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/* -*- 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.
*
* ------------------------------------------------------------------------- */
#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
extern int pty_limit; /* Config limit on Unix98 ptys */
static DEFINE_MUTEX(allocated_ptys_lock);
static struct vfsmount *devpts_mnt;
struct pts_mount_opts {
int setuid;
int setgid;
uid_t uid;
gid_t gid;
umode_t mode;
umode_t ptmxmode;
int newinstance;
};
enum {
Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance,
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"},
#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;
opts->setuid = 0;
opts->setgid = 0;
opts->uid = 0;
opts->gid = 0;
opts->mode = DEVPTS_DEFAULT_MODE;
opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
/* 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;
opts->uid = option;
opts->setuid = 1;
break;
case Opt_gid:
if (match_int(&args[0], &option))
return -EINVAL;
opts->gid = option;
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;
#endif
default:
printk(KERN_ERR "devpts: 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;
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));
d_add(dentry, inode);
fsi->ptmx_dentry = dentry;
rc = 0;
out:
mutex_unlock(&root->d_inode->i_mutex);
return rc;
}
static void update_ptmx_mode(struct pts_fs_info *fsi)
{
struct inode *inode;
if (fsi->ptmx_dentry) {
inode = fsi->ptmx_dentry->d_inode;
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;
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", 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
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