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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
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_mount()
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 mount_single().
349 *
350 * Mounts with 'newinstance' option create a new, private namespace.
351 *
352 * NOTE:
353 *
354 * For single-mount semantics, devpts cannot use mount_single(),
355 * because mount_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 mount_single() would pick the newinstance
358 * super-block instead of the initial super-block.
359 */
360static struct dentry *devpts_mount(struct file_system_type *fs_type,
361 int flags, const char *dev_name, void *data)
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 ERR_PTR(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 ERR_CAST(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 return dget(s->s_root);
394
395out_undo_sget:
396 deactivate_locked_super(s);
397 return ERR_PTR(error);
398}
399
400#else
401/*
402 * This supports only the legacy single-instance semantics (no
403 * multiple-instance semantics)
404 */
405static struct dentry *devpts_mount(struct file_system_type *fs_type, int flags,
406 const char *dev_name, void *data)
407{
408 return mount_single(fs_type, flags, data, devpts_fill_super);
409}
410#endif
411
412static void devpts_kill_sb(struct super_block *sb)
413{
414 struct pts_fs_info *fsi = DEVPTS_SB(sb);
415
416 kfree(fsi);
417 kill_litter_super(sb);
418}
419
420static struct file_system_type devpts_fs_type = {
421 .name = "devpts",
422 .mount = devpts_mount,
423 .kill_sb = devpts_kill_sb,
424};
425
426/*
427 * The normal naming convention is simply /dev/pts/<number>; this conforms
428 * to the System V naming convention
429 */
430
431int devpts_new_index(struct inode *ptmx_inode)
432{
433 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
434 struct pts_fs_info *fsi = DEVPTS_SB(sb);
435 int index;
436 int ida_ret;
437
438retry:
439 if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
440 return -ENOMEM;
441
442 mutex_lock(&allocated_ptys_lock);
443 ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
444 if (ida_ret < 0) {
445 mutex_unlock(&allocated_ptys_lock);
446 if (ida_ret == -EAGAIN)
447 goto retry;
448 return -EIO;
449 }
450
451 if (index >= pty_limit) {
452 ida_remove(&fsi->allocated_ptys, index);
453 mutex_unlock(&allocated_ptys_lock);
454 return -EIO;
455 }
456 mutex_unlock(&allocated_ptys_lock);
457 return index;
458}
459
460void devpts_kill_index(struct inode *ptmx_inode, int idx)
461{
462 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
463 struct pts_fs_info *fsi = DEVPTS_SB(sb);
464
465 mutex_lock(&allocated_ptys_lock);
466 ida_remove(&fsi->allocated_ptys, idx);
467 mutex_unlock(&allocated_ptys_lock);
468}
469
470int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
471{
472 /* tty layer puts index from devpts_new_index() in here */
473 int number = tty->index;
474 struct tty_driver *driver = tty->driver;
475 dev_t device = MKDEV(driver->major, driver->minor_start+number);
476 struct dentry *dentry;
477 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
478 struct inode *inode = new_inode(sb);
479 struct dentry *root = sb->s_root;
480 struct pts_fs_info *fsi = DEVPTS_SB(sb);
481 struct pts_mount_opts *opts = &fsi->mount_opts;
482 int ret = 0;
483 char s[12];
484
485 /* We're supposed to be given the slave end of a pty */
486 BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
487 BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
488
489 if (!inode)
490 return -ENOMEM;
491
492 inode->i_ino = number + 3;
493 inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
494 inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
495 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
496 init_special_inode(inode, S_IFCHR|opts->mode, device);
497 inode->i_private = tty;
498 tty->driver_data = inode;
499
500 sprintf(s, "%d", number);
501
502 mutex_lock(&root->d_inode->i_mutex);
503
504 dentry = d_alloc_name(root, s);
505 if (dentry) {
506 d_add(dentry, inode);
507 fsnotify_create(root->d_inode, dentry);
508 } else {
509 iput(inode);
510 ret = -ENOMEM;
511 }
512
513 mutex_unlock(&root->d_inode->i_mutex);
514
515 return ret;
516}
517
518struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
519{
520 struct dentry *dentry;
521 struct tty_struct *tty;
522
523 BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
524
525 /* Ensure dentry has not been deleted by devpts_pty_kill() */
526 dentry = d_find_alias(pts_inode);
527 if (!dentry)
528 return NULL;
529
530 tty = NULL;
531 if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
532 tty = (struct tty_struct *)pts_inode->i_private;
533
534 dput(dentry);
535
536 return tty;
537}
538
539void devpts_pty_kill(struct tty_struct *tty)
540{
541 struct inode *inode = tty->driver_data;
542 struct super_block *sb = pts_sb_from_inode(inode);
543 struct dentry *root = sb->s_root;
544 struct dentry *dentry;
545
546 BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
547
548 mutex_lock(&root->d_inode->i_mutex);
549
550 dentry = d_find_alias(inode);
551
552 inode->i_nlink--;
