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_readdir(struct file * filp, void * dirent, filldir_t filldir)
 100 {
 101         struct dentry *dentry = filp->f_dentry;
 102         struct dentry *cursor = filp->private_data;
 103         struct list_head *p, *q = &cursor->d_child;
 104         ino_t ino;
 105         int i = filp->f_pos;
 106
 107         switch (i) {
 108                 case 0:
 109                         ino = dentry->d_inode->i_ino;
 110                         if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
 111                                 break;
 112                         filp->f_pos++;
 113                         i++;
 114                         /* fallthrough */
 115                 case 1:
 116                         ino = parent_ino(dentry);
 117                         if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
 118                                 break;
 119                         filp->f_pos++;
 120                         i++;
 121                         /* fallthrough */
 122                 default:
 123                         spin_lock(&dcache_lock);
 124                         if (filp->f_pos == 2) {
 125                                 list_del(q);
 126                                 list_add(q, &dentry->d_subdirs);
 127                         }
 128                         for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
 129                                 struct dentry *next;
 130                                 next = list_entry(p, struct dentry, d_child);
 131                                 if (d_unhashed(next) || !next->d_inode)
 132                                         continue;
 133                                 if (!vx_check(next->d_inode->i_xid, VX_IDENT))
 134                                         continue;
 135
 136                                 spin_unlock(&dcache_lock);
 137                                 if (filldir(dirent, next->d_name.name,
 138                                         next->d_name.len, filp->f_pos,
 139                                         next->d_inode->i_ino, DT_CHR) < 0)
 140                                         return 0;
 141                                 spin_lock(&dcache_lock);
 142                                 /* next is still alive */
 143                                 list_del(q);
 144                                 list_add(q, p);
 145                                 p = q;
 146                                 filp->f_pos++;
 147                         }
 148                         spin_unlock(&dcache_lock);
 149         }
 150         return 0;
 151 }
 152
 153 static struct file_operations devpts_dir_operations = {
 154         .open           = dcache_dir_open,
 155         .release        = dcache_dir_close,
 156         .llseek         = dcache_dir_lseek,
 157         .read           = generic_read_dir,
 158         .readdir        = devpts_readdir,
 159 };
 160
 161 static struct super_operations devpts_sops = {
 162         .statfs         = simple_statfs,
 163         .remount_fs     = devpts_remount,
 164 };
 165
 166 static int
 167 devpts_fill_super(struct super_block *s, void *data, int silent)
 168 {
 169         struct inode * inode;
 170
 171         s->s_blocksize = 1024;
 172         s->s_blocksize_bits = 10;
 173         s->s_magic = DEVPTS_SUPER_MAGIC;
 174         s->s_op = &devpts_sops;
 175         s->s_xattr = devpts_xattr_handlers;
 176         s->s_time_gran = 1;
 177
 178         inode = new_inode(s);
 179         if (!inode)
 180                 goto fail;
 181         inode->i_ino = 1;
 182         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 183         inode->i_blocks = 0;
 184         inode->i_blksize = 1024;
 185         inode->i_uid = inode->i_gid = 0;
 186         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
 187         inode->i_op = &simple_dir_inode_operations;
 188         inode->i_fop = &devpts_dir_operations;
 189         inode->i_nlink = 2;
 190         inode->i_xid = vx_current_xid();
 191
 192         devpts_root = s->s_root = d_alloc_root(inode);
 193         if (s->s_root)
 194                 return 0;
 195
 196         printk("devpts: get root dentry failed\n");
 197         iput(inode);
 198 fail:
 199         return -ENOMEM;
 200 }
 201
 202 static struct super_block *devpts_get_sb(struct file_system_type *fs_type,
 203         int flags, const char *dev_name, void *data)
 204 {
 205         return get_sb_single(fs_type, flags, data, devpts_fill_super);
 206 }
 207
 208 static struct file_system_type devpts_fs_type = {
 209         .owner          = THIS_MODULE,
 210         .name           = "devpts",
 211         .get_sb         = devpts_get_sb,
 212         .kill_sb        = kill_anon_super,
 213 };
 214
 215 /*
 216  * The normal naming convention is simply /dev/pts/<number>; this conforms
 217  * to the System V naming convention
 218  */
 219
 220 static struct dentry *get_node(int num)
 221 {
 222         char s[12];
 223         struct dentry *root = devpts_root;
 224         down(&root->d_inode->i_sem);
 225         return lookup_one_len(s, root, sprintf(s, "%d", num));
 226 }
 227
 228 int devpts_pty_new(struct tty_struct *tty)
 229 {
 230         int number = tty->index;
 231         struct tty_driver *driver = tty->driver;
 232         dev_t device = MKDEV(driver->major, driver->minor_start+number);
 233         struct dentry *dentry;
 234         struct inode *inode = new_inode(devpts_mnt->mnt_sb);
 235
 236         /* We're supposed to be given the slave end of a pty */
 237         BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
 238         BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
 239
 240         if (!inode)
 241                 return -ENOMEM;
 242
 243         inode->i_ino = number+2;
 244         inode->i_blksize = 1024;
 245         inode->i_uid = config.setuid ? config.uid : current->fsuid;
 246         inode->i_gid = config.setgid ? config.gid : current->fsgid;
 247         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 248         init_special_inode(inode, S_IFCHR|config.mode, device);
 249         inode->i_xid = vx_current_xid();
 250         inode->i_op = &devpts_file_inode_operations;
 251         inode->u.generic_ip = tty;
 252
 253         dentry = get_node(number);
 254         if (!IS_ERR(dentry) && !dentry->d_inode)
 255                 d_instantiate(dentry, inode);
 256
 257         up(&devpts_root->d_inode->i_sem);
 258
 259         return 0;
 260 }
 261
 262 struct tty_struct *devpts_get_tty(int number)
 263 {
 264         struct dentry *dentry = get_node(number);
 265         struct tty_struct *tty;
 266
 267         tty = NULL;
 268         if (!IS_ERR(dentry)) {
 269                 if (dentry->d_inode)
 270                         tty = dentry->d_inode->u.generic_ip;
 271                 dput(dentry);
 272         }
 273
 274         up(&devpts_root->d_inode->i_sem);
 275
 276         return tty;
 277 }
 278
 279 void devpts_pty_kill(int number)
 280 {
 281         struct dentry *dentry = get_node(number);
 282
 283         if (!IS_ERR(dentry)) {
 284                 struct inode *inode = dentry->d_inode;
 285                 if (inode) {
 286                         inode->i_nlink--;
 287                         d_delete(dentry);
 288                         dput(dentry);
 289                 }
 290                 dput(dentry);
 291         }
 292         up(&devpts_root->d_inode->i_sem);
 293 }
 294
 295 static int __init init_devpts_fs(void)
 296 {
 297         int err = register_filesystem(&devpts_fs_type);
 298         if (!err) {
 299                 devpts_mnt = kern_mount(&devpts_fs_type);
 300                 if (IS_ERR(devpts_mnt))
 301                         err = PTR_ERR(devpts_mnt);
 302         }
 303         return err;
 304 }
 305
 306 static void __exit exit_devpts_fs(void)
 307 {
 308         unregister_filesystem(&devpts_fs_type);
 309         mntput(devpts_mnt);
 310 }
 311
 312 module_init(init_devpts_fs)
 313 module_exit(exit_devpts_fs)
 314 MODULE_LICENSE("GPL");