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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 | |
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 | /* |
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 | */ |
102 | static 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 |
166 | static 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; |
210 | out: |
211 | mutex_unlock(&root->d_inode->i_mutex); |
212 | return rc; |
213 | } |
214 | |
215 | static 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 |
224 | static inline void update_ptmx_mode(struct pts_fs_info *fsi) |
225 | { |
226 | return; |
227 | } |
228 | #endif |
229 | |
230 | static 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 | |
249 | static 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 | |
266 | static const struct super_operations devpts_sops = { |
267 | .statfs = simple_statfs, |
268 | .remount_fs = devpts_remount, |
269 | .show_options = devpts_show_options, |
270 | }; |
271 | |
272 | static 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 | |
287 | static int |
288 | devpts_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 | |
319 | free_fsi: |
320 | kfree(s->s_fs_info); |
321 | fail: |
322 | return -ENOMEM; |
323 | } |
324 | |
325 | #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES |
326 | static 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 | */ |
360 | static 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 | simple_set_mnt(mnt, s); |
388 | |
389 | memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts)); |
390 | |
391 | error = mknod_ptmx(s); |
392 | if (error) |
393 | goto out_dput; |
394 | |
395 | return 0; |
396 | |
397 | out_dput: |
398 | dput(s->s_root); /* undo dget() in simple_set_mnt() */ |
399 | |
400 | out_undo_sget: |
401 | deactivate_locked_super(s); |
402 | return error; |
403 | } |
404 | |
405 | #else |
406 | /* |
407 | * This supports only the legacy single-instance semantics (no |
408 | * multiple-instance semantics) |
409 | */ |
410 | static int devpts_get_sb(struct file_system_type *fs_type, int flags, |
411 | const char *dev_name, void *data, struct vfsmount *mnt) |
412 | { |
413 | return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt); |
414 | } |
415 | #endif |
416 | |
417 | static void devpts_kill_sb(struct super_block *sb) |
418 | { |
419 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
420 | |
421 | kfree(fsi); |
422 | kill_litter_super(sb); |
423 | } |
424 | |
425 | static struct file_system_type devpts_fs_type = { |
426 | .name = "devpts", |
427 | .get_sb = devpts_get_sb, |
428 | .kill_sb = devpts_kill_sb, |
429 | }; |
430 | |
431 | /* |
432 | * The normal naming convention is simply /dev/pts/<number>; this conforms |
433 | * to the System V naming convention |
434 | */ |
435 | |
436 | int devpts_new_index(struct inode *ptmx_inode) |
437 | { |
438 | struct super_block *sb = pts_sb_from_inode(ptmx_inode); |
439 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
440 | int index; |
441 | int ida_ret; |
442 | |
443 | retry: |
444 | if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) |
445 | return -ENOMEM; |
446 | |
447 | mutex_lock(&allocated_ptys_lock); |
448 | ida_ret = ida_get_new(&fsi->allocated_ptys, &index); |
449 | if (ida_ret < 0) { |
450 | mutex_unlock(&allocated_ptys_lock); |
451 | if (ida_ret == -EAGAIN) |
452 | goto retry; |
453 | return -EIO; |
454 | } |
455 | |
456 | if (index >= pty_limit) { |
457 | ida_remove(&fsi->allocated_ptys, index); |
458 | mutex_unlock(&allocated_ptys_lock); |
459 | return -EIO; |
460 | } |
461 | mutex_unlock(&allocated_ptys_lock); |
462 | return index; |
463 | } |
464 | |
465 | void devpts_kill_index(struct inode *ptmx_inode, int idx) |
