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 7531af0abbSSukadev Bhattiprolu struct pts_mount_opts { 761da177e4SLinus Torvalds int setuid; 771da177e4SLinus Torvalds int setgid; 78f04c6ce2SEric W. Biederman kuid_t uid; 79f04c6ce2SEric W. Biederman kgid_t gid; 801da177e4SLinus Torvalds umode_t mode; 811f8f1e29SSukadev Bhattiprolu umode_t ptmxmode; 82eedf265aSEric W. Biederman int reserve; 83e9aba515SKonstantin Khlebnikov int max; 8431af0abbSSukadev Bhattiprolu }; 851da177e4SLinus Torvalds 867a673c6bSDomen Puncer enum { 87e9aba515SKonstantin Khlebnikov Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, Opt_max, 887a673c6bSDomen Puncer Opt_err 897a673c6bSDomen Puncer }; 907a673c6bSDomen Puncer 91a447c093SSteven Whitehouse static const match_table_t tokens = { 927a673c6bSDomen Puncer {Opt_uid, "uid=%u"}, 937a673c6bSDomen Puncer {Opt_gid, "gid=%u"}, 947a673c6bSDomen Puncer {Opt_mode, "mode=%o"}, 951f8f1e29SSukadev Bhattiprolu {Opt_ptmxmode, "ptmxmode=%o"}, 962a1b2dc0SSukadev Bhattiprolu {Opt_newinstance, "newinstance"}, 97e9aba515SKonstantin Khlebnikov {Opt_max, "max=%d"}, 987a673c6bSDomen Puncer {Opt_err, NULL} 997a673c6bSDomen Puncer }; 1007a673c6bSDomen Puncer 101e76b7c01SSukadev Bhattiprolu struct pts_fs_info { 102e76b7c01SSukadev Bhattiprolu struct ida allocated_ptys; 10331af0abbSSukadev Bhattiprolu struct pts_mount_opts mount_opts; 10467245ff3SLinus Torvalds struct super_block *sb; 1051f8f1e29SSukadev Bhattiprolu struct dentry *ptmx_dentry; 106e76b7c01SSukadev Bhattiprolu }; 107e76b7c01SSukadev Bhattiprolu 108e76b7c01SSukadev Bhattiprolu static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb) 109e76b7c01SSukadev Bhattiprolu { 110e76b7c01SSukadev Bhattiprolu return sb->s_fs_info; 111e76b7c01SSukadev Bhattiprolu } 112e76b7c01SSukadev Bhattiprolu 113311fc65cSEric W. Biederman static int devpts_ptmx_path(struct path *path) 114311fc65cSEric W. Biederman { 115311fc65cSEric W. Biederman struct super_block *sb; 116311fc65cSEric W. Biederman int err; 117311fc65cSEric W. Biederman 118311fc65cSEric W. Biederman /* Is a devpts filesystem at "pts" in the same directory? */ 119311fc65cSEric W. Biederman err = path_pts(path); 120311fc65cSEric W. Biederman if (err) 121311fc65cSEric W. Biederman return err; 122311fc65cSEric W. Biederman 123311fc65cSEric W. Biederman /* Is the path the root of a devpts filesystem? */ 124311fc65cSEric W. Biederman sb = path->mnt->mnt_sb; 125311fc65cSEric W. Biederman if ((sb->s_magic != DEVPTS_SUPER_MAGIC) || 126311fc65cSEric W. Biederman (path->mnt->mnt_root != sb->s_root)) 127311fc65cSEric W. Biederman return -ENODEV; 128311fc65cSEric W. Biederman 129311fc65cSEric W. Biederman return 0; 130311fc65cSEric W. Biederman } 131311fc65cSEric W. Biederman 1324e15f760SChristian Brauner /* 1334e15f760SChristian Brauner * Try to find a suitable devpts filesystem. We support the following 1344e15f760SChristian Brauner * scenarios: 1354e15f760SChristian Brauner * - The ptmx device node is located in the same directory as the devpts 1364e15f760SChristian Brauner * mount where the pts device nodes are located. 1374e15f760SChristian Brauner * This is e.g. the case when calling open on the /dev/pts/ptmx device 1384e15f760SChristian Brauner * node when the devpts filesystem is mounted at /dev/pts. 1394e15f760SChristian Brauner * - The ptmx device node is located outside the devpts filesystem mount 1404e15f760SChristian Brauner * where the pts device nodes are located. For example, the ptmx device 1414e15f760SChristian Brauner * is a symlink, separate device node, or bind-mount. 