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