LCOV - code coverage report
Current view: top level - fs/devpts - inode.c (source / functions) Hit Total Coverage
Test: landlock.info Lines: 116 269 43.1 %
Date: 2021-04-22 12:43:58 Functions: 7 18 38.9 %

          Line data    Source code
       1             : // SPDX-License-Identifier: GPL-2.0-or-later
       2             : /* -*- linux-c -*- --------------------------------------------------------- *
       3             :  *
       4             :  * linux/fs/devpts/inode.c
       5             :  *
       6             :  *  Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
       7             :  *
       8             :  * ------------------------------------------------------------------------- */
       9             : 
      10             : #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
      11             : 
      12             : #include <linux/module.h>
      13             : #include <linux/init.h>
      14             : #include <linux/fs.h>
      15             : #include <linux/sched.h>
      16             : #include <linux/namei.h>
      17             : #include <linux/slab.h>
      18             : #include <linux/mount.h>
      19             : #include <linux/tty.h>
      20             : #include <linux/mutex.h>
      21             : #include <linux/magic.h>
      22             : #include <linux/idr.h>
      23             : #include <linux/devpts_fs.h>
      24             : #include <linux/parser.h>
      25             : #include <linux/fsnotify.h>
      26             : #include <linux/seq_file.h>
      27             : 
      28             : #define DEVPTS_DEFAULT_MODE 0600
      29             : /*
      30             :  * ptmx is a new node in /dev/pts and will be unused in legacy (single-
      31             :  * instance) mode. To prevent surprises in user space, set permissions of
      32             :  * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful
      33             :  * permissions.
      34             :  */
      35             : #define DEVPTS_DEFAULT_PTMX_MODE 0000
      36             : #define PTMX_MINOR      2
      37             : 
      38             : /*
      39             :  * sysctl support for setting limits on the number of Unix98 ptys allocated.
      40             :  * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
      41             :  */
      42             : static int pty_limit = NR_UNIX98_PTY_DEFAULT;
      43             : static int pty_reserve = NR_UNIX98_PTY_RESERVE;
      44             : static int pty_limit_min;
      45             : static int pty_limit_max = INT_MAX;
      46             : static atomic_t pty_count = ATOMIC_INIT(0);
      47             : 
      48             : static struct ctl_table pty_table[] = {
      49             :         {
      50             :                 .procname       = "max",
      51             :                 .maxlen         = sizeof(int),
      52             :                 .mode           = 0644,
      53             :                 .data           = &pty_limit,
      54             :                 .proc_handler   = proc_dointvec_minmax,
      55             :                 .extra1         = &pty_limit_min,
      56             :                 .extra2         = &pty_limit_max,
      57             :         }, {
      58             :                 .procname       = "reserve",
      59             :                 .maxlen         = sizeof(int),
      60             :                 .mode           = 0644,
      61             :                 .data           = &pty_reserve,
      62             :                 .proc_handler   = proc_dointvec_minmax,
      63             :                 .extra1         = &pty_limit_min,
      64             :                 .extra2         = &pty_limit_max,
      65             :         }, {
      66             :                 .procname       = "nr",
      67             :                 .maxlen         = sizeof(int),
      68             :                 .mode           = 0444,
      69             :                 .data           = &pty_count,
      70             :                 .proc_handler   = proc_dointvec,
      71             :         },
      72             :         {}
      73             : };
      74             : 
      75             : static struct ctl_table pty_kern_table[] = {
      76             :         {
      77             :                 .procname       = "pty",
      78             :                 .mode           = 0555,
      79             :                 .child          = pty_table,
      80             :         },
      81             :         {}
      82             : };
      83             : 
      84             : static struct ctl_table pty_root_table[] = {
      85             :         {
      86             :                 .procname       = "kernel",
      87             :                 .mode           = 0555,
      88             :                 .child          = pty_kern_table,
      89             :         },
      90             :         {}
      91             : };
      92             : 
      93             : struct pts_mount_opts {
      94             :         int setuid;
      95             :         int setgid;
      96             :         kuid_t   uid;
      97             :         kgid_t   gid;
      98             :         umode_t mode;
      99             :         umode_t ptmxmode;
     100             :         int reserve;
     101             :         int max;
     102             : };
     103             : 
     104             : enum {
     105             :         Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance,  Opt_max,
     106             :         Opt_err
     107             : };
     108             : 
     109             : static const match_table_t tokens = {
     110             :         {Opt_uid, "uid=%u"},
     111             :         {Opt_gid, "gid=%u"},
     112             :         {Opt_mode, "mode=%o"},
     113             :         {Opt_ptmxmode, "ptmxmode=%o"},
     114             :         {Opt_newinstance, "newinstance"},
     115             :         {Opt_max, "max=%d"},
     116             :         {Opt_err, NULL}
     117             : };
     118             : 
     119             : struct pts_fs_info {
     120             :         struct ida allocated_ptys;
     121             :         struct pts_mount_opts mount_opts;
