/*
* 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);
}
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;
}
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;
}
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);
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 >= pty_limit) {
ida_remove(&fsi->allocated_ptys, index);
mutex_unlock(&allocated_ptys_lock);
return -EIO;
}
mutex_unlock(&allocated_ptys_lock);
return index;
}
static void devpts_kill_sb(struct super_block *sb)
{
struct pts_fs_info *fsi = DEVPTS_SB(sb);
kfree(fsi);
kill_litter_super(sb);
}
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 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(&root->d_inode->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) {
printk(KERN_NOTICE "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) {
printk(KERN_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(&root->d_inode->i_mutex);
return rc;
}
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);
mutex_unlock(&allocated_ptys_lock);
}
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);
update_ptmx_mode(fsi);
return err;
}
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 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_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;
}
static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
struct pts_mount_opts *opts = &fsi->mount_opts;
if (opts->setuid)
seq_printf(seq, ",uid=%u", opts->uid);
if (opts->setgid)
seq_printf(seq, ",gid=%u", opts->gid);
seq_printf(seq, ",mode=%03o", opts->mode);
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
#endif
return 0;
}
int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
{
int number = tty->index;
struct tty_driver *driver = tty->driver;
dev_t device = MKDEV(driver->major, driver->minor_start+number);
struct dentry *dentry;
struct super_block *sb = pts_sb_from_inode(ptmx_inode);
struct inode *inode = new_inode(sb);
struct dentry *root = sb->s_root;
struct pts_fs_info *fsi = DEVPTS_SB(sb);
struct pts_mount_opts *opts = &fsi->mount_opts;
int ret = 0;
char s[12];
BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
if (!inode)
return -ENOMEM;
inode->i_ino = number + 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 = tty;
tty->driver_data = inode;
sprintf(s, "%d", number);
mutex_lock(&root->d_inode->i_mutex);
dentry = d_alloc_name(root, s);
if (dentry) {
d_add(dentry, inode);
fsnotify_create(root->d_inode, dentry);
} else {
iput(inode);
ret = -ENOMEM;
}
mutex_unlock(&root->d_inode->i_mutex);
return ret;
}
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;
mutex_lock(&root->d_inode->i_mutex);
if (fsi->ptmx_dentry) {
rc = 0;
goto out;
}
dentry = d_alloc_name(root, "ptmx");
if (!dentry) {
printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
goto out;
}
inode = new_inode(sb);
if (!inode) {
printk(KERN_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));
d_add(dentry, inode);
fsi->ptmx_dentry = dentry;
rc = 0;
out:
mutex_unlock(&root->d_inode->i_mutex);
return rc;
}
/*
* 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);
}
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", opts->uid);
if (opts->setgid)
seq_printf(seq, ",gid=%u", 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 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 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;
}
/*
* devpts_get_sb()
*
* 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 get_sb_single().
*
* Mounts with 'newinstance' option create a new, private namespace.
*
* NOTE:
*
* For single-mount semantics, devpts cannot use get_sb_single(),
* because get_sb_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 get_sb_single() would pick the newinstance
* super-block instead of the initial super-block.
*/
static int devpts_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
int error;
struct pts_mount_opts opts;
struct super_block *s;
error = parse_mount_options(data, PARSE_MOUNT, &opts);
if (error)
return error;
if (opts.newinstance)
s = sget(fs_type, NULL, set_anon_super, NULL);
else
s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
if (IS_ERR(s))
return PTR_ERR(s);
if (!s->s_root) {
s->s_flags = flags;
error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
if (error)
goto out_undo_sget;
s->s_flags |= MS_ACTIVE;
}
simple_set_mnt(mnt, s);
memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
error = mknod_ptmx(s);
if (error)
goto out_dput;
return 0;
out_dput:
dput(s->s_root); /* undo dget() in simple_set_mnt() */
out_undo_sget:
deactivate_locked_super(s);
return error;
}
/**
* 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(&root->d_inode->i_mutex);
dentry = d_alloc_name(root, s);
if (dentry) {
d_add(dentry, inode);
fsnotify_create(root->d_inode, dentry);
} else {
iput(inode);
inode = ERR_PTR(-ENOMEM);
}
mutex_unlock(&root->d_inode->i_mutex);
return inode;
}
