This source file includes following definitions.
- DEVPTS_SB
- devpts_ptmx_path
- devpts_mntget
- devpts_acquire
- devpts_release
- parse_mount_options
- mknod_ptmx
- update_ptmx_mode
- devpts_remount
- devpts_show_options
- new_pts_fs_info
- devpts_fill_super
- devpts_mount
- devpts_kill_sb
- devpts_new_index
- devpts_kill_index
- devpts_pty_new
- devpts_get_priv
- devpts_pty_kill
- init_devpts_fs
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10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/fs.h>
15 #include <linux/sched.h>
16 #include <linux/namei.h>
17 #include <linux/slab.h>
18 #include <linux/mount.h>
19 #include <linux/tty.h>
20 #include <linux/mutex.h>
21 #include <linux/magic.h>
22 #include <linux/idr.h>
23 #include <linux/devpts_fs.h>
24 #include <linux/parser.h>
25 #include <linux/fsnotify.h>
26 #include <linux/seq_file.h>
27
28 #define DEVPTS_DEFAULT_MODE 0600
29
30
31
32
33
34
35 #define DEVPTS_DEFAULT_PTMX_MODE 0000
36 #define PTMX_MINOR 2
37
38
39
40
41
42 static int pty_limit = NR_UNIX98_PTY_DEFAULT;
43 static int pty_reserve = NR_UNIX98_PTY_RESERVE;
44 static int pty_limit_min;
45 static int pty_limit_max = INT_MAX;
46 static atomic_t pty_count = ATOMIC_INIT(0);
47
48 static struct ctl_table pty_table[] = {
49 {
50 .procname = "max",
51 .maxlen = sizeof(int),
52 .mode = 0644,
53 .data = &pty_limit,
54 .proc_handler = proc_dointvec_minmax,
55 .extra1 = &pty_limit_min,
56 .extra2 = &pty_limit_max,
57 }, {
58 .procname = "reserve",
59 .maxlen = sizeof(int),
60 .mode = 0644,
61 .data = &pty_reserve,
62 .proc_handler = proc_dointvec_minmax,
63 .extra1 = &pty_limit_min,
64 .extra2 = &pty_limit_max,
65 }, {
66 .procname = "nr",
67 .maxlen = sizeof(int),
68 .mode = 0444,
69 .data = &pty_count,
70 .proc_handler = proc_dointvec,
71 },
72 {}
73 };
74
75 static struct ctl_table pty_kern_table[] = {
76 {
77 .procname = "pty",
78 .mode = 0555,
79 .child = pty_table,
80 },
81 {}
82 };
83
84 static struct ctl_table pty_root_table[] = {
85 {
86 .procname = "kernel",
87 .mode = 0555,
88 .child = pty_kern_table,
89 },
90 {}
91 };
92
93 struct pts_mount_opts {
94 int setuid;
95 int setgid;
96 kuid_t uid;
97 kgid_t gid;
98 umode_t mode;
99 umode_t ptmxmode;
100 int reserve;
101 int max;
102 };
103
104 enum {
105 Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, Opt_max,
106 Opt_err
107 };
108
109 static const match_table_t tokens = {
110 {Opt_uid, "uid=%u"},
111 {Opt_gid, "gid=%u"},
112 {Opt_mode, "mode=%o"},
113 {Opt_ptmxmode, "ptmxmode=%o"},
114 {Opt_newinstance, "newinstance"},
115 {Opt_max, "max=%d"},
116 {Opt_err, NULL}
117 };
118
119 struct pts_fs_info {
120 struct ida allocated_ptys;
121 struct pts_mount_opts mount_opts;
122 struct super_block *sb;
123 struct dentry *ptmx_dentry;
124 };
125
126 static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
127 {
128 return sb->s_fs_info;
129 }
130
131 static int devpts_ptmx_path(struct path *path)
132 {
133 struct super_block *sb;
134 int err;
135
136
137 err = path_pts(path);
138 if (err)
139 return err;
140
141
142 sb = path->mnt->mnt_sb;
143 if ((sb->s_magic != DEVPTS_SUPER_MAGIC) ||
144 (path->mnt->mnt_root != sb->s_root))
145 return -ENODEV;
146
147 return 0;
148 }
149
150
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153
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156
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158
159
160
161
162
163
