1d6910058SThomas Gleixner // SPDX-License-Identifier: GPL-2.0-or-later 21da177e4SLinus Torvalds /* -*- linux-c -*- --------------------------------------------------------- * 31da177e4SLinus Torvalds * 41da177e4SLinus Torvalds * linux/fs/devpts/inode.c 51da177e4SLinus Torvalds * 61da177e4SLinus Torvalds * Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved 71da177e4SLinus Torvalds * 81da177e4SLinus Torvalds * ------------------------------------------------------------------------- */ 91da177e4SLinus Torvalds 1004541a2fSFabian Frederick #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 1104541a2fSFabian Frederick 121da177e4SLinus Torvalds #include <linux/module.h> 131da177e4SLinus Torvalds #include <linux/init.h> 141da177e4SLinus Torvalds #include <linux/fs.h> 151da177e4SLinus Torvalds #include <linux/sched.h> 161da177e4SLinus Torvalds #include <linux/namei.h> 175a0e3ad6STejun Heo #include <linux/slab.h> 181da177e4SLinus Torvalds #include <linux/mount.h> 191da177e4SLinus Torvalds #include <linux/tty.h> 20718a9163SSukadev Bhattiprolu #include <linux/mutex.h> 211fd7317dSNick Black #include <linux/magic.h> 22718a9163SSukadev Bhattiprolu #include <linux/idr.h> 231da177e4SLinus Torvalds #include <linux/devpts_fs.h> 247a673c6bSDomen Puncer #include <linux/parser.h> 253972b7f6SFlorin Malita #include <linux/fsnotify.h> 26b87a267eSMiklos Szeredi #include <linux/seq_file.h> 271da177e4SLinus Torvalds 28b87a267eSMiklos Szeredi #define DEVPTS_DEFAULT_MODE 0600 291f8f1e29SSukadev Bhattiprolu /* 301f8f1e29SSukadev Bhattiprolu * ptmx is a new node in /dev/pts and will be unused in legacy (single- 311f8f1e29SSukadev Bhattiprolu * instance) mode. To prevent surprises in user space, set permissions of 321f8f1e29SSukadev Bhattiprolu * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful 331f8f1e29SSukadev Bhattiprolu * permissions. 341f8f1e29SSukadev Bhattiprolu */ 351f8f1e29SSukadev Bhattiprolu #define DEVPTS_DEFAULT_PTMX_MODE 0000 36527b3e47SSukadev Bhattiprolu #define PTMX_MINOR 2 37b87a267eSMiklos Szeredi 38a4834c10SKonstantin Khlebnikov /* 39a4834c10SKonstantin Khlebnikov * sysctl support for setting limits on the number of Unix98 ptys allocated. 40a4834c10SKonstantin Khlebnikov * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly. 41a4834c10SKonstantin Khlebnikov */ 42a4834c10SKonstantin Khlebnikov static int pty_limit = NR_UNIX98_PTY_DEFAULT; 43e9aba515SKonstantin Khlebnikov static int pty_reserve = NR_UNIX98_PTY_RESERVE; 44a4834c10SKonstantin Khlebnikov static int pty_limit_min; 45e9aba515SKonstantin Khlebnikov static int pty_limit_max = INT_MAX; 460f0a0e54SMatthew Wilcox static atomic_t pty_count = ATOMIC_INIT(0); 47a4834c10SKonstantin Khlebnikov 48a4834c10SKonstantin Khlebnikov static struct ctl_table pty_table[] = { 49a4834c10SKonstantin Khlebnikov { 50a4834c10SKonstantin Khlebnikov .procname = "max", 51a4834c10SKonstantin Khlebnikov .maxlen = sizeof(int), 52a4834c10SKonstantin Khlebnikov .mode = 0644, 53a4834c10SKonstantin Khlebnikov .data = &pty_limit, 54a4834c10SKonstantin Khlebnikov .proc_handler = proc_dointvec_minmax, 55a4834c10SKonstantin Khlebnikov .extra1 = &pty_limit_min, 56a4834c10SKonstantin Khlebnikov .extra2 = &pty_limit_max, 57a4834c10SKonstantin Khlebnikov }, { 58e9aba515SKonstantin Khlebnikov .procname = "reserve", 59e9aba515SKonstantin Khlebnikov .maxlen = sizeof(int), 60e9aba515SKonstantin Khlebnikov .mode = 0644, 61e9aba515SKonstantin Khlebnikov .data = &pty_reserve, 62e9aba515SKonstantin Khlebnikov .proc_handler = proc_dointvec_minmax, 63e9aba515SKonstantin Khlebnikov .extra1 = &pty_limit_min, 64e9aba515SKonstantin Khlebnikov .extra2 = &pty_limit_max, 65e9aba515SKonstantin Khlebnikov }, { 66a4834c10SKonstantin Khlebnikov .procname = "nr", 67a4834c10SKonstantin Khlebnikov .maxlen = sizeof(int), 68a4834c10SKonstantin Khlebnikov .mode = 0444, 69a4834c10SKonstantin Khlebnikov .data = &pty_count, 70a4834c10SKonstantin Khlebnikov .proc_handler = proc_dointvec, 71a4834c10SKonstantin Khlebnikov }, 72a4834c10SKonstantin Khlebnikov {} 73a4834c10SKonstantin Khlebnikov }; 74a4834c10SKonstantin Khlebnikov 75a4834c10SKonstantin