1424e15f760SChristian Brauner * A supported scenario is bind-mounting /dev/pts/ptmx to /dev/ptmx and 1434e15f760SChristian Brauner * then calling open on /dev/ptmx. In this case a suitable pts 1444e15f760SChristian Brauner * subdirectory can be found in the common parent directory /dev of the 1454e15f760SChristian Brauner * devpts mount and the ptmx bind-mount, after resolving the /dev/ptmx 1464e15f760SChristian Brauner * bind-mount. 1474e15f760SChristian Brauner * If no suitable pts subdirectory can be found this function will fail. 1484e15f760SChristian Brauner * This is e.g. the case when bind-mounting /dev/pts/ptmx to /ptmx. 1494e15f760SChristian Brauner */ 150311fc65cSEric W. Biederman struct vfsmount *devpts_mntget(struct file *filp, struct pts_fs_info *fsi) 151311fc65cSEric W. Biederman { 152311fc65cSEric W. Biederman struct path path; 1537d71109dSChristian Brauner int err = 0; 154311fc65cSEric W. Biederman 155311fc65cSEric W. Biederman path = filp->f_path; 156311fc65cSEric W. Biederman path_get(&path); 157311fc65cSEric W. Biederman 158a319b01dSChristian Brauner /* Walk upward while the start point is a bind mount of 159a319b01dSChristian Brauner * a single file. 160a319b01dSChristian Brauner */ 161a319b01dSChristian Brauner while (path.mnt->mnt_root == path.dentry) 162a319b01dSChristian Brauner if (follow_up(&path) == 0) 163a319b01dSChristian Brauner break; 164a319b01dSChristian Brauner 165a319b01dSChristian Brauner /* devpts_ptmx_path() finds a devpts fs or returns an error. */ 166a319b01dSChristian Brauner if ((path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) || 167a319b01dSChristian Brauner (DEVPTS_SB(path.mnt->mnt_sb) != fsi)) 168311fc65cSEric W. Biederman err = devpts_ptmx_path(&path); 169311fc65cSEric W. Biederman dput(path.dentry); 170a319b01dSChristian Brauner if (!err) { 171a319b01dSChristian Brauner if (DEVPTS_SB(path.mnt->mnt_sb) == fsi) 172a319b01dSChristian Brauner return path.mnt; 173a319b01dSChristian Brauner 174a319b01dSChristian Brauner err = -ENODEV; 175a319b01dSChristian Brauner } 176a319b01dSChristian Brauner 177311fc65cSEric W. Biederman mntput(path.mnt); 178c9cc8d01SEric Biggers return ERR_PTR(err); 179311fc65cSEric W. Biederman } 1807d71109dSChristian Brauner 181143c97ccSLinus Torvalds struct pts_fs_info *devpts_acquire(struct file *filp) 18259e55e6cSSukadev Bhattiprolu { 183eedf265aSEric W. Biederman struct pts_fs_info *result; 184eedf265aSEric W. Biederman struct path path; 185eedf265aSEric W. Biederman struct super_block *sb; 186eedf265aSEric W. Biederman 187eedf265aSEric W. Biederman path = filp->f_path; 188eedf265aSEric W. Biederman path_get(&path); 189eedf265aSEric W. Biederman 1907d71109dSChristian Brauner /* Has the devpts filesystem already been found? */ 1917d71109dSChristian Brauner if (path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) { 1927d71109dSChristian Brauner int err; 1937d71109dSChristian Brauner 194311fc65cSEric W. Biederman err = devpts_ptmx_path(&path); 195eedf265aSEric W. Biederman if (err) { 196eedf265aSEric W. Biederman result = ERR_PTR(err); 197eedf265aSEric W. Biederman goto out; 198eedf265aSEric W. Biederman } 1997d71109dSChristian Brauner } 200eedf265aSEric W. Biederman 201eedf265aSEric W. Biederman /* 202eedf265aSEric W. Biederman * pty code needs to hold extra references in case of last /dev/tty close 203eedf265aSEric W. Biederman */ 204311fc65cSEric W. Biederman sb = path.mnt->mnt_sb; 205eedf265aSEric