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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/*
40 * sysctl support for setting limits on the number of Unix98 ptys allocated.
41 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
42 */
43static int pty_limit = NR_UNIX98_PTY_DEFAULT;
44static int pty_reserve = NR_UNIX98_PTY_RESERVE;
45static int pty_limit_min;
46static int pty_limit_max = INT_MAX;
47static int pty_count;
48
49static struct ctl_table pty_table[] = {
50 {
51 .procname = "max",
52 .maxlen = sizeof(int),
53 .mode = 0644,
54 .data = &pty_limit,
55 .proc_handler = proc_dointvec_minmax,
56 .extra1 = &pty_limit_min,
57 .extra2 = &pty_limit_max,
58 }, {
59 .procname = "reserve",
60 .maxlen = sizeof(int),
61 .mode = 0644,
62 .data = &pty_reserve,
63 .proc_handler = proc_dointvec_minmax,
64 .extra1 = &pty_limit_min,
65 .extra2 = &pty_limit_max,
66 }, {
67 .procname = "nr",
68 .maxlen = sizeof(int),
69 .mode = 0444,
70 .data = &pty_count,
71 .proc_handler = proc_dointvec,
72 },
73 {}
74};
75
76static struct ctl_table pty_kern_table[] = {
77 {
78 .procname = "pty",
79 .mode = 0555,
80 .child = pty_table,
81 },
82 {}
83};
84
85static struct ctl_table pty_root_table[] = {
86 {
87 .procname = "kernel",
88 .mode = 0555,
89 .child = pty_kern_table,
90 },
91 {}
92};
93
94static DEFINE_MUTEX(allocated_ptys_lock);
95
96static struct vfsmount *devpts_mnt;
97
98struct pts_mount_opts {
99 int setuid;
100 int setgid;
101 kuid_t uid;
102 kgid_t gid;
103 umode_t mode;
104 umode_t ptmxmode;
105 int newinstance;
106 int max;
107};
108
109enum {
110 Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, Opt_max,
111 Opt_err
112};
113
114static const match_table_t tokens = {
115 {Opt_uid, "uid=%u"},
116 {Opt_gid, "gid=%u"},
117 {Opt_mode, "mode=%o"},
118#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
119 {Opt_ptmxmode, "ptmxmode=%o"},
120 {Opt_newinstance, "newinstance"},
121 {Opt_max, "max=%d"},
122#endif
123 {Opt_err, NULL}
124};
125
126struct pts_fs_info {
127 struct ida allocated_ptys;
128 struct pts_mount_opts mount_opts;
129 struct dentry *ptmx_dentry;
130};
131
132static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
133{
134 return sb->s_fs_info;
135}
136
137static inline struct super_block *pts_sb_from_inode(struct inode *inode)
138{
139#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
140 if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
141 return inode->i_sb;
142#endif
143 return devpts_mnt->mnt_sb;
144}
145
146#define PARSE_MOUNT 0
147#define PARSE_REMOUNT 1
148
149/*
150 * parse_mount_options():
151 * Set @opts to mount options specified in @data. If an option is not
152 * specified in @data, set it to its default value. The exception is
153 * 'newinstance' option which can only be set/cleared on a mount (i.e.
154 * cannot be changed during remount).
155 *
156 * Note: @data may be NULL (in which case all options are set to default).