Khlebnikov static struct ctl_table pty_kern_table[] = { 76a4834c10SKonstantin Khlebnikov { 77a4834c10SKonstantin Khlebnikov .procname = "pty", 78a4834c10SKonstantin Khlebnikov .mode = 0555, 79a4834c10SKonstantin Khlebnikov .child = pty_table, 80a4834c10SKonstantin Khlebnikov }, 81a4834c10SKonstantin Khlebnikov {} 82a4834c10SKonstantin Khlebnikov }; 83a4834c10SKonstantin Khlebnikov 84a4834c10SKonstantin Khlebnikov static struct ctl_table pty_root_table[] = { 85a4834c10SKonstantin Khlebnikov { 86a4834c10SKonstantin Khlebnikov .procname = "kernel", 87a4834c10SKonstantin Khlebnikov .mode = 0555, 88a4834c10SKonstantin Khlebnikov .child = pty_kern_table, 89a4834c10SKonstantin Khlebnikov }, 90a4834c10SKonstantin Khlebnikov {} 91a4834c10SKonstantin Khlebnikov }; 92a4834c10SKonstantin Khlebnikov 9331af0abbSSukadev Bhattiprolu struct pts_mount_opts { 941da177e4SLinus Torvalds int setuid; 951da177e4SLinus Torvalds int setgid; 96f04c6ce2SEric W. Biederman kuid_t uid; 97f04c6ce2SEric W. Biederman kgid_t gid; 981da177e4SLinus Torvalds umode_t mode; 991f8f1e29SSukadev Bhattiprolu umode_t ptmxmode; 100eedf265aSEric W. Biederman int reserve; 101e9aba515SKonstantin Khlebnikov int max; 10231af0abbSSukadev Bhattiprolu }; 1031da177e4SLinus Torvalds 1047a673c6bSDomen Puncer enum { 105e9aba515SKonstantin Khlebnikov Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, Opt_max, 1067a673c6bSDomen Puncer Opt_err 1077a673c6bSDomen Puncer }; 1087a673c6bSDomen Puncer 109a447c093SSteven Whitehouse static const match_table_t tokens = { 1107a673c6bSDomen Puncer {Opt_uid, "uid=%u"}, 1117a673c6bSDomen Puncer {Opt_gid, "gid=%u"}, 1127a673c6bSDomen Puncer {Opt_mode, "mode=%o"}, 1131f8f1e29SSukadev Bhattiprolu {Opt_ptmxmode, "ptmxmode=%o"}, 1142a1b2dc0SSukadev Bhattiprolu {Opt_newinstance, "newinstance"}, 115e9aba515SKonstantin Khlebnikov {Opt_max, "max=%d"}, 1167a673c6bSDomen Puncer {Opt_err, NULL} 1177a673c6bSDomen Puncer }; 1187a673c6bSDomen Puncer 119e76b7c01SSukadev Bhattiprolu struct pts_fs_info { 120e76b7c01SSukadev Bhattiprolu struct ida allocated_ptys; 12131af0abbSSukadev Bhattiprolu struct pts_mount_opts mount_opts; 12267245ff3SLinus Torvalds struct super_block *sb; 1231f8f1e29SSukadev Bhattiprolu struct dentry *ptmx_dentry; 124e76b7c01SSukadev Bhattiprolu }; 125e76b7c01SSukadev Bhattiprolu 126e76b7c01SSukadev Bhattiprolu static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb) 127e76b7c01SSukadev Bhattiprolu { 128e76b7c01SSukadev Bhattiprolu return sb->s_fs_info; 129e76b7c01SSukadev Bhattiprolu } 130e76b7c01SSukadev Bhattiprolu 131311fc65cSEric W. Biederman static int devpts_ptmx_path(struct path *path) 132311fc65cSEric W. Biederman { 133311fc65cSEric W. Biederman struct super_block *sb; 134311fc65cSEric W. Biederman int err; 135311fc65cSEric W. Biederman 136311fc65cSEric W. Biederman /* Is a devpts filesystem at "pts" in the same directory? */ 137311fc65cSEric W. Biederman err = path_pts(path); 138311fc65cSEric W. Biederman if (err) 139311fc65cSEric W. Biederman return err; 140311fc65cSEric W. Biederman 141311fc65cSEric W. Biederman /* Is the path the root of a devpts filesystem? */ 142311fc65cSEric W. Biederman sb = path->mnt->mnt_sb; 143311fc65cSEric W. Biederman if ((sb->s_magic != DEVPTS_SUPER_MAGIC) || 144311fc65cSEric W. Biederman (path->mnt->mnt_root != sb->s_root)) 145311fc65cSEric W. Biederman return -ENODEV; 146311fc65cSEric W. Biederman 147311fc65cSEric W. Biederman return 0; 148311fc65cSEric W. Biederman } 149311fc65cSEric W. Biederman 1504e15f760SChristian Brauner /* 1514e15f760SChristian Brauner * Try to find a suitable devpts filesystem. We support the following 1524e15f760SChristian Brauner * scenarios: 1534e15f760SChristian Brauner * - The ptmx device node is located in the same directory as the devpts 1544e15f760SChristian Brauner * mount where the pts device nodes are located. 1554e15f760SChristian Brauner * This is e.g. the case when calling open on the /dev/pts/ptmx device 1564e15f760SChristian Brauner * node when the devpts filesystem is mounted at /dev/pts. 1574e15f760SChristian Brauner * - The ptmx device node is located outside the devpts filesystem mount 1584e15f760SChristian Brauner * where the pts device nodes are located. For example, the ptmx device 1594e15f760SChristian Brauner * is a symlink, separate device node, or bind-mount. 