W. Biederman atomic_inc(&sb->s_active); 206eedf265aSEric W. Biederman result = DEVPTS_SB(sb); 207eedf265aSEric W. Biederman 208eedf265aSEric W. Biederman out: 209eedf265aSEric W. Biederman path_put(&path); 210eedf265aSEric W. Biederman return result; 211eedf265aSEric W. Biederman } 212eedf265aSEric W. Biederman 213eedf265aSEric W. Biederman void devpts_release(struct pts_fs_info *fsi) 214eedf265aSEric W. Biederman { 215eedf265aSEric W. Biederman deactivate_super(fsi->sb); 21659e55e6cSSukadev Bhattiprolu } 21759e55e6cSSukadev Bhattiprolu 2182a1b2dc0SSukadev Bhattiprolu #define PARSE_MOUNT 0 2192a1b2dc0SSukadev Bhattiprolu #define PARSE_REMOUNT 1 2202a1b2dc0SSukadev Bhattiprolu 2211f71ebedSSukadev Bhattiprolu /* 2221f71ebedSSukadev Bhattiprolu * parse_mount_options(): 2231f71ebedSSukadev Bhattiprolu * Set @opts to mount options specified in @data. If an option is not 224eedf265aSEric W. Biederman * specified in @data, set it to its default value. 2251f71ebedSSukadev Bhattiprolu * 2261f71ebedSSukadev Bhattiprolu * Note: @data may be NULL (in which case all options are set to default). 2271f71ebedSSukadev Bhattiprolu */ 2282a1b2dc0SSukadev Bhattiprolu static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts) 2291da177e4SLinus Torvalds { 2307a673c6bSDomen Puncer char *p; 231f04c6ce2SEric W. Biederman kuid_t uid; 232f04c6ce2SEric W. Biederman kgid_t gid; 2331da177e4SLinus Torvalds 23431af0abbSSukadev Bhattiprolu opts->setuid = 0; 23531af0abbSSukadev Bhattiprolu opts->setgid = 0; 236f04c6ce2SEric W. Biederman opts->uid = GLOBAL_ROOT_UID; 237f04c6ce2SEric W. Biederman opts->gid = GLOBAL_ROOT_GID; 23831af0abbSSukadev Bhattiprolu opts->mode = DEVPTS_DEFAULT_MODE; 2391f8f1e29SSukadev Bhattiprolu opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; 240e9aba515SKonstantin Khlebnikov opts->max = NR_UNIX98_PTY_MAX; 2417a673c6bSDomen Puncer 242eedf265aSEric W. Biederman /* Only allow instances mounted from the initial mount 243eedf265aSEric W. Biederman * namespace to tap the reserve pool of ptys. 244eedf265aSEric W. Biederman */ 2452a1b2dc0SSukadev Bhattiprolu if (op == PARSE_MOUNT) 246eedf265aSEric W. Biederman opts->reserve = 247eedf265aSEric W. Biederman (current->nsproxy->mnt_ns == init_task.nsproxy->mnt_ns); 2482a1b2dc0SSukadev Bhattiprolu 2497a673c6bSDomen Puncer while ((p = strsep(&data, ",")) != NULL) { 2507a673c6bSDomen Puncer substring_t args[MAX_OPT_ARGS]; 2517a673c6bSDomen Puncer int token; 2527a673c6bSDomen Puncer int option; 2537a673c6bSDomen Puncer 2547a673c6bSDomen Puncer if (!*p) 2551da177e4SLinus Torvalds continue; 2567a673c6bSDomen Puncer 2577a673c6bSDomen Puncer token = match_token(p, tokens, args); 2587a673c6bSDomen Puncer switch (token) { 2597a673c6bSDomen Puncer case Opt_uid: 2607a673c6bSDomen Puncer if (match_int(&args[0], &option)) 2617a673c6bSDomen Puncer return -EINVAL; 262f04c6ce2SEric W. Biederman uid = make_kuid(current_user_ns(), option); 263f04c6ce2SEric W. Biederman if (!uid_valid(uid)) 264f04c6ce2SEric W. Biederman return -EINVAL; 265f04c6ce2SEric W. Biederman opts->uid = uid; 26631af0abbSSukadev Bhattiprolu opts->setuid = 1; 2677a673c6bSDomen Puncer break; 2687a673c6bSDomen Puncer case Opt_gid: 2697a673c6bSDomen Puncer if (match_int(&args[0], &option)) 2707a673c6bSDomen Puncer return -EINVAL; 271f04c6ce2SEric W. Biederman gid = make_kgid(current_user_ns(), option); 272f04c6ce2SEric W. Biederman if (!gid_valid(gid)) 273f04c6ce2SEric W. Biederman return -EINVAL; 274f04c6ce2SEric W. Biederman opts->gid = gid; 27531af0abbSSukadev Bhattiprolu opts->setgid = 1; 2767a673c6bSDomen Puncer break; 2777a673c6bSDomen Puncer case Opt_mode: 2787a673c6bSDomen Puncer if (match_octal(&args[0], &option)) 2797a673c6bSDomen Puncer return -EINVAL; 28031af0abbSSukadev Bhattiprolu opts->mode = option & S_IALLUGO; 2817a673c6bSDomen Puncer break; 2821f8f1e29SSukadev Bhattiprolu case Opt_ptmxmode: 2831f8f1e29SSukadev Bhattiprolu if (match_octal(&args[0], &option)) 2841f8f1e29SSukadev Bhattiprolu return -EINVAL; 2851f8f1e29SSukadev Bhattiprolu opts->ptmxmode = option & S_IALLUGO; 2861f8f1e29SSukadev Bhattiprolu break; 2872a1b2dc0SSukadev Bhattiprolu case Opt_newinstance: 2882a1b2dc0SSukadev Bhattiprolu break; 289e9aba515SKonstantin Khlebnikov case Opt_max: 290e9aba515SKonstantin Khlebnikov if (match_int(&args[0], &option) || 291e9aba515SKonstantin Khlebnikov option < 0 || option > NR_UNIX98_PTY_MAX) 292e9aba515SKonstantin Khlebnikov return -EINVAL; 293e9aba515SKonstantin Khlebnikov opts->max = option; 294e9aba515SKonstantin Khlebnikov break; 2957a673c6bSDomen Puncer default: 29604541a2fSFabian Frederick pr_err("called with bogus options\n"); 2971da177e4SLinus Torvalds return -EINVAL; 2981da177e4SLinus Torvalds } 2991da177e4SLinus Torvalds } 3001da177e4SLinus Torvalds 3011da177e4SLinus Torvalds return 0; 3021da177e4SLinus Torvalds } 3031da177e4SLinus Torvalds 3041f8f1e29SSukadev Bhattiprolu static int mknod_ptmx(struct super_block *sb) 30553af8ee4SSukadev Bhattiprolu { 3061f8f1e29SSukadev Bhattiprolu int mode; 3071f8f1e29SSukadev Bhattiprolu int rc = -ENOMEM; 3081f8f1e29SSukadev Bhattiprolu struct dentry *dentry; 3091f8f1e29SSukadev Bhattiprolu struct inode *inode; 3101f8f1e29SSukadev Bhattiprolu struct dentry *root = sb->s_root; 31153af8ee4SSukadev Bhattiprolu struct pts_fs_info *fsi = DEVPTS_SB(sb); 31253af8ee4SSukadev Bhattiprolu struct pts_mount_opts *opts = &fsi->mount_opts; 313e98d4137SEric W. Biederman kuid_t ptmx_uid = current_fsuid(); 314e98d4137SEric W. Biederman kgid_t ptmx_gid = current_fsgid(); 31553af8ee4SSukadev Bhattiprolu 3165955102cSAl Viro inode_lock(d_inode(root)); 3171f8f1e29SSukadev Bhattiprolu 3181f8f1e29SSukadev Bhattiprolu /* If we have already created ptmx node, return */ 3191f8f1e29SSukadev Bhattiprolu if (fsi->ptmx_dentry) { 3201f8f1e29SSukadev Bhattiprolu rc = 0; 3211f8f1e29SSukadev Bhattiprolu goto out; 3221f8f1e29SSukadev Bhattiprolu } 3231f8f1e29SSukadev Bhattiprolu 3241f8f1e29SSukadev Bhattiprolu dentry = d_alloc_name(root, "ptmx"); 3251f8f1e29SSukadev Bhattiprolu if (!dentry) { 32604541a2fSFabian Frederick pr_err("Unable to alloc dentry for ptmx node\n"); 3271f8f1e29SSukadev Bhattiprolu goto out; 3281f8f1e29SSukadev Bhattiprolu } 3291f8f1e29SSukadev Bhattiprolu 3301f8f1e29SSukadev Bhattiprolu /* 3311f8f1e29SSukadev Bhattiprolu * Create a new 'ptmx' node in this mount of devpts. 3321f8f1e29SSukadev Bhattiprolu */ 3331f8f1e29SSukadev Bhattiprolu inode = new_inode(sb); 3341f8f1e29SSukadev Bhattiprolu if (!inode) { 33504541a2fSFabian Frederick pr_err("Unable to alloc inode for ptmx node\n"); 3361f8f1e29SSukadev Bhattiprolu dput(dentry); 3371f8f1e29SSukadev Bhattiprolu goto out; 3381f8f1e29SSukadev Bhattiprolu } 3391f8f1e29SSukadev Bhattiprolu 3401f8f1e29SSukadev Bhattiprolu inode->i_ino = 2; 341078cd827SDeepa Dinamani inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); 3421f8f1e29SSukadev Bhattiprolu 3431f8f1e29SSukadev Bhattiprolu mode = S_IFCHR|opts->ptmxmode; 3441f8f1e29SSukadev Bhattiprolu