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/slab.h> 19#include <linux/mount.h> 20#include <linux/tty.h> 21#include <linux/mutex.h> 22#include <linux/magic.h> 23#include <linux/idr.h> 24#include <linux/devpts_fs.h> 25#include <linux/parser.h> 26#include <linux/fsnotify.h> 27#include <linux/seq_file.h> 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 39extern int pty_limit; /* Config limit on Unix98 ptys */ 40static DEFINE_MUTEX(allocated_ptys_lock); 41 42static struct vfsmount *devpts_mnt; 43 44struct 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 54enum { 55 Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, 56 Opt_err 57}; 58 59static 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 70struct pts_fs_info { 71 struct ida allocated_ptys; 72 struct pts_mount_opts mount_opts; 73 struct dentry *ptmx_dentry; 74}; 75 76static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb) 77{ 78 return sb->s_fs_info; 79} 80 81static 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/* 94 * parse_mount_options(): 95 * Set @opts to mount options specified in @data. If an option is not 96 * specified in @data, set it to its default value. The exception is 97 * 'newinstance' option which can only be set/cleared on a mount (i.e. 98 * cannot be changed during remount). 99 * 100 * Note: @data may be NULL (in which case all options are set to default). 101 */ 102static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts) 103{ 104 char *p; 105 106 opts->setuid = 0; 107 opts->setgid = 0; 108 opts->uid = 0; 109 opts->gid = 0; 110 opts->mode = DEVPTS_DEFAULT_MODE; 111 opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; 112 113 /* newinstance makes sense only on initial mount */ 114 if (op == PARSE_MOUNT) 115 opts->newinstance = 0; 116 117 while ((p = strsep(&data, ",")) != NULL) { 118 substring_t args[MAX_OPT_ARGS]; 119 int token; 120 int option; 121 122 if (!*p) 123 continue; 124 125 token = match_token(p, tokens, args); 126 switch (token) { 127 case Opt_uid: 128 if (match_int(&args[0], &option)) 129 return -EINVAL; 130 opts->uid = option; 131 opts->setuid = 1; 132 break; 133 case Opt_gid: 134 if (match_int(&args[0], &option)) 135 return -EINVAL; 136 opts->gid = option; 137 opts->setgid = 1; 138 break; 139 case Opt_mode: 140 if (match_octal(&args[0], &option)) 141 return -EINVAL; 142 opts->mode = option & S_IALLUGO; 143 break; 144#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES 145 case Opt_ptmxmode: 146 if (match_octal(&args[0], &option)) 147 return -EINVAL; 148 opts->ptmxmode = option & S_IALLUGO; 149 break; 150 case Opt_newinstance: 151 /* newinstance makes sense only on initial mount */ 152 if (op == PARSE_MOUNT) 153 opts->newinstance = 1; 154 break; 155#endif 156 default: 157 printk(KERN_ERR "devpts: called with bogus options\n"); 158 return -EINVAL; 159 } 160 } 161 162 return 0; 163} 164 165#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES 166static int mknod_ptmx(struct super_block *sb) 167{ 168 int mode; 169 int rc = -ENOMEM; 170 struct dentry *dentry; 171 struct inode *inode; 172 struct dentry *root = sb->s_root; 173 struct pts_fs_info *fsi = DEVPTS_SB(sb); 174 struct pts_mount_opts *opts = &fsi->mount_opts; 175 176 mutex_lock(&root->d_inode->i_mutex); 177 178 /* If we have already created ptmx node, return */ 179 if (fsi->ptmx_dentry) { 180 rc = 0; 181 goto out; 182 } 183 184 dentry = d_alloc_name(root, "ptmx"); 185 if (!dentry) { 186 printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n"); 187 goto out; 188 } 189 190 /* 191 * Create a new 'ptmx' node in this mount of devpts. 192 */ 193 inode = new_inode(sb); 194 if (!inode) { 195 printk(KERN_ERR "Unable to alloc inode for ptmx node\n"); 196 dput(dentry); 197 goto out; 198 } 199 200 inode->i_ino = 2; 201 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; 202 203 mode = S_IFCHR|opts->ptmxmode; 204 init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2)); 205 206 d_add(dentry, inode); 207 208 fsi->ptmx_dentry = dentry; 209 rc = 0; 210out: 211 mutex_unlock(&root->d_inode->i_mutex); 212 return rc; 213} 214 215static void update_ptmx_mode(struct pts_fs_info *fsi) 216{ 217 struct inode *inode; 218 if (fsi->ptmx_dentry) { 219 inode = fsi->ptmx_dentry->d_inode; 220 inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode; 221 } 222} 223#else 224static inline void update_ptmx_mode(struct pts_fs_info *fsi) 225{ 226 return; 227} 228#endif 229 230static int devpts_remount(struct super_block *sb, int *flags, char *data) 231{ 232 int err; 233 struct pts_fs_info *fsi = DEVPTS_SB(sb); 234 struct pts_mount_opts *opts = &fsi->mount_opts; 235 236 err = parse_mount_options(data, PARSE_REMOUNT, opts); 237 238 /* 239 * parse_mount_options() restores options to default values 240 * before parsing and may have changed ptmxmode. So, update the 241 * mode in the inode too. Bogus options don't fail the remount, 242 * so do this even on error return. 