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165
166
167
168 struct vfsmount *devpts_mntget(struct file *filp, struct pts_fs_info *fsi)
169 {
170 struct path path;
171 int err = 0;
172
173 path = filp->f_path;
174 path_get(&path);
175
176
177
178
179 while (path.mnt->mnt_root == path.dentry)
180 if (follow_up(&path) == 0)
181 break;
182
183
184 if ((path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) ||
185 (DEVPTS_SB(path.mnt->mnt_sb) != fsi))
186 err = devpts_ptmx_path(&path);
187 dput(path.dentry);
188 if (!err) {
189 if (DEVPTS_SB(path.mnt->mnt_sb) == fsi)
190 return path.mnt;
191
192 err = -ENODEV;
193 }
194
195 mntput(path.mnt);
196 return ERR_PTR(err);
197 }
198
199 struct pts_fs_info *devpts_acquire(struct file *filp)
200 {
201 struct pts_fs_info *result;
202 struct path path;
203 struct super_block *sb;
204
205 path = filp->f_path;
206 path_get(&path);
207
208
209 if (path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) {
210 int err;
211
212 err = devpts_ptmx_path(&path);
213 if (err) {
214 result = ERR_PTR(err);
215 goto out;
216 }
217 }
218
219
220
221
222 sb = path.mnt->mnt_sb;
223 atomic_inc(&sb->s_active);
224 result = DEVPTS_SB(sb);
225
226 out:
227 path_put(&path);
228 return result;
229 }
230
231 void devpts_release(struct pts_fs_info *fsi)
232 {
233 deactivate_super(fsi->sb);
234 }
235
236 #define PARSE_MOUNT 0
237 #define PARSE_REMOUNT 1
238
239
240
241
242
243
244
245
246 static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
247 {
248 char *p;
249 kuid_t uid;
250 kgid_t gid;
251
252 opts->setuid = 0;
253 opts->setgid = 0;
254 opts->uid = GLOBAL_ROOT_UID;
255 opts->gid = GLOBAL_ROOT_GID;
256 opts->mode = DEVPTS_DEFAULT_MODE;
257 opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
258 opts->max = NR_UNIX98_PTY_MAX;
259
260
261
262
263 if (op == PARSE_MOUNT)
264 opts->reserve =
265 (current->nsproxy->mnt_ns == init_task.nsproxy->mnt_ns);
266
267 while ((p = strsep(&data, ",")) != NULL) {
268 substring_t args[MAX_OPT_ARGS];
269 int token;
270 int option;
271
272 if (!*p)
273 continue;
274
275 token = match_token(p, tokens, args);
276 switch (token) {
277 case Opt_uid:
278 if (match_int(&args[0], &option))
279 return -EINVAL;
280 uid = make_kuid(current_user_ns(), option);
281 if (!uid_valid(uid))
282 return -EINVAL;
283 opts->uid = uid;
284 opts->setuid = 1;
285 break;
286 case Opt_gid:
287 if (match_int(&args[0], &option))
288 return -EINVAL;
289 gid = make_kgid(current_user_ns(), option);
290 if (!gid_valid(gid))
291 return -EINVAL;
292 opts->gid = gid;
293 opts->setgid = 1;
294 break;
295 case Opt_mode:
296 if (match_octal(&args[0], &option))
297 return -EINVAL;
298 opts->mode = option & S_IALLUGO;
299 break;
300 case Opt_ptmxmode:
301 if (match_octal(&args[0], &option))
302 return -EINVAL;
303 opts->ptmxmode = option & S_IALLUGO;
304 break;
305 case Opt_newinstance:
306 break;
307 case Opt_max:
308 if (match_int(&args[0], &option) ||
309 option < 0 || option > NR_UNIX98_PTY_MAX)
310 return -EINVAL;
311 opts->max = option;
312 break;
313 default:
314 pr_err("called with bogus options\n");
315 return -EINVAL;
316 }
317 }
318
319 return 0;
320 }
321
322 static int mknod_ptmx(struct super_block *sb)
323 {
324 int mode;
325 int rc = -ENOMEM;
326 struct dentry *dentry;
327 struct inode *inode;
328 struct dentry *root = sb->s_root;
329 struct pts_fs_info *fsi = DEVPTS_SB(sb);
330 struct pts_mount_opts *opts = &fsi->mount_opts;
