->mount_opts.max) {
e76b7c01	503	ida_remove(&fsi->allocated_ptys, index);
718a9163	504	mutex_unlock(&allocated_ptys_lock);
e9aba515	505	return -ENOSPC;
718a9163	506	}
a4834c10	507	pty_count++;
718a9163 SB	508	mutex_unlock(&allocated_ptys_lock);
	509	return index;
	510	}
	511
67245ff3	512	void devpts_kill_index(struct pts_fs_info *fsi, int idx)
718a9163 SB	513	{
718a9163 SB	514	mutex_lock(&allocated_ptys_lock);
e76b7c01	515	ida_remove(&fsi->allocated_ptys, idx);
a4834c10	516	pty_count--;
718a9163 SB	517	mutex_unlock(&allocated_ptys_lock);
	518	}
	519
1dcb8e6d JS	520	/**
	521	* devpts_pty_new -- create a new inode in /dev/pts/
	522	* @ptmx_inode: inode of the master
	523	* @device: major+minor of the node to be created
	524	* @index: used as a name of the node
	525	* @priv: what's given back by devpts_get_priv
	526	*
	527	* The created inode is returned. Remove it from /dev/pts/ by devpts_pty_kill.
	528	*/
8ead9dd5	529	struct dentry devpts_pty_new(struct pts_fs_info fsi, int index, void *priv)
1da177e4	530	{
1da177e4	531	struct dentry *dentry;
eedf265a	532	struct super_block *sb = fsi->sb;
162b97cf	533	struct inode *inode;
9ce71148	534	struct dentry *root;
9ce71148	535	struct pts_mount_opts *opts;
89a52e10	536	char s[12];
1da177e4	537
9ce71148	538	root = sb->s_root;
9ce71148 JT	539	opts = &fsi->mount_opts;
9ce71148 JT	540
162b97cf	541	inode = new_inode(sb);
1da177e4	542	if (!inode)
162b97cf	543	return ERR_PTR(-ENOMEM);
1da177e4	544
f11afb61	545	inode->i_ino = index + 3;
d0eafc7d DH	546	inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
d0eafc7d DH	547	inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
1da177e4	548	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
8ead9dd5	549	init_special_inode(inode, S_IFCHR\|opts->mode, MKDEV(UNIX98_PTY_SLAVE_MAJOR, index));
1da177e4	550
f11afb61	551	sprintf(s, "%d", index);
89a52e10	552
59e55e6c	553	dentry = d_alloc_name(root, s);
b12d1259	554	if (dentry) {
8ead9dd5	555	dentry->d_fsdata = priv;
89a52e10	556	d_add(dentry, inode);
2b0143b5	557	fsnotify_create(d_inode(root), dentry);
aa597bc1 AV	558	} else {
aa597bc1 AV	559	iput(inode);
8ead9dd5	560	dentry = ERR_PTR(-ENOMEM);
3972b7f6	561	}
1da177e4	562
8ead9dd5	563	return dentry;
1da177e4 LT	564	}
1da177e4 LT	565
1dcb8e6d JS	566	/**
	567	* devpts_get_priv -- get private data for a slave
	568	* @pts_inode: inode of the slave
	569	*
	570	* Returns whatever was passed as priv in devpts_pty_new for a given inode.
	571	*/
8ead9dd5	572	void devpts_get_priv(struct dentry dentry)
1da177e4	573	{
3e423945 LT	574	if (dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC)
3e423945 LT	575	return NULL;
8ead9dd5	576	return dentry->d_fsdata;
1da177e4 LT	577	}
1da177e4 LT	578
1dcb8e6d JS	579	/**
	580	* devpts_pty_kill -- remove inode form /dev/pts/
	581	* @inode: inode of the slave to be removed
	582	*
	583	* This is an inverse operation of devpts_pty_new.
	584	*/
8ead9dd5	585	void devpts_pty_kill(struct dentry *dentry)
1da177e4	586	{
8ead9dd5	587	WARN_ON_ONCE(dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC);
1da177e4	588
8ead9dd5 LT	589	dentry->d_fsdata = NULL;
8ead9dd5 LT	590	drop_nlink(dentry->d_inode);
aa597bc1 AV	591	d_delete(dentry);
aa597bc1 AV	592	dput(dentry); /* d_alloc_name() in devpts_pty_new() */
1da177e4 LT	593	}
	594
	595	static int __init init_devpts_fs(void)
	596	{
	597	int err = register_filesystem(&devpts_fs_type);
	598	if (!err) {
eedf265a	599	register_sysctl_table(pty_root_table);
1da177e4 LT	600	}
	601	return err;
	602	}
1da177e4	603	module_init(init_devpts_fs)