1604e15f760SChristian Brauner * A supported scenario is bind-mounting /dev/pts/ptmx to /dev/ptmx and 1614e15f760SChristian Brauner * then calling open on /dev/ptmx. In this case a suitable pts 1624e15f760SChristian Brauner * subdirectory can be found in the common parent directory /dev of the 1634e15f760SChristian Brauner * devpts mount and the ptmx bind-mount, after resolving the /dev/ptmx 1644e15f760SChristian Brauner * bind-mount. 1654e15f760SChristian Brauner * If no suitable pts subdirectory can be found this function will fail. 1664e15f760SChristian Brauner * This is e.g. the case when bind-mounting /dev/pts/ptmx to /ptmx. 1674e15f760SChristian Brauner */ 168311fc65cSEric W. Biederman struct vfsmount *devpts_mntget(struct file *filp, struct pts_fs_info *fsi) 169311fc65cSEric W. Biederman { 170311fc65cSEric W. Biederman struct path path; 1717d71109dSChristian Brauner int err = 0; 172311fc65cSEric W. Biederman 173311fc65cSEric W. Biederman path = filp->f_path; 174311fc65cSEric W. Biederman path_get(&path); 175311fc65cSEric W. Biederman 176a319b01dSChristian Brauner /* Walk upward while the start point is a bind mount of 177a319b01dSChristian Brauner * a single file. 178a319b01dSChristian Brauner */ 179a319b01dSChristian Brauner while (path.mnt->mnt_root == path.dentry) 180a319b01dSChristian Brauner if (follow_up(&path) == 0) 181a319b01dSChristian Brauner break; 182a319b01dSChristian Brauner 183a319b01dSChristian Brauner /* devpts_ptmx_path() finds a devpts fs or returns an error. */ 184a319b01dSChristian Brauner if ((path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) || 185a319b01dSChristian Brauner (DEVPTS_SB(path.mnt->mnt_sb) != fsi)) 186311fc65cSEric W. Biederman err = devpts_ptmx_path(&path); 187311fc65cSEric W. Biederman dput(path.dentry); 188a319b01dSChristian Brauner if (!err) { 189a319b01dSChristian Brauner if (DEVPTS_SB(path.mnt->mnt_sb) == fsi) 190a319b01dSChristian Brauner return path.mnt; 191a319b01dSChristian Brauner 192a319b01dSChristian Brauner err = -ENODEV; 193a319b01dSChristian Brauner } 194a319b01dSChristian Brauner 195311fc65cSEric W. Biederman mntput(path.mnt); 196c9cc8d01SEric Biggers return ERR_PTR(err); 197311fc65cSEric W. Biederman } 1987d71109dSChristian Brauner 199143c97ccSLinus Torvalds struct pts_fs_info *devpts_acquire(struct file *filp) 20059e55e6cSSukadev Bhattiprolu { 201eedf265aSEric W. Biederman struct pts_fs_info *result; 202eedf265aSEric W. Biederman struct path path; 203eedf265aSEric W. Biederman struct super_block *sb; 204eedf265aSEric W. Biederman 205eedf265aSEric W. Biederman path = filp->f_path; 206eedf265aSEric W. Biederman path_get(&path); 207eedf265aSEric W. Biederman 2087d71109dSChristian Brauner /* Has the devpts filesystem already been found? */ 2097d71109dSChristian Brauner if (path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) { 2107d71109dSChristian Brauner int err; 2117d71109dSChristian Brauner 212311fc65cSEric W. Biederman err = devpts_ptmx_path(&path); 213eedf265aSEric W. Biederman if (err) { 214eedf265aSEric W. Biederman result = ERR_PTR(err); 215eedf265aSEric W. Biederman goto out; 216eedf265aSEric W. Biederman } 2177d71109dSChristian Brauner } 218eedf265aSEric W. Biederman 219eedf265aSEric W. Biederman /* 220eedf265aSEric W. Biederman * pty code needs to hold extra references in case of last /dev/tty close 221eedf265aSEric W. Biederman */ 222311fc65cSEric W. Biederman sb = path.mnt->mnt_sb; 223eedf265aSEric W. Biederman atomic_inc(&sb->s_active); 224eedf265aSEric W. Biederman result = DEVPTS_SB(sb); 225eedf265aSEric W. Biederman 226eedf265aSEric W. Biederman out: 227eedf265aSEric W. Biederman path_put(&path); 228eedf265aSEric W. Biederman return result; 229eedf265aSEric W. Biederman } 230eedf265aSEric W. Biederman 231eedf265aSEric W. Biederman void devpts_release(struct pts_fs_info *fsi) 232eedf265aSEric W. Biederman { 233eedf265aSEric W. Biederman deactivate_super(fsi->sb); 23459e55e6cSSukadev Bhattiprolu } 23559e55e6cSSukadev Bhattiprolu 2362a1b2dc0SSukadev Bhattiprolu #define PARSE_MOUNT 0 2372a1b2dc0SSukadev Bhattiprolu #define PARSE_REMOUNT 1 2382a1b2dc0SSukadev Bhattiprolu 2391f71ebedSSukadev Bhattiprolu /* 2401f71ebedSSukadev Bhattiprolu * parse_mount_options(): 2411f71ebedSSukadev Bhattiprolu * Set @opts to mount options specified in @data. If an option is not 242eedf265aSEric W. Biederman * specified in @data, set it to its default value. 