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