157 */
158static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
159{
160 char *p;
161 kuid_t uid;
162 kgid_t gid;
163
164 opts->setuid = 0;
165 opts->setgid = 0;
166 opts->uid = GLOBAL_ROOT_UID;
167 opts->gid = GLOBAL_ROOT_GID;
168 opts->mode = DEVPTS_DEFAULT_MODE;
169 opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
170 opts->max = NR_UNIX98_PTY_MAX;
171
172 /* newinstance makes sense only on initial mount */
173 if (op == PARSE_MOUNT)
174 opts->newinstance = 0;
175
176 while ((p = strsep(&data, ",")) != NULL) {
177 substring_t args[MAX_OPT_ARGS];
178 int token;
179 int option;
180
181 if (!*p)
182 continue;
183
184 token = match_token(p, tokens, args);
185 switch (token) {
186 case Opt_uid:
187 if (match_int(&args[0], &option))
188 return -EINVAL;
189 uid = make_kuid(current_user_ns(), option);
190 if (!uid_valid(uid))
191 return -EINVAL;
192 opts->uid = uid;
193 opts->setuid = 1;
194 break;
195 case Opt_gid:
196 if (match_int(&args[0], &option))
197 return -EINVAL;
198 gid = make_kgid(current_user_ns(), option);
199 if (!gid_valid(gid))
200 return -EINVAL;
201 opts->gid = gid;
202 opts->setgid = 1;
203 break;
204 case Opt_mode:
205 if (match_octal(&args[0], &option))
206 return -EINVAL;
207 opts->mode = option & S_IALLUGO;
208 break;
209#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
210 case Opt_ptmxmode:
211 if (match_octal(&args[0], &option))
212 return -EINVAL;
213 opts->ptmxmode = option & S_IALLUGO;
214 break;
215 case Opt_newinstance:
216 /* newinstance makes sense only on initial mount */
217 if (op == PARSE_MOUNT)
218 opts->newinstance = 1;
219 break;
220 case Opt_max:
221 if (match_int(&args[0], &option) ||
222 option < 0 || option > NR_UNIX98_PTY_MAX)
223 return -EINVAL;
224 opts->max = option;
225 break;
226#endif
227 default:
228 printk(KERN_ERR "devpts: called with bogus options\n");
229 return -EINVAL;
230 }
231 }
232
233 return 0;
234}
235
236#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
237static int mknod_ptmx(struct super_block *sb)
238{
239 int mode;
240 int rc = -ENOMEM;
241 struct dentry *dentry;
242 struct inode *inode;
243 struct dentry *root = sb->s_root;
244 struct pts_fs_info *fsi = DEVPTS_SB(sb);
245 struct pts_mount_opts *opts = &fsi->mount_opts;
246
247 mutex_lock(&root->d_inode->i_mutex);
248
249 /* If we have already created ptmx node, return */
250 if (fsi->ptmx_dentry) {
251 rc = 0;
252 goto out;
253 }
254
255 dentry = d_alloc_name(root, "ptmx");
256 if (!dentry) {
257 printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
258 goto out;
259 }
260
261 /*
262 * Create a new 'ptmx' node in this mount of devpts.
263 */
264 inode = new_inode(sb);
265 if (!inode) {
266 printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
267 dput(dentry);
268 goto out;
269 }
270
271 inode->i_ino = 2;
272 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
273
274 mode = S_IFCHR|opts->ptmxmode;
275 init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
276
277 d_add(dentry, inode);
278
279 fsi->ptmx_dentry = dentry;
280 rc = 0;
281out:
282 mutex_unlock(&root->d_inode->i_mutex);
283 return rc;
284}
285
286static void update_ptmx_mode(struct pts_fs_info *fsi)
287{
288 struct inode *inode;
289 if (fsi->ptmx_dentry) {
290 inode = fsi->ptmx_dentry->d_inode;
291 inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
292 }
293}
294#else
295static inline void update_ptmx_mode(struct pts_fs_info *fsi)
296{
297 return;
298}
299#endif
300
301static int devpts_remount(struct super_block *sb, int *flags, char *data)
302{
303 int err;
304 struct pts_fs_info *fsi = DEVPTS_SB(sb);
305 struct pts_mount_opts *opts = &fsi->mount_opts;
306
307 err = parse_mount_options(data, PARSE_REMOUNT, opts);
308
309 /*
310 * parse_mount_options() restores options to default values
311 * before parsing and may have changed ptmxmode. So, update the
312 * mode in the inode too. Bogus options don't fail the remount,
313 * so do this even on error return.
314 */
315 update_ptmx_mode(fsi);
316
317 return err;
318}
319
320static int devpts_show_options(struct seq_file *seq, struct dentry *root)
321{
322 struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb);
323 struct pts_mount_opts *opts = &fsi->mount_opts;
324
325 if (opts->setuid)
326 seq_printf(seq, ",uid=%u", from_kuid_munged(&init_user_ns, opts->uid));
327 if (opts->setgid)
328 seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, opts->gid));
329 seq_printf(seq, ",mode=%03o", opts->mode);
330#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
331 seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
332 if (opts->max < NR_UNIX98_PTY_MAX)
333 seq_printf(seq, ",max=%d", opts->max);
334#endif
335
336 return 0;
337}
338
339static const struct super_operations devpts_sops = {
340 .statfs = simple_statfs,
341 .remount_fs = devpts_remount,
342 .show_options = devpts_show_options,
343};
344
345static void *new_pts_fs_info(void)
346{
347 struct pts_fs_info *fsi;
348
349 fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
350 if (!fsi)
351 return NULL;
352
353 ida_init(&fsi->allocated_ptys);
354 fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
355 fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
356
357 return fsi;
358}
359
360static int
361devpts_fill_super(struct super_block *s, void *data, int silent)
362{
363 struct inode *inode;
364
365 s->s_blocksize = 1024;
366 s->s_blocksize_bits = 10;
367 s->s_magic = DEVPTS_SUPER_MAGIC;
368 s->s_op = &devpts_sops;
369 s->s_time_gran = 1;
370
371 s->s_fs_info = new_pts_fs_info();
372 if (!s->s_fs_info)
373 goto fail;
374
375 inode = new_inode(s);
376 if (!inode)
377 goto fail;
378 inode->i_ino = 1;
379 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
380 inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
381 inode->i_op = &simple_dir_inode_operations;
382 inode->i_fop = &simple_dir_operations;
383 set_nlink(inode, 2);
384
385 s->s_root = d_make_root(inode);
386 if (s->s_root)
387 return 0;
388
389 printk(KERN_ERR "devpts: get root dentry failed\n");
390
391fail:
392 return -ENOMEM;
393}
394
395#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
396static int compare_init_pts_sb(struct super_block *s, void *p)
397{
398 if (devpts_mnt)
399 return devpts_mnt->mnt_sb == s;
400 return 0;
401}
402
403/*
404 * devpts_mount()
405 *
406 * If the '-o newinstance' mount option was specified, mount a new
407 * (private) instance of devpts. PTYs created in this instance are
408 * independent of the PTYs in other devpts instances.