331 kuid_t ptmx_uid = current_fsuid();
332 kgid_t ptmx_gid = current_fsgid();
333
334 inode_lock(d_inode(root));
335
336
337 if (fsi->ptmx_dentry) {
338 rc = 0;
339 goto out;
340 }
341
342 dentry = d_alloc_name(root, "ptmx");
343 if (!dentry) {
344 pr_err("Unable to alloc dentry for ptmx node\n");
345 goto out;
346 }
347
348
349
350
351 inode = new_inode(sb);
352 if (!inode) {
353 pr_err("Unable to alloc inode for ptmx node\n");
354 dput(dentry);
355 goto out;
356 }
357
358 inode->i_ino = 2;
359 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
360
361 mode = S_IFCHR|opts->ptmxmode;
362 init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
363 inode->i_uid = ptmx_uid;
364 inode->i_gid = ptmx_gid;
365
366 d_add(dentry, inode);
367
368 fsi->ptmx_dentry = dentry;
369 rc = 0;
370 out:
371 inode_unlock(d_inode(root));
372 return rc;
373 }
374
375 static void update_ptmx_mode(struct pts_fs_info *fsi)
376 {
377 struct inode *inode;
378 if (fsi->ptmx_dentry) {
379 inode = d_inode(fsi->ptmx_dentry);
380 inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
381 }
382 }
383
384 static int devpts_remount(struct super_block *sb, int *flags, char *data)
385 {
386 int err;
387 struct pts_fs_info *fsi = DEVPTS_SB(sb);
388 struct pts_mount_opts *opts = &fsi->mount_opts;
389
390 err = parse_mount_options(data, PARSE_REMOUNT, opts);
391
392
393
394
395
396
397
398 update_ptmx_mode(fsi);
399
400 return err;
401 }
402
403 static int devpts_show_options(struct seq_file *seq, struct dentry *root)
404 {
405 struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb);
406 struct pts_mount_opts *opts = &fsi->mount_opts;
407
408 if (opts->setuid)
409 seq_printf(seq, ",uid=%u",
410 from_kuid_munged(&init_user_ns, opts->uid));
411 if (opts->setgid)
412 seq_printf(seq, ",gid=%u",
413 from_kgid_munged(&init_user_ns, opts->gid));
414 seq_printf(seq, ",mode=%03o", opts->mode);
415 seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
416 if (opts->max < NR_UNIX98_PTY_MAX)
417 seq_printf(seq, ",max=%d", opts->max);
418
419 return 0;
420 }
421
422 static const struct super_operations devpts_sops = {
423 .statfs = simple_statfs,
424 .remount_fs = devpts_remount,
425 .show_options = devpts_show_options,
426 };
427
428 static void *new_pts_fs_info(struct super_block *sb)
429 {
430 struct pts_fs_info *fsi;
431
432 fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
433 if (!fsi)
434 return NULL;
435
436 ida_init(&fsi->allocated_ptys);
437 fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
438 fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
439 fsi->sb = sb;
440
441 return fsi;
442 }
443
444 static int
445 devpts_fill_super(struct super_block *s, void *data, int silent)
446 {
447 struct inode *inode;
448 int error;
449
450 s->s_iflags &= ~SB_I_NODEV;
451 s->s_blocksize = 1024;
452 s->s_blocksize_bits = 10;
453 s->s_magic = DEVPTS_SUPER_MAGIC;
454 s->s_op = &devpts_sops;
455 s->s_d_op = &simple_dentry_operations;
456 s->s_time_gran = 1;
457
458 error = -ENOMEM;
459 s->s_fs_info = new_pts_fs_info(s);
460 if (!s->s_fs_info)
461 goto fail;
462
463 error = parse_mount_options(data, PARSE_MOUNT, &DEVPTS_SB(s)->mount_opts);
464 if (error)
465 goto fail;
466
467 error = -ENOMEM;
468 inode = new_inode(s);
469 if (!inode)
470 goto fail;
471 inode->i_ino = 1;
472 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
