// SPDX-License-Identifier: GPL-2.0-or-later/* -*- linux-c -*- --------------------------------------------------------- * * * linux/fs/devpts/inode.c * * Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved * * ------------------------------------------------------------------------- */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/module.h>#include <linux/init.h>#include <linux/fs.h>#include <linux/sched.h>#include <linux/namei.h>#include <linux/slab.h>#include <linux/mount.h>#include <linux/tty.h>#include <linux/mutex.h>#include <linux/magic.h>#include <linux/idr.h>#include <linux/devpts_fs.h>#include <linux/parser.h>#include <linux/fsnotify.h>#include <linux/seq_file.h> #define DEVPTS_DEFAULT_MODE 0600/* * ptmx is a new node in /dev/pts and will be unused in legacy (single- * instance) mode. To prevent surprises in user space, set permissions of * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful * permissions. */#define DEVPTS_DEFAULT_PTMX_MODE 0000#define PTMX_MINOR 2 /* * sysctl support for setting limits on the number of Unix98 ptys allocated. * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly. */static int pty_limit = NR_UNIX98_PTY_DEFAULT;static int pty_reserve = NR_UNIX98_PTY_RESERVE;static int pty_limit_min;static int pty_limit_max = INT_MAX;static atomic_t pty_count = ATOMIC_INIT(0); static struct ctl_table pty_table[] = { { .procname = "max", .maxlen = sizeof(int), .mode = 0644, .data = &pty_limit, .proc_handler = proc_dointvec_minmax, .extra1 = &pty_limit_min, .extra2 = &pty_limit_max, }, { .procname = "reserve", .maxlen = sizeof(int), .mode = 0644, .data = &pty_reserve, .proc_handler = proc_dointvec_minmax, .extra1 = &pty_limit_min, .extra2 = &pty_limit_max, }, { .procname = "nr", .maxlen = sizeof(int), .mode = 0444, .data = &pty_count, .proc_handler = proc_dointvec, }, {}}; static struct ctl_table pty_kern_table[] = { { .procname = "pty", .mode = 0555, .child = pty_table, }, {}}; static struct ctl_table pty_root_table[] = { { .procname = "kernel", .mode = 0555, .child = pty_kern_table, }, {}}; struct pts_mount_opts { int setuid; int setgid; kuid_t uid; kgid_t gid; umode_t mode; umode_t ptmxmode; int reserve; int max;}; enum { Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, Opt_max, Opt_err}; static const match_table_t tokens = { {Opt_uid, "uid=%u"}, {Opt_gid, "gid=%u"}, {Opt_mode, "mode=%o"}, {Opt_ptmxmode, "ptmxmode=%o"}, {Opt_newinstance, "newinstance"}, {Opt_max, "max=%d"}, {Opt_err, NULL}}; struct pts_fs_info { struct ida allocated_ptys; struct pts_mount_opts mount_opts; struct super_block *sb; struct dentry *ptmx_dentry;}; static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb){ return sb->s_fs_info;} static int devpts_ptmx_path(struct path *path){ struct super_block *sb; int err; /* Is a devpts filesystem at "pts" in the same directory? */ err = path_pts(path); if (err) return err; /* Is the path the root of a devpts filesystem? */ sb = path->mnt->mnt_sb; if ((sb->s_magic != DEVPTS_SUPER_MAGIC) || (path->mnt->mnt_root != sb->s_root)) return -ENODEV; return 0;} /* * Try to find a suitable devpts filesystem. We support the following * scenarios: * - The ptmx device node is located in the same directory as the devpts * mount where the pts device nodes are located. * This is e.g. the case when calling open on the /dev/pts/ptmx device * node when the devpts filesystem is mounted at /dev/pts. * - The ptmx device node is located outside the devpts filesystem mount * where the pts device nodes are located. For example, the ptmx device * is a symlink, separate device node, or bind-mount. * A supported scenario is bind-mounting /dev/pts/ptmx to /dev/ptmx