409 *
410 * If the '-o newinstance' option was not specified, mount/remount the
411 * initial kernel mount of devpts. This type of mount gives the
412 * legacy, single-instance semantics.
413 *
414 * The 'newinstance' option is needed to support multiple namespace
415 * semantics in devpts while preserving backward compatibility of the
416 * current 'single-namespace' semantics. i.e all mounts of devpts
417 * without the 'newinstance' mount option should bind to the initial
418 * kernel mount, like mount_single().
419 *
420 * Mounts with 'newinstance' option create a new, private namespace.
421 *
422 * NOTE:
423 *
424 * For single-mount semantics, devpts cannot use mount_single(),
425 * because mount_single()/sget() find and use the super-block from
426 * the most recent mount of devpts. But that recent mount may be a
427 * 'newinstance' mount and mount_single() would pick the newinstance
428 * super-block instead of the initial super-block.
429 */
430static struct dentry *devpts_mount(struct file_system_type *fs_type,
431 int flags, const char *dev_name, void *data)
432{
433 int error;
434 struct pts_mount_opts opts;
435 struct super_block *s;
436
437 error = parse_mount_options(data, PARSE_MOUNT, &opts);
438 if (error)
439 return ERR_PTR(error);
440
441 if (opts.newinstance)
442 s = sget(fs_type, NULL, set_anon_super, NULL);
443 else
444 s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
445
446 if (IS_ERR(s))
447 return ERR_CAST(s);
448
449 if (!s->s_root) {
450 s->s_flags = flags;
451 error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
452 if (error)
453 goto out_undo_sget;
454 s->s_flags |= MS_ACTIVE;
455 }
456
457 memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
458
459 error = mknod_ptmx(s);
460 if (error)
461 goto out_undo_sget;
462
463 return dget(s->s_root);
464
465out_undo_sget:
466 deactivate_locked_super(s);
467 return ERR_PTR(error);
468}
469
470#else
471/*
472 * This supports only the legacy single-instance semantics (no
473 * multiple-instance semantics)
474 */
475static struct dentry *devpts_mount(struct file_system_type *fs_type, int flags,
476 const char *dev_name, void *data)
477{
478 return mount_single(fs_type, flags, data, devpts_fill_super);
479}
480#endif
481
482static void devpts_kill_sb(struct super_block *sb)
483{
484 struct pts_fs_info *fsi = DEVPTS_SB(sb);
485
486 kfree(fsi);
487 kill_litter_super(sb);
488}
489
490static struct file_system_type devpts_fs_type = {
491 .name = "devpts",
492 .mount = devpts_mount,
493 .kill_sb = devpts_kill_sb,
494};
495
496/*
497 * The normal naming convention is simply /dev/pts/<number>; this conforms
498 * to the System V naming convention
499 */
500
501int devpts_new_index(struct inode *ptmx_inode)
502{
503 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
504 struct pts_fs_info *fsi = DEVPTS_SB(sb);
505 int index;
506 int ida_ret;
507
508retry:
509 if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
510 return -ENOMEM;
511
512 mutex_lock(&allocated_ptys_lock);
513 if (pty_count >= pty_limit -
514 (fsi->mount_opts.newinstance ? pty_reserve : 0)) {
515 mutex_unlock(&allocated_ptys_lock);
516 return -ENOSPC;
517 }
518
519 ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
520 if (ida_ret < 0) {
521 mutex_unlock(&allocated_ptys_lock);
522 if (ida_ret == -EAGAIN)
523 goto retry;
524 return -EIO;
525 }
526
527 if (index >= fsi->mount_opts.max) {
528 ida_remove(&fsi->allocated_ptys, index);
529 mutex_unlock(&allocated_ptys_lock);
530 return -ENOSPC;
531 }
532 pty_count++;
533 mutex_unlock(&allocated_ptys_lock);
534 return index;
535}
536
537void devpts_kill_index(struct inode *ptmx_inode, int idx)
538{
539 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
540 struct pts_fs_info *fsi = DEVPTS_SB(sb);
541
542 mutex_lock(&allocated_ptys_lock);
543 ida_remove(&fsi->allocated_ptys, idx);
544 pty_count--;
545 mutex_unlock(&allocated_ptys_lock);