2431f71ebedSSukadev Bhattiprolu * 2441f71ebedSSukadev Bhattiprolu * Note: @data may be NULL (in which case all options are set to default). 2451f71ebedSSukadev Bhattiprolu */ 2462a1b2dc0SSukadev Bhattiprolu static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts) 2471da177e4SLinus Torvalds { 2487a673c6bSDomen Puncer char *p; 249f04c6ce2SEric W. Biederman kuid_t uid; 250f04c6ce2SEric W. Biederman kgid_t gid; 2511da177e4SLinus Torvalds 25231af0abbSSukadev Bhattiprolu opts->setuid = 0; 25331af0abbSSukadev Bhattiprolu opts->setgid = 0; 254f04c6ce2SEric W. Biederman opts->uid = GLOBAL_ROOT_UID; 255f04c6ce2SEric W. Biederman opts->gid = GLOBAL_ROOT_GID; 25631af0abbSSukadev Bhattiprolu opts->mode = DEVPTS_DEFAULT_MODE; 2571f8f1e29SSukadev Bhattiprolu opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; 258e9aba515SKonstantin Khlebnikov opts->max = NR_UNIX98_PTY_MAX; 2597a673c6bSDomen Puncer 260eedf265aSEric W. Biederman /* Only allow instances mounted from the initial mount 261eedf265aSEric W. Biederman * namespace to tap the reserve pool of ptys. 262eedf265aSEric W. Biederman */ 2632a1b2dc0SSukadev Bhattiprolu if (op == PARSE_MOUNT) 264eedf265aSEric W. Biederman opts->reserve = 265eedf265aSEric W. Biederman (current->nsproxy->mnt_ns == init_task.nsproxy->mnt_ns); 2662a1b2dc0SSukadev Bhattiprolu 2677a673c6bSDomen Puncer while ((p = strsep(&data, ",")) != NULL) { 2687a673c6bSDomen Puncer substring_t args[MAX_OPT_ARGS]; 2697a673c6bSDomen Puncer int token; 2707a673c6bSDomen Puncer int option; 2717a673c6bSDomen Puncer 2727a673c6bSDomen Puncer if (!*p) 2731da177e4SLinus Torvalds continue; 2747a673c6bSDomen Puncer 2757a673c6bSDomen Puncer token = match_token(p, tokens, args); 2767a673c6bSDomen Puncer switch (token) { 2777a673c6bSDomen Puncer case Opt_uid: 2787a673c6bSDomen Puncer if (match_int(&args[0], &option)) 2797a673c6bSDomen Puncer return -EINVAL; 280f04c6ce2SEric W. Biederman uid = make_kuid(current_user_ns(), option); 281f04c6ce2SEric W. Biederman if (!uid_valid(uid)) 282f04c6ce2SEric W. Biederman return -EINVAL; 283f04c6ce2SEric W. Biederman opts->uid = uid; 28431af0abbSSukadev Bhattiprolu opts->setuid = 1; 2857a673c6bSDomen Puncer break; 2867a673c6bSDomen Puncer case Opt_gid: 2877a673c6bSDomen Puncer if (match_int(&args[0], &option)) 2887a673c6bSDomen Puncer return -EINVAL; 289f04c6ce2SEric W. Biederman gid = make_kgid(current_user_ns(), option); 290f04c6ce2SEric W. Biederman if (!gid_valid(gid)) 291f04c6ce2SEric W. Biederman return -EINVAL; 292f04c6ce2SEric W. Biederman opts->gid = gid; 29331af0abbSSukadev Bhattiprolu opts->setgid = 1; 2947a673c6bSDomen Puncer break; 2957a673c6bSDomen Puncer case Opt_mode: 2967a673c6bSDomen Puncer if (match_octal(&args[0], &option)) 2977a673c6bSDomen Puncer return -EINVAL; 29831af0abbSSukadev Bhattiprolu opts->mode = option & S_IALLUGO; 2997a673c6bSDomen Puncer break; 3001f8f1e29SSukadev Bhattiprolu case Opt_ptmxmode: 3011f8f1e29SSukadev Bhattiprolu if (match_octal(&args[0], &option)) 3021f8f1e29SSukadev Bhattiprolu return -EINVAL; 3031f8f1e29SSukadev Bhattiprolu opts->ptmxmode = option & S_IALLUGO; 3041f8f1e29SSukadev Bhattiprolu break; 3052a1b2dc0SSukadev Bhattiprolu case Opt_newinstance: 3062a1b2dc0SSukadev Bhattiprolu break; 307e9aba515SKonstantin Khlebnikov case Opt_max: 308e9aba515SKonstantin Khlebnikov if (match_int(&args[0], &option) || 309e9aba515SKonstantin Khlebnikov option < 0 || option > NR_UNIX98_PTY_MAX) 310e9aba515SKonstantin Khlebnikov return -EINVAL; 311e9aba515SKonstantin Khlebnikov opts->max = option; 312e9aba515SKonstantin Khlebnikov break; 3137a673c6bSDomen Puncer