// 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/fs_context.h>#include <linux/fs_parser.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/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 const 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, },}; 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 struct fs_parameter_spec devpts_param_specs[] = { fsparam_gid ("gid", Opt_gid), fsparam_s32 ("max", Opt_max), fsparam_u32oct ("mode", Opt_mode), fsparam_flag ("newinstance", Opt_newinstance), fsparam_u32oct ("ptmxmode", Opt_ptmxmode), fsparam_uid ("uid", Opt_uid), {}}; struct pts_fs_info { struct ida allocated_ptys; struct pts_mount_opts mount_opts; struct super_block *sb; struct inode *ptmx_inode; // borrowed}; 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);} /* * devpts_parse_param - Parse mount parameters */static int devpts_parse_param(struct fs_context *fc, struct fs_parameter *param){ struct pts_fs_info *fsi = fc->s_fs_info; struct pts_mount_opts *opts = &fsi->mount_opts; struct fs_parse_result result; int opt; opt = fs_parse(fc, devpts_param_specs, param, &result); if (opt < 0) return opt; switch (opt) { case Opt_uid: opts->uid = result.uid; opts->setuid = 1; break; case Opt_gid: opts->gid = result.gid; opts->setgid = 1; break; case Opt_mode: opts->mode = result.uint_32 & S_IALLUGO; break; case Opt_ptmxmode: opts->ptmxmode = result.uint_32 & S_IALLUGO; break; case Opt_newinstance: break; case Opt_max: if (result.uint_32 > NR_UNIX98_PTY_MAX) return invalf(fc, "max out of range"); opts->max = result.uint_32; break; } return 0;} static int mknod_ptmx(struct super_block *sb, struct fs_context *fc){ int mode; 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(); dentry = simple_start_creating(root, "ptmx"); if (IS_ERR(dentry)) { pr_err("Unable to alloc dentry for ptmx node\n"); return PTR_ERR(dentry); } /* * Create a new 'ptmx' node in this mount of devpts. */ inode = new_inode(sb); if (!inode) { simple_done_creating(dentry); pr_err("Unable to alloc inode for ptmx node\n"); return -ENOMEM; } inode->i_ino = 2; simple_inode_init_ts(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; fsi->ptmx_inode = inode; d_make_persistent(dentry, inode); simple_done_creating(dentry); return 0;} static void update_ptmx_mode(struct pts_fs_info *fsi){ fsi->ptmx_inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;} static int devpts_reconfigure(struct fs_context *fc){ struct pts_fs_info *fsi = DEVPTS_SB(fc->root->d_sb); struct pts_fs_info *new = fc->s_fs_info; /* Apply the revised options. We don't want to change ->reserve. * Ideally, we'd update each option conditionally on it having been * explicitly changed, but the default is to reset everything so that * would break UAPI... */ fsi->mount_opts.setuid = new->mount_opts.setuid; fsi->mount_opts.setgid = new->mount_opts.setgid; fsi->mount_opts.uid = new->mount_opts.uid; fsi->mount_opts.gid = new->mount_opts.gid; fsi->mount_opts.mode = new->mount_opts.mode; fsi->mount_opts.ptmxmode = new->mount_opts.ptmxmode; fsi->mount_opts.max = new->mount_opts.max; /* * 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 0;} 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, .show_options = devpts_show_options,}; static int devpts_fill_super(struct super_block *s, struct fs_context *fc){ struct pts_fs_info *fsi = DEVPTS_SB(s); struct inode *inode; 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_flags = DCACHE_DONTCACHE; s->s_time_gran = 1; fsi->sb = s; inode = new_inode(s); if (!inode) return -ENOMEM; inode->i_ino = 1; simple_inode_init_ts(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"); return -ENOMEM; } return mknod_ptmx(s, fc);} /* * devpts_get_tree() * * Mount a new (private) instance of devpts. PTYs created in this * instance are independent of the PTYs in other devpts instances. */static int devpts_get_tree(struct fs_context *fc){ return get_tree_nodev(fc, devpts_fill_super);} static void devpts_free_fc(struct fs_context *fc){ kfree(fc->s_fs_info);} static const struct fs_context_operations devpts_context_ops = { .free = devpts_free_fc, .parse_param = devpts_parse_param, .get_tree = devpts_get_tree, .reconfigure = devpts_reconfigure,}; /* * Set up the filesystem mount context. */static int devpts_init_fs_context(struct fs_context *fc){ struct pts_fs_info *fsi; fsi = kzalloc_obj(struct pts_fs_info); if (!fsi) return -ENOMEM; ida_init(&fsi->allocated_ptys); fsi->mount_opts.uid = GLOBAL_ROOT_UID; fsi->mount_opts.gid = GLOBAL_ROOT_GID; fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE; fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; fsi->mount_opts.max = NR_UNIX98_PTY_MAX; if (fc->purpose == FS_CONTEXT_FOR_MOUNT && current->nsproxy->mnt_ns == init_task.nsproxy->mnt_ns) fsi->mount_opts.reserve = true; fc->s_fs_info = fsi; fc->ops = &devpts_context_ops; return 0;} static void devpts_kill_sb(struct super_block *sb){ struct pts_fs_info *fsi = DEVPTS_SB(sb); if (fsi) ida_destroy(&fsi->allocated_ptys); kfree(fsi); kill_anon_super(sb);} static struct file_system_type devpts_fs_type = { .name = "devpts", .init_fs_context = devpts_init_fs_context, .parameters = devpts_param_specs, .kill_sb = devpts_kill_sb, .fs_flags = FS_USERNS_MOUNT,}; /* * The normal naming convention is simply /dev/pts/<number>; this conforms * to the System V naming convention */ int devpts_new_index(struct pts_fs_info *fsi){ int index = -ENOSPC; if (atomic_inc_return(&pty_count) >= (pty_limit - (fsi->mount_opts.reserve ? 0 : pty_reserve))) goto out; index = ida_alloc_max(&fsi->allocated_ptys, fsi->mount_opts.max - 1, GFP_KERNEL); out: if (index < 0) atomic_dec(&pty_count); return index;} void devpts_kill_index(struct pts_fs_info *fsi, int idx){ ida_free(&fsi->allocated_ptys, idx); atomic_dec(&pty_count);} /** * devpts_pty_new -- create a new inode in /dev/pts/ * @fsi: Filesystem info for this instance. * @index: used as a name of the node * @priv: what's given back by devpts_get_priv * * The dentry for the created inode is returned. * Remove it from /dev/pts/ with devpts_pty_kill(). */struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv){ struct dentry *dentry;Lines 1–500 of 572. 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/fs_context.h> #include <linux/fs_parser.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/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 const 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, }, }; 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 struct fs_parameter_spec devpts_param_specs[] = { fsparam_gid ("gid", Opt_gid), fsparam_s32 ("max", Opt_max), fsparam_u32oct ("mode", Opt_mode), fsparam_flag ("newinstance", Opt_newinstance), fsparam_u32oct ("ptmxmode", Opt_ptmxmode), fsparam_uid ("uid", Opt_uid), {} }; struct pts_fs_info { struct ida allocated_ptys; struct pts_mount_opts mount_opts; struct super_block *sb; struct inode *ptmx_inode; // borrowed }; 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); } /* * devpts_parse_param - Parse mount parameters */ static int devpts_parse_param(struct fs_context *fc, struct fs_parameter *param) { struct pts_fs_info *fsi = fc->s_fs_info; struct pts_mount_opts *opts = &fsi->mount_opts; struct fs_parse_result result; int opt; opt = fs_parse(fc, devpts_param_specs, param, &result); if (opt < 0) return opt; switch (opt) { case Opt_uid: opts->uid = result.uid; opts->setuid = 1; break; case Opt_gid: opts->gid = result.gid; opts->setgid = 1; break; case Opt_mode: opts->mode = result.uint_32 & S_IALLUGO; break; case Opt_ptmxmode: opts->ptmxmode = result.uint_32 & S_IALLUGO; break; case Opt_newinstance: break; case Opt_max: if (result.uint_32 > NR_UNIX98_PTY_MAX) return invalf(fc, "max out of range"); opts->max = result.uint_32; break; } return 0; } static int mknod_ptmx(struct super_block *sb, struct fs_context *fc) { int mode; 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(); dentry = simple_start_creating(root, "ptmx"); if (IS_ERR(dentry)) { pr_err("Unable to alloc dentry for ptmx node\n"); return PTR_ERR(dentry); } /* * Create a new 'ptmx' node in this mount of devpts. */ inode = new_inode(sb); if (!inode) { simple_done_creating(dentry); pr_err("Unable to alloc inode for ptmx node\n"); return -ENOMEM; } inode->i_ino = 2; simple_inode_init_ts(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; fsi->ptmx_inode = inode; d_make_persistent(dentry, inode); simple_done_creating(dentry); return 0; } static void update_ptmx_mode(struct pts_fs_info *fsi) { fsi->ptmx_inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode; } static int devpts_reconfigure(struct fs_context *fc) { struct pts_fs_info *fsi = DEVPTS_SB(fc->root->d_sb); struct pts_fs_info *new = fc->s_fs_info; /* Apply the revised options. We don't want to change ->reserve. * Ideally, we'd update each option conditionally on it having been * explicitly changed, but the default is to reset everything so that * would break UAPI... */ fsi->mount_opts.setuid = new->mount_opts.setuid; fsi->mount_opts.setgid = new->mount_opts.setgid; fsi->mount_opts.uid = new->mount_opts.uid; fsi->mount_opts.gid = new->mount_opts.gid; fsi->mount_opts.mode = new->mount_opts.mode; fsi->mount_opts.ptmxmode = new->mount_opts.ptmxmode; fsi->mount_opts.max = new->mount_opts.max; /* * 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 0; } 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, .show_options = devpts_show_options, }; static int devpts_fill_super(struct super_block *s, struct fs_context *fc) { struct pts_fs_info *fsi = DEVPTS_SB(s); struct inode *inode; 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_flags = DCACHE_DONTCACHE; s->s_time_gran = 1; fsi->sb = s; inode = new_inode(s); if (!inode) return -ENOMEM; inode->i_ino = 1; simple_inode_init_ts(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"); return -ENOMEM; } return mknod_ptmx(s, fc); } /* * devpts_get_tree() * * Mount a new (private) instance of devpts. PTYs created in this * instance are independent of the PTYs in other devpts instances. */ static int devpts_get_tree(struct fs_context *fc) { return get_tree_nodev(fc, devpts_fill_super); } static void devpts_free_fc(struct fs_context *fc) { kfree(fc->s_fs_info); } static const struct fs_context_operations devpts_context_ops = { .free = devpts_free_fc, .parse_param = devpts_parse_param, .get_tree = devpts_get_tree, .reconfigure = devpts_reconfigure, }; /* * Set up the filesystem mount context. */ static int devpts_init_fs_context(struct fs_context *fc) { struct pts_fs_info *fsi; fsi = kzalloc_obj(struct pts_fs_info); if (!fsi) return -ENOMEM; ida_init(&fsi->allocated_ptys); fsi->mount_opts.uid = GLOBAL_ROOT_UID; fsi->mount_opts.gid = GLOBAL_ROOT_GID; fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE; fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; fsi->mount_opts.max = NR_UNIX98_PTY_MAX; if (fc->purpose == FS_CONTEXT_FOR_MOUNT && current->nsproxy->mnt_ns == init_task.nsproxy->mnt_ns) fsi->mount_opts.reserve = true; fc->s_fs_info = fsi; fc->ops = &devpts_context_ops; return 0; } static void devpts_kill_sb(struct super_block *sb) { struct pts_fs_info *fsi = DEVPTS_SB(sb); if (fsi) ida_destroy(&fsi->allocated_ptys); kfree(fsi); kill_anon_super(sb); } static struct file_system_type devpts_fs_type = { .name = "devpts", .init_fs_context = devpts_init_fs_context, .parameters = devpts_param_specs, .kill_sb = devpts_kill_sb, .fs_flags = FS_USERNS_MOUNT, }; /* * The normal naming convention is simply /dev/pts/<number>; this conforms * to the System V naming convention */ int devpts_new_index(struct pts_fs_info *fsi) { int index = -ENOSPC; if (atomic_inc_return(&pty_count) >= (pty_limit - (fsi->mount_opts.reserve ? 0 : pty_reserve))) goto out; index = ida_alloc_max(&fsi->allocated_ptys, fsi->mount_opts.max - 1, GFP_KERNEL); out: if (index < 0) atomic_dec(&pty_count); return index; } void devpts_kill_index(struct pts_fs_info *fsi, int idx) { ida_free(&fsi->allocated_ptys, idx); atomic_dec(&pty_count); } /** * devpts_pty_new -- create a new inode in /dev/pts/ * @fsi: Filesystem info for this instance. * @index: used as a name of the node * @priv: what's given back by devpts_get_priv * * The dentry for the created inode is returned. * Remove it from /dev/pts/ with devpts_pty_kill(). */ struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv) { struct dentry *dentry;