546}
547
548int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
549{
550 /* tty layer puts index from devpts_new_index() in here */
551 int number = tty->index;
552 struct tty_driver *driver = tty->driver;
553 dev_t device = MKDEV(driver->major, driver->minor_start+number);
554 struct dentry *dentry;
555 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
556 struct inode *inode = new_inode(sb);
557 struct dentry *root = sb->s_root;
558 struct pts_fs_info *fsi = DEVPTS_SB(sb);
559 struct pts_mount_opts *opts = &fsi->mount_opts;
560 int ret = 0;
561 char s[12];
562
563 /* We're supposed to be given the slave end of a pty */
564 BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
565 BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
566
567 if (!inode)
568 return -ENOMEM;
569
570 inode->i_ino = number + 3;
571 inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
572 inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
573 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
574 init_special_inode(inode, S_IFCHR|opts->mode, device);
575 inode->i_private = tty;
576 tty->driver_data = inode;
577
578 sprintf(s, "%d", number);
579
580 mutex_lock(&root->d_inode->i_mutex);
581
582 dentry = d_alloc_name(root, s);
583 if (dentry) {
584 d_add(dentry, inode);
585 fsnotify_create(root->d_inode, dentry);
586 } else {
587 iput(inode);
588 ret = -ENOMEM;
589 }
590
591 mutex_unlock(&root->d_inode->i_mutex);
592
593 return ret;
594}
595
596struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
597{
598 struct dentry *dentry;
599 struct tty_struct *tty;
600
601 BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
602
603 /* Ensure dentry has not been deleted by devpts_pty_kill() */
604 dentry = d_find_alias(pts_inode);
605 if (!dentry)
606 return NULL;
607
608 tty = NULL;
609 if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
610 tty = (struct tty_struct *)pts_inode->i_private;
611
612 dput(dentry);
613
614 return tty;
615}
616
617void devpts_pty_kill(struct tty_struct *tty)
618{
619 struct inode *inode = tty->driver_data;
620 struct super_block *sb = pts_sb_from_inode(inode);
621 struct dentry *root = sb->s_root;
622 struct dentry *dentry;
623
624 BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
625
626 mutex_lock(&root->d_inode->i_mutex);
627
628 dentry = d_find_alias(inode);
629
630 drop_nlink(inode);
631 d_delete(dentry);
632 dput(dentry); /* d_alloc_name() in devpts_pty_new() */
633 dput(dentry); /* d_find_alias above */
634
635 mutex_unlock(&root->d_inode->i_mutex);
636}
637
638static int __init init_devpts_fs(void)
639{
640 int err = register_filesystem(&devpts_fs_type);
641 struct ctl_table_header *table;
642
643 if (!err) {
644 table = register_sysctl_table(pty_root_table);
645 devpts_mnt = kern_mount(&devpts_fs_type);
646 if (IS_ERR(devpts_mnt)) {
647 err = PTR_ERR(devpts_mnt);
648 unregister_filesystem(&devpts_fs_type);
649 unregister_sysctl_table(table);
650 }
651 }
652 return err;
653}
654module_init(init_devpts_fs)
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14
15#include <linux/module.h>
16#include <linux/init.h>
17#include <linux/fs.h>
18#include <linux/sched.h>
19#include <linux/namei.h>
20#include <linux/slab.h>
21#include <linux/mount.h>
22#include <linux/tty.h>
23#include <linux/mutex.h>
24#include <linux/magic.h>
25#include <linux/idr.h>
26#include <linux/devpts_fs.h>
27#include <linux/parser.h>
28#include <linux/fsnotify.h>
29#include <linux/seq_file.h>
30
31#define DEVPTS_DEFAULT_MODE 0600
32/*
33 * ptmx is a new node in /dev/pts and will be unused in legacy (single-
34 * instance) mode. To prevent surprises in user space, set permissions of
35 * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful
36 * permissions.
37 */
38#define DEVPTS_DEFAULT_PTMX_MODE 0000
39#define PTMX_MINOR 2
40
41/*
42 * sysctl support for setting limits on the number of Unix98 ptys allocated.
