fs/devpts/inode.c

   1 /* -*- linux-c -*- --------------------------------------------------------- *
   2  *
   3  * linux/fs/devpts/inode.c
   4  *
   5  *  Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
   6  *
   7  * This file is part of the Linux kernel and is made available under
   8  * the terms of the GNU General Public License, version 2, or at your
   9  * option, any later version, incorporated herein by reference.
  10  *
  11  * ------------------------------------------------------------------------- */
  12
  13 #include <linux/module.h>
  14 #include <linux/init.h>
  15 #include <linux/fs.h>
  16 #include <linux/sched.h>
  17 #include <linux/namei.h>
  18 #include <linux/mount.h>
  19 #include <linux/tty.h>
  20 #include <linux/devpts_fs.h>
  21 #include <linux/parser.h>
  22 #include <linux/vs_base.h>
  23
  24
  25 static int devpts_permission(struct inode *inode, int mask, struct nameidata *nd)
  26 {
  27         int ret = -EACCES;
  28
  29         if (vx_check(inode->i_xid, VX_IDENT))
  30                 ret = generic_permission(inode, mask, NULL);
  31         return ret;
  32 }
  33
  34 static struct inode_operations devpts_file_inode_operations = {
  35         .permission     = devpts_permission,
  36 };
  37
  38 static struct vfsmount *devpts_mnt;
  39 static struct dentry *devpts_root;
  40
  41 static struct {
  42         int setuid;
  43         int setgid;
  44         uid_t   uid;
  45         gid_t   gid;
  46         umode_t mode;
  47 } config = {.mode = 0600};
  48
  49 enum {
  50         Opt_uid, Opt_gid, Opt_mode,
  51         Opt_err
  52 };
  53
  54 static match_table_t tokens = {
  55         {Opt_uid, "uid=%u"},
  56         {Opt_gid, "gid=%u"},
  57         {Opt_mode, "mode=%o"},
  58         {Opt_err, NULL}
  59 };
  60
  61 static int devpts_remount(struct super_block *sb, int *flags, char *data)
  62 {
  63         char *p;
  64
  65         config.setuid  = 0;
  66         config.setgid  = 0;
  67         config.uid     = 0;
  68         config.gid     = 0;
  69         config.mode    = 0600;
  70
  71         while ((p = strsep(&data, ",")) != NULL) {
  72                 substring_t args[MAX_OPT_ARGS];
  73                 int token;
  74                 int option;
  75
  76                 if (!*p)
  77                         continue;
  78
  79                 token = match_token(p, tokens, args);
  80                 switch (token) {
  81                 case Opt_uid:
  82                         if (match_int(&args[0], &option))
  83                                 return -EINVAL;
  84                         config.uid = option;
  85                         config.setuid = 1;
  86                         break;
  87                 case Opt_gid:
  88                         if (match_int(&args[0], &option))
  89                                 return -EINVAL;
  90                         config.gid = option;
  91                         config.setgid = 1;
  92                         break;
  93                 case Opt_mode:
  94                         if (match_octal(&args[0], &option))
  95                                 return -EINVAL;
  96                         config.mode = option & ~S_IFMT;
  97                         break;
  98                 default:
  99                         printk(KERN_ERR "devpts: called with bogus options\n");
 100                         return -EINVAL;
 101                 }
 102         }
 103
 104         return 0;
 105 }
 106
 107 static int devpts_filter(struct dentry *de)
 108 {
 109         return vx_check(de->d_inode->i_xid, VX_IDENT);
 110 }
 111
 112 static int devpts_readdir(struct file * filp, void * dirent, filldir_t filldir)
 113 {
 114         return dcache_readdir_filter(filp, dirent, filldir, devpts_filter);
 115 }
 116
 117 static struct file_operations devpts_dir_operations = {
 118         .open           = dcache_dir_open,
 119         .release        = dcache_dir_close,
 120         .llseek         = dcache_dir_lseek,
 121         .read           = generic_read_dir,
 122         .readdir        = devpts_readdir,
 123 };
 124
 125 static struct super_operations devpts_sops = {
 126         .statfs         = simple_statfs,
 127         .remount_fs     = devpts_remount,
 128 };
 129
 130 static int
 131 devpts_fill_super(struct super_block *s, void *data, int silent)
 132 {
 133         struct inode * inode;
 134
 135         s->s_blocksize = 1024;
 136         s->s_blocksize_bits = 10;
 137         s->s_magic = DEVPTS_SUPER_MAGIC;
 138         s->s_op = &devpts_sops;