     122             :         struct super_block *sb;
     123             :         struct dentry *ptmx_dentry;
     124             : };
     125             : 
     126         287 : static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
     127             : {
     128         287 :         return sb->s_fs_info;
     129             : }
     130             : 
     131           0 : static int devpts_ptmx_path(struct path *path)
     132             : {
     133           0 :         struct super_block *sb;
     134           0 :         int err;
     135             : 
     136             :         /* Is a devpts filesystem at "pts" in the same directory? */
     137           0 :         err = path_pts(path);
     138           0 :         if (err)
     139             :                 return err;
     140             : 
     141             :         /* Is the path the root of a devpts filesystem? */
     142           0 :         sb = path->mnt->mnt_sb;
     143           0 :         if ((sb->s_magic != DEVPTS_SUPER_MAGIC) ||
     144           0 :             (path->mnt->mnt_root != sb->s_root))
     145           0 :                 return -ENODEV;
     146             : 
     147             :         return 0;
     148             : }
     149             : 
     150             : /*
     151             :  * Try to find a suitable devpts filesystem. We support the following
     152             :  * scenarios:
     153             :  * - The ptmx device node is located in the same directory as the devpts
     154             :  *   mount where the pts device nodes are located.
     155             :  *   This is e.g. the case when calling open on the /dev/pts/ptmx device
     156             :  *   node when the devpts filesystem is mounted at /dev/pts.
     157             :  * - The ptmx device node is located outside the devpts filesystem mount
     158             :  *   where the pts device nodes are located. For example, the ptmx device
     159             :  *   is a symlink, separate device node, or bind-mount.
     160             :  *   A supported scenario is bind-mounting /dev/pts/ptmx to /dev/ptmx and
     161             :  *   then calling open on /dev/ptmx. In this case a suitable pts
     162             :  *   subdirectory can be found in the common parent directory /dev of the
     163             :  *   devpts mount and the ptmx bind-mount, after resolving the /dev/ptmx
     164             :  *   bind-mount.
     165             :  *   If no suitable pts subdirectory can be found this function will fail.
     166             :  *   This is e.g. the case when bind-mounting /dev/pts/ptmx to /ptmx.
     167             :  */
     168           0 : struct vfsmount *devpts_mntget(struct file *filp, struct pts_fs_info *fsi)
     169             : {
     170           0 :         struct path path;
     171           0 :         int err = 0;
     172             : 
     173           0 :         path = filp->f_path;
     174           0 :         path_get(&path);
     175             : 
     176             :         /* Walk upward while the start point is a bind mount of
     177             :          * a single file.
     178             :          */
     179           0 :         while (path.mnt->mnt_root == path.dentry)
     180           0 :                 if (follow_up(&path) == 0)
     181             :                         break;
     182             : 
     183             :         /* devpts_ptmx_path() finds a devpts fs or returns an error. */
     184           0 :         if ((path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) ||
     185           0 :             (DEVPTS_SB(path.mnt->mnt_sb) != fsi))
     186           0 :                 err = devpts_ptmx_path(&path);
     187           0 :         dput(path.dentry);
     188           0 :         if (!err) {
     189           0 :                 if (DEVPTS_SB(path.mnt->mnt_sb) == fsi)
     190             :                         return path.mnt;
     191             : 
     192             :                 err = -ENODEV;
     193             :         }
     194             : 
     195           0 :         mntput(path.mnt);
     196           0 :         return ERR_PTR(err);
     197             : }
     198             : 
     199           0 : struct pts_fs_info *devpts_acquire(struct file *filp)
     200             : {
     201           0 :         struct pts_fs_info *result;
     202           0 :         struct path path;
     203           0 :         struct super_block *sb;
     204             : 
     205           0 :         path = filp->f_path;
     206           0 :         path_get(&path);
     207             : 
     208             :         /* Has the devpts filesystem already been found? */
     209           0 :         if (path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) {
     210           0 :                 int err;
     211             : 
     212           0 :                 err = devpts_ptmx_path(&path);
     213           0 :                 if (err) {
     214           0 :                         result = ERR_PTR(err);
     215           0 :                         goto out;
     216             :                 }
     217             :         }
     218             : 
     219             :         /*
     220             :          * pty code needs to hold extra references in case of last /dev/tty close
     221             :          */
     222           0 :         sb = path.mnt->mnt_sb;
     223           0 :         atomic_inc(&sb->s_active);
     224           0 :         result = DEVPTS_SB(sb);
     225             : 
     226           0 : out:
     227           0 :         path_put(&path);
     228           0 :         return result;
     229             : }
     230             : 
     231           0 : void devpts_release(struct pts_fs_info *fsi)
     232             : {
     233           0 :         deactivate_super(fsi->sb);
     234           0 : }
     235             : 
     236             : #define PARSE_MOUNT     0
     237             : #define PARSE_REMOUNT   1
     238             : 
     239             : /*
     240             :  * parse_mount_options():
     241             :  *      Set @opts to mount options specified in @data. If an option is not
     242             :  *      specified in @data, set it to its default value.