default: 31404541a2fSFabian Frederick pr_err("called with bogus options\n"); 3151da177e4SLinus Torvalds return -EINVAL; 3161da177e4SLinus Torvalds } 3171da177e4SLinus Torvalds } 3181da177e4SLinus Torvalds 3191da177e4SLinus Torvalds return 0; 3201da177e4SLinus Torvalds } 3211da177e4SLinus Torvalds 3221f8f1e29SSukadev Bhattiprolu static int mknod_ptmx(struct super_block *sb) 32353af8ee4SSukadev Bhattiprolu { 3241f8f1e29SSukadev Bhattiprolu int mode; 3251f8f1e29SSukadev Bhattiprolu int rc = -ENOMEM; 3261f8f1e29SSukadev Bhattiprolu struct dentry *dentry; 3271f8f1e29SSukadev Bhattiprolu struct inode *inode; 3281f8f1e29SSukadev Bhattiprolu struct dentry *root = sb->s_root; 32953af8ee4SSukadev Bhattiprolu struct pts_fs_info *fsi = DEVPTS_SB(sb); 33053af8ee4SSukadev Bhattiprolu struct pts_mount_opts *opts = &fsi->mount_opts; 331e98d4137SEric W. Biederman kuid_t ptmx_uid = current_fsuid(); 332e98d4137SEric W. Biederman kgid_t ptmx_gid = current_fsgid(); 33353af8ee4SSukadev Bhattiprolu 3345955102cSAl Viro inode_lock(d_inode(root)); 3351f8f1e29SSukadev Bhattiprolu 3361f8f1e29SSukadev Bhattiprolu /* If we have already created ptmx node, return */ 3371f8f1e29SSukadev Bhattiprolu if (fsi->ptmx_dentry) { 3381f8f1e29SSukadev Bhattiprolu rc = 0; 3391f8f1e29SSukadev Bhattiprolu goto out; 3401f8f1e29SSukadev Bhattiprolu } 3411f8f1e29SSukadev Bhattiprolu 3421f8f1e29SSukadev Bhattiprolu dentry = d_alloc_name(root, "ptmx"); 3431f8f1e29SSukadev Bhattiprolu if (!dentry) { 34404541a2fSFabian Frederick pr_err("Unable to alloc dentry for ptmx node\n"); 3451f8f1e29SSukadev Bhattiprolu goto out; 3461f8f1e29SSukadev Bhattiprolu } 3471f8f1e29SSukadev Bhattiprolu 3481f8f1e29SSukadev Bhattiprolu /* 3491f8f1e29SSukadev Bhattiprolu * Create a new 'ptmx' node in this mount of devpts. 3501f8f1e29SSukadev Bhattiprolu */ 3511f8f1e29SSukadev Bhattiprolu inode = new_inode(sb); 3521f8f1e29SSukadev Bhattiprolu if (!inode) { 35304541a2fSFabian Frederick pr_err("Unable to alloc inode for ptmx node\n"); 3541f8f1e29SSukadev Bhattiprolu dput(dentry); 3551f8f1e29SSukadev Bhattiprolu goto out; 3561f8f1e29SSukadev Bhattiprolu } 3571f8f1e29SSukadev Bhattiprolu 3581f8f1e29SSukadev Bhattiprolu inode->i_ino = 2; 359078cd827SDeepa Dinamani inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); 3601f8f1e29SSukadev Bhattiprolu 3611f8f1e29SSukadev Bhattiprolu mode = S_IFCHR|opts->ptmxmode; 3621f8f1e29SSukadev Bhattiprolu init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2)); 363e98d4137SEric W. Biederman inode->i_uid = ptmx_uid; 364e98d4137SEric W. Biederman inode->i_gid = ptmx_gid; 3651f8f1e29SSukadev Bhattiprolu 3661f8f1e29SSukadev Bhattiprolu d_add(dentry, inode); 3671f8f1e29SSukadev Bhattiprolu 3681f8f1e29SSukadev Bhattiprolu fsi->ptmx_dentry = dentry; 3691f8f1e29SSukadev Bhattiprolu rc = 0; 3701f8f1e29SSukadev Bhattiprolu out: 3715955102cSAl Viro inode_unlock(d_inode(root)); 3721f8f1e29SSukadev Bhattiprolu return rc; 3731f8f1e29SSukadev Bhattiprolu } 3741f8f1e29SSukadev Bhattiprolu 3751f8f1e29SSukadev Bhattiprolu static void update_ptmx_mode(struct pts_fs_info *fsi) 3761f8f1e29SSukadev Bhattiprolu { 3771f8f1e29SSukadev Bhattiprolu struct inode *inode; 3781f8f1e29SSukadev Bhattiprolu if (fsi->ptmx_dentry) { 3792b0143b5SDavid Howells inode = d_inode(fsi->ptmx_dentry); 3801f8f1e29SSukadev Bhattiprolu inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode; 3811f8f1e29SSukadev Bhattiprolu } 3821f8f1e29SSukadev Bhattiprolu } 3831f8f1e29SSukadev Bhattiprolu 3841f8f1e29SSukadev Bhattiprolu static int devpts_remount(struct super_block *sb, int *flags, char *data) 3851f8f1e29SSukadev Bhattiprolu { 3861f8f1e29SSukadev Bhattiprolu int err; 3871f8f1e29SSukadev Bhattiprolu struct pts_fs_info *fsi = DEVPTS_SB(sb); 3881f8f1e29SSukadev Bhattiprolu struct pts_mount_opts *opts = &fsi->mount_opts; 3891f8f1e29SSukadev Bhattiprolu 3902a1b2dc0SSukadev Bhattiprolu err = parse_mount_options(data, PARSE_REMOUNT, opts); 3911f8f1e29SSukadev Bhattiprolu 3921f8f1e29SSukadev Bhattiprolu /* 3931f8f1e29SSukadev Bhattiprolu * parse_mount_options() restores options to default values 3941f8f1e29SSukadev Bhattiprolu * before parsing and may have changed ptmxmode. So, update the 3951f8f1e29SSukadev Bhattiprolu * mode in the inode too. Bogus options don't fail the remount, 3961f8f1e29SSukadev Bhattiprolu * so do this even on error return. 