init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2)); 345e98d4137SEric W. Biederman inode->i_uid = ptmx_uid; 346e98d4137SEric W. Biederman inode->i_gid = ptmx_gid; 3471f8f1e29SSukadev Bhattiprolu 3481f8f1e29SSukadev Bhattiprolu d_add(dentry, inode); 3491f8f1e29SSukadev Bhattiprolu 3501f8f1e29SSukadev Bhattiprolu fsi->ptmx_dentry = dentry; 3511f8f1e29SSukadev Bhattiprolu rc = 0; 3521f8f1e29SSukadev Bhattiprolu out: 3535955102cSAl Viro inode_unlock(d_inode(root)); 3541f8f1e29SSukadev Bhattiprolu return rc; 3551f8f1e29SSukadev Bhattiprolu } 3561f8f1e29SSukadev Bhattiprolu 3571f8f1e29SSukadev Bhattiprolu static void update_ptmx_mode(struct pts_fs_info *fsi) 3581f8f1e29SSukadev Bhattiprolu { 3591f8f1e29SSukadev Bhattiprolu struct inode *inode; 3601f8f1e29SSukadev Bhattiprolu if (fsi->ptmx_dentry) { 3612b0143b5SDavid Howells inode = d_inode(fsi->ptmx_dentry); 3621f8f1e29SSukadev Bhattiprolu inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode; 3631f8f1e29SSukadev Bhattiprolu } 3641f8f1e29SSukadev Bhattiprolu } 3651f8f1e29SSukadev Bhattiprolu 3661f8f1e29SSukadev Bhattiprolu static int devpts_remount(struct super_block *sb, int *flags, char *data) 3671f8f1e29SSukadev Bhattiprolu { 3681f8f1e29SSukadev Bhattiprolu int err; 3691f8f1e29SSukadev Bhattiprolu struct pts_fs_info *fsi = DEVPTS_SB(sb); 3701f8f1e29SSukadev Bhattiprolu struct pts_mount_opts *opts = &fsi->mount_opts; 3711f8f1e29SSukadev Bhattiprolu 3722a1b2dc0SSukadev Bhattiprolu err = parse_mount_options(data, PARSE_REMOUNT, opts); 3731f8f1e29SSukadev Bhattiprolu 3741f8f1e29SSukadev Bhattiprolu /* 3751f8f1e29SSukadev Bhattiprolu * parse_mount_options() restores options to default values 3761f8f1e29SSukadev Bhattiprolu * before parsing and may have changed ptmxmode. So, update the 3771f8f1e29SSukadev Bhattiprolu * mode in the inode too. Bogus options don't fail the remount, 3781f8f1e29SSukadev Bhattiprolu * so do this even on error return. 3791f8f1e29SSukadev Bhattiprolu */ 3801f8f1e29SSukadev Bhattiprolu update_ptmx_mode(fsi); 3811f8f1e29SSukadev Bhattiprolu 3821f8f1e29SSukadev Bhattiprolu return err; 38353af8ee4SSukadev Bhattiprolu } 38453af8ee4SSukadev Bhattiprolu 38534c80b1dSAl Viro static int devpts_show_options(struct seq_file *seq, struct dentry *root) 386b87a267eSMiklos Szeredi { 38734c80b1dSAl Viro struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb); 38831af0abbSSukadev Bhattiprolu struct pts_mount_opts *opts = &fsi->mount_opts; 38931af0abbSSukadev Bhattiprolu 39031af0abbSSukadev Bhattiprolu if (opts->setuid) 39104541a2fSFabian Frederick seq_printf(seq, ",uid=%u", 39204541a2fSFabian Frederick from_kuid_munged(&init_user_ns, opts->uid)); 39331af0abbSSukadev Bhattiprolu if (opts->setgid) 39404541a2fSFabian Frederick seq_printf(seq, ",gid=%u", 39504541a2fSFabian Frederick from_kgid_munged(&init_user_ns, opts->gid)); 39631af0abbSSukadev Bhattiprolu seq_printf(seq, ",mode=%03o", opts->mode); 3971f8f1e29SSukadev Bhattiprolu seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode); 398e9aba515SKonstantin Khlebnikov if (opts->max < NR_UNIX98_PTY_MAX) 399e9aba515SKonstantin Khlebnikov seq_printf(seq, ",max=%d", opts->max); 400b87a267eSMiklos Szeredi 401b87a267eSMiklos Szeredi return 0; 402b87a267eSMiklos Szeredi } 403b87a267eSMiklos Szeredi 404ee9b6d61SJosef 'Jeff' Sipek static const struct super_operations devpts_sops = { 4051da177e4SLinus Torvalds .statfs = simple_statfs, 4061da177e4SLinus Torvalds .remount_fs = devpts_remount, 407b87a267eSMiklos Szeredi .show_options = devpts_show_options, 