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/mutex.h> 21 #include <linux/idr.h> 22 #include <linux/devpts_fs.h> 23 #include <linux/parser.h> 24 #include <linux/fsnotify.h> 25 #include <linux/seq_file.h> 26 27 #define DEVPTS_SUPER_MAGIC 0x1cd1 28 29 #define DEVPTS_DEFAULT_MODE 0600 30 /* 31 * ptmx is a new node in /dev/pts and will be unused in legacy (single- 32 * instance) mode. To prevent surprises in user space, set permissions of 33 * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful 34 * permissions. 35 */ 36 #define DEVPTS_DEFAULT_PTMX_MODE 0000 37 #define PTMX_MINOR 2 38 39 extern int pty_limit; /* Config limit on Unix98 ptys */ 40 static DEFINE_MUTEX(allocated_ptys_lock); 41 42 static struct vfsmount *devpts_mnt; 43 44 struct pts_mount_opts { 45 int setuid; 46 int setgid; 47 uid_t uid; 48 gid_t gid; 49 umode_t mode; 50 umode_t ptmxmode; 51 int newinstance; 52 }; 53 54 enum { 55 Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, 56 Opt_err 57 }; 58 59 static const match_table_t tokens = { 60 {Opt_uid, "uid=%u"}, 61 {Opt_gid, "gid=%u"}, 62 {Opt_mode, "mode=%o"}, 63 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES 64 {Opt_ptmxmode, "ptmxmode=%o"}, 65 {Opt_newinstance, "newinstance"}, 66 #endif 67 {Opt_err, NULL} 68 }; 69 70 struct pts_fs_info { 71 struct ida allocated_ptys; 72 struct pts_mount_opts mount_opts; 73 struct dentry *ptmx_dentry; 74 }; 75 76 static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb) 77 { 78 return sb->s_fs_info; 79 } 80 81 static inline struct super_block *pts_sb_from_inode(struct inode *inode) 82 { 83 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES 84 if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC) 85 return inode->i_sb; 86 #endif 87 return devpts_mnt->mnt_sb; 88 } 89 90 #define PARSE_MOUNT 0 91 #define PARSE_REMOUNT 1 92 93 static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts) 94 { 95 char *p; 96 97 opts->setuid = 0; 98 opts->setgid = 0; 99 opts->uid = 0; 100 opts->gid = 0; 101 opts->mode = DEVPTS_DEFAULT_MODE; 102 opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; 103 104 /* newinstance makes sense only on initial mount */ 105 if (op == PARSE_MOUNT) 106 opts->newinstance = 0; 107 108 while ((p = strsep(&data, ",")) != NULL) { 109 substring_t args[MAX_OPT_ARGS]; 110 int token; 111 int option; 112 113 if (!*p) 114 continue; 115 116 token = match_token(p, tokens, args); 117 switch (token) { 118 case Opt_uid: 119 if (match_int(&args[0], &option)) 120 return -EINVAL; 121 opts->uid = option; 122 opts->setuid = 1; 123 break; 124 case Opt_gid: 125 if (match_int(&args[0], &option)) 126 return -EINVAL; 127 opts->gid = option; 128 opts->setgid = 1; 129 break; 130 case Opt_mode: 131 if (match_octal(&args[0], &option)) 132 return -EINVAL; 133 opts->mode = option & S_IALLUGO; 134 break; 135 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES 136 case Opt_ptmxmode: 137 if (match_octal(&args[0], &option)) 138 return -EINVAL; 139 opts->ptmxmode = option & S_IALLUGO; 140 break; 141 case Opt_newinstance: 142 /* newinstance makes sense only on initial mount */ 143 if (op == PARSE_MOUNT) 144 opts->newinstance = 1; 145 break; 146 #endif 147 default: 148 printk(KERN_ERR "devpts: called with bogus options\n"); 149 return -EINVAL; 150 } 151 } 152 153 return 0; 154 } 155 156 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES 157 static int mknod_ptmx(struct super_block *sb) 158 { 159 int mode; 160 int rc = -ENOMEM; 161 struct dentry *dentry; 162 struct inode *inode; 163 struct dentry *root = sb->s_root; 164 struct pts_fs_info *fsi = DEVPTS_SB(sb); 165 struct pts_mount_opts *opts = &fsi->mount_opts; 166 167 mutex_lock(&root->d_inode->i_mutex); 168 169 /* If we have already created ptmx node, return */ 170 if (fsi->ptmx_dentry) { 171 rc = 0; 172 goto out; 173 } 174 175 dentry = d_alloc_name(root, "ptmx"); 176 if (!dentry) { 177 printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n"); 178 goto out; 179 } 180 181 /* 182 * Create a new 'ptmx' node in this mount of devpts. 