--- /dev/null
+/* -*- 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 int pty_count;
+
+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,
+ },
+ {}
+};
+
+static DEFINE_MUTEX(allocated_ptys_lock);
+
+static struct vfsmount *devpts_mnt;
+
+struct pts_mount_opts {
+ int setuid;
+ int setgid;
+ kuid_t uid;
+ kgid_t gid;
+ umode_t mode;
+ umode_t ptmxmode;
+ int newinstance;
+ 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"},
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ {Opt_ptmxmode, "ptmxmode=%o"},
+ {Opt_newinstance, "newinstance"},
+ {Opt_max, "max=%d"},
+#endif
+ {Opt_err, NULL}
+};
+
+struct pts_fs_info {
+ struct ida allocated_ptys;
+ struct pts_mount_opts mount_opts;
+ struct dentry *ptmx_dentry;
+};
+
+static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
+{
+ return sb->s_fs_info;
+}
+
+static inline struct super_block *pts_sb_from_inode(struct inode *inode)
+{
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
+ return inode->i_sb;
+#endif
+ return devpts_mnt->mnt_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. The exception is
+ * 'newinstance' option which can only be set/cleared on a mount (i.e.
+ * cannot be changed during remount).
+ *
+ * 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;
+
+ /* newinstance makes sense only on initial mount */
+ if (op == PARSE_MOUNT)
+ opts->newinstance = 0;
+
+ 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;
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ case Opt_ptmxmode:
+ if (match_octal(&args[0], &option))
+ return -EINVAL;
+ opts->ptmxmode = option & S_IALLUGO;
+ break;
+ case Opt_newinstance:
+ /* newinstance makes sense only on initial mount */
+ if (op == PARSE_MOUNT)
+ opts->newinstance = 1;
+ break;
+ case Opt_max:
+ if (match_int(&args[0], &option) ||
+ option < 0 || option > NR_UNIX98_PTY_MAX)
+ return -EINVAL;
+ opts->max = option;
+ break;
+#endif
+ default:
+ pr_err("called with bogus options\n");
+ return -EINVAL;
+ }
+ }
+
+ return 0;
+}
+
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+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 root_uid;
+ kgid_t root_gid;
+
+ root_uid = make_kuid(current_user_ns(), 0);
+ root_gid = make_kgid(current_user_ns(), 0);
+ if (!uid_valid(root_uid) || !gid_valid(root_gid))
+ return -EINVAL;
+
+ mutex_lock(&d_inode(root)->i_mutex);
+
+ /* 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;
+
+ mode = S_IFCHR|opts->ptmxmode;
+ init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
+ inode->i_uid = root_uid;
+ inode->i_gid = root_gid;
+
+ d_add(dentry, inode);
+
+ fsi->ptmx_dentry = dentry;
+ rc = 0;
+out:
+ mutex_unlock(&d_inode(root)->i_mutex);
+ 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;
+ }
+}
+#else
+static inline void update_ptmx_mode(struct pts_fs_info *fsi)
+{
+ return;
+}
+#endif
+
+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;
+
+ sync_filesystem(sb);
+ 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);
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
+ if (opts->max < NR_UNIX98_PTY_MAX)
+ seq_printf(seq, ",max=%d", opts->max);
+#endif
+
+ 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(void)
+{
+ 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;
+
+ return fsi;
+}
+
+static int
+devpts_fill_super(struct super_block *s, void *data, int silent)
+{
+ struct inode *inode;
+
+ s->s_blocksize = 1024;
+ s->s_blocksize_bits = 10;
+ s->s_magic = DEVPTS_SUPER_MAGIC;
+ s->s_op = &devpts_sops;
+ s->s_time_gran = 1;
+
+ s->s_fs_info = new_pts_fs_info();
+ if (!s->s_fs_info)
+ goto fail;
+
+ inode = new_inode(s);
+ if (!inode)
+ goto fail;
+ inode->i_ino = 1;
+ inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
+ 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)
+ return 0;
+
+ pr_err("get root dentry failed\n");
+
+fail:
+ return -ENOMEM;
+}
+
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+static int compare_init_pts_sb(struct super_block *s, void *p)
+{
+ if (devpts_mnt)
+ return devpts_mnt->mnt_sb == s;
+ return 0;
+}
+
+/*
+ * devpts_mount()
+ *
+ * If the '-o newinstance' mount option was specified, mount a new
+ * (private) instance of devpts. PTYs created in this instance are
+ * independent of the PTYs in other devpts instances.