4081da177e4SLinus Torvalds }; 4091da177e4SLinus Torvalds 41067245ff3SLinus Torvalds static void *new_pts_fs_info(struct super_block *sb) 411e76b7c01SSukadev Bhattiprolu { 412e76b7c01SSukadev Bhattiprolu struct pts_fs_info *fsi; 413e76b7c01SSukadev Bhattiprolu 414e76b7c01SSukadev Bhattiprolu fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL); 415e76b7c01SSukadev Bhattiprolu if (!fsi) 416e76b7c01SSukadev Bhattiprolu return NULL; 417e76b7c01SSukadev Bhattiprolu 418e76b7c01SSukadev Bhattiprolu ida_init(&fsi->allocated_ptys); 41931af0abbSSukadev Bhattiprolu fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE; 4201f8f1e29SSukadev Bhattiprolu fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; 42167245ff3SLinus Torvalds fsi->sb = sb; 422e76b7c01SSukadev Bhattiprolu 423e76b7c01SSukadev Bhattiprolu return fsi; 424e76b7c01SSukadev Bhattiprolu } 425e76b7c01SSukadev Bhattiprolu 4261da177e4SLinus Torvalds static int 4271da177e4SLinus Torvalds devpts_fill_super(struct super_block *s, void *data, int silent) 4281da177e4SLinus Torvalds { 4291da177e4SLinus Torvalds struct inode *inode; 430dee87d47SEric W. Biederman int error; 4311da177e4SLinus Torvalds 432cc50a07aSEric W. Biederman s->s_iflags &= ~SB_I_NODEV; 4331da177e4SLinus Torvalds s->s_blocksize = 1024; 4341da177e4SLinus Torvalds s->s_blocksize_bits = 10; 4351da177e4SLinus Torvalds s->s_magic = DEVPTS_SUPER_MAGIC; 4361da177e4SLinus Torvalds s->s_op = &devpts_sops; 43773052b0dSVarad Gautam s->s_d_op = &simple_dentry_operations; 4381da177e4SLinus Torvalds s->s_time_gran = 1; 4391da177e4SLinus Torvalds 440dee87d47SEric W. Biederman error = -ENOMEM; 44167245ff3SLinus Torvalds s->s_fs_info = new_pts_fs_info(s); 442e76b7c01SSukadev Bhattiprolu if (!s->s_fs_info) 443e76b7c01SSukadev Bhattiprolu goto fail; 444e76b7c01SSukadev Bhattiprolu 445dee87d47SEric W. Biederman error = parse_mount_options(data, PARSE_MOUNT, &DEVPTS_SB(s)->mount_opts); 446dee87d47SEric W. Biederman if (error) 447dee87d47SEric W. Biederman goto fail; 448dee87d47SEric W. Biederman 449dee87d47SEric W. Biederman error = -ENOMEM; 4501da177e4SLinus Torvalds inode = new_inode(s); 4511da177e4SLinus Torvalds if (!inode) 4523850aba7SAl Viro goto fail; 4531da177e4SLinus Torvalds inode->i_ino = 1; 454078cd827SDeepa Dinamani inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); 4551da177e4SLinus Torvalds inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR; 4561da177e4SLinus Torvalds inode->i_op = &simple_dir_inode_operations; 4571da177e4SLinus Torvalds inode->i_fop = &simple_dir_operations; 458bfe86848SMiklos Szeredi set_nlink(inode, 2); 4591da177e4SLinus Torvalds 46048fde701SAl Viro s->s_root = d_make_root(inode); 461180d9044SEric W. Biederman if (!s->s_root) { 46204541a2fSFabian Frederick pr_err("get root dentry failed\n"); 463180d9044SEric W. Biederman goto fail; 464180d9044SEric W. Biederman } 465e76b7c01SSukadev Bhattiprolu 466180d9044SEric W. Biederman error = mknod_ptmx(s); 467180d9044SEric W. Biederman if (error) 468180d9044SEric W. Biederman goto fail_dput; 469180d9044SEric W. Biederman 470180d9044SEric W. Biederman return 0; 471180d9044SEric W. Biederman fail_dput: 472180d9044SEric W. Biederman dput(s->s_root); 473180d9044SEric W. Biederman s->s_root = NULL; 4741da177e4SLinus Torvalds fail: 475dee87d47SEric W. Biederman return error; 4761da177e4SLinus Torvalds } 4771da177e4SLinus Torvalds 4782a1b2dc0SSukadev Bhattiprolu /* 479fc14f2feSAl Viro * devpts_mount() 480289f00e2SSukadev Bhattiprolu * 481eedf265aSEric W. Biederman * Mount a new (private) instance of devpts. PTYs created in this 482eedf265aSEric W. Biederman * instance are independent of the PTYs in other devpts instances. 