43 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
44 */
45static int pty_limit = NR_UNIX98_PTY_DEFAULT;
46static int pty_reserve = NR_UNIX98_PTY_RESERVE;
47static int pty_limit_min;
48static int pty_limit_max = INT_MAX;
49static int pty_count;
50
51static struct ctl_table pty_table[] = {
52 {
53 .procname = "max",
54 .maxlen = sizeof(int),
55 .mode = 0644,
56 .data = &pty_limit,
57 .proc_handler = proc_dointvec_minmax,
58 .extra1 = &pty_limit_min,
59 .extra2 = &pty_limit_max,
60 }, {
61 .procname = "reserve",
62 .maxlen = sizeof(int),
63 .mode = 0644,
64 .data = &pty_reserve,
65 .proc_handler = proc_dointvec_minmax,
66 .extra1 = &pty_limit_min,
67 .extra2 = &pty_limit_max,
68 }, {
69 .procname = "nr",
70 .maxlen = sizeof(int),
71 .mode = 0444,
72 .data = &pty_count,
73 .proc_handler = proc_dointvec,
74 },
75 {}
76};
77
78static struct ctl_table pty_kern_table[] = {
79 {
80 .procname = "pty",
81 .mode = 0555,
82 .child = pty_table,
83 },
84 {}
85};
86
87static struct ctl_table pty_root_table[] = {
88 {
89 .procname = "kernel",
90 .mode = 0555,
91 .child = pty_kern_table,
92 },
93 {}
94};
95
96static DEFINE_MUTEX(allocated_ptys_lock);
97
98struct pts_mount_opts {
99 int setuid;
100 int setgid;
101 kuid_t uid;
102 kgid_t gid;
103 umode_t mode;
104 umode_t ptmxmode;
105 int reserve;
106 int max;
107};
108
109enum {
110 Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, Opt_max,
111 Opt_err
112};
113
114static const match_table_t tokens = {
115 {Opt_uid, "uid=%u"},
116 {Opt_gid, "gid=%u"},
117 {Opt_mode, "mode=%o"},
118 {Opt_ptmxmode, "ptmxmode=%o"},
119 {Opt_newinstance, "newinstance"},
120 {Opt_max, "max=%d"},
121 {Opt_err, NULL}
122};
123
124struct pts_fs_info {
125 struct ida allocated_ptys;
126 struct pts_mount_opts mount_opts;
127 struct super_block *sb;
128 struct dentry *ptmx_dentry;
129};
130
131static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
132{
133 return sb->s_fs_info;
134}
135
136static int devpts_ptmx_path(struct path *path)
137{
138 struct super_block *sb;
139 int err;
140
141 /* Is a devpts filesystem at "pts" in the same directory? */
142 err = path_pts(path);
143 if (err)
144 return err;
145
146 /* Is the path the root of a devpts filesystem? */
147 sb = path->mnt->mnt_sb;
148 if ((sb->s_magic != DEVPTS_SUPER_MAGIC) ||
149 (path->mnt->mnt_root != sb->s_root))
150 return -ENODEV;
151
152 return 0;
153}
154
155/*
156 * Try to find a suitable devpts filesystem. We support the following
157 * scenarios:
158 * - The ptmx device node is located in the same directory as the devpts
159 * mount where the pts device nodes are located.
160 * This is e.g. the case when calling open on the /dev/pts/ptmx device
161 * node when the devpts filesystem is mounted at /dev/pts.
162 * - The ptmx device node is located outside the devpts filesystem mount
163 * where the pts device nodes are located. For example, the ptmx device
164 * is a symlink, separate device node, or bind-mount.
165 * A supported scenario is bind-mounting /dev/pts/ptmx to /dev/ptmx and
166 * then calling open on /dev/ptmx. In this case a suitable pts
167 * subdirectory can be found in the common parent directory /dev of the
168 * devpts mount and the ptmx bind-mount, after resolving the /dev/ptmx
169 * bind-mount.
170 * If no suitable pts subdirectory can be found this function will fail.
171 * This is e.g. the case when bind-mounting /dev/pts/ptmx to /ptmx.
172 */
173struct vfsmount *devpts_mntget(struct file *filp, struct pts_fs_info *fsi)
174{
175 struct path path;
176 int err = 0;
177
178 path = filp->f_path;
179 path_get(&path);
180
181 /* Walk upward while the start point is a bind mount of
182 * a single file.