3971f8f1e29SSukadev Bhattiprolu */ 3981f8f1e29SSukadev Bhattiprolu update_ptmx_mode(fsi); 3991f8f1e29SSukadev Bhattiprolu 4001f8f1e29SSukadev Bhattiprolu return err; 40153af8ee4SSukadev Bhattiprolu } 40253af8ee4SSukadev Bhattiprolu 40334c80b1dSAl Viro static int devpts_show_options(struct seq_file *seq, struct dentry *root) 404b87a267eSMiklos Szeredi { 40534c80b1dSAl Viro struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb); 40631af0abbSSukadev Bhattiprolu struct pts_mount_opts *opts = &fsi->mount_opts; 40731af0abbSSukadev Bhattiprolu 40831af0abbSSukadev Bhattiprolu if (opts->setuid) 40904541a2fSFabian Frederick seq_printf(seq, ",uid=%u", 41004541a2fSFabian Frederick from_kuid_munged(&init_user_ns, opts->uid)); 41131af0abbSSukadev Bhattiprolu if (opts->setgid) 41204541a2fSFabian Frederick seq_printf(seq, ",gid=%u", 41304541a2fSFabian Frederick from_kgid_munged(&init_user_ns, opts->gid)); 41431af0abbSSukadev Bhattiprolu seq_printf(seq, ",mode=%03o", opts->mode); 4151f8f1e29SSukadev Bhattiprolu seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode); 416e9aba515SKonstantin Khlebnikov if (opts->max < NR_UNIX98_PTY_MAX) 417e9aba515SKonstantin Khlebnikov seq_printf(seq, ",max=%d", opts->max); 418b87a267eSMiklos Szeredi 419b87a267eSMiklos Szeredi return 0; 420b87a267eSMiklos Szeredi } 421b87a267eSMiklos Szeredi 422ee9b6d61SJosef 'Jeff' Sipek static const struct super_operations devpts_sops = { 4231da177e4SLinus Torvalds .statfs = simple_statfs, 4241da177e4SLinus Torvalds .remount_fs = devpts_remount, 425b87a267eSMiklos Szeredi .show_options = devpts_show_options, 4261da177e4SLinus Torvalds }; 4271da177e4SLinus Torvalds 42867245ff3SLinus Torvalds static void *new_pts_fs_info(struct super_block *sb) 429e76b7c01SSukadev Bhattiprolu { 430e76b7c01SSukadev Bhattiprolu struct pts_fs_info *fsi; 431e76b7c01SSukadev Bhattiprolu 432e76b7c01SSukadev Bhattiprolu fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL); 433e76b7c01SSukadev Bhattiprolu if (!fsi) 434e76b7c01SSukadev Bhattiprolu return NULL; 435e76b7c01SSukadev Bhattiprolu 436e76b7c01SSukadev Bhattiprolu ida_init(&fsi->allocated_ptys); 43731af0abbSSukadev Bhattiprolu fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE; 4381f8f1e29SSukadev Bhattiprolu fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; 43967245ff3SLinus Torvalds fsi->sb = sb; 440e76b7c01SSukadev Bhattiprolu 441e76b7c01SSukadev Bhattiprolu return fsi; 442e76b7c01SSukadev Bhattiprolu } 443e76b7c01SSukadev Bhattiprolu 4441da177e4SLinus Torvalds static int 4451da177e4SLinus Torvalds devpts_fill_super(struct super_block *s, void *data, int silent) 4461da177e4SLinus Torvalds { 4471da177e4SLinus Torvalds struct inode *inode; 448dee87d47SEric W. Biederman int error; 4491da177e4SLinus Torvalds 450cc50a07aSEric W. Biederman s->s_iflags &= ~SB_I_NODEV; 4511da177e4SLinus Torvalds s->s_blocksize = 1024; 4521da177e4SLinus Torvalds s->s_blocksize_bits = 10; 4531da177e4SLinus Torvalds s->s_magic = DEVPTS_SUPER_MAGIC; 4541da177e4SLinus Torvalds s->s_op = &devpts_sops; 45573052b0dSVarad Gautam s->s_d_op = &simple_dentry_operations; 4561da177e4SLinus Torvalds s->s_time_gran = 1; 4571da177e4SLinus Torvalds 458dee87d47SEric W. Biederman error = -ENOMEM; 45967245ff3SLinus Torvalds s->s_fs_info = new_pts_fs_info(s); 460e76b7c01SSukadev Bhattiprolu if (!s->s_fs_info) 461e76b7c01SSukadev Bhattiprolu goto fail; 462e76b7c01SSukadev Bhattiprolu 463dee87d47SEric W. Biederman error = parse_mount_options(data, PARSE_MOUNT, &DEVPTS_SB(s)->mount_opts); 464dee87d47SEric W. Biederman if (error) 465dee87d47SEric W. Biederman goto fail; 466dee87d47SEric W. Biederman 467dee87d47SEric W. Biederman error = -ENOMEM; 4681da177e4SLinus Torvalds inode = new_inode(s); 4691da177e4SLinus Torvalds if (!inode) 4703850aba7SAl Viro goto fail; 4711da177e4SLinus Torvalds inode->i_ino = 1; 472078cd827SDeepa Dinamani inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); 4731da177e4SLinus Torvalds inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR; 4741da177e4SLinus Torvalds inode->i_op = &simple_dir_inode_operations; 4751da177e4SLinus Torvalds inode->i_fop = &simple_dir_operations; 476bfe86848SMiklos Szeredi set_nlink(inode, 2); 4771da177e4SLinus Torvalds 47848fde701SAl Viro s->s_root = d_make_root(inode); 479180d9044SEric W. Biederman if (!s->s_root) { 48004541a2fSFabian Frederick pr_err("get root dentry failed\n"); 481180d9044SEric W. Biederman goto fail; 482180d9044SEric W. Biederman } 483e76b7c01SSukadev Bhattiprolu 484180d9044SEric W. Biederman error = mknod_ptmx(s); 485180d9044SEric W. Biederman if (error) 486180d9044SEric W. Biederman goto fail_dput; 487180d9044SEric W. Biederman 488180d9044SEric W. Biederman return 0; 489180d9044SEric W. Biederman fail_dput: 490180d9044SEric W. Biederman dput(s->s_root); 491180d9044SEric W. Biederman s->s_root = NULL; 4921da177e4SLinus Torvalds fail: 493dee87d47SEric W. Biederman return error; 4941da177e4SLinus Torvalds } 4951da177e4SLinus Torvalds 4962a1b2dc0SSukadev Bhattiprolu /* 497fc14f2feSAl Viro * devpts_mount() 498289f00e2SSukadev Bhattiprolu * 499eedf265aSEric W. Biederman * Mount a new (private) instance of devpts. PTYs created in this 500eedf265aSEric W. Biederman * instance are independent of the PTYs in other devpts instances. 501d4076ac5SSukadev Bhattiprolu */ 502fc14f2feSAl Viro static struct dentry *devpts_mount(struct file_system_type *fs_type, 503fc14f2feSAl Viro int flags, const char *dev_name, void *data) 5041da177e4SLinus Torvalds { 505c1b241f0SEric W. Biederman return mount_nodev(fs_type, flags, data, devpts_fill_super); 506482984f0SSukadev Bhattiprolu } 507482984f0SSukadev Bhattiprolu 508e76b7c01SSukadev Bhattiprolu static void devpts_kill_sb(struct super_block *sb) 509e76b7c01SSukadev Bhattiprolu { 510e76b7c01SSukadev Bhattiprolu struct pts_fs_info *fsi = DEVPTS_SB(sb); 511e76b7c01SSukadev Bhattiprolu 51240b320e1SEric W. Biederman if (fsi) 51366da0e1fSIlija Hadzic ida_destroy(&fsi->allocated_ptys); 514e76b7c01SSukadev Bhattiprolu kfree(fsi); 5151f8f1e29SSukadev Bhattiprolu kill_litter_super(sb); 516e76b7c01SSukadev Bhattiprolu } 517e76b7c01SSukadev Bhattiprolu 5181da177e4SLinus Torvalds static struct file_system_type devpts_fs_type = { 5191da177e4SLinus Torvalds .name = "devpts", 520fc14f2feSAl Viro .mount = devpts_mount, 521e76b7c01SSukadev Bhattiprolu .kill_sb = devpts_kill_sb, 522cc50a07aSEric W. Biederman .fs_flags = FS_USERNS_MOUNT, 5231da177e4SLinus Torvalds }; 5241da177e4SLinus Torvalds 5251da177e4SLinus Torvalds /* 5261da177e4SLinus Torvalds * The normal naming convention is simply /dev/pts/<number>; this conforms 5271da177e4SLinus Torvalds * to the System V naming convention 5281da177e4SLinus Torvalds */ 5291da177e4SLinus Torvalds 53067245ff3SLinus Torvalds int devpts_new_index(struct pts_fs_info *fsi) 531718a9163SSukadev Bhattiprolu { 5320f0a0e54SMatthew Wilcox int index = -ENOSPC; 533718a9163SSukadev Bhattiprolu 5340f0a0e54SMatthew Wilcox if (atomic_inc_return(&pty_count) >= (pty_limit - 5350f0a0e54SMatthew Wilcox (fsi->mount_opts.reserve ? 0 : pty_reserve))) 5360f0a0e54SMatthew Wilcox goto out; 537718a9163SSukadev Bhattiprolu 5380f0a0e54SMatthew Wilcox index = ida_alloc_max(&fsi->allocated_ptys, fsi->mount_opts.max - 1, 5390f0a0e54SMatthew Wilcox GFP_KERNEL); 540e9aba515SKonstantin Khlebnikov 5410f0a0e54SMatthew Wilcox out: 5420f0a0e54SMatthew Wilcox if (index < 0) 5430f0a0e54SMatthew Wilcox atomic_dec(&pty_count); 544718a9163SSukadev Bhattiprolu return index; 545718a9163SSukadev Bhattiprolu } 546718a9163SSukadev Bhattiprolu 54767245ff3SLinus Torvalds void devpts_kill_index(struct pts_fs_info *fsi, int idx) 548718a9163SSukadev Bhattiprolu { 5490f0a0e54SMatthew Wilcox ida_free(&fsi->allocated_ptys, idx); 5500f0a0e54SMatthew Wilcox atomic_dec(&pty_count); 551718a9163SSukadev Bhattiprolu } 552718a9163SSukadev Bhattiprolu 5531dcb8e6dSJiri Slaby /** 5541dcb8e6dSJiri Slaby * devpts_pty_new -- create a new inode in /dev/pts/ 5551dcb8e6dSJiri Slaby * @ptmx_inode: inode of the