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/vs_base.h>
  22 #include <linux/xattr.h>
  23
  24 #define DEVPTS_SUPER_MAGIC 0x1cd1
  25
  26 extern struct xattr_handler devpts_xattr_security_handler;
  27
  28 static struct xattr_handler *devpts_xattr_handlers[] = {
  29 #ifdef CONFIG_DEVPTS_FS_SECURITY
  30         &devpts_xattr_security_handler,
  31 #endif
  32         NULL
  33 };
  34
  35 static int devpts_permission(struct inode *inode, int mask, struct nameidata *nd)
  36 {
  37         int ret = -EACCES;
  38
  39         if (vx_check(inode->i_xid, VX_IDENT))
  40                 ret = generic_permission(inode, mask, NULL);
  41         return ret;
  42 }
  43
  44 struct inode_operations devpts_file_inode_operations = {
  45 #ifdef CONFIG_DEVPTS_FS_XATTR
  46         .setxattr       = generic_setxattr,
  47         .getxattr       = generic_getxattr,
  48         .listxattr      = generic_listxattr,
  49         .removexattr    = generic_removexattr,
  50 #endif
  51         .permission     = devpts_permission,
  52 };
  53
  54 static struct vfsmount *devpts_mnt;
  55 static struct dentry *devpts_root;
  56
  57 static struct {
  58         int setuid;
  59         int setgid;
  60         uid_t   uid;
  61         gid_t   gid;
  62         umode_t mode;
  63 } config = {.mode = 0600};
  64
  65 static int devpts_remount(struct super_block *sb, int *flags, char *data)
  66 {
  67         int setuid = 0;
  68         int setgid = 0;
  69         uid_t uid = 0;
  70         gid_t gid = 0;
  71         umode_t mode = 0600;
  72         char *this_char;
  73
  74         this_char = NULL;
  75         while ((this_char = strsep(&data, ",")) != NULL) {
  76                 int n;
  77                 char dummy;
  78                 if (!*this_char)
  79                         continue;
  80                 if (sscanf(this_char, "uid=%i%c", &n, &dummy) == 1) {
  81                         setuid = 1;
  82                         uid = n;
  83                 } else if (sscanf(this_char, "gid=%i%c", &n, &dummy) == 1) {
  84                         setgid = 1;
  85                         gid = n;
  86                 } else if (sscanf(this_char, "mode=%o%c", &n, &dummy) == 1)
  87                         mode = n & ~S_IFMT;
  88                 else {
  89                         printk("devpts: called with bogus options\n");
  90                         return -EINVAL;
  91                 }
  92         }
  93         config.setuid  = setuid;
  94         config.setgid  = setgid;
  95         config.uid     = uid;
  96         config.gid     = gid;
  97         config.mode    = mode;
  98
  99         return 0;
 100 }
 101
 102 static int devpts_readdir(struct file * filp, void * dirent, filldir_t filldir)
 103 {
 104         struct dentry *dentry = filp->f_dentry;
 105         struct dentry *cursor = filp->private_data;
 106         struct list_head *p, *q = &cursor->d_child;
 107         ino_t ino;
 108         int i = filp->f_pos;
 109
 110         switch (i) {
 111                 case 0:
 112                         ino = dentry->d_inode->i_ino;
 113                         if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
 114                                 break;
 115                         filp->f_pos++;
 116                         i++;
 117                         /* fallthrough */
 118                 case 1:
 119                         ino = parent_ino(dentry);
 120                         if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
 121                                 break;
 122                         filp->f_pos++;
 123                         i++;
 124                         /* fallthrough */
 125                 default:
 126                         spin_lock(&dcache_lock);
 127                         if (filp->f_pos == 2) {
 128                                 list_del(q);
 129                                 list_add(q, &dentry->d_subdirs);
 130                         }
 131                         for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
 132                                 struct dentry *next;
 133                                 next = list_entry(p, struct dentry, d_child);
 134                                 if (d_unhashed(next) || !next->d_inode)
 135                                         continue;
 136                                 if (!vx_check(next->d_inode->i_xid, VX_IDENT))
 137                                         continue;
 138
 139                                 spin_unlock(&dcache_lock);
 140                                 if (filldir(dirent, next->d_name.name,
 141                                         next->d_name.len, filp->f_pos,
 142                                         next->d_inode->i_ino, DT_CHR) < 0)
 143                                         return 0;
 144                                 spin_lock(&dcache_lock);
 145                                 /* next is still alive */
 146                                 list_del(q);
 147                                 list_add(q, p);
 148                                 p = q;
 149                                 filp->f_pos++;
 150                         }
 151                         spin_unlock(&dcache_lock);
 152         }
 153         return 0;
 154 }
 155
 156 static struct file_operations devpts_dir_operations = {