183 */
184 while (path.mnt->mnt_root == path.dentry)
185 if (follow_up(&path) == 0)
186 break;
187
188 /* devpts_ptmx_path() finds a devpts fs or returns an error. */
189 if ((path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) ||
190 (DEVPTS_SB(path.mnt->mnt_sb) != fsi))
191 err = devpts_ptmx_path(&path);
192 dput(path.dentry);
193 if (!err) {
194 if (DEVPTS_SB(path.mnt->mnt_sb) == fsi)
195 return path.mnt;
196
197 err = -ENODEV;
198 }
199
200 mntput(path.mnt);
201 return ERR_PTR(err);
202}
203
204struct pts_fs_info *devpts_acquire(struct file *filp)
205{
206 struct pts_fs_info *result;
207 struct path path;
208 struct super_block *sb;
209
210 path = filp->f_path;
211 path_get(&path);
212
213 /* Has the devpts filesystem already been found? */
214 if (path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) {
215 int err;
216
217 err = devpts_ptmx_path(&path);
218 if (err) {
219 result = ERR_PTR(err);
220 goto out;
221 }
222 }
223
224 /*
225 * pty code needs to hold extra references in case of last /dev/tty close
226 */
227 sb = path.mnt->mnt_sb;
228 atomic_inc(&sb->s_active);
229 result = DEVPTS_SB(sb);
230
231out:
232 path_put(&path);
233 return result;
234}
235
236void devpts_release(struct pts_fs_info *fsi)
237{
238 deactivate_super(fsi->sb);
239}
240
241#define PARSE_MOUNT 0
242#define PARSE_REMOUNT 1
243
244/*
245 * parse_mount_options():
246 * Set @opts to mount options specified in @data. If an option is not
247 * specified in @data, set it to its default value.
248 *
249 * Note: @data may be NULL (in which case all options are set to default).
250 */
251static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
252{
253 char *p;
254 kuid_t uid;
255 kgid_t gid;
256
257 opts->setuid = 0;
258 opts->setgid = 0;
259 opts->uid = GLOBAL_ROOT_UID;
260 opts->gid = GLOBAL_ROOT_GID;
261 opts->mode = DEVPTS_DEFAULT_MODE;
262 opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
263 opts->max = NR_UNIX98_PTY_MAX;
264
265 /* Only allow instances mounted from the initial mount
266 * namespace to tap the reserve pool of ptys.
267 */
268 if (op == PARSE_MOUNT)
269 opts->reserve =
270 (current->nsproxy->mnt_ns == init_task.nsproxy->mnt_ns);
271
272 while ((p = strsep(&data, ",")) != NULL) {
273 substring_t args[MAX_OPT_ARGS];
274 int token;
275 int option;
276
277 if (!*p)
278 continue;
279
280 token = match_token(p, tokens, args);
281 switch (token) {
282 case Opt_uid:
283 if (match_int(&args[0], &option))
284 return -EINVAL;
285 uid = make_kuid(current_user_ns(), option);
286 if (!uid_valid(uid))
287 return -EINVAL;
288 opts->uid = uid;
289 opts->setuid = 1;
290 break;
291 case Opt_gid:
292 if (match_int(&args[0], &option))
293 return -EINVAL;
294 gid = make_kgid(current_user_ns(), option);
295 if (!gid_valid(gid))
296 return -EINVAL;
297 opts->gid = gid;
298 opts->setgid = 1;
299 break;
300 case Opt_mode:
301 if (match_octal(&args[0], &option))
302 return -EINVAL;
303 opts->mode = option & S_IALLUGO;
304 break;
305 case Opt_ptmxmode:
306 if (match_octal(&args[0], &option))
307 return -EINVAL;
308 opts->ptmxmode = option & S_IALLUGO;
309 break;
310 case Opt_newinstance:
311 break;
312 case Opt_max:
313 if (match_int(&args[0], &option) ||
314 option < 0 || option > NR_UNIX98_PTY_MAX)
315 return -EINVAL;
316 opts->max = option;
317 break;
318 default:
319 pr_err("called with bogus options\n");
320 return -EINVAL;
321 }
322 }
323
324 return 0;
325}
326
327static int mknod_ptmx(struct super_block *sb)
328{
329 int mode;
330 int rc = -ENOMEM;
331 struct dentry *dentry;
332 struct inode *inode;
333 struct dentry *root = sb->s_root;
334 struct pts_fs_info *fsi = DEVPTS_SB(sb);
335 struct pts_mount_opts *opts = &fsi->mount_opts;
336 kuid_t ptmx_uid = current_fsuid();
337 kgid_t ptmx_gid = current_fsgid();
338
339 inode_lock(d_inode(root));
340
341 /* If we have already created ptmx node, return */
342 if (fsi->ptmx_dentry) {
343 rc = 0;
344 goto out;
345 }
346
347 dentry = d_alloc_name(root, "ptmx");
348 if (!dentry) {
349 pr_err("Unable to alloc dentry for ptmx node\n");
350 goto out;
351 }
352
353 /*
354 * Create a new 'ptmx' node in this mount of devpts.