183 */ 184 inode = new_inode(sb); 185 if (!inode) { 186 printk(KERN_ERR "Unable to alloc inode for ptmx node\n"); 187 dput(dentry); 188 goto out; 189 } 190 191 inode->i_ino = 2; 192 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; 193 194 mode = S_IFCHR|opts->ptmxmode; 195 init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2)); 196 197 d_add(dentry, inode); 198 199 fsi->ptmx_dentry = dentry; 200 rc = 0; 201 out: 202 mutex_unlock(&root->d_inode->i_mutex); 203 return rc; 204 } 205 206 static void update_ptmx_mode(struct pts_fs_info *fsi) 207 { 208 struct inode *inode; 209 if (fsi->ptmx_dentry) { 210 inode = fsi->ptmx_dentry->d_inode; 211 inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode; 212 } 213 } 214 #else 215 static inline void update_ptmx_mode(struct pts_fs_info *fsi) 216 { 217 return; 218 } 219 #endif 220 221 static int devpts_remount(struct super_block *sb, int *flags, char *data) 222 { 223 int err; 224 struct pts_fs_info *fsi = DEVPTS_SB(sb); 225 struct pts_mount_opts *opts = &fsi->mount_opts; 226 227 err = parse_mount_options(data, PARSE_REMOUNT, opts); 228 229 /* 230 * parse_mount_options() restores options to default values 231 * before parsing and may have changed ptmxmode. So, update the 232 * mode in the inode too. Bogus options don't fail the remount, 233 * so do this even on error return. 234 */ 235 update_ptmx_mode(fsi); 236 237 return err; 238 } 239 240 static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs) 241 { 242 struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb); 243 struct pts_mount_opts *opts = &fsi->mount_opts; 244 245 if (opts->setuid) 246 seq_printf(seq, ",uid=%u", opts->uid); 247 if (opts->setgid) 248 seq_printf(seq, ",gid=%u", opts->gid); 249 seq_printf(seq, ",mode=%03o", opts->mode); 250 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES 251 seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode); 252 #endif 253 254 return 0; 255 } 256 257 static const struct super_operations devpts_sops = { 258 .statfs = simple_statfs, 259 .remount_fs = devpts_remount, 260 .show_options = devpts_show_options, 261 }; 262 263 static void *new_pts_fs_info(void) 264 { 265 struct pts_fs_info *fsi; 266 267 fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL); 268 if (!fsi) 269 return NULL; 270 271 ida_init(&fsi->allocated_ptys); 272 fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE; 273 fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; 274 275 return fsi; 276 } 277 278 static int 279 devpts_fill_super(struct super_block *s, void *data, int silent) 280 { 281 struct inode *inode; 282 283 s->s_blocksize = 1024; 284 s->s_blocksize_bits = 10; 285 s->s_magic = DEVPTS_SUPER_MAGIC; 286 s->s_op = &devpts_sops; 287 s->s_time_gran = 1; 288 289 s->s_fs_info = new_pts_fs_info(); 290 if (!s->s_fs_info) 291 goto fail; 292 293 inode = new_inode(s); 294 if (!inode) 295 goto free_fsi; 296 inode->i_ino = 1; 297 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; 298 inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR; 299 inode->i_op = &simple_dir_inode_operations; 300 inode->i_fop = &simple_dir_operations; 301 inode->i_nlink = 2; 302 303 s->s_root = d_alloc_root(inode); 304 if (s->s_root) 305 return 0; 306 307 printk(KERN_ERR "devpts: get root dentry failed\n"); 308 iput(inode); 309 310 free_fsi: 311 kfree(s->s_fs_info); 312 fail: 313 return -ENOMEM; 314 } 315 316 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES 317 static int compare_init_pts_sb(struct super_block *s, void *p) 318 { 319 if (devpts_mnt) 320 return devpts_mnt->mnt_sb == s; 321 return 0; 322 } 323 324 /* 325 * Mount a new (private) instance of devpts. PTYs created in this 326 * instance are independent of the PTYs in other devpts instances. 