 139         s->s_time_gran = 1;
 140
 141         inode = new_inode(s);
 142         if (!inode)
 143                 goto fail;
 144         inode->i_ino = 1;
 145         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 146         inode->i_blocks = 0;
 147         inode->i_uid = inode->i_gid = 0;
 148         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
 149         inode->i_op = &simple_dir_inode_operations;
 150         inode->i_fop = &devpts_dir_operations;
 151         inode->i_nlink = 2;
 152         inode->i_xid = vx_current_xid();
 153
 154         devpts_root = s->s_root = d_alloc_root(inode);
 155         if (s->s_root)
 156                 return 0;
 157
 158         printk("devpts: get root dentry failed\n");
 159         iput(inode);
 160 fail:
 161         return -ENOMEM;
 162 }
 163
 164 static int devpts_get_sb(struct file_system_type *fs_type,
 165         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 166 {
 167         return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
 168 }
 169
 170 static struct file_system_type devpts_fs_type = {
 171         .owner          = THIS_MODULE,
 172         .name           = "devpts",
 173         .get_sb         = devpts_get_sb,
 174         .kill_sb        = kill_anon_super,
 175 };
 176
 177 /*
 178  * The normal naming convention is simply /dev/pts/<number>; this conforms
 179  * to the System V naming convention
 180  */
 181
 182 static struct dentry *get_node(int num)
 183 {
 184         char s[12];
 185         struct dentry *root = devpts_root;
 186         mutex_lock(&root->d_inode->i_mutex);
 187         return lookup_one_len(s, root, sprintf(s, "%d", num));
 188 }
 189
 190 int devpts_pty_new(struct tty_struct *tty)
 191 {
 192         int number = tty->index;
 193         struct tty_driver *driver = tty->driver;
 194         dev_t device = MKDEV(driver->major, driver->minor_start+number);
 195         struct dentry *dentry;
 196         struct inode *inode = new_inode(devpts_mnt->mnt_sb);
 197
 198         /* We're supposed to be given the slave end of a pty */
 199         BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
 200         BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
 201
 202         if (!inode)
 203                 return -ENOMEM;
 204
 205         inode->i_ino = number+2;
 206         inode->i_uid = config.setuid ? config.uid : current->fsuid;
 207         inode->i_gid = config.setgid ? config.gid : current->fsgid;
 208         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 209         init_special_inode(inode, S_IFCHR|config.mode, device);
 210         inode->i_xid = vx_current_xid();
 211         inode->i_op = &devpts_file_inode_operations;
 212         inode->i_private = tty;
 213
 214         dentry = get_node(number);
 215         if (!IS_ERR(dentry) && !dentry->d_inode)
 216                 d_instantiate(dentry, inode);
 217
 218         mutex_unlock(&devpts_root->d_inode->i_mutex);
 219
 220         return 0;
 221 }
 222
 223 struct tty_struct *devpts_get_tty(int number)
 224 {
 225         struct dentry *dentry = get_node(number);
 226         struct tty_struct *tty;
 227
 228         tty = NULL;
 229         if (!IS_ERR(dentry)) {
 230                 if (dentry->d_inode)
 231                         tty = dentry->d_inode->i_private;
 232                 dput(dentry);
 233         }
 234
 235         mutex_unlock(&devpts_root->d_inode->i_mutex);
 236
 237         return tty;
 238 }
 239
 240 void devpts_pty_kill(int number)
 241 {
 242         struct dentry *dentry = get_node(number);
 243
 244         if (!IS_ERR(dentry)) {
 245                 struct inode *inode = dentry->d_inode;
 246                 if (inode) {
 247                         inode->i_nlink--;
 248                         d_delete(dentry);
 249                         dput(dentry);
 250                 }
 251                 dput(dentry);
 252         }
 253         mutex_unlock(&devpts_root->d_inode->i_mutex);
 254 }
 255
 256 static int __init init_devpts_fs(void)
 257 {
 258         int err = register_filesystem(&devpts_fs_type);
 259         if (!err) {
 260                 devpts_mnt = kern_mount(&devpts_fs_type);
 261                 if (IS_ERR(devpts_mnt))
 262                         err = PTR_ERR(devpts_mnt);
 263         }
 264         return err;
 265 }
 266
 267 static void __exit exit_devpts_fs(void)
 268 {
 269         unregister_filesystem(&devpts_fs_type);
 270         mntput(devpts_mnt);
 271 }
 272
 273 module_init(init_devpts_fs)
 274 module_exit(exit_devpts_fs)
 275 MODULE_LICENSE("GPL");