| /* -*- 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/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 |
| |
| 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; |
| int newinstance; |
| }; |
| |
| enum { |
| Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, |
| 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"}, |
| {Opt_newinstance, "newinstance"}, |
| #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) |
| { |
| #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES |
| if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC) |
| return inode->i_sb; |
| #endif |
| return devpts_mnt->mnt_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. 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; |
| |
| opts->setuid = 0; |
| opts->setgid = 0; |
| opts->uid = 0; |
| opts->gid = 0; |
| opts->mode = DEVPTS_DEFAULT_MODE; |
| opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; |
| |
| /* newinstance makes sense only on initial mount */ |
| if (op == PARSE_MOUNT) |
| opts->newinstance = 0; |
| |
| 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; |
| case Opt_newinstance: |
| /* newinstance makes sense only on initial mount */ |
| if (op == PARSE_MOUNT) |
| opts->newinstance = 1; |
| 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_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; |
| 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, 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 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_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(KERN_ERR "devpts: get root dentry failed\n"); |
| iput(inode); |
| |
| free_fsi: |
| kfree(s->s_fs_info); |
| fail: |
| return -ENOMEM; |
| } |
| |
| #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES |
| static int compare_init_pts_sb(struct super_block *s, void *p) |
| { |
| if (devpts_mnt) |
| return devpts_mnt->mnt_sb == s; |
| return 0; |
| } |
| |
| /* |
| * devpts_mount() |
| * |
| * 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. |
| * |
| * 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. |
| * |
| * 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(). |
| * |
| * Mounts with 'newinstance' option create a new, private namespace. |
| * |
| * NOTE: |
| * |
| * 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 mount_single() would pick the newinstance |
| * super-block instead of the initial super-block. |
| */ |
| static struct dentry *devpts_mount(struct file_system_type *fs_type, |
| int flags, const char *dev_name, void *data) |
| { |
| 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); |
| |
| if (opts.newinstance) |
| s = sget(fs_type, NULL, set_anon_super, NULL); |
| else |
| s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL); |
| |
| if (IS_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) |
| goto out_undo_sget; |
| s->s_flags |= MS_ACTIVE; |
| } |
| |
| memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts)); |
| |
| error = mknod_ptmx(s); |
| if (error) |
| goto out_undo_sget; |
| |
| return dget(s->s_root); |
| |
| out_undo_sget: |
| deactivate_locked_super(s); |
| return ERR_PTR(error); |
| } |
| |
| #else |
| /* |
| * This supports only the legacy single-instance semantics (no |
| * multiple-instance semantics) |
| */ |
| static struct dentry *devpts_mount(struct file_system_type *fs_type, int flags, |
| const char *dev_name, void *data) |
| { |
| return mount_single(fs_type, flags, data, devpts_fill_super); |
| } |
| #endif |
| |
| 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 = { |
| .name = "devpts", |
| .mount = devpts_mount, |
| .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) |
| { |
| /* 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 dentry *root = sb->s_root; |
| struct pts_fs_info *fsi = DEVPTS_SB(sb); |
| struct pts_mount_opts *opts = &fsi->mount_opts; |
| int ret = 0; |
| 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 + 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; |
| |
| 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); |
| } else { |
| iput(inode); |
| ret = -ENOMEM; |
| } |
| |
| mutex_unlock(&root->d_inode->i_mutex); |
| |
| return ret; |
| } |
| |
| struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number) |
| { |
| struct dentry *dentry; |
| struct tty_struct *tty; |
| |
| 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; |
| |
| tty = NULL; |
| if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC) |
| tty = (struct tty_struct *)pts_inode->i_private; |
| |
| dput(dentry); |
| |
| return tty; |
| } |
| |
| 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); |
| |
| inode->i_nlink--; |
| d_delete(dentry); |
| dput(dentry); /* d_alloc_name() in devpts_pty_new() */ |
| dput(dentry); /* d_find_alias above */ |
| |
| 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); |
| unregister_filesystem(&devpts_fs_type); |
| } |
| } |
| return err; |
| } |
| module_init(init_devpts_fs) |