355 */
356 inode = new_inode(sb);
357 if (!inode) {
358 pr_err("Unable to alloc inode for ptmx node\n");
359 dput(dentry);
360 goto out;
361 }
362
363 inode->i_ino = 2;
364 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
365
366 mode = S_IFCHR|opts->ptmxmode;
367 init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
368 inode->i_uid = ptmx_uid;
369 inode->i_gid = ptmx_gid;
370
371 d_add(dentry, inode);
372
373 fsi->ptmx_dentry = dentry;
374 rc = 0;
375out:
376 inode_unlock(d_inode(root));
377 return rc;
378}
379
380static void update_ptmx_mode(struct pts_fs_info *fsi)
381{
382 struct inode *inode;
383 if (fsi->ptmx_dentry) {
384 inode = d_inode(fsi->ptmx_dentry);
385 inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
386 }
387}
388
389static int devpts_remount(struct super_block *sb, int *flags, char *data)
390{
391 int err;
392 struct pts_fs_info *fsi = DEVPTS_SB(sb);
393 struct pts_mount_opts *opts = &fsi->mount_opts;
394
395 err = parse_mount_options(data, PARSE_REMOUNT, opts);
396
397 /*
398 * parse_mount_options() restores options to default values
399 * before parsing and may have changed ptmxmode. So, update the
400 * mode in the inode too. Bogus options don't fail the remount,
401 * so do this even on error return.
402 */
403 update_ptmx_mode(fsi);
404
405 return err;
406}
407
408static int devpts_show_options(struct seq_file *seq, struct dentry *root)
409{
410 struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb);
411 struct pts_mount_opts *opts = &fsi->mount_opts;
412
413 if (opts->setuid)
414 seq_printf(seq, ",uid=%u",
415 from_kuid_munged(&init_user_ns, opts->uid));
416 if (opts->setgid)
417 seq_printf(seq, ",gid=%u",
418 from_kgid_munged(&init_user_ns, opts->gid));
419 seq_printf(seq, ",mode=%03o", opts->mode);
420 seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
421 if (opts->max < NR_UNIX98_PTY_MAX)
422 seq_printf(seq, ",max=%d", opts->max);
423
424 return 0;
425}
426
427static const struct super_operations devpts_sops = {
428 .statfs = simple_statfs,
429 .remount_fs = devpts_remount,
430 .show_options = devpts_show_options,
431};
432
433static void *new_pts_fs_info(struct super_block *sb)
434{
435 struct pts_fs_info *fsi;
436
437 fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
438 if (!fsi)
439 return NULL;
440
441 ida_init(&fsi->allocated_ptys);
442 fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
443 fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
444 fsi->sb = sb;
445
446 return fsi;
447}
448
449static int
450devpts_fill_super(struct super_block *s, void *data, int silent)
451{
452 struct inode *inode;
453 int error;
454
455 s->s_iflags &= ~SB_I_NODEV;
456 s->s_blocksize = 1024;
457 s->s_blocksize_bits = 10;
458 s->s_magic = DEVPTS_SUPER_MAGIC;
459 s->s_op = &devpts_sops;
460 s->s_time_gran = 1;
461
462 error = -ENOMEM;
463 s->s_fs_info = new_pts_fs_info(s);
464 if (!s->s_fs_info)
465 goto fail;
466
467 error = parse_mount_options(data, PARSE_MOUNT, &DEVPTS_SB(s)->mount_opts);
468 if (error)
469 goto fail;
470
471 error = -ENOMEM;
472 inode = new_inode(s);
473 if (!inode)
474 goto fail;
475 inode->i_ino = 1;
476 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
477 inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
478 inode->i_op = &simple_dir_inode_operations;
479 inode->i_fop = &simple_dir_operations;
480 set_nlink(inode, 2);
481
482 s->s_root = d_make_root(inode);
483 if (!s->s_root) {
484 pr_err("get root dentry failed\n");
485 goto fail;
486 }
487
488 error = mknod_ptmx(s);
489 if (error)
490 goto fail_dput;
491
492 return 0;
493fail_dput:
494 dput(s->s_root);
495 s->s_root = NULL;
496fail:
497 return error;
498}
499
500/*
501 * devpts_mount()
502 *
503 * Mount a new (private) instance of devpts. PTYs created in this
504 * instance are independent of the PTYs in other devpts instances.
