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         /* devpts is xid tagged */
  30         if (vx_check((xid_t)inode->i_tag, VS_WATCH_P|VS_IDENT))
  31                 ret = generic_permission(inode, mask, NULL);
  32         return ret;
  33 }
  34
  35 static struct inode_operations devpts_file_inode_operations = {
  36         .permission     = devpts_permission,
  37 };
  38
  39 static struct vfsmount *devpts_mnt;
  40 static struct dentry *devpts_root;
  41
  42 static struct {
  43         int setuid;
  44         int setgid;
  45         uid_t   uid;
  46         gid_t   gid;
  47         umode_t mode;
  48 } config = {.mode = 0600};
  49
  50 enum {
  51         Opt_uid, Opt_gid, Opt_mode,
  52         Opt_err
  53 };
  54
  55 static match_table_t tokens = {
  56         {Opt_uid, "uid=%u"},
  57         {Opt_gid, "gid=%u"},
  58         {Opt_mode, "mode=%o"},
  59         {Opt_err, NULL}
  60 };
  61
  62 static int devpts_remount(struct super_block *sb, int *flags, char *data)
  63 {
  64         char *p;
  65
  66         config.setuid  = 0;
  67         config.setgid  = 0;
  68         config.uid     = 0;
  69         config.gid     = 0;
  70         config.mode    = 0600;
  71
  72         while ((p = strsep(&data, ",")) != NULL) {
  73                 substring_t args[MAX_OPT_ARGS];
  74                 int token;
  75                 int option;
  76
  77                 if (!*p)
  78                         continue;
  79
  80                 token = match_token(p, tokens, args);
  81                 switch (token) {
  82                 case Opt_uid:
  83                         if (match_int(&args[0], &option))
  84                                 return -EINVAL;
  85                         config.uid = option;
  86                         config.setuid = 1;
  87                         break;
  88                 case Opt_gid:
  89                         if (match_int(&args[0], &option))
  90                                 return -EINVAL;
  91                         config.gid = option;
  92                         config.setgid = 1;
  93                         break;
  94                 case Opt_mode:
  95                         if (match_octal(&args[0], &option))
  96                                 return -EINVAL;
  97                         config.mode = option & ~S_IFMT;
  98                         break;
  99                 default:
 100                         printk(KERN_ERR "devpts: called with bogus options\n");
 101                         return -EINVAL;
 102                 }
 103         }
 104
 105         return 0;
 106 }
 107
 108 static int devpts_filter(struct dentry *de)
 109 {
 110         /* devpts is xid tagged */
 111         return vx_check((xid_t)de->d_inode->i_tag, VS_WATCH_P|VS_IDENT);
 112 }
 113
 114 static int devpts_readdir(struct file * filp, void * dirent, filldir_t filldir)
 115 {
 116         return dcache_readdir_filter(filp, dirent, filldir, devpts_filter);
 117 }
 118
 119 static struct file_operations devpts_dir_operations = {
 120         .open           = dcache_dir_open,
 121         .release        = dcache_dir_close,
 122         .llseek         = dcache_dir_lseek,
 123         .read           = generic_read_dir,
 124         .readdir        = devpts_readdir,
 125 };
 126
 127 static struct super_operations devpts_sops = {
 128         .statfs         = simple_statfs,
 129         .remount_fs     = devpts_remount,
 130 };
 131
 132 static int
 133 devpts_fill_super(struct super_block *s, void *data, int silent)
 134 {
 135         struct inode * inode;
 136
 137         s->s_blocksize = 1024;
 138         s->s_blocksize_bits = 10;
 139         s->s_magic = DEVPTS_SUPER_MAGIC;
 140         s->s_op = &devpts_sops;
 141         s->s_time_gran = 1;
 142
 143         inode = new_inode(s);
 144         if (!inode)
 145                 goto fail;
 146         inode->i_ino = 1;
 147         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 148         inode->i_blocks = 0;
 149         inode->i_uid = inode->i_gid = 0;
 150         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
 151         inode->i_op = &simple_dir_inode_operations;
 152         inode->i_fop = &devpts_dir_operations;