483d4076ac5SSukadev Bhattiprolu */ 484fc14f2feSAl Viro static struct dentry *devpts_mount(struct file_system_type *fs_type, 485fc14f2feSAl Viro int flags, const char *dev_name, void *data) 4861da177e4SLinus Torvalds { 487c1b241f0SEric W. Biederman return mount_nodev(fs_type, flags, data, devpts_fill_super); 488482984f0SSukadev Bhattiprolu } 489482984f0SSukadev Bhattiprolu 490e76b7c01SSukadev Bhattiprolu static void devpts_kill_sb(struct super_block *sb) 491e76b7c01SSukadev Bhattiprolu { 492e76b7c01SSukadev Bhattiprolu struct pts_fs_info *fsi = DEVPTS_SB(sb); 493e76b7c01SSukadev Bhattiprolu 49440b320e1SEric W. Biederman if (fsi) 49566da0e1fSIlija Hadzic ida_destroy(&fsi->allocated_ptys); 496e76b7c01SSukadev Bhattiprolu kfree(fsi); 4971f8f1e29SSukadev Bhattiprolu kill_litter_super(sb); 498e76b7c01SSukadev Bhattiprolu } 499e76b7c01SSukadev Bhattiprolu 5001da177e4SLinus Torvalds static struct file_system_type devpts_fs_type = { 5011da177e4SLinus Torvalds .name = "devpts", 502fc14f2feSAl Viro .mount = devpts_mount, 503e76b7c01SSukadev Bhattiprolu .kill_sb = devpts_kill_sb, 504cc50a07aSEric W. Biederman .fs_flags = FS_USERNS_MOUNT, 5051da177e4SLinus Torvalds }; 5061da177e4SLinus Torvalds 5071da177e4SLinus Torvalds /* 5081da177e4SLinus Torvalds * The normal naming convention is simply /dev/pts/<number>; this conforms 5091da177e4SLinus Torvalds * to the System V naming convention 5101da177e4SLinus Torvalds */ 5111da177e4SLinus Torvalds 51267245ff3SLinus Torvalds int devpts_new_index(struct pts_fs_info *fsi) 513718a9163SSukadev Bhattiprolu { 5140f0a0e54SMatthew Wilcox int index = -ENOSPC; 515718a9163SSukadev Bhattiprolu 5160f0a0e54SMatthew Wilcox if (atomic_inc_return(&pty_count) >= (pty_limit - 5170f0a0e54SMatthew Wilcox (fsi->mount_opts.reserve ? 0 : pty_reserve))) 5180f0a0e54SMatthew Wilcox goto out; 519718a9163SSukadev Bhattiprolu 5200f0a0e54SMatthew Wilcox index = ida_alloc_max(&fsi->allocated_ptys, fsi->mount_opts.max - 1, 5210f0a0e54SMatthew Wilcox GFP_KERNEL); 522e9aba515SKonstantin Khlebnikov 5230f0a0e54SMatthew Wilcox out: 5240f0a0e54SMatthew Wilcox if (index < 0) 5250f0a0e54SMatthew Wilcox atomic_dec(&pty_count); 526718a9163SSukadev Bhattiprolu return index; 527718a9163SSukadev Bhattiprolu } 528718a9163SSukadev Bhattiprolu 52967245ff3SLinus Torvalds void devpts_kill_index(struct pts_fs_info *fsi, int idx) 530718a9163SSukadev Bhattiprolu { 5310f0a0e54SMatthew Wilcox ida_free(&fsi->allocated_ptys, idx); 5320f0a0e54SMatthew Wilcox atomic_dec(&pty_count); 533718a9163SSukadev Bhattiprolu } 534718a9163SSukadev Bhattiprolu 5351dcb8e6dSJiri Slaby /** 5361dcb8e6dSJiri Slaby * devpts_pty_new -- create a new inode in /dev/pts/ 5371dcb8e6dSJiri Slaby * @ptmx_inode: inode of the master 5381dcb8e6dSJiri Slaby * @device: major+minor of the node to be created 5391dcb8e6dSJiri Slaby * @index: used as a name of the node 5401dcb8e6dSJiri Slaby * @priv: what's given back by devpts_get_priv 5411dcb8e6dSJiri Slaby * 5421dcb8e6dSJiri Slaby * The created inode is returned. Remove it from /dev/pts/ by devpts_pty_kill. 5431dcb8e6dSJiri Slaby */ 5448ead9dd5SLinus Torvalds struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv) 5451da177e4SLinus Torvalds { 5461da177e4SLinus Torvalds struct dentry *dentry; 547eedf265aSEric W. Biederman struct super_block *sb = fsi->sb; 548162b97cfSJiri Slaby