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