466 | { |
467 | struct super_block *sb = pts_sb_from_inode(ptmx_inode); |
468 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
469 | |
470 | mutex_lock(&allocated_ptys_lock); |
471 | ida_remove(&fsi->allocated_ptys, idx); |
472 | mutex_unlock(&allocated_ptys_lock); |
473 | } |
474 | |
475 | int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty) |
476 | { |
477 | /* tty layer puts index from devpts_new_index() in here */ |
478 | int number = tty->index; |
479 | struct tty_driver *driver = tty->driver; |
480 | dev_t device = MKDEV(driver->major, driver->minor_start+number); |
481 | struct dentry *dentry; |
482 | struct super_block *sb = pts_sb_from_inode(ptmx_inode); |
483 | struct inode *inode = new_inode(sb); |
484 | struct dentry *root = sb->s_root; |
485 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
486 | struct pts_mount_opts *opts = &fsi->mount_opts; |
487 | char s[12]; |
488 | |
489 | /* We're supposed to be given the slave end of a pty */ |
490 | BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY); |
491 | BUG_ON(driver->subtype != PTY_TYPE_SLAVE); |
492 | |
493 | if (!inode) |
494 | return -ENOMEM; |
495 | |
496 | inode->i_ino = number + 3; |
497 | inode->i_uid = opts->setuid ? opts->uid : current_fsuid(); |
498 | inode->i_gid = opts->setgid ? opts->gid : current_fsgid(); |
499 | inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; |
500 | init_special_inode(inode, S_IFCHR|opts->mode, device); |
501 | inode->i_private = tty; |
502 | tty->driver_data = inode; |
503 | |
504 | sprintf(s, "%d", number); |
505 | |
506 | mutex_lock(&root->d_inode->i_mutex); |
507 | |
508 | dentry = d_alloc_name(root, s); |
509 | if (!IS_ERR(dentry)) { |
510 | d_add(dentry, inode); |
511 | fsnotify_create(root->d_inode, dentry); |
512 | } |
513 | |
514 | mutex_unlock(&root->d_inode->i_mutex); |
515 | |
516 | return 0; |
517 | } |
518 | |
519 | struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number) |
520 | { |
521 | struct dentry *dentry; |
522 | struct tty_struct *tty; |
523 | |
524 | BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)); |
525 | |
526 | /* Ensure dentry has not been deleted by devpts_pty_kill() */ |
527 | dentry = d_find_alias(pts_inode); |
528 | if (!dentry) |
529 | return NULL; |
530 | |
531 | tty = NULL; |
532 | if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC) |
533 | tty = (struct tty_struct *)pts_inode->i_private; |
534 | |
535 | dput(dentry); |
536 | |
537 | return tty; |
538 | } |
539 | |
540 | void devpts_pty_kill(struct tty_struct *tty) |
541 | { |
542 | struct inode *inode = tty->driver_data; |
543 | struct super_block *sb = pts_sb_from_inode(inode); |
544 | struct dentry *root = sb->s_root; |
545 | struct dentry *dentry; |
546 | |
547 | BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)); |
548 | |
549 | mutex_lock(&root->d_inode->i_mutex); |
550 | |
551 | dentry = d_find_alias(inode); |
552 | if (IS_ERR(dentry)) |
553 | goto out; |
554 | |
555 | if (dentry) { |
556 | inode->i_nlink--; |
557 | d_delete(dentry); |
558 | dput(dentry); /* d_alloc_name() in devpts_pty_new() */ |
559 | } |
560 | |
561 | dput(dentry); /* d_find_alias above */ |
562 | out: |
563 | mutex_unlock(&root->d_inode->i_mutex); |
564 | } |
565 | |
566 | static int __init init_devpts_fs(void) |
567 | { |
568 | int err = register_filesystem(&devpts_fs_type); |
569 | if (!err) { |
570 | devpts_mnt = kern_mount(&devpts_fs_type); |
571 | if (IS_ERR(devpts_mnt)) { |
572 | err = PTR_ERR(devpts_mnt); |
573 | unregister_filesystem(&devpts_fs_type); |
574 | } |
575 | } |
576 | return err; |
577 | } |
578 | module_init(init_devpts_fs) |
579 |
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