243 */ 244 update_ptmx_mode(fsi); 245 246 return err; 247} 248 249static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs) 250{ 251 struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb); 252 struct pts_mount_opts *opts = &fsi->mount_opts; 253 254 if (opts->setuid) 255 seq_printf(seq, ",uid=%u", opts->uid); 256 if (opts->setgid) 257 seq_printf(seq, ",gid=%u", opts->gid); 258 seq_printf(seq, ",mode=%03o", opts->mode); 259#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES 260 seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode); 261#endif 262 263 return 0; 264} 265 266static const struct super_operations devpts_sops = { 267 .statfs = simple_statfs, 268 .remount_fs = devpts_remount, 269 .show_options = devpts_show_options, 270}; 271 272static void *new_pts_fs_info(void) 273{ 274 struct pts_fs_info *fsi; 275 276 fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL); 277 if (!fsi) 278 return NULL; 279 280 ida_init(&fsi->allocated_ptys); 281 fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE; 282 fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; 283 284 return fsi; 285} 286 287static int 288devpts_fill_super(struct super_block *s, void *data, int silent) 289{ 290 struct inode *inode; 291 292 s->s_blocksize = 1024; 293 s->s_blocksize_bits = 10; 294 s->s_magic = DEVPTS_SUPER_MAGIC; 295 s->s_op = &devpts_sops; 296 s->s_time_gran = 1; 297 298 s->s_fs_info = new_pts_fs_info(); 299 if (!s->s_fs_info) 300 goto fail; 301 302 inode = new_inode(s); 303 if (!inode) 304 goto free_fsi; 305 inode->i_ino = 1; 306 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; 307 inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR; 308 inode->i_op = &simple_dir_inode_operations; 309 inode->i_fop = &simple_dir_operations; 310 inode->i_nlink = 2; 311 312 s->s_root = d_alloc_root(inode); 313 if (s->s_root) 314 return 0; 315 316 printk(KERN_ERR "devpts: get root dentry failed\n"); 317 iput(inode); 318 319free_fsi: 320 kfree(s->s_fs_info); 321fail: 322 return -ENOMEM; 323} 324 325#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES 326static int compare_init_pts_sb(struct super_block *s, void *p) 327{ 328 if (devpts_mnt) 329 return devpts_mnt->mnt_sb == s; 330 return 0; 331} 332 333/* 334 * devpts_get_sb() 335 * 336 * If the '-o newinstance' mount option was specified, mount a new 337 * (private) instance of devpts. PTYs created in this instance are 338 * independent of the PTYs in other devpts instances. 339 * 340 * If the '-o newinstance' option was not specified, mount/remount the 341 * initial kernel mount of devpts. This type of mount gives the 342 * legacy, single-instance semantics. 343 * 344 * The 'newinstance' option is needed to support multiple namespace 345 * semantics in devpts while preserving backward compatibility of the 346 * current 'single-namespace' semantics. i.e all mounts of devpts 347 * without the 'newinstance' mount option should bind to the initial 348 * kernel mount, like get_sb_single(). 349 * 350 * Mounts with 'newinstance' option create a new, private namespace. 351 * 352 * NOTE: 353 * 354 * For single-mount semantics, devpts cannot use get_sb_single(), 355 * because get_sb_single()/sget() find and use the super-block from 356 * the most recent mount of devpts. But that recent mount may be a 357 * 'newinstance' mount and get_sb_single() would pick the newinstance 358 * super-block instead of the initial super-block. 359 */ 360static int devpts_get_sb(struct file_system_type *fs_type, 361 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 362{ 363 int error; 364 struct pts_mount_opts opts; 365 struct super_block *s; 366 367 error = parse_mount_options(data, PARSE_MOUNT, &opts); 368 if (error) 369 return error; 370 371 if (opts.newinstance) 372 s = sget(fs_type, NULL, set_anon_super, NULL); 373 else 374 s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL); 375 376 if (IS_ERR(s)) 377 return PTR_ERR(s); 378 379 if (!s->s_root) { 380 s->s_flags = flags; 381 error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0); 382 if (error) 383 goto out_undo_sget; 384 s->s_flags |= MS_ACTIVE; 385 } 386 387 memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts)); 388 389 error = mknod_ptmx(s); 390 if (error) 391 goto out_undo_sget; 392 393 simple_set_mnt(mnt, s); 394 395 return 0; 396 397out_undo_sget: 398 deactivate_locked_super(s); 399 return error; 400} 401 402#else 403/* 404 * This supports only