     243             :  *
     244             :  * Note: @data may be NULL (in which case all options are set to default).
     245             :  */
     246           1 : static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
     247             : {
     248           1 :         char *p;
     249           1 :         kuid_t uid;
     250           1 :         kgid_t gid;
     251             : 
     252           1 :         opts->setuid  = 0;
     253           1 :         opts->setgid  = 0;
     254           1 :         opts->uid     = GLOBAL_ROOT_UID;
     255           1 :         opts->gid     = GLOBAL_ROOT_GID;
     256           1 :         opts->mode    = DEVPTS_DEFAULT_MODE;
     257           1 :         opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
     258           1 :         opts->max     = NR_UNIX98_PTY_MAX;
     259             : 
     260             :         /* Only allow instances mounted from the initial mount
     261             :          * namespace to tap the reserve pool of ptys.
     262             :          */
     263           1 :         if (op == PARSE_MOUNT)
     264           1 :                 opts->reserve =
     265           1 :                         (current->nsproxy->mnt_ns == init_task.nsproxy->mnt_ns);
     266             : 
     267           3 :         while ((p = strsep(&data, ",")) != NULL) {
     268           2 :                 substring_t args[MAX_OPT_ARGS];
     269           2 :                 int token;
     270           2 :                 int option;
     271             : 
     272           2 :                 if (!*p)
     273           0 :                         continue;
     274             : 
     275           2 :                 token = match_token(p, tokens, args);
     276           2 :                 switch (token) {
     277           0 :                 case Opt_uid:
     278           0 :                         if (match_int(&args[0], &option))
     279           0 :                                 return -EINVAL;
     280           0 :                         uid = make_kuid(current_user_ns(), option);
     281           0 :                         if (!uid_valid(uid))
     282             :                                 return -EINVAL;
     283           0 :                         opts->uid = uid;
     284           0 :                         opts->setuid = 1;
     285           0 :                         break;
     286           1 :                 case Opt_gid:
     287           1 :                         if (match_int(&args[0], &option))
     288             :                                 return -EINVAL;
     289           1 :                         gid = make_kgid(current_user_ns(), option);
     290           1 :                         if (!gid_valid(gid))
     291             :                                 return -EINVAL;
     292           1 :                         opts->gid = gid;
     293           1 :                         opts->setgid = 1;
     294           1 :                         break;
     295           1 :                 case Opt_mode:
     296           1 :                         if (match_octal(&args[0], &option))
     297             :                                 return -EINVAL;
     298           1 :                         opts->mode = option & S_IALLUGO;
     299           1 :                         break;
     300           0 :                 case Opt_ptmxmode:
     301           0 :                         if (match_octal(&args[0], &option))
     302             :                                 return -EINVAL;
     303           0 :                         opts->ptmxmode = option & S_IALLUGO;
     304           0 :                         break;
     305             :                 case Opt_newinstance:
     306             :                         break;
     307           0 :                 case Opt_max:
     308           0 :                         if (match_int(&args[0], &option) ||
     309           0 :                             option < 0 || option > NR_UNIX98_PTY_MAX)
     310             :                                 return -EINVAL;
     311           0 :                         opts->max = option;
     312           0 :                         break;