327 */ 328 static int new_pts_mount(struct file_system_type *fs_type, int flags, 329 void *data, struct pts_mount_opts *opts, struct vfsmount *mnt) 330 { 331 int err; 332 struct pts_fs_info *fsi; 333 334 err = get_sb_nodev(fs_type, flags, data, devpts_fill_super, mnt); 335 if (err) 336 return err; 337 338 fsi = DEVPTS_SB(mnt->mnt_sb); 339 memcpy(&fsi->mount_opts, opts, sizeof(opts)); 340 341 return 0; 342 } 343 344 /* 345 * get_init_pts_sb() 346 * 347 * This interface is needed to support multiple namespace semantics in 348 * devpts while preserving backward compatibility of the current 'single- 349 * namespace' semantics. i.e all mounts of devpts without the 'newinstance' 350 * mount option should bind to the initial kernel mount, like 351 * get_sb_single(). 352 * 353 * Mounts with 'newinstance' option create a new private namespace. 354 * 355 * But for single-mount semantics, devpts cannot use get_sb_single(), 356 * because get_sb_single()/sget() find and use the super-block from 357 * the most recent mount of devpts. But that recent mount may be a 358 * 'newinstance' mount and get_sb_single() would pick the newinstance 359 * super-block instead of the initial super-block. 360 * 361 * This interface is identical to get_sb_single() except that it 362 * consistently selects the 'single-namespace' superblock even in the 363 * presence of the private namespace (i.e 'newinstance') super-blocks. 364 */ 365 static int get_init_pts_sb(struct file_system_type *fs_type, int flags, 366 void *data, struct pts_mount_opts *opts, struct vfsmount *mnt) 367 { 368 struct super_block *s; 369 struct pts_fs_info *fsi; 370 int error; 371 372 s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL); 373 if (IS_ERR(s)) 374 return PTR_ERR(s); 375 376 if (!s->s_root) { 377 s->s_flags = flags; 378 error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0); 379 if (error) { 380 up_write(&s->s_umount); 381 deactivate_super(s); 382 return error; 383 } 384 s->s_flags |= MS_ACTIVE; 385 } 386 387 simple_set_mnt(mnt, s); 388 389 fsi = DEVPTS_SB(mnt->mnt_sb); 390 memcpy(&fsi->mount_opts, opts, sizeof(opts)); 391 392 return 0; 393 } 394 395 /* 396 * Mount or remount the initial kernel mount of devpts. This type of 397 * mount maintains the legacy, single-instance semantics, while the 398 * kernel still allows multiple-instances. 399 */ 400 static int init_pts_mount(struct file_system_type *fs_type, int flags, 401 void *data, struct pts_mount_opts *opts, struct vfsmount *mnt) 402 { 403 int err; 404 405 err = get_init_pts_sb(fs_type, flags, data, opts, mnt); 406 if (err) 407 return err; 408 409 return err; 410 } 411 412 static int devpts_get_sb(struct file_system_type *fs_type, 413 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 414 { 415 int error; 416 struct pts_mount_opts opts; 417 418 memset(&opts, 0, sizeof(opts)); 419 if (data) { 420 error = parse_mount_options(data, PARSE_MOUNT, &opts); 421 if (error) 422 return error; 423 } 424 425 if (opts.newinstance) 426 error = new_pts_mount(fs_type, flags, data, &opts, mnt); 427 else 428 error = init_pts_mount(fs_type, flags, data, &opts, mnt); 429 430 if (error) 431 return error; 432 433 error = mknod_ptmx(mnt->mnt_sb); 434 if (error) 435 goto out_dput; 436 437 return 0; 438 439 out_dput: 440 dput(mnt->mnt_sb->s_root); 441 up_write(&mnt->mnt_sb->s_umount); 442 deactivate_super(mnt->mnt_sb); 443 return error; 444 } 445 446 #else 447 /* 448 * This supports only the legacy single-instance semantics (no 449 * multiple-instance semantics) 450 */ 451 static int devpts_get_sb(struct file_system_type *fs_type, int flags, 452 const char *dev_name, void *data, struct vfsmount *mnt) 453 { 454 return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt); 455 } 456 #endif 457 458 static void devpts_kill_sb(struct super_block *sb) 459 { 460 struct pts_fs_info *fsi = DEVPTS_SB(sb); 461 462 kfree(fsi); 463 kill_litter_super(sb); 464 } 465 466 static struct file_system_type devpts_fs_type = { 467 .owner = THIS_MODULE, 468 .name = "devpts", 469 .get_sb = devpts_get_sb, 470 .kill_sb = devpts_kill_sb, 471 }; 472 473 /* 474 * The normal