the legacy single-instance semantics (no 405 * multiple-instance semantics) 406 */ 407static int devpts_get_sb(struct file_system_type *fs_type, int flags, 408 const char *dev_name, void *data, struct vfsmount *mnt) 409{ 410 return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt); 411} 412#endif 413 414static void devpts_kill_sb(struct super_block *sb) 415{ 416 struct pts_fs_info *fsi = DEVPTS_SB(sb); 417 418 kfree(fsi); 419 kill_litter_super(sb); 420} 421 422static struct file_system_type devpts_fs_type = { 423 .name = "devpts", 424 .get_sb = devpts_get_sb, 425 .kill_sb = devpts_kill_sb, 426}; 427 428/* 429 * The normal naming convention is simply /dev/pts/<number>; this conforms 430 * to the System V naming convention 431 */ 432 433int devpts_new_index(struct inode *ptmx_inode) 434{ 435 struct super_block *sb = pts_sb_from_inode(ptmx_inode); 436 struct pts_fs_info *fsi = DEVPTS_SB(sb); 437 int index; 438 int ida_ret; 439 440retry: 441 if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) 442 return -ENOMEM; 443 444 mutex_lock(&allocated_ptys_lock); 445 ida_ret = ida_get_new(&fsi->allocated_ptys, &index); 446 if (ida_ret < 0) { 447 mutex_unlock(&allocated_ptys_lock); 448 if (ida_ret == -EAGAIN) 449 goto retry; 450 return -EIO; 451 } 452 453 if (index >= pty_limit) { 454 ida_remove(&fsi->allocated_ptys, index); 455 mutex_unlock(&allocated_ptys_lock); 456 return -EIO; 457 } 458 mutex_unlock(&allocated_ptys_lock); 459 return index; 460} 461 462void devpts_kill_index(struct inode *ptmx_inode, int idx) 463{ 464 struct super_block *sb = pts_sb_from_inode(ptmx_inode); 465 struct pts_fs_info *fsi = DEVPTS_SB(sb); 466 467 mutex_lock(&allocated_ptys_lock); 468 ida_remove(&fsi->allocated_ptys, idx); 469 mutex_unlock(&allocated_ptys_lock); 470} 471 472int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty) 473{ 474 /* tty layer puts index from devpts_new_index() in here */ 475 int number = tty->index; 476 struct tty_driver *driver = tty->driver; 477 dev_t device = MKDEV(driver->major, driver->minor_start+number); 478 struct dentry *dentry; 479 struct super_block *sb = pts_sb_from_inode(ptmx_inode); 480 struct inode *inode = new_inode(sb); 481 struct dentry *root = sb->s_root; 482 struct pts_fs_info *fsi = DEVPTS_SB(sb); 483 struct pts_mount_opts *opts = &fsi->mount_opts; 484 char s[12]; 485 486 /* We're supposed to be given the slave end of a pty */ 487 BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY); 488 BUG_ON(driver->subtype != PTY_TYPE_SLAVE); 489 490 if (!inode) 491 return -ENOMEM; 492 493 inode->i_ino = number + 3; 494 inode->i_uid = opts->setuid ? opts->uid : current_fsuid(); 495 inode->i_gid = opts->setgid ? opts->gid : current_fsgid(); 496 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; 497 init_special_inode(inode, S_IFCHR|opts->mode, device); 498 inode->i_private = tty; 499 tty->driver_data = inode; 500 501 sprintf(s, "%d", number); 502 503 mutex_lock(&root->d_inode->i_mutex); 504 505 dentry = d_alloc_name(root, s); 506 if (!IS_ERR(dentry)) { 507 d_add(dentry, inode); 508 fsnotify_create(root->d_inode, dentry); 509 } 510 511 mutex_unlock(&root->d_inode->i_mutex); 512 513 return 0; 514} 515 516struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number) 517{ 518 struct dentry *dentry; 519 struct tty_struct *tty; 520 521 BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)); 522 523 /* Ensure dentry has not been deleted by devpts_pty_kill() */ 524 dentry = d_find_alias(pts_inode); 525 if (!dentry) 526 return NULL; 527 528 tty = NULL; 529 if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC) 530 tty = (struct tty_struct *)pts_inode->i_private; 531 532 dput(dentry); 533 534 return tty; 535} 536 537void devpts_pty_kill(struct tty_struct *tty) 538{ 539 struct inode *inode = tty->driver_data; 540 struct super_block *sb = pts_sb_from_inode(inode); 541 struct dentry *root = sb->s_root; 542 struct dentry *dentry; 543 544 BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)); 545 546 mutex_lock(&root->d_inode->i_mutex); 547 548 dentry = d_find_alias(inode); 549 if (IS_ERR(dentry)) 550 goto out; 551 552 if (dentry) { 553 inode->i_nlink--; 554 d_delete(dentry); 555 dput(dentry); /* d_alloc_name() in devpts_pty_new() */ 556 } 557 558 dput(dentry); /* d_find_alias above */ 559out: 560 mutex_unlock(&root->d_inode->i_mutex); 561} 562 563static int __init init_devpts_fs(void) 564{ 565 int err = register_filesystem(&devpts_fs_type); 566 if (!err) { 567 devpts_mnt = kern_mount(&devpts_fs_type); 568 if (IS_ERR(devpts_mnt)) { 569 err = PTR_ERR(devpts_mnt); 570 unregister_filesystem(&devpts_fs_type); 571 } 572 } 573 return err; 574} 575module_init(init_devpts_fs) 576