     313           0 :                 default:
     314           0 :                         pr_err("called with bogus options\n");
     315           0 :                         return -EINVAL;
     316             :                 }
     317             :         }
     318             : 
     319             :         return 0;
     320             : }
     321             : 
     322           1 : static int mknod_ptmx(struct super_block *sb)
     323             : {
     324           1 :         int mode;
     325           1 :         int rc = -ENOMEM;
     326           1 :         struct dentry *dentry;
     327           1 :         struct inode *inode;
     328           1 :         struct dentry *root = sb->s_root;
     329           1 :         struct pts_fs_info *fsi = DEVPTS_SB(sb);
     330           1 :         struct pts_mount_opts *opts = &fsi->mount_opts;
     331           1 :         kuid_t ptmx_uid = current_fsuid();
     332           1 :         kgid_t ptmx_gid = current_fsgid();
     333             : 
     334           1 :         inode_lock(d_inode(root));
     335             : 
     336             :         /* If we have already created ptmx node, return */
     337           1 :         if (fsi->ptmx_dentry) {
     338           0 :                 rc = 0;
     339           0 :                 goto out;
     340             :         }
     341             : 
     342           1 :         dentry = d_alloc_name(root, "ptmx");
     343           1 :         if (!dentry) {
     344           0 :                 pr_err("Unable to alloc dentry for ptmx node\n");
     345           0 :                 goto out;
     346             :         }
     347             : 
     348             :         /*
     349             :          * Create a new 'ptmx' node in this mount of devpts.
     350             :          */
     351           1 :         inode = new_inode(sb);
     352           1 :         if (!inode) {
     353           0 :                 pr_err("Unable to alloc inode for ptmx node\n");
     354           0 :                 dput(dentry);
     355           0 :                 goto out;
     356             :         }
     357             : 
     358           1 :         inode->i_ino = 2;
     359           1 :         inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
     360             : 
     361           1 :         mode = S_IFCHR|opts->ptmxmode;
     362           1 :         init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
     363           1 :         inode->i_uid = ptmx_uid;
     364           1 :         inode->i_gid = ptmx_gid;
     365             : 
     366           1 :         d_add(dentry, inode);
     367             : 
     368           1 :         fsi->ptmx_dentry = dentry;
     369           1 :         rc = 0;
     370           1 : out:
     371           1 :         inode_unlock(d_inode(root));
     372           1 :         return rc;
     373             : }
     374             : 
     375           0 : static void update_ptmx_mode(struct pts_fs_info *fsi)
     376             : {
     377           0 :         struct inode *inode;
     378           0 :         if (fsi->ptmx_dentry) {
     379           0 :                 inode = d_inode(fsi->ptmx_dentry);
     380           0 :                 inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
     381             :         }
     382             : }
     383             : 
     384           0 : static int devpts_remount(struct super_block *sb, int *flags, char *data)
     385             : {
     386           0 :         int err;
     387           0 :         struct pts_fs_info *fsi = DEVPTS_SB(sb);
     388           0 :         struct pts_mount_opts *opts = &fsi->mount_opts;
     389             : 
     390           0 :         err = parse_mount_options(data, PARSE_REMOUNT, opts);
     391             : 
     392             :         /*
     393             :          * parse_mount_options() restores options to default values
     394             :          * before parsing and may have changed ptmxmode. So, update the
     395             :          * mode in the inode too. Bogus options don't fail the remount,
     396             :          * so do this even on error return.
