diff options
Diffstat (limited to 'fs/devpts')
| -rw-r--r-- | fs/devpts/Makefile | 7 | ||||
| -rw-r--r-- | fs/devpts/inode.c | 639 |
2 files changed, 646 insertions, 0 deletions
diff --git a/fs/devpts/Makefile b/fs/devpts/Makefile new file mode 100644 index 000000000..236696efc --- /dev/null +++ b/fs/devpts/Makefile @@ -0,0 +1,7 @@ +# +# Makefile for the Linux /dev/pts virtual filesystem. +# + +obj-$(CONFIG_UNIX98_PTYS) += devpts.o + +devpts-$(CONFIG_UNIX98_PTYS) := inode.o diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c new file mode 100644 index 000000000..553a3f330 --- /dev/null +++ b/fs/devpts/inode.c @@ -0,0 +1,639 @@ +/* -*- linux-c -*- --------------------------------------------------------- * + * + * linux/fs/devpts/inode.c + * + * Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved + * + * This file is part of the Linux kernel and is made available under + * the terms of the GNU General Public License, version 2, or at your + * option, any later version, incorporated herein by reference. + * + * ------------------------------------------------------------------------- */ + +#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. + */ +static struct dentry *devpts_mount(struct file_system_type *fs_type, + int flags, const char *dev_name, void *data) +{ + return mount_nodev(fs_type, flags, data, devpts_fill_super); +} + +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_litter_super(sb); +} + +static struct file_system_type devpts_fs_type = { + .name = "devpts", + .mount = devpts_mount, + .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/ + * @ptmx_inode: inode of the master + * @device: major+minor of the node to be created + * @index: used as a name of the node + * @priv: what's given back by devpts_get_priv + * + * The created inode is returned. Remove it from /dev/pts/ by devpts_pty_kill. + */ +struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv) +{ + struct dentry *dentry; + struct super_block *sb = fsi->sb; + struct inode *inode; + struct dentry *root; + struct pts_mount_opts *opts; + char s[12]; + + root = sb->s_root; + opts = &fsi->mount_opts; + + inode = new_inode(sb); + if (!inode) + return ERR_PTR(-ENOMEM); + + inode->i_ino = index + 3; + inode->i_uid = opts->setuid ? opts->uid : current_fsuid(); + inode->i_gid = opts->setgid ? opts->gid : current_fsgid(); + inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); + init_special_inode(inode, S_IFCHR|opts->mode, MKDEV(UNIX98_PTY_SLAVE_MAJOR, index)); + + sprintf(s, "%d", index); + + dentry = d_alloc_name(root, s); + if (dentry) { + dentry->d_fsdata = priv; + d_add(dentry, inode); + fsnotify_create(d_inode(root), dentry); + } else { + iput(inode); + dentry = ERR_PTR(-ENOMEM); + } + + return dentry; +} + +/** + * devpts_get_priv -- get private data for a slave + * @pts_inode: inode of the slave + * + * Returns whatever was passed as priv in devpts_pty_new for a given inode. + */ +void *devpts_get_priv(struct dentry *dentry) +{ + if (dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC) + return NULL; + return dentry->d_fsdata; +} + +/** + * devpts_pty_kill -- remove inode form /dev/pts/ + * @inode: inode of the slave to be removed + * + * This is an inverse operation of devpts_pty_new. + */ +void devpts_pty_kill(struct dentry *dentry) +{ + WARN_ON_ONCE(dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC); + + dentry->d_fsdata = NULL; + drop_nlink(dentry->d_inode); + d_delete(dentry); + dput(dentry); /* d_alloc_name() in devpts_pty_new() */ +} + +static int __init init_devpts_fs(void) +{ + int err = register_filesystem(&devpts_fs_type); + if (!err) { + register_sysctl_table(pty_root_table); + } + return err; +} +module_init(init_devpts_fs) |