+ *
+ * If the '-o newinstance' option was not specified, mount/remount the
+ * initial kernel mount of devpts. This type of mount gives the
+ * legacy, single-instance semantics.
+ *
+ * The 'newinstance' option is needed to support multiple namespace
+ * semantics in devpts while preserving backward compatibility of the
+ * current 'single-namespace' semantics. i.e all mounts of devpts
+ * without the 'newinstance' mount option should bind to the initial
+ * kernel mount, like mount_single().
+ *
+ * Mounts with 'newinstance' option create a new, private namespace.
+ *
+ * NOTE:
+ *
+ * For single-mount semantics, devpts cannot use mount_single(),
+ * because mount_single()/sget() find and use the super-block from
+ * the most recent mount of devpts. But that recent mount may be a
+ * 'newinstance' mount and mount_single() would pick the newinstance
+ * super-block instead of the initial super-block.
+ */
+static struct dentry *devpts_mount(struct file_system_type *fs_type,
+ int flags, const char *dev_name, void *data)
+{
+ int error;
+ struct pts_mount_opts opts;
+ struct super_block *s;
+
+ error = parse_mount_options(data, PARSE_MOUNT, &opts);
+ if (error)
+ return ERR_PTR(error);
+
+ /* Require newinstance for all user namespace mounts to ensure
+ * the mount options are not changed.
+ */
+ if ((current_user_ns() != &init_user_ns) && !opts.newinstance)
+ return ERR_PTR(-EINVAL);
+
+ if (opts.newinstance)
+ s = sget(fs_type, NULL, set_anon_super, flags, NULL);
+ else
+ s = sget(fs_type, compare_init_pts_sb, set_anon_super, flags,
+ NULL);
+
+ if (IS_ERR(s))
+ return ERR_CAST(s);
+
+ if (!s->s_root) {
+ error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
+ if (error)
+ goto out_undo_sget;
+ s->s_flags |= MS_ACTIVE;
+ }
+
+ memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
+
+ error = mknod_ptmx(s);
+ if (error)
+ goto out_undo_sget;
+
+ return dget(s->s_root);
+
+out_undo_sget:
+ deactivate_locked_super(s);
+ return ERR_PTR(error);
+}
+
+#else
+/*
+ * This supports only the legacy single-instance semantics (no
+ * multiple-instance semantics)
+ */
+static struct dentry *devpts_mount(struct file_system_type *fs_type, int flags,
+ const char *dev_name, void *data)
+{
+ return mount_single(fs_type, flags, data, devpts_fill_super);
+}
+#endif
+
+static void devpts_kill_sb(struct super_block *sb)
+{
+ struct pts_fs_info *fsi = DEVPTS_SB(sb);
+
+ 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,
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ .fs_flags = FS_USERNS_MOUNT | FS_USERNS_DEV_MOUNT,
+#endif
+};
+
+/*
+ * The normal naming convention is simply /dev/pts/<number>; this conforms
+ * to the System V naming convention
+ */
+
+int devpts_new_index(struct inode *ptmx_inode)
+{
+ struct super_block *sb = pts_sb_from_inode(ptmx_inode);
+ struct pts_fs_info *fsi = DEVPTS_SB(sb);
+ int index;
+ int ida_ret;
+
+retry:
+ if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
+ return -ENOMEM;
+
+ mutex_lock(&allocated_ptys_lock);