struct inode *inode; 5499ce71148SJosh Triplett struct dentry *root; 5509ce71148SJosh Triplett struct pts_mount_opts *opts; 55189a52e10SSukadev Bhattiprolu char s[12]; 5521da177e4SLinus Torvalds 5539ce71148SJosh Triplett root = sb->s_root; 5549ce71148SJosh Triplett opts = &fsi->mount_opts; 5559ce71148SJosh Triplett 556162b97cfSJiri Slaby inode = new_inode(sb); 5571da177e4SLinus Torvalds if (!inode) 558162b97cfSJiri Slaby return ERR_PTR(-ENOMEM); 5591da177e4SLinus Torvalds 560f11afb61SJiri Slaby inode->i_ino = index + 3; 561d0eafc7dSDavid Howells inode->i_uid = opts->setuid ? opts->uid : current_fsuid(); 562d0eafc7dSDavid Howells inode->i_gid = opts->setgid ? opts->gid : current_fsgid(); 563078cd827SDeepa Dinamani inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); 5648ead9dd5SLinus Torvalds init_special_inode(inode, S_IFCHR|opts->mode, MKDEV(UNIX98_PTY_SLAVE_MAJOR, index)); 5651da177e4SLinus Torvalds 566f11afb61SJiri Slaby sprintf(s, "%d", index); 56789a52e10SSukadev Bhattiprolu 56859e55e6cSSukadev Bhattiprolu dentry = d_alloc_name(root, s); 569b12d1259SAndrey Vagin if (dentry) { 5708ead9dd5SLinus Torvalds dentry->d_fsdata = priv; 57189a52e10SSukadev Bhattiprolu d_add(dentry, inode); 5722b0143b5SDavid Howells fsnotify_create(d_inode(root), dentry); 573aa597bc1SAndrey Vagin } else { 574aa597bc1SAndrey Vagin iput(inode); 5758ead9dd5SLinus Torvalds dentry = ERR_PTR(-ENOMEM); 5763972b7f6SFlorin Malita } 5771da177e4SLinus Torvalds 5788ead9dd5SLinus Torvalds return dentry; 5791da177e4SLinus Torvalds } 5801da177e4SLinus Torvalds 5811dcb8e6dSJiri Slaby /** 5821dcb8e6dSJiri Slaby * devpts_get_priv -- get private data for a slave 5831dcb8e6dSJiri Slaby * @pts_inode: inode of the slave 5841dcb8e6dSJiri Slaby * 5851dcb8e6dSJiri Slaby * Returns whatever was passed as priv in devpts_pty_new for a given inode. 5861dcb8e6dSJiri Slaby */ 5878ead9dd5SLinus Torvalds void *devpts_get_priv(struct dentry *dentry) 5881da177e4SLinus Torvalds { 5893e423945SLinus Torvalds if (dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC) 5903e423945SLinus Torvalds return NULL; 5918ead9dd5SLinus Torvalds return dentry->d_fsdata; 5921da177e4SLinus Torvalds } 5931da177e4SLinus Torvalds 5941dcb8e6dSJiri Slaby /** 5951dcb8e6dSJiri Slaby * devpts_pty_kill -- remove inode form /dev/pts/ 5961dcb8e6dSJiri Slaby * @inode: inode of the slave to be removed 5971dcb8e6dSJiri Slaby * 5981dcb8e6dSJiri Slaby * This is an inverse operation of devpts_pty_new. 5991dcb8e6dSJiri Slaby */ 6008ead9dd5SLinus Torvalds void devpts_pty_kill(struct dentry *dentry) 6011da177e4SLinus Torvalds { 6028ead9dd5SLinus Torvalds WARN_ON_ONCE(dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC); 6031da177e4SLinus Torvalds 6048ead9dd5SLinus Torvalds dentry->d_fsdata = NULL; 6058ead9dd5SLinus Torvalds drop_nlink(dentry->d_inode); 60646c46f8dSAl Viro d_drop(dentry); 60729044daeSAmir Goldstein fsnotify_unlink(d_inode(dentry->d_parent), dentry); 608835aa440SAlan Cox dput(dentry); /* d_alloc_name() in devpts_pty_new() */ 6091da177e4SLinus Torvalds } 6101da177e4SLinus Torvalds 6111da177e4SLinus Torvalds static int __init init_devpts_fs(void) 6121da177e4SLinus Torvalds { 6131da177e4SLinus Torvalds int err = register_filesystem(&devpts_fs_type); 6141da177e4SLinus Torvalds if (!err) { 615*3e27877aSLuis Chamberlain register_sysctl("kernel/pty", pty_table); 6161da177e4SLinus Torvalds } 6171da177e4SLinus Torvalds return err; 6181da177e4SLinus Torvalds } 6191da177e4SLinus Torvalds module_init(init_devpts_fs) 620