and * then calling open on /dev/ptmx. In this case a suitable pts * subdirectory can be found in the common parent directory /dev of the * devpts mount and the ptmx bind-mount, after resolving the /dev/ptmx * bind-mount. * If no suitable pts subdirectory can be found this function will fail. * This is e.g. the case when bind-mounting /dev/pts/ptmx to /ptmx. */struct vfsmount *devpts_mntget(struct file *filp, struct pts_fs_info *fsi){ struct path path; int err = 0; path = filp->f_path; path_get(&path); /* Walk upward while the start point is a bind mount of * a single file. */ while (path.mnt->mnt_root == path.dentry) if (follow_up(&path) == 0) break; /* devpts_ptmx_path() finds a devpts fs or returns an error. */ if ((path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) || (DEVPTS_SB(path.mnt->mnt_sb) != fsi)) err = devpts_ptmx_path(&path); dput(path.dentry); if (!err) { if (DEVPTS_SB(path.mnt->mnt_sb) == fsi) return path.mnt; err = -ENODEV; } mntput(path.mnt); return ERR_PTR(err);} struct pts_fs_info *devpts_acquire(struct file *filp){ struct pts_fs_info *result; struct path path; struct super_block *sb; path = filp->f_path; path_get(&path); /* Has the devpts filesystem already been found? */ if (path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) { int err; err = devpts_ptmx_path(&path); if (err) { result = ERR_PTR(err); goto out; } } /* * pty code needs to hold extra references in case of last /dev/tty close */ sb = path.mnt->mnt_sb; atomic_inc(&sb->s_active); result = DEVPTS_SB(sb); out: path_put(&path); return result;} void devpts_release(struct pts_fs_info *fsi){ deactivate_super(fsi->sb);} #define PARSE_MOUNT 0#define PARSE_REMOUNT 1 /* * parse_mount_options(): * Set @opts to mount options specified in @data. If an option is not * specified in @data, set it to its default value. * * Note: @data may be NULL (in which case all options are set to default). */static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts){ char *p; kuid_t uid; kgid_t gid; opts->setuid = 0; opts->setgid = 0; opts->uid = GLOBAL_ROOT_UID; opts->gid = GLOBAL_ROOT_GID; opts->mode = DEVPTS_DEFAULT_MODE; opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; opts->max = NR_UNIX98_PTY_MAX; /* Only allow instances mounted from the initial mount * namespace to tap the reserve pool of ptys. */ if (op == PARSE_MOUNT) opts->reserve = (current->nsproxy->mnt_ns == init_task.nsproxy->mnt_ns); while ((p = strsep(&data, ",")) != NULL) { substring_t args[MAX_OPT_ARGS]; int token; int option; if (!*p) continue; token = match_token(p, tokens, args); switch (token) { case Opt_uid: if (match_int(&args[0], &option)) return -EINVAL; uid = make_kuid(current_user_ns(), option); if (!uid_valid(uid)) return -EINVAL; opts->uid = uid; opts->setuid = 1; break; case Opt_gid: if (match_int(&args[0], &option)) return -EINVAL; gid = make_kgid(current_user_ns(), option); if (!gid_valid(gid)) return -EINVAL; opts->gid = gid; opts->setgid = 1; break; case Opt_mode: if (match_octal(&args[0], &option)) return -EINVAL; opts->mode = option & S_IALLUGO; break; case Opt_ptmxmode: if (match_octal(&args[0], &option)) return -EINVAL; opts->ptmxmode = option & S_IALLUGO; break; case Opt_newinstance: break; case Opt_max: if (match_int(&args[0], &option) || option < 0 || option > NR_UNIX98_PTY_MAX) return -EINVAL; opts->max = option; break; default: pr_err("called with bogus options\n"); return -EINVAL; } } return 0;} static int mknod_ptmx(struct super_block *sb){ int mode; int rc = -ENOMEM; struct dentry *dentry; struct inode *inode; struct dentry *root = sb->s_root; struct pts_fs_info *fsi = DEVPTS_SB(sb); struct pts_mount_opts *opts = &fsi->mount_opts; kuid_t ptmx_uid = current_fsuid(); kgid_t ptmx_gid = current_fsgid(); inode_lock(d_inode(root)); /* If we have already created ptmx node, return */ if (fsi->ptmx_dentry) { rc = 0; goto out; } dentry = d_alloc_name(root, "ptmx"); if (!dentry) { pr_err("Unable to alloc dentry for ptmx node\n"); goto out; } /* * Create a new 'ptmx' node in this mount of devpts. */ inode = new_inode(sb); if (!inode) { pr_err("Unable to alloc inode for ptmx node\n"); dput(dentry); goto out; } inode->i_ino = 2; inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); mode = S_IFCHR|opts->ptmxmode; init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2)); inode->i_uid = ptmx_uid; inode->i_gid = ptmx_gid; d_add(dentry, inode); fsi->ptmx_dentry = dentry; rc = 0;out: inode_unlock(d_inode(root)); return rc;} static void update_ptmx_mode(struct pts_fs_info *fsi){ struct inode *inode; if (fsi->ptmx_dentry) { inode = d_inode(fsi->ptmx_dentry); inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode; }} static int devpts_remount(struct super_block *sb, int *flags, char *data){ int err; struct pts_fs_info *fsi = DEVPTS_SB(sb); struct pts_mount_opts *opts = &fsi->mount_opts; err = parse_mount_options(data, PARSE_REMOUNT, opts); /* * parse_mount_options() restores options to default values * before parsing and may have changed ptmxmode. So, update the * mode in the inode too. Bogus options don't fail the remount, * so do this even on error return. */ update_ptmx_mode(fsi); return err;} static int devpts_show_options(struct seq_file *seq, struct dentry *root){ struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb); struct pts_mount_opts *opts = &fsi->mount_opts; if (opts->setuid) seq_printf(seq, ",uid=%u", from_kuid_munged(&init_user_ns, opts->uid)); if (opts->setgid) seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, opts->gid)); seq_printf(seq, ",mode=%03o", opts->mode); seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode); if (opts->max < NR_UNIX98_PTY_MAX) seq_printf(seq, ",max=%d", opts->max); return 0;} static const struct super_operations devpts_sops = { .statfs = simple_statfs, .remount_fs = devpts_remount, .show_options = devpts_show_options,}; static void *new_pts_fs_info(struct super_block *sb){ struct pts_fs_info *fsi; fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL); if (!fsi) return NULL; ida_init(&fsi->allocated_ptys); fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE; fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; fsi->sb = sb; return fsi;} static intdevpts_fill_super(struct super_block *s, void *data, int silent){ struct inode *inode; int error; s->s_iflags &= ~SB_I_NODEV; s->s_blocksize = 1024; s->s_blocksize_bits = 10; s->s_magic = DEVPTS_SUPER_MAGIC; s->s_op = &devpts_sops; s->s_d_op = &simple_dentry_operations; s->s_time_gran = 1; error = -ENOMEM; s->s_fs_info = new_pts_fs_info(s); if (!s->s_fs_info) goto fail; error = parse_mount_options(data, PARSE_MOUNT, &DEVPTS_SB(s)->mount_opts); if (error) goto fail; error = -ENOMEM; inode = new_inode(s); if (!inode) goto fail; inode->i_ino = 1; inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR; inode->i_op = &simple_dir_inode_operations; inode->i_fop = &simple_dir_operations; set_nlink(inode, 2); s->s_root = d_make_root(inode); if (!s->s_root) { pr_err("get root dentry failed\n"); goto fail; } error = mknod_ptmx(s); if (error) goto fail_dput; return 0;fail_dput: dput(s->s_root); s->s_root = NULL;fail: return error;} /* * devpts_mount() * * Mount a new (private) instance of devpts. PTYs created in this * instance are independent of the PTYs in other devpts instances.Lines 1–500 of 637. Load more