master 5561dcb8e6dSJiri Slaby * @device: major+minor of the node to be created 5571dcb8e6dSJiri Slaby * @index: used as a name of the node 5581dcb8e6dSJiri Slaby * @priv: what's given back by devpts_get_priv 5591dcb8e6dSJiri Slaby * 5601dcb8e6dSJiri Slaby * The created inode is returned. Remove it from /dev/pts/ by devpts_pty_kill. 5611dcb8e6dSJiri Slaby */ 5628ead9dd5SLinus Torvalds struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv) 5631da177e4SLinus Torvalds { 5641da177e4SLinus Torvalds struct dentry *dentry; 565eedf265aSEric W. Biederman struct super_block *sb = fsi->sb; 566162b97cfSJiri Slaby struct inode *inode; 5679ce71148SJosh Triplett struct dentry *root; 5689ce71148SJosh Triplett struct pts_mount_opts *opts; 56989a52e10SSukadev Bhattiprolu char s[12]; 5701da177e4SLinus Torvalds 5719ce71148SJosh Triplett root = sb->s_root; 5729ce71148SJosh Triplett opts = &fsi->mount_opts; 5739ce71148SJosh Triplett 574162b97cfSJiri Slaby inode = new_inode(sb); 5751da177e4SLinus Torvalds if (!inode) 576162b97cfSJiri Slaby return ERR_PTR(-ENOMEM); 5771da177e4SLinus Torvalds 578f11afb61SJiri Slaby inode->i_ino = index + 3; 579d0eafc7dSDavid Howells inode->i_uid = opts->setuid ? opts->uid : current_fsuid(); 580d0eafc7dSDavid Howells inode->i_gid = opts->setgid ? opts->gid : current_fsgid(); 581078cd827SDeepa Dinamani inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); 5828ead9dd5SLinus Torvalds init_special_inode(inode, S_IFCHR|opts->mode, MKDEV(UNIX98_PTY_SLAVE_MAJOR, index)); 5831da177e4SLinus Torvalds 584f11afb61SJiri Slaby sprintf(s, "%d", index); 58589a52e10SSukadev Bhattiprolu 58659e55e6cSSukadev Bhattiprolu dentry = d_alloc_name(root, s); 587b12d1259SAndrey Vagin if (dentry) { 5888ead9dd5SLinus Torvalds dentry->d_fsdata = priv; 58989a52e10SSukadev Bhattiprolu d_add(dentry, inode); 5902b0143b5SDavid Howells fsnotify_create(d_inode(root), dentry); 591aa597bc1SAndrey Vagin } else { 592aa597bc1SAndrey Vagin iput(inode); 5938ead9dd5SLinus Torvalds dentry = ERR_PTR(-ENOMEM); 5943972b7f6SFlorin Malita } 5951da177e4SLinus Torvalds 5968ead9dd5SLinus Torvalds return dentry; 5971da177e4SLinus Torvalds } 5981da177e4SLinus Torvalds 5991dcb8e6dSJiri Slaby /** 6001dcb8e6dSJiri Slaby * devpts_get_priv -- get private data for a slave 6011dcb8e6dSJiri Slaby * @pts_inode: inode of the slave 6021dcb8e6dSJiri Slaby * 6031dcb8e6dSJiri Slaby * Returns whatever was passed as priv in devpts_pty_new for a given inode. 6041dcb8e6dSJiri Slaby */ 6058ead9dd5SLinus Torvalds void *devpts_get_priv(struct dentry *dentry) 6061da177e4SLinus Torvalds { 6073e423945SLinus Torvalds if (dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC) 6083e423945SLinus Torvalds return NULL; 6098ead9dd5SLinus Torvalds return dentry->d_fsdata; 6101da177e4SLinus Torvalds } 6111da177e4SLinus Torvalds 6121dcb8e6dSJiri Slaby /** 6131dcb8e6dSJiri Slaby * devpts_pty_kill -- remove inode form /dev/pts/ 6141dcb8e6dSJiri Slaby * @inode: inode of the slave to be removed 6151dcb8e6dSJiri Slaby * 6161dcb8e6dSJiri Slaby * This is an inverse operation of devpts_pty_new. 6171dcb8e6dSJiri Slaby */ 6188ead9dd5SLinus Torvalds void devpts_pty_kill(struct dentry *dentry) 6191da177e4SLinus Torvalds { 6208ead9dd5SLinus Torvalds WARN_ON_ONCE(dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC); 6211da177e4SLinus Torvalds 6228ead9dd5SLinus Torvalds dentry->d_fsdata = NULL; 6238ead9dd5SLinus Torvalds drop_nlink(dentry->d_inode); 624fd0d506fSAmir Goldstein fsnotify_unlink(d_inode(dentry->d_parent), dentry); 62546c46f8dSAl Viro d_drop(dentry); 626835aa440SAlan Cox dput(dentry); /* d_alloc_name() in devpts_pty_new() */ 6271da177e4SLinus Torvalds } 6281da177e4SLinus Torvalds 6291da177e4SLinus Torvalds static int __init init_devpts_fs(void) 6301da177e4SLinus Torvalds { 6311da177e4SLinus Torvalds int err = register_filesystem(&devpts_fs_type); 6321da177e4SLinus Torvalds if (!err) { 633eedf265aSEric W. Biederman register_sysctl_table(pty_root_table); 6341da177e4SLinus Torvalds } 6351da177e4SLinus Torvalds return err; 6361da177e4SLinus Torvalds } 6371da177e4SLinus Torvalds module_init(init_devpts_fs) 638