 153         inode->i_nlink = 2;
 154         /* devpts is xid tagged */
 155         inode->i_tag = (tag_t)vx_current_xid();
 156
 157         devpts_root = s->s_root = d_alloc_root(inode);
 158         if (s->s_root)
 159                 return 0;
 160
 161         printk("devpts: get root dentry failed\n");
 162         iput(inode);
 163 fail:
 164         return -ENOMEM;
 165 }
 166
 167 static int devpts_get_sb(struct file_system_type *fs_type,
 168         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 169 {
 170         return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
 171 }
 172
 173 static struct file_system_type devpts_fs_type = {
 174         .owner          = THIS_MODULE,
 175         .name           = "devpts",
 176         .get_sb         = devpts_get_sb,
 177         .kill_sb        = kill_anon_super,
 178 };
 179
 180 /*
 181  * The normal naming convention is simply /dev/pts/<number>; this conforms
 182  * to the System V naming convention
 183  */
 184
 185 static struct dentry *get_node(int num)
 186 {
 187         char s[12];
 188         struct dentry *root = devpts_root;
 189         mutex_lock(&root->d_inode->i_mutex);
 190         return lookup_one_len(s, root, sprintf(s, "%d", num));
 191 }
 192
 193 int devpts_pty_new(struct tty_struct *tty)
 194 {
 195         int number = tty->index;
 196         struct tty_driver *driver = tty->driver;
 197         dev_t device = MKDEV(driver->major, driver->minor_start+number);
 198         struct dentry *dentry;
 199         struct inode *inode = new_inode(devpts_mnt->mnt_sb);
 200
 201         /* We're supposed to be given the slave end of a pty */
 202         BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
 203         BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
 204
 205         if (!inode)
 206                 return -ENOMEM;
 207
 208         inode->i_ino = number+2;
 209         inode->i_uid = config.setuid ? config.uid : current->fsuid;
 210         inode->i_gid = config.setgid ? config.gid : current->fsgid;
 211         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 212         init_special_inode(inode, S_IFCHR|config.mode, device);
 213         /* devpts is xid tagged */
 214         inode->i_tag = (tag_t)vx_current_xid();
 215         inode->i_op = &devpts_file_inode_operations;
 216         inode->i_private = tty;
 217
 218         dentry = get_node(number);
 219         if (!IS_ERR(dentry) && !dentry->d_inode)
 220                 d_instantiate(dentry, inode);
 221
 222         mutex_unlock(&devpts_root->d_inode->i_mutex);
 223
 224         return 0;
 225 }
 226
 227 struct tty_struct *devpts_get_tty(int number)
 228 {
 229         struct dentry *dentry = get_node(number);
 230         struct tty_struct *tty;
 231
 232         tty = NULL;
 233         if (!IS_ERR(dentry)) {
 234                 if (dentry->d_inode)
 235                         tty = dentry->d_inode->i_private;
 236                 dput(dentry);
 237         }
 238
 239         mutex_unlock(&devpts_root->d_inode->i_mutex);
 240
 241         return tty;
 242 }
 243
 244 void devpts_pty_kill(int number)
 245 {
 246         struct dentry *dentry = get_node(number);
 247
 248         if (!IS_ERR(dentry)) {
 249                 struct inode *inode = dentry->d_inode;
 250                 if (inode) {
 251                         inode->i_nlink--;
 252                         d_delete(dentry);
 253                         dput(dentry);
 254                 }
 255                 dput(dentry);
 256         }
 257         mutex_unlock(&devpts_root->d_inode->i_mutex);
 258 }
 259
 260 static int __init init_devpts_fs(void)
 261 {
 262         int err = register_filesystem(&devpts_fs_type);
 263         if (!err) {
 264                 devpts_mnt = kern_mount(&devpts_fs_type);
 265                 if (IS_ERR(devpts_mnt))
 266                         err = PTR_ERR(devpts_mnt);
 267         }
 268         return err;
 269 }
 270
 271 static void __exit exit_devpts_fs(void)
 272 {
 273         unregister_filesystem(&devpts_fs_type);
 274         mntput(devpts_mnt);
 275 }
 276
 277 module_init(init_devpts_fs)
 278 module_exit(exit_devpts_fs)
 279 MODULE_LICENSE("GPL");