// SPDX-License-Identifier: GPL-2.0-or-later /* -*- linux-c -*- --------------------------------------------------------- * * * linux/fs/devpts/inode.c * * Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved * * ------------------------------------------------------------------------- */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/module.h> #include <linux/init.h> #include <linux/fs.h> #include <linux/sched.h> #include <linux/namei.h> #include <linux/slab.h> #include <linux/mount.h> #include <linux/tty.h> #include <linux/mutex.h> #include <linux/magic.h> #include <linux/idr.h> #include <linux/devpts_fs.h> #include <linux/parser.h> #include <linux/fsnotify.h> #include <linux/seq_file.h> #define DEVPTS_DEFAULT_MODE 0600 /* * ptmx is a new node in /dev/pts and will be unused in legacy (single- * instance) mode. To prevent surprises in user space, set permissions of * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful * permissions. */ #define DEVPTS_DEFAULT_PTMX_MODE 0000 #define PTMX_MINOR 2 /* * sysctl support for setting limits on the number of Unix98 ptys allocated. * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly. */ static int pty_limit = NR_UNIX98_PTY_DEFAULT; static int pty_reserve = NR_UNIX98_PTY_RESERVE; static int pty_limit_min; static int pty_limit_max = INT_MAX; static atomic_t pty_count = ATOMIC_INIT(0); static struct ctl_table pty_table[] = { { .procname = "max", .maxlen = sizeof(int), .mode = 0644, .data = &pty_limit, .proc_handler = proc_dointvec_minmax, .extra1 = &pty_limit_min, .extra2 = &pty_limit_max, }, { .procname = "reserve", .maxlen = sizeof(int), .mode = 0644, .data = &pty_reserve, .proc_handler = proc_dointvec_minmax, .extra1 = &pty_limit_min, .extra2 = &pty_limit_max, }, { .procname = "nr", .maxlen = sizeof(int), .mode = 0444, .data = &pty_count, .proc_handler = proc_dointvec, }, {} }; static struct ctl_table pty_kern_table[] = { { .procname = "pty", .mode = 0555, .child = pty_table, }, {} }; static struct ctl_table pty_root_table[] = { { .procname = "kernel", .mode = 0555, .child = pty_kern_table, }, {} }; struct pts_mount_opts { int setuid; int setgid; kuid_t uid; kgid_t gid; umode_t mode; umode_t ptmxmode; int reserve; int max; }; enum { Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, Opt_max, Opt_err }; static const match_table_t tokens = { {Opt_uid, "uid=%u"}, {Opt_gid, "gid=%u"}, {Opt_mode, "mode=%o"}, {Opt_ptmxmode, "ptmxmode=%o"}, {Opt_newinstance, "newinstance"}, {Opt_max, "max=%d"}, {Opt_err, NULL} }; struct pts_fs_info { struct ida allocated_ptys; struct pts_mount_opts mount_opts; struct super_block *sb; struct dentry *ptmx_dentry; }; static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb) { return sb->s_fs_info; } static int devpts_ptmx_path(struct path *path) { struct super_block *sb; int err; /* Is a devpts filesystem at "pts" in the same directory? */ err = path_pts(path); if (err) return err; /* Is the path the root of a devpts filesystem? */ sb = path->mnt->mnt_sb; if ((sb->s_magic != DEVPTS_SUPER_MAGIC) || (path->mnt->mnt_root != sb->s_root)) return -ENODEV; return 0; } /* * Try to find a suitable devpts filesystem. We support the following * scenarios: * - The ptmx device node is located in the same directory as the devpts * mount where the pts device nodes are located. * This is e.g. the case when calling open on the /dev/pts/ptmx device * node when the devpts filesystem is mounted at /dev/pts. * - The ptmx device node is located outside the devpts filesystem mount * where the pts device nodes are located. For example, the ptmx device * is a symlink, separate device node, or bind-mount. * A supported scenario is bind-mounting /dev/pts/ptmx