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