     397             :          */
     398           0 :         update_ptmx_mode(fsi);
     399             : 
     400           0 :         return err;
     401             : }
     402             : 
     403         285 : static int devpts_show_options(struct seq_file *seq, struct dentry *root)
     404             : {
     405         285 :         struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb);
     406         285 :         struct pts_mount_opts *opts = &fsi->mount_opts;
     407             : 
     408         285 :         if (opts->setuid)
     409           0 :                 seq_printf(seq, ",uid=%u",
     410             :                            from_kuid_munged(&init_user_ns, opts->uid));
     411         285 :         if (opts->setgid)
     412         285 :                 seq_printf(seq, ",gid=%u",
     413             :                            from_kgid_munged(&init_user_ns, opts->gid));
     414         285 :         seq_printf(seq, ",mode=%03o", opts->mode);
     415         285 :         seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
     416         285 :         if (opts->max < NR_UNIX98_PTY_MAX)
     417           0 :                 seq_printf(seq, ",max=%d", opts->max);
     418             : 
     419         285 :         return 0;
     420             : }
     421             : 
     422             : static const struct super_operations devpts_sops = {
     423             :         .statfs         = simple_statfs,
     424             :         .remount_fs     = devpts_remount,
     425             :         .show_options   = devpts_show_options,
     426             : };
     427             : 
     428           1 : static void *new_pts_fs_info(struct super_block *sb)
     429             : {
     430           1 :         struct pts_fs_info *fsi;
     431             : 
     432           1 :         fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
     433           1 :         if (!fsi)
     434             :                 return NULL;
     435             : 
     436           1 :         ida_init(&fsi->allocated_ptys);
     437           1 :         fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
     438           1 :         fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
     439           1 :         fsi->sb = sb;
     440             : 
     441           1 :         return fsi;
     442             : }
     443             : 
     444             : static int
     445           1 : devpts_fill_super(struct super_block *s, void *data, int silent)
     446             : {
     447           1 :         struct inode *inode;
     448           1 :         int error;
     449             : 
     450           1 :         s->s_iflags &= ~SB_I_NODEV;
     451           1 :         s->s_blocksize = 1024;
     452           1 :         s->s_blocksize_bits = 10;
     453           1 :         s->s_magic = DEVPTS_SUPER_MAGIC;
     454           1 :         s->s_op = &devpts_sops;
     455           1 :         s->s_d_op = &simple_dentry_operations;
     456           1 :         s->s_time_gran = 1;
     457             : 
     458           1 :         error = -ENOMEM;
     459           1 :         s->s_fs_info = new_pts_fs_info(s);
     460           1 :         if (!s->s_fs_info)
     461           0 :                 goto fail;
     462             : 
     463           1 :         error = parse_mount_options(data, PARSE_MOUNT, &DEVPTS_SB(s)->mount_opts);
     464           1 :         if (error)
     465           0 :                 goto fail;
     466             : 
     467           1 :         error = -ENOMEM;
     468           1 :         inode = new_inode(s);
     469           1 :         if (!inode)
     470           0 :                 goto fail;
     471           1 :         inode->i_ino = 1;
     472           1 :         inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
     473           1 :         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
     474           1 :         inode->i_op = &simple_dir_inode_operations;
     475           1 :         inode->i_fop = &simple_dir_operations;
     476           1 :         set_nlink(inode, 2);
     477             : 
     478           1 :         s->s_root = d_make_root(inode);
     479           1 :         if (!s->s_root) {
     480           0 :                 pr_err("get root dentry failed\n");
     481           0 :                 goto fail;
     482             :         }
     483             : 
     484           1 :         error = mknod_ptmx(s);
     485           1 :         if (error)
     486           0 :                 goto fail_dput;
     487             : 
     488             :         return 0;
     489           0 : fail_dput:
     490           0 :         dput(s->s_root);
     491           0 :         s->s_root = NULL;
     492             : fail:
     493             :         return error;
     494             : }
     495             : 
     496             : /*
     497             :  * devpts_mount()
     498             :  *
     499             :  *     Mount a new (private) instance of devpts.  PTYs created in this
     500             :  *     instance are independent of the PTYs in other devpts instances.