to /dev/ptmx and * then calling open on /dev/ptmx. In this case a suitable pts * subdirectory can be found in the common parent directory /dev of the * devpts mount and the ptmx bind-mount, after resolving the /dev/ptmx * bind-mount. * If no suitable pts subdirectory can be found this function will fail. * This is e.g. the case when bind-mounting /dev/pts/ptmx to /ptmx. */ struct vfsmount *devpts_mntget(struct file *filp, struct pts_fs_info *fsi) { struct path path; int err = 0; path = filp->f_path; path_get(&path); /* Walk upward while the start point is a bind mount of * a single file. */ while (path.mnt->mnt_root == path.dentry) if (follow_up(&path) == 0) break; /* devpts_ptmx_path() finds a devpts fs or returns an error. */ if ((path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) || (DEVPTS_SB(path.mnt->mnt_sb) != fsi)) err = devpts_ptmx_path(&path); dput(path.dentry); if (!err) { if (DEVPTS_SB(path.mnt->mnt_sb) == fsi) return path.mnt; err = -ENODEV; } mntput(path.mnt); return ERR_PTR(err); } struct pts_fs_info *devpts_acquire(struct file *filp) { struct pts_fs_info *result; struct path path; struct super_block *sb; path = filp->f_path; path_get(&path); /* Has the devpts filesystem already been found? */ if (path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) { int err; err = devpts_ptmx_path(&path); if (err) { result = ERR_PTR(err); goto out; } } /* * pty code needs to hold extra references in case of last /dev/tty close */ sb = path.mnt->mnt_sb; atomic_inc(&sb->s_active); result = DEVPTS_SB(sb); out: path_put(&path); return result; } void devpts_release(struct pts_fs_info *fsi) { deactivate_super(fsi->sb); } #define PARSE_MOUNT 0 #define PARSE_REMOUNT 1 /* * parse_mount_options(): * Set @opts to mount options specified in @data. If an option is not * specified in @data, set it to its default value. * * Note: @data may be NULL (in which case all options are set to default). */ static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts) { char *p; kuid_t uid; kgid_t gid; opts->setuid = 0; opts->setgid = 0; opts->uid = GLOBAL_ROOT_UID; opts->gid = GLOBAL_ROOT_GID; opts->mode = DEVPTS_DEFAULT_MODE; opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; opts->max = NR_UNIX98_PTY_MAX; /* Only allow instances mounted from the initial mount * namespace to tap the reserve pool of ptys. */ if (op == PARSE_MOUNT) opts->reserve = (current->nsproxy->mnt_ns == init_task.nsproxy->mnt_ns); while ((p = strsep(&data, ",")) != NULL) { substring_t args[MAX_OPT_ARGS]; int token; int option; if (!*p) continue; token = match_token(p, tokens, args); switch (token) { case Opt_uid: if (match_int(&args[0], &option)) return -EINVAL; uid = make_kuid(current_user_ns(), option); if (!uid_valid(uid)) return -EINVAL; opts->uid = uid; opts->setuid = 1; break; case Opt_gid: if (match_int(&args[0], &option)) return -EINVAL; gid = make_kgid(current_user_ns(), option); if (!gid_valid(gid)) return -EINVAL; opts->gid = gid; opts->setgid = 1; break; case Opt_mode: if (match_octal(&args[0], &option)) return -EINVAL; opts->mode = option & S_IALLUGO; break; case Opt_ptmxmode: if (match_octal(&args[0], &option)) return -EINVAL; opts->ptmxmode = option & S_IALLUGO; break; case Opt_newinstance: break; case Opt_max: if (match_int(&args[0], &option) || option < 0 || option > NR_UNIX98_PTY_MAX) return -EINVAL; opts->max = option; break; default: pr_err("called with bogus options\n"); return -EINVAL; } } return 0; } static int mknod_ptmx(struct super_block *sb) { int mode; int rc = -ENOMEM; struct dentry *dentry; struct inode *inode; struct dentry *root = sb->s_root; struct pts_fs_info *fsi = DEVPTS_SB(sb); struct