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