     501             :  */
     502           1 : static struct dentry *devpts_mount(struct file_system_type *fs_type,
     503             :         int flags, const char *dev_name, void *data)
     504             : {
     505           1 :         return mount_nodev(fs_type, flags, data, devpts_fill_super);
     506             : }
     507             : 
     508           0 : static void devpts_kill_sb(struct super_block *sb)
     509             : {
     510           0 :         struct pts_fs_info *fsi = DEVPTS_SB(sb);
     511             : 
     512           0 :         if (fsi)
     513           0 :                 ida_destroy(&fsi->allocated_ptys);
     514           0 :         kfree(fsi);
     515           0 :         kill_litter_super(sb);
     516           0 : }
     517             : 
     518             : static struct file_system_type devpts_fs_type = {
     519             :         .name           = "devpts",
     520             :         .mount          = devpts_mount,
     521             :         .kill_sb        = devpts_kill_sb,
     522             :         .fs_flags       = FS_USERNS_MOUNT,
     523             : };
     524             : 
     525             : /*
     526             :  * The normal naming convention is simply /dev/pts/<number>; this conforms
     527             :  * to the System V naming convention
     528             :  */
     529             : 
     530           0 : int devpts_new_index(struct pts_fs_info *fsi)
     531             : {
     532           0 :         int index = -ENOSPC;
     533             : 
     534           0 :         if (atomic_inc_return(&pty_count) >= (pty_limit -
     535           0 :                           (fsi->mount_opts.reserve ? 0 : pty_reserve)))
     536           0 :                 goto out;
     537             : 
     538           0 :         index = ida_alloc_max(&fsi->allocated_ptys, fsi->mount_opts.max - 1,
     539             :                         GFP_KERNEL);
     540             : 
     541           0 : out:
     542           0 :         if (index < 0)
     543           0 :                 atomic_dec(&pty_count);
     544           0 :         return index;
     545             : }
     546             : 
     547           0 : void devpts_kill_index(struct pts_fs_info *fsi, int idx)
     548             : {
     549           0 :         ida_free(&fsi->allocated_ptys, idx);
     550           0 :         atomic_dec(&pty_count);
     551           0 : }
     552             : 
     553             : /**
     554             :  * devpts_pty_new -- create a new inode in /dev/pts/
     555             :  * @ptmx_inode: inode of the master
     556             :  * @device: major+minor of the node to be created
     557             :  * @index: used as a name of the node
     558             :  * @priv: what's given back by devpts_get_priv
     559             :  *
     560             :  * The created inode is returned. Remove it from /dev/pts/ by devpts_pty_kill.
     561             :  */
     562           0 : struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv)
     563             : {
     564           0 :         struct dentry *dentry;
     565           0 :         struct super_block *sb = fsi->sb;
     566           0 :         struct inode *inode;
     567           0 :         struct dentry *root;
     568           0 :         struct pts_mount_opts *opts;
     569           0 :         char s[12];
     570             : 
     571           0 :         root = sb->s_root;
     572           0 :         opts = &fsi->mount_opts;
     573             : 
     574           0 :         inode = new_inode(sb);
     575           0 :         if (!inode)
     576           0 :                 return ERR_PTR(-ENOMEM);
     577             : 
     578           0 :         inode->i_ino = index + 3;
     579           0 :         inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
     580           0 :         inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
     581           0 :         inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
     582           0 :         init_special_inode(inode, S_IFCHR|opts->mode, MKDEV(UNIX98_PTY_SLAVE_MAJOR, index));
     583             : 
     584           0 :         sprintf(s, "%d", index);
     585             : 
     586           0 :         dentry = d_alloc_name(root, s);
     587           0 :         if (dentry) {
     588           0 :                 dentry->d_fsdata = priv;
     589           0 :                 d_add(dentry, inode);
     590           0 :                 fsnotify_create(d_inode(root), dentry);
     591             :         } else {
     592           0 :                 iput(inode);
     593           0 :                 dentry = ERR_PTR(-ENOMEM);
     594             :         }
     595             : 
     596             :         return dentry;
     597             : }
     598             : 
     599             : /**
     600             :  * devpts_get_priv -- get private data for a slave
     601             :  * @pts_inode: inode of the slave
     602             :  *
     603             :  * Returns whatever was passed as priv in devpts_pty_new for a given inode.
     604             :  */
     605           0 : void *devpts_get_priv(struct dentry *dentry)
     606             : {
     607           0 :         if (dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC)
     608             :                 return NULL;
     609           0 :         return dentry->d_fsdata;
     610             : }
     611             : 
     612             : /**
     613             :  * devpts_pty_kill -- remove inode form /dev/pts/
     614             :  * @inode: inode of the slave to be removed
     615             :  *
     616             :  * This is an inverse operation of devpts_pty_new.
     617             :  */
     618           0 : void devpts_pty_kill(struct dentry *dentry)
     619             : {
     620           0 :         WARN_ON_ONCE(dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC);
     621             : 
     622           0 :         dentry->d_fsdata = NULL;
     623           0 :         drop_nlink(dentry->d_inode);
     624           0 :         fsnotify_unlink(d_inode(dentry->d_parent), dentry);
     625           0 :         d_drop(dentry);
     626           0 :         dput(dentry);   /* d_alloc_name() in devpts_pty_new() */
     627           0 : }
     628             : 
     629           1 : static int __init init_devpts_fs(void)
     630             : {
     631           1 :         int err = register_filesystem(&devpts_fs_type);
     632           1 :         if (!err) {
     633           1 :                 register_sysctl_table(pty_root_table);
     634             :         }
     635           1 :         return err;
     636             : }
     637             : module_init(init_devpts_fs)

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