553 d_delete(dentry);
554 dput(dentry); /* d_alloc_name() in devpts_pty_new() */
555 dput(dentry); /* d_find_alias above */
556
557 mutex_unlock(&root->d_inode->i_mutex);
558}
559
560static int __init init_devpts_fs(void)
561{
562 int err = register_filesystem(&devpts_fs_type);
563 if (!err) {
564 devpts_mnt = kern_mount(&devpts_fs_type);
565 if (IS_ERR(devpts_mnt)) {
566 err = PTR_ERR(devpts_mnt);
567 unregister_filesystem(&devpts_fs_type);
568 }
569 }
570 return err;
571}
572module_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#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 kuid_t root_uid;
247 kgid_t root_gid;
248
249 root_uid = make_kuid(current_user_ns(), 0);
250 root_gid = make_kgid(current_user_ns(), 0);
251 if (!uid_valid(root_uid) || !gid_valid(root_gid))
252 return -EINVAL;
253
254 mutex_lock(&root->d_inode->i_mutex);
255
256 /* If we have already created ptmx node, return */
257 if (fsi->ptmx_dentry) {
258 rc = 0;
259 goto out;
260 }
261
262 dentry = d_alloc_name(root, "ptmx");
263 if (!dentry) {
264 printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
265 goto out;
266 }
267
268 /*
269 * Create a new 'ptmx' node in this mount of devpts.
270 */
271 inode = new_inode(sb);
272 if (!inode) {
273 printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
274 dput(dentry);
275 goto out;
276 }
277
278 inode->i_ino = 2;
279 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
280
281 mode = S_IFCHR|opts->ptmxmode;
282 init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
283 inode->i_uid = root_uid;
284 inode->i_gid = root_gid;
285
286 d_add(dentry, inode);
287
288 fsi->ptmx_dentry = dentry;
289 rc = 0;
290out:
291 mutex_unlock(&root->d_inode->i_mutex);
292 return rc;
293}
294
295static void update_ptmx_mode(struct pts_fs_info *fsi)
296{
297 struct inode *inode;
298 if (fsi->ptmx_dentry) {
299 inode = fsi->ptmx_dentry->d_inode;
300 inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
301 }
302}
303#else
304static inline void update_ptmx_mode(struct pts_fs_info *fsi)
305{
306 return;
307}
308#endif
309
310static int devpts_remount(struct super_block *sb, int *flags, char *data)
311{
312 int err;
313 struct pts_fs_info *fsi = DEVPTS_SB(sb);
314 struct pts_mount_opts *opts = &fsi->mount_opts;
315
316 sync_filesystem(sb);
317 err = parse_mount_options(data, PARSE_REMOUNT, opts);
318
319 /*
320 * parse_mount_options() restores options to default values
321 * before parsing and may have changed ptmxmode. So, update the
322 * mode in the inode too. Bogus options don't fail the remount,
323 * so do this even on error return.
324 */
325 update_ptmx_mode(fsi);
326
327 return err;
328}
329
330static int devpts_show_options(struct seq_file *seq, struct dentry *root)
331{
332 struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb);
333 struct pts_mount_opts *opts = &fsi->mount_opts;
334
335 if (opts->setuid)
336 seq_printf(seq, ",uid=%u", from_kuid_munged(&init_user_ns, opts->uid));
337 if (opts->setgid)
338 seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, opts->gid));
339 seq_printf(seq, ",mode=%03o", opts->mode);
340#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
341 seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
342 if (opts->max < NR_UNIX98_PTY_MAX)
343 seq_printf(seq, ",max=%d", opts->max);
344#endif
345
346 return 0;
347}
348
349static const struct super_operations devpts_sops = {
350 .statfs = simple_statfs,
351 .remount_fs = devpts_remount,
352 .show_options = devpts_show_options,
353};
354
355static void *new_pts_fs_info(void)
356{
357 struct pts_fs_info *fsi;
358
359 fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
360 if (!fsi)
361 return NULL;
362
363 ida_init(&fsi->allocated_ptys);
364 fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
365 fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
366
367 return fsi;
368}
369
370static int
371devpts_fill_super(struct super_block *s, void *data, int silent)
372{
373 struct inode *inode;
374
375 s->s_blocksize = 1024;
376 s->s_blocksize_bits = 10;
377 s->s_magic = DEVPTS_SUPER_MAGIC;
378 s->s_op = &devpts_sops;
379 s->s_time_gran = 1;
380
381 s->s_fs_info = new_pts_fs_info();
382 if (!s->s_fs_info)
383 goto fail;
384
385 inode = new_inode(s);
386 if (!inode)
387 goto fail;
388 inode->i_ino = 1;
389 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
390 inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
391 inode->i_op = &simple_dir_inode_operations;
392 inode->i_fop = &simple_dir_operations;
393 set_nlink(inode, 2);
394
395 s->s_root = d_make_root(inode);
396 if (s->s_root)
397 return 0;
398
399 printk(KERN_ERR "devpts: get root dentry failed\n");
400
401fail:
402 return -ENOMEM;
403}
404
405#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
406static int compare_init_pts_sb(struct super_block *s, void *p)
407{
408 if (devpts_mnt)
409 return devpts_mnt->mnt_sb == s;
410 return 0;
411}
412
413/*
414 * devpts_mount()
415 *
416 * If the '-o newinstance' mount option was specified, mount a new
417 * (private) instance of devpts. PTYs created in this instance are
418 * independent of the PTYs in other devpts instances.