505 */
506static struct dentry *devpts_mount(struct file_system_type *fs_type,
507 int flags, const char *dev_name, void *data)
508{
509 return mount_nodev(fs_type, flags, data, devpts_fill_super);
510}
511
512static void devpts_kill_sb(struct super_block *sb)
513{
514 struct pts_fs_info *fsi = DEVPTS_SB(sb);
515
516 if (fsi)
517 ida_destroy(&fsi->allocated_ptys);
518 kfree(fsi);
519 kill_litter_super(sb);
520}
521
522static struct file_system_type devpts_fs_type = {
523 .name = "devpts",
524 .mount = devpts_mount,
525 .kill_sb = devpts_kill_sb,
526 .fs_flags = FS_USERNS_MOUNT,
527};
528
529/*
530 * The normal naming convention is simply /dev/pts/<number>; this conforms
531 * to the System V naming convention
532 */
533
534int devpts_new_index(struct pts_fs_info *fsi)
535{
536 int index;
537 int ida_ret;
538
539retry:
540 if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
541 return -ENOMEM;
542
543 mutex_lock(&allocated_ptys_lock);
544 if (pty_count >= (pty_limit -
545 (fsi->mount_opts.reserve ? 0 : pty_reserve))) {
546 mutex_unlock(&allocated_ptys_lock);
547 return -ENOSPC;
548 }
549
550 ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
551 if (ida_ret < 0) {
552 mutex_unlock(&allocated_ptys_lock);
553 if (ida_ret == -EAGAIN)
554 goto retry;
555 return -EIO;
556 }
557
558 if (index >= fsi->mount_opts.max) {
559 ida_remove(&fsi->allocated_ptys, index);
560 mutex_unlock(&allocated_ptys_lock);
561 return -ENOSPC;
562 }
563 pty_count++;
564 mutex_unlock(&allocated_ptys_lock);
565 return index;
566}
567
568void devpts_kill_index(struct pts_fs_info *fsi, int idx)
569{
570 mutex_lock(&allocated_ptys_lock);
571 ida_remove(&fsi->allocated_ptys, idx);
572 pty_count--;
573 mutex_unlock(&allocated_ptys_lock);
574}
575
576/**
577 * devpts_pty_new -- create a new inode in /dev/pts/
578 * @ptmx_inode: inode of the master
579 * @device: major+minor of the node to be created
580 * @index: used as a name of the node
581 * @priv: what's given back by devpts_get_priv
582 *
583 * The created inode is returned. Remove it from /dev/pts/ by devpts_pty_kill.
584 */
585struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv)
586{
587 struct dentry *dentry;
588 struct super_block *sb = fsi->sb;
589 struct inode *inode;
590 struct dentry *root;
591 struct pts_mount_opts *opts;
592 char s[12];
593
594 root = sb->s_root;
595 opts = &fsi->mount_opts;
596
597 inode = new_inode(sb);
598 if (!inode)
599 return ERR_PTR(-ENOMEM);
600
601 inode->i_ino = index + 3;
602 inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
603 inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
604 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
605 init_special_inode(inode, S_IFCHR|opts->mode, MKDEV(UNIX98_PTY_SLAVE_MAJOR, index));
606
607 sprintf(s, "%d", index);
608
609 dentry = d_alloc_name(root, s);
610 if (dentry) {
611 dentry->d_fsdata = priv;
612 d_add(dentry, inode);
613 fsnotify_create(d_inode(root), dentry);
614 } else {
615 iput(inode);
616 dentry = ERR_PTR(-ENOMEM);
617 }
618
619 return dentry;
620}
621
622/**
623 * devpts_get_priv -- get private data for a slave
624 * @pts_inode: inode of the slave
625 *
626 * Returns whatever was passed as priv in devpts_pty_new for a given inode.
627 */
628void *devpts_get_priv(struct dentry *dentry)
629{
630 if (dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC)
631 return NULL;
632 return dentry->d_fsdata;
633}
634
635/**
636 * devpts_pty_kill -- remove inode form /dev/pts/
637 * @inode: inode of the slave to be removed
638 *
639 * This is an inverse operation of devpts_pty_new.
640 */
641void devpts_pty_kill(struct dentry *dentry)
642{
643 WARN_ON_ONCE(dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC);
644
645 dentry->d_fsdata = NULL;
646 drop_nlink(dentry->d_inode);
647 d_delete(dentry);
648 dput(dentry); /* d_alloc_name() in devpts_pty_new() */
649}
650
651static int __init init_devpts_fs(void)
652{
653 int err = register_filesystem(&devpts_fs_type);
654 if (!err) {
655 register_sysctl_table(pty_root_table);
656 }
657 return err;
658}
659module_init(init_devpts_fs)