+ if (pty_count >= pty_limit -
+ (fsi->mount_opts.newinstance ? pty_reserve : 0)) {
+ mutex_unlock(&allocated_ptys_lock);
+ return -ENOSPC;
+ }
+
+ ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
+ if (ida_ret < 0) {
+ mutex_unlock(&allocated_ptys_lock);
+ if (ida_ret == -EAGAIN)
+ goto retry;
+ return -EIO;
+ }
+
+ if (index >= fsi->mount_opts.max) {
+ ida_remove(&fsi->allocated_ptys, index);
+ mutex_unlock(&allocated_ptys_lock);
+ return -ENOSPC;
+ }
+ pty_count++;
+ mutex_unlock(&allocated_ptys_lock);
+ return index;
+}
+
+void devpts_kill_index(struct inode *ptmx_inode, int idx)
+{
+ struct super_block *sb = pts_sb_from_inode(ptmx_inode);
+ struct pts_fs_info *fsi = DEVPTS_SB(sb);
+
+ mutex_lock(&allocated_ptys_lock);
+ ida_remove(&fsi->allocated_ptys, idx);
+ pty_count--;
+ mutex_unlock(&allocated_ptys_lock);
+}
+
+/**
+ * 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 inode *devpts_pty_new(struct inode *ptmx_inode, dev_t device, int index,
+ void *priv)
+{
+ struct dentry *dentry;
+ struct super_block *sb = pts_sb_from_inode(ptmx_inode);
+ 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;
+ char s[12];
+
+ 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;
+ init_special_inode(inode, S_IFCHR|opts->mode, device);
+ inode->i_private = priv;
+
+ sprintf(s, "%d", index);
+
+ mutex_lock(&d_inode(root)->i_mutex);
+
+ dentry = d_alloc_name(root, s);
+ if (dentry) {
+ d_add(dentry, inode);
+ fsnotify_create(d_inode(root), dentry);
+ } else {
+ iput(inode);
+ inode = ERR_PTR(-ENOMEM);
+ }
+
+ mutex_unlock(&d_inode(root)->i_mutex);
+
+ return inode;
+}
+
+/**
+ * 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 inode *pts_inode)
+{
+ struct dentry *dentry;
+ void *priv = NULL;
+
+ BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
+
+ /* Ensure dentry has not been deleted by devpts_pty_kill() */
+ dentry = d_find_alias(pts_inode);
+ if (!dentry)
+ return NULL;
+
+ if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
+ priv = pts_inode->i_private;
+
+ dput(dentry);
+
+ return priv;
+}
+
+/**
+ * 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 inode *inode)
+{
+ struct super_block *sb = pts_sb_from_inode(inode);
+ struct dentry *root = sb->s_root;
+ struct dentry *dentry;
+
+ BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
+
+ mutex_lock(&d_inode(root)->i_mutex);
+
+ dentry = d_find_alias(inode);
+
+ drop_nlink(inode);
+ d_delete(dentry);
+ dput(dentry); /* d_alloc_name() in devpts_pty_new() */
+ dput(dentry); /* d_find_alias above */
+
+ mutex_unlock(&d_inode(root)->i_mutex);
+}
+
+static int __init init_devpts_fs(void)
+{
+ int err = register_filesystem(&devpts_fs_type);
+ struct ctl_table_header *table;
+
+ if (!err) {
+ table = register_sysctl_table(pty_root_table);
+ devpts_mnt = kern_mount(&devpts_fs_type);
+ if (IS_ERR(devpts_mnt)) {
+ err = PTR_ERR(devpts_mnt);
+ unregister_filesystem(&devpts_fs_type);
+ unregister_sysctl_table(table);
+ }
+ }
+ return err;
+}
+module_init(init_devpts_fs)
Code Review / kvmfornfv.git / blobdiff