419 *
420 * If the '-o newinstance' option was not specified, mount/remount the
421 * initial kernel mount of devpts. This type of mount gives the
422 * legacy, single-instance semantics.
423 *
424 * The 'newinstance' option is needed to support multiple namespace
425 * semantics in devpts while preserving backward compatibility of the
426 * current 'single-namespace' semantics. i.e all mounts of devpts
427 * without the 'newinstance' mount option should bind to the initial
428 * kernel mount, like mount_single().
429 *
430 * Mounts with 'newinstance' option create a new, private namespace.
431 *
432 * NOTE:
433 *
434 * For single-mount semantics, devpts cannot use mount_single(),
435 * because mount_single()/sget() find and use the super-block from
436 * the most recent mount of devpts. But that recent mount may be a
437 * 'newinstance' mount and mount_single() would pick the newinstance
438 * super-block instead of the initial super-block.
439 */
440static struct dentry *devpts_mount(struct file_system_type *fs_type,
441 int flags, const char *dev_name, void *data)
442{
443 int error;
444 struct pts_mount_opts opts;
445 struct super_block *s;
446
447 error = parse_mount_options(data, PARSE_MOUNT, &opts);
448 if (error)
449 return ERR_PTR(error);
450
451 /* Require newinstance for all user namespace mounts to ensure
452 * the mount options are not changed.
453 */
454 if ((current_user_ns() != &init_user_ns) && !opts.newinstance)
455 return ERR_PTR(-EINVAL);
456
457 if (opts.newinstance)
458 s = sget(fs_type, NULL, set_anon_super, flags, NULL);
459 else
460 s = sget(fs_type, compare_init_pts_sb, set_anon_super, flags,
461 NULL);
462
463 if (IS_ERR(s))
464 return ERR_CAST(s);
465
466 if (!s->s_root) {
467 error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
468 if (error)
469 goto out_undo_sget;
470 s->s_flags |= MS_ACTIVE;
471 }
472
473 memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
474
475 error = mknod_ptmx(s);
476 if (error)
477 goto out_undo_sget;
478
479 return dget(s->s_root);
480
481out_undo_sget:
482 deactivate_locked_super(s);
483 return ERR_PTR(error);
484}
485
486#else
487/*
488 * This supports only the legacy single-instance semantics (no
489 * multiple-instance semantics)
490 */
491static struct dentry *devpts_mount(struct file_system_type *fs_type, int flags,
492 const char *dev_name, void *data)
493{
494 return mount_single(fs_type, flags, data, devpts_fill_super);
495}
496#endif
497
498static void devpts_kill_sb(struct super_block *sb)
499{
500 struct pts_fs_info *fsi = DEVPTS_SB(sb);
501
502 ida_destroy(&fsi->allocated_ptys);
503 kfree(fsi);
504 kill_litter_super(sb);
505}
506
507static struct file_system_type devpts_fs_type = {
508 .name = "devpts",
509 .mount = devpts_mount,
510 .kill_sb = devpts_kill_sb,
511#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
512 .fs_flags = FS_USERNS_MOUNT | FS_USERNS_DEV_MOUNT,
513#endif
514};
515
516/*
517 * The normal naming convention is simply /dev/pts/<number>; this conforms
518 * to the System V naming convention
519 */
520
521int devpts_new_index(struct inode *ptmx_inode)
522{
523 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
524 struct pts_fs_info *fsi = DEVPTS_SB(sb);
525 int index;
526 int ida_ret;
527
528retry:
529 if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
530 return -ENOMEM;
531
532 mutex_lock(&allocated_ptys_lock);
533 if (pty_count >= pty_limit -
534 (fsi->mount_opts.newinstance ? pty_reserve : 0)) {
535 mutex_unlock(&allocated_ptys_lock);
536 return -ENOSPC;
537 }
538
539 ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
540 if (ida_ret < 0) {
541 mutex_unlock(&allocated_ptys_lock);
542 if (ida_ret == -EAGAIN)
543 goto retry;
544 return -EIO;
545 }
546
547 if (index >= fsi->mount_opts.max) {