 157         .open           = dcache_dir_open,
 158         .release        = dcache_dir_close,
 159         .llseek         = dcache_dir_lseek,
 160         .read           = generic_read_dir,
 161         .readdir        = devpts_readdir,
 162 };
 163
 164 static struct super_operations devpts_sops = {
 165         .statfs         = simple_statfs,
 166         .remount_fs     = devpts_remount,
 167 };
 168
 169 static int
 170 devpts_fill_super(struct super_block *s, void *data, int silent)
 171 {
 172         struct inode * inode;
 173
 174         s->s_blocksize = 1024;
 175         s->s_blocksize_bits = 10;
 176         s->s_magic = DEVPTS_SUPER_MAGIC;
 177         s->s_op = &devpts_sops;
 178         s->s_xattr = devpts_xattr_handlers;
 179
 180         inode = new_inode(s);
 181         if (!inode)
 182                 goto fail;
 183         inode->i_ino = 1;
 184         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 185         inode->i_blocks = 0;
 186         inode->i_blksize = 1024;
 187         inode->i_uid = inode->i_gid = 0;
 188         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
 189         inode->i_op = &simple_dir_inode_operations;
 190         inode->i_fop = &devpts_dir_operations;
 191         inode->i_nlink = 2;
 192         inode->i_xid = vx_current_xid();
 193
 194         devpts_root = s->s_root = d_alloc_root(inode);
 195         if (s->s_root)
 196                 return 0;
 197
 198         printk("devpts: get root dentry failed\n");
 199         iput(inode);
 200 fail:
 201         return -ENOMEM;
 202 }
 203
 204 static struct super_block *devpts_get_sb(struct file_system_type *fs_type,
 205         int flags, const char *dev_name, void *data)
 206 {
 207         return get_sb_single(fs_type, flags, data, devpts_fill_super);
 208 }
 209
 210 static struct file_system_type devpts_fs_type = {
 211         .owner          = THIS_MODULE,
 212         .name           = "devpts",
 213         .get_sb         = devpts_get_sb,
 214         .kill_sb        = kill_anon_super,
 215 };
 216
 217 /*
 218  * The normal naming convention is simply /dev/pts/<number>; this conforms
 219  * to the System V naming convention
 220  */
 221
 222 static struct dentry *get_node(int num)
 223 {
 224         char s[12];
 225         struct dentry *root = devpts_root;
 226         down(&root->d_inode->i_sem);
 227         return lookup_one_len(s, root, sprintf(s, "%d", num));
 228 }
 229
 230
 231 int devpts_pty_new(struct tty_struct *tty)
 232 {
 233         int number = tty->index;
 234         struct tty_driver *driver = tty->driver;
 235         dev_t device = MKDEV(driver->major, driver->minor_start+number);
 236         struct dentry *dentry;
 237         struct inode *inode = new_inode(devpts_mnt->mnt_sb);
 238
 239         /* We're supposed to be given the slave end of a pty */
 240         BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
 241         BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
 242
 243         if (!inode)
 244                 return -ENOMEM;
 245
 246         inode->i_ino = number+2;
 247         inode->i_blksize = 1024;
 248         inode->i_uid = config.setuid ? config.uid : current->fsuid;
 249         inode->i_gid = config.setgid ? config.gid : current->fsgid;
 250         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 251         init_special_inode(inode, S_IFCHR|config.mode, device);
 252         inode->i_xid = vx_current_xid();
 253         inode->i_op = &devpts_file_inode_operations;
 254         inode->u.generic_ip = tty;
 255
 256         dentry = get_node(number);
 257         if (!IS_ERR(dentry) && !dentry->d_inode)
 258                 d_instantiate(dentry, inode);
 259
 260         up(&devpts_root->d_inode->i_sem);
 261
 262         return 0;
 263 }
 264
 265 struct tty_struct *devpts_get_tty(int number)
 266 {
 267         struct dentry *dentry = get_node(number);
 268         struct tty_struct *tty;
 269
 270         tty = NULL;
 271         if (!IS_ERR(dentry)) {
 272                 if (dentry->d_inode)
 273                         tty = dentry->d_inode->u.generic_ip;
 274                 dput(dentry);
 275         }
 276
 277         up(&devpts_root->d_inode->i_sem);
 278
 279         return tty;
 280 }
 281
 282 void devpts_pty_kill(int number)
 283 {
 284         struct dentry *dentry = get_node(number);
 285
 286         if (!IS_ERR(dentry)) {
 287                 struct inode *inode = dentry->d_inode;
 288                 if (inode) {
 289                         inode->i_nlink--;
 290                         d_delete(dentry);
 291                         dput(dentry);
 292                 }
 293                 dput(dentry);
 294         }
 295         up(&devpts_root->d_inode->i_sem);
 296 }
 297
 298 static int __init init_devpts_fs(void)
 299 {
 300         int err = register_filesystem(&devpts_fs_type);
 301         if (!err) {
 302                 devpts_mnt = kern_mount(&devpts_fs_type);
 303                 if (IS_ERR(devpts_mnt))
 304                         err = PTR_ERR(devpts_mnt);
 305         }
 306         return err;
 307 }
 308
 309 static void __exit exit_devpts_fs(void)
 310 {
 311         unregister_filesystem(&devpts_fs_type);
 312         mntput(devpts_mnt);
 313 }
 314
 315 module_init(init_devpts_fs)
 316 module_exit(exit_devpts_fs)
 317 MODULE_LICENSE("GPL");