pts_mount_opts *opts = &fsi->mount_opts; kuid_t ptmx_uid = current_fsuid(); kgid_t ptmx_gid = current_fsgid(); inode_lock(d_inode(root)); /* If we have already created ptmx node, return */ if (fsi->ptmx_dentry) { rc = 0; goto out; } dentry = d_alloc_name(root, "ptmx"); if (!dentry) { pr_err("Unable to alloc dentry for ptmx node\n"); goto out; } /* * Create a new 'ptmx' node in this mount of devpts. */ inode = new_inode(sb); if (!inode) { pr_err("Unable to alloc inode for ptmx node\n"); dput(dentry); goto out; } inode->i_ino = 2; inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); mode = S_IFCHR|opts->ptmxmode; init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2)); inode->i_uid = ptmx_uid; inode->i_gid = ptmx_gid; d_add(dentry, inode); fsi->ptmx_dentry = dentry; rc = 0; out: inode_unlock(d_inode(root)); return rc; } static void update_ptmx_mode(struct pts_fs_info *fsi) { struct inode *inode; if (fsi->ptmx_dentry) { inode = d_inode(fsi->ptmx_dentry); inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode; } } static int devpts_remount(struct super_block *sb, int *flags, char *data) { int err; struct pts_fs_info *fsi = DEVPTS_SB(sb); struct pts_mount_opts *opts = &fsi->mount_opts; err = parse_mount_options(data, PARSE_REMOUNT, opts); /* * parse_mount_options() restores options to default values * before parsing and may have changed ptmxmode. So, update the * mode in the inode too. Bogus options don't fail the remount, * so do this even on error return. */ update_ptmx_mode(fsi); return err; } static int devpts_show_options(struct seq_file *seq, struct dentry *root) { struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb); struct pts_mount_opts *opts = &fsi->mount_opts; if (opts->setuid) seq_printf(seq, ",uid=%u", from_kuid_munged(&init_user_ns, opts->uid)); if (opts->setgid) seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, opts->gid)); seq_printf(seq, ",mode=%03o", opts->mode); seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode); if (opts->max < NR_UNIX98_PTY_MAX) seq_printf(seq, ",max=%d", opts->max); return 0; } static const struct super_operations devpts_sops = { .statfs = simple_statfs, .remount_fs = devpts_remount, .show_options = devpts_show_options, }; static void *new_pts_fs_info(struct super_block *sb) { struct pts_fs_info *fsi; fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL); if (!fsi) return NULL; ida_init(&fsi->allocated_ptys); fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE; fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; fsi->sb = sb; return fsi; } static int devpts_fill_super(struct super_block *s, void *data, int silent) { struct inode *inode; int error; s->s_iflags &= ~SB_I_NODEV; s->s_blocksize = 1024; s->s_blocksize_bits = 10; s->s_magic = DEVPTS_SUPER_MAGIC; s->s_op = &devpts_sops; s->s_d_op = &simple_dentry_operations; s->s_time_gran = 1; error = -ENOMEM; s->s_fs_info = new_pts_fs_info(s); if (!s->s_fs_info) goto fail; error = parse_mount_options(data, PARSE_MOUNT, &DEVPTS_SB(s)->mount_opts); if (error) goto fail; error = -ENOMEM; inode = new_inode(s); if (!inode) goto fail; inode->i_ino = 1; inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR; inode->i_op = &simple_dir_inode_operations; inode->i_fop = &simple_dir_operations; set_nlink(inode, 2); s->s_root = d_make_root(inode); if (!s->s_root) { pr_err("get root dentry failed\n"); goto fail; } error = mknod_ptmx(s); if (error) goto fail_dput; return 0; fail_dput: dput(s->s_root); s->s_root = NULL; fail: return error; } /* * devpts_mount() * * Mount a new (private) instance of devpts. PTYs created in this * instance are independent of the PTYs in other devpts instances.