548 ida_remove(&fsi->allocated_ptys, index);
549 mutex_unlock(&allocated_ptys_lock);
550 return -ENOSPC;
551 }
552 pty_count++;
553 mutex_unlock(&allocated_ptys_lock);
554 return index;
555}
556
557void devpts_kill_index(struct inode *ptmx_inode, int idx)
558{
559 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
560 struct pts_fs_info *fsi = DEVPTS_SB(sb);
561
562 mutex_lock(&allocated_ptys_lock);
563 ida_remove(&fsi->allocated_ptys, idx);
564 pty_count--;
565 mutex_unlock(&allocated_ptys_lock);
566}
567
568/**
569 * devpts_pty_new -- create a new inode in /dev/pts/
570 * @ptmx_inode: inode of the master
571 * @device: major+minor of the node to be created
572 * @index: used as a name of the node
573 * @priv: what's given back by devpts_get_priv
574 *
575 * The created inode is returned. Remove it from /dev/pts/ by devpts_pty_kill.
576 */
577struct inode *devpts_pty_new(struct inode *ptmx_inode, dev_t device, int index,
578 void *priv)
579{
580 struct dentry *dentry;
581 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
582 struct inode *inode;
583 struct dentry *root = sb->s_root;
584 struct pts_fs_info *fsi = DEVPTS_SB(sb);
585 struct pts_mount_opts *opts = &fsi->mount_opts;
586 char s[12];
587
588 inode = new_inode(sb);
589 if (!inode)
590 return ERR_PTR(-ENOMEM);
591
592 inode->i_ino = index + 3;
593 inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
594 inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
595 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
596 init_special_inode(inode, S_IFCHR|opts->mode, device);
597 inode->i_private = priv;
598
599 sprintf(s, "%d", index);
600
601 mutex_lock(&root->d_inode->i_mutex);
602
603 dentry = d_alloc_name(root, s);
604 if (dentry) {
605 d_add(dentry, inode);
606 fsnotify_create(root->d_inode, dentry);
607 } else {
608 iput(inode);
609 inode = ERR_PTR(-ENOMEM);
610 }
611
612 mutex_unlock(&root->d_inode->i_mutex);
613
614 return inode;
615}
616
617/**
618 * devpts_get_priv -- get private data for a slave
619 * @pts_inode: inode of the slave
620 *
621 * Returns whatever was passed as priv in devpts_pty_new for a given inode.
622 */
623void *devpts_get_priv(struct inode *pts_inode)
624{
625 struct dentry *dentry;
626 void *priv = NULL;
627
628 BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
629
630 /* Ensure dentry has not been deleted by devpts_pty_kill() */
631 dentry = d_find_alias(pts_inode);
632 if (!dentry)
633 return NULL;
634
635 if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
636 priv = pts_inode->i_private;
637
638 dput(dentry);
639
640 return priv;
641}
642
643/**
644 * devpts_pty_kill -- remove inode form /dev/pts/
645 * @inode: inode of the slave to be removed
646 *
647 * This is an inverse operation of devpts_pty_new.
648 */
649void devpts_pty_kill(struct inode *inode)
650{
651 struct super_block *sb = pts_sb_from_inode(inode);
652 struct dentry *root = sb->s_root;
653 struct dentry *dentry;
654
655 BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
656
657 mutex_lock(&root->d_inode->i_mutex);
658
659 dentry = d_find_alias(inode);
660
661 drop_nlink(inode);
662 d_delete(dentry);
663 dput(dentry); /* d_alloc_name() in devpts_pty_new() */
664 dput(dentry); /* d_find_alias above */
665
666 mutex_unlock(&root->d_inode->i_mutex);
667}
668
669static int __init init_devpts_fs(void)
670{
671 int err = register_filesystem(&devpts_fs_type);
672 struct ctl_table_header *table;
673
674 if (!err) {
675 table = register_sysctl_table(pty_root_table);
676 devpts_mnt = kern_mount(&devpts_fs_type);
677 if (IS_ERR(devpts_mnt)) {
678 err = PTR_ERR(devpts_mnt);
679 unregister_filesystem(&devpts_fs_type);
680 unregister_sysctl_table(table);
681 }
682 }
683 return err;
684}
685module_init(init_devpts_fs)