473 inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
474 inode->i_op = &simple_dir_inode_operations;
475 inode->i_fop = &simple_dir_operations;
476 set_nlink(inode, 2);
477
478 s->s_root = d_make_root(inode);
479 if (!s->s_root) {
480 pr_err("get root dentry failed\n");
481 goto fail;
482 }
483
484 error = mknod_ptmx(s);
485 if (error)
486 goto fail_dput;
487
488 return 0;
489 fail_dput:
490 dput(s->s_root);
491 s->s_root = NULL;
492 fail:
493 return error;
494 }
495
496
497
498
499
500
501
502 static struct dentry *devpts_mount(struct file_system_type *fs_type,
503 int flags, const char *dev_name, void *data)
504 {
505 return mount_nodev(fs_type, flags, data, devpts_fill_super);
506 }
507
508 static void devpts_kill_sb(struct super_block *sb)
509 {
510 struct pts_fs_info *fsi = DEVPTS_SB(sb);
511
512 if (fsi)
513 ida_destroy(&fsi->allocated_ptys);
514 kfree(fsi);
515 kill_litter_super(sb);
516 }
517
518 static struct file_system_type devpts_fs_type = {
519 .name = "devpts",
520 .mount = devpts_mount,
521 .kill_sb = devpts_kill_sb,
522 .fs_flags = FS_USERNS_MOUNT,
523 };
524
525
526
527
528
529
530 int devpts_new_index(struct pts_fs_info *fsi)
531 {
532 int index = -ENOSPC;
533
534 if (atomic_inc_return(&pty_count) >= (pty_limit -
535 (fsi->mount_opts.reserve ? 0 : pty_reserve)))
536 goto out;
537
538 index = ida_alloc_max(&fsi->allocated_ptys, fsi->mount_opts.max - 1,
539 GFP_KERNEL);
540
541 out:
542 if (index < 0)
543 atomic_dec(&pty_count);
544 return index;
545 }
546
547 void devpts_kill_index(struct pts_fs_info *fsi, int idx)
548 {
549 ida_free(&fsi->allocated_ptys, idx);
550 atomic_dec(&pty_count);
551 }
552
553
554
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556
557
558
559
560
561
562 struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv)
563 {
564 struct dentry *dentry;
565 struct super_block *sb = fsi->sb;
566 struct inode *inode;
567 struct dentry *root;
568 struct pts_mount_opts *opts;
569 char s[12];
570
571 root = sb->s_root;
572 opts = &fsi->mount_opts;
573
574 inode = new_inode(sb);
575 if (!inode)
576 return ERR_PTR(-ENOMEM);
577
578 inode->i_ino = index + 3;
579 inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
580 inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
581 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
582 init_special_inode(inode, S_IFCHR|opts->mode, MKDEV(UNIX98_PTY_SLAVE_MAJOR, index));
583
584 sprintf(s, "%d", index);
585
586 dentry = d_alloc_name(root, s);
587 if (dentry) {
588 dentry->d_fsdata = priv;
589 d_add(dentry, inode);
590 fsnotify_create(d_inode(root), dentry);
591 } else {
592 iput(inode);
593 dentry = ERR_PTR(-ENOMEM);
594 }
595
596 return dentry;
597 }
598
599
600
601
602
603
604
605 void *devpts_get_priv(struct dentry *dentry)
606 {
607 if (dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC)
608 return NULL;
609 return dentry->d_fsdata;
610 }
611
612
613
614
615
616
617
618 void devpts_pty_kill(struct dentry *dentry)
619 {
620 WARN_ON_ONCE(dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC);
621
622 dentry->d_fsdata = NULL;
623 drop_nlink(dentry->d_inode);
624 fsnotify_unlink(d_inode(dentry->d_parent), dentry);
625 d_drop(dentry);
626 dput(dentry);
627 }
628
629 static int __init init_devpts_fs(void)
630 {
631 int err = register_filesystem(&devpts_fs_type);
632 if (!err) {
633 register_sysctl_table(pty_root_table);
634 }
635 return err;
636 }
637 module_init(init_devpts_fs)