naming convention is simply /dev/pts/<number>; this conforms 475 * to the System V naming convention 476 */ 477 478 int devpts_new_index(struct inode *ptmx_inode) 479 { 480 struct super_block *sb = pts_sb_from_inode(ptmx_inode); 481 struct pts_fs_info *fsi = DEVPTS_SB(sb); 482 int index; 483 int ida_ret; 484 485 retry: 486 if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) 487 return -ENOMEM; 488 489 mutex_lock(&allocated_ptys_lock); 490 ida_ret = ida_get_new(&fsi->allocated_ptys, &index); 491 if (ida_ret < 0) { 492 mutex_unlock(&allocated_ptys_lock); 493 if (ida_ret == -EAGAIN) 494 goto retry; 495 return -EIO; 496 } 497 498 if (index >= pty_limit) { 499 ida_remove(&fsi->allocated_ptys, index); 500 mutex_unlock(&allocated_ptys_lock); 501 return -EIO; 502 } 503 mutex_unlock(&allocated_ptys_lock); 504 return index; 505 } 506 507 void devpts_kill_index(struct inode *ptmx_inode, int idx) 508 { 509 struct super_block *sb = pts_sb_from_inode(ptmx_inode); 510 struct pts_fs_info *fsi = DEVPTS_SB(sb); 511 512 mutex_lock(&allocated_ptys_lock); 513 ida_remove(&fsi->allocated_ptys, idx); 514 mutex_unlock(&allocated_ptys_lock); 515 } 516 517 int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty) 518 { 519 /* tty layer puts index from devpts_new_index() in here */ 520 int number = tty->index; 521 struct tty_driver *driver = tty->driver; 522 dev_t device = MKDEV(driver->major, driver->minor_start+number); 523 struct dentry *dentry; 524 struct super_block *sb = pts_sb_from_inode(ptmx_inode); 525 struct inode *inode = new_inode(sb); 526 struct dentry *root = sb->s_root; 527 struct pts_fs_info *fsi = DEVPTS_SB(sb); 528 struct pts_mount_opts *opts = &fsi->mount_opts; 529 char s[12]; 530 531 /* We're supposed to be given the slave end of a pty */ 532 BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY); 533 BUG_ON(driver->subtype != PTY_TYPE_SLAVE); 534 535 if (!inode) 536 return -ENOMEM; 537 538 inode->i_ino = number + 3; 539 inode->i_uid = opts->setuid ? opts->uid : current_fsuid(); 540 inode->i_gid = opts->setgid ? opts->gid : current_fsgid(); 541 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; 542 init_special_inode(inode, S_IFCHR|opts->mode, device); 543 inode->i_private = tty; 544 tty->driver_data = inode; 545 546 sprintf(s, "%d", number); 547 548 mutex_lock(&root->d_inode->i_mutex); 549 550 dentry = d_alloc_name(root, s); 551 if (!IS_ERR(dentry)) { 552 d_add(dentry, inode); 553 fsnotify_create(root->d_inode, dentry); 554 } 555 556 mutex_unlock(&root->d_inode->i_mutex); 557 558 return 0; 559 } 560 561 struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number) 562 { 563 BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)); 564 565 if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC) 566 return (struct tty_struct *)pts_inode->i_private; 567 return NULL; 568 } 569 570 void devpts_pty_kill(struct tty_struct *tty) 571 { 572 struct inode *inode = tty->driver_data; 573 struct super_block *sb = pts_sb_from_inode(inode); 574 struct dentry *root = sb->s_root; 575 struct dentry *dentry; 576 577 BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)); 578 579 mutex_lock(&root->d_inode->i_mutex); 580 581 dentry = d_find_alias(inode); 582 if (IS_ERR(dentry)) 583 goto out; 584 585 if (dentry) { 586 inode->i_nlink--; 587 d_delete(dentry); 588 dput(dentry); /* d_alloc_name() in devpts_pty_new() */ 589 } 590 591 dput(dentry); /* d_find_alias above */ 592 out: 593 mutex_unlock(&root->d_inode->i_mutex); 594 } 595 596 static int __init init_devpts_fs(void) 597 { 598 int err = register_filesystem(&devpts_fs_type); 599 if (!err) { 600 devpts_mnt = kern_mount(&devpts_fs_type); 601 if (IS_ERR(devpts_mnt)) 602 err = PTR_ERR(devpts_mnt); 603 } 604 return err; 605 } 606 607 static void __exit exit_devpts_fs(void) 608 { 609 unregister_filesystem(&devpts_fs_type); 610 mntput(devpts_mnt); 611 } 612 613 module_init(init_devpts_fs) 614 module_exit(exit_devpts_fs) 615 MODULE_LICENSE("GPL"); 616