blob: 14afbabe65464e226549894404ec1af9d1a3f747 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* -*- 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>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090018#include <linux/slab.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070019#include <linux/mount.h>
20#include <linux/tty.h>
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -070021#include <linux/mutex.h>
Nick Black1fd7317d2009-09-22 16:43:33 -070022#include <linux/magic.h>
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -070023#include <linux/idr.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070024#include <linux/devpts_fs.h>
Domen Puncer7a673c62006-03-23 03:00:59 -080025#include <linux/parser.h>
Florin Malita3972b7f2007-05-08 00:24:18 -070026#include <linux/fsnotify.h>
Miklos Szeredib87a2672008-02-08 04:21:41 -080027#include <linux/seq_file.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070028
Miklos Szeredib87a2672008-02-08 04:21:41 -080029#define DEVPTS_DEFAULT_MODE 0600
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +000030/*
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
Sukadev Bhattiprolu527b3e42008-10-13 10:43:08 +010037#define PTMX_MINOR 2
Miklos Szeredib87a2672008-02-08 04:21:41 -080038
Konstantin Khlebnikova4834c12012-01-05 13:06:02 +040039/*
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;
Konstantin Khlebnikove9aba512012-01-05 13:06:11 +040044static int pty_reserve = NR_UNIX98_PTY_RESERVE;
Konstantin Khlebnikova4834c12012-01-05 13:06:02 +040045static int pty_limit_min;
Konstantin Khlebnikove9aba512012-01-05 13:06:11 +040046static int pty_limit_max = INT_MAX;
Konstantin Khlebnikova4834c12012-01-05 13:06:02 +040047static 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 }, {
Konstantin Khlebnikove9aba512012-01-05 13:06:11 +040059 .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 }, {
Konstantin Khlebnikova4834c12012-01-05 13:06:02 +040067 .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
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -070094static DEFINE_MUTEX(allocated_ptys_lock);
95
Linus Torvalds1da177e2005-04-16 15:20:36 -070096static struct vfsmount *devpts_mnt;
Linus Torvalds1da177e2005-04-16 15:20:36 -070097
Sukadev Bhattiprolu31af0ab2009-01-02 13:41:33 +000098struct pts_mount_opts {
Linus Torvalds1da177e2005-04-16 15:20:36 -070099 int setuid;
100 int setgid;
Eric W. Biedermanf04c6ce2012-02-07 16:22:56 -0800101 kuid_t uid;
102 kgid_t gid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103 umode_t mode;
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000104 umode_t ptmxmode;
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000105 int newinstance;
Konstantin Khlebnikove9aba512012-01-05 13:06:11 +0400106 int max;
Sukadev Bhattiprolu31af0ab2009-01-02 13:41:33 +0000107};
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108
Domen Puncer7a673c62006-03-23 03:00:59 -0800109enum {
Konstantin Khlebnikove9aba512012-01-05 13:06:11 +0400110 Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, Opt_max,
Domen Puncer7a673c62006-03-23 03:00:59 -0800111 Opt_err
112};
113
Steven Whitehousea447c092008-10-13 10:46:57 +0100114static const match_table_t tokens = {
Domen Puncer7a673c62006-03-23 03:00:59 -0800115 {Opt_uid, "uid=%u"},
116 {Opt_gid, "gid=%u"},
117 {Opt_mode, "mode=%o"},
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000118#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
119 {Opt_ptmxmode, "ptmxmode=%o"},
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000120 {Opt_newinstance, "newinstance"},
Konstantin Khlebnikove9aba512012-01-05 13:06:11 +0400121 {Opt_max, "max=%d"},
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000122#endif
Domen Puncer7a673c62006-03-23 03:00:59 -0800123 {Opt_err, NULL}
124};
125
Sukadev Bhattiprolue76b7c02009-01-02 13:41:21 +0000126struct pts_fs_info {
127 struct ida allocated_ptys;
Sukadev Bhattiprolu31af0ab2009-01-02 13:41:33 +0000128 struct pts_mount_opts mount_opts;
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000129 struct dentry *ptmx_dentry;
Sukadev Bhattiprolue76b7c02009-01-02 13:41:21 +0000130};
131
132static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
133{
134 return sb->s_fs_info;
135}
136
Sukadev Bhattiprolu59e55e62009-01-02 13:41:11 +0000137static inline struct super_block *pts_sb_from_inode(struct inode *inode)
138{
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000139#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
Sukadev Bhattiprolu59e55e62009-01-02 13:41:11 +0000140 if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
141 return inode->i_sb;
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000142#endif
Sukadev Bhattiprolu59e55e62009-01-02 13:41:11 +0000143 return devpts_mnt->mnt_sb;
144}
145
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000146#define PARSE_MOUNT 0
147#define PARSE_REMOUNT 1
148
Sukadev Bhattiprolu1f71ebe2009-05-14 19:38:24 -0700149/*
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 */
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000158static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159{
Domen Puncer7a673c62006-03-23 03:00:59 -0800160 char *p;
Eric W. Biedermanf04c6ce2012-02-07 16:22:56 -0800161 kuid_t uid;
162 kgid_t gid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700163
Sukadev Bhattiprolu31af0ab2009-01-02 13:41:33 +0000164 opts->setuid = 0;
165 opts->setgid = 0;
Eric W. Biedermanf04c6ce2012-02-07 16:22:56 -0800166 opts->uid = GLOBAL_ROOT_UID;
167 opts->gid = GLOBAL_ROOT_GID;
Sukadev Bhattiprolu31af0ab2009-01-02 13:41:33 +0000168 opts->mode = DEVPTS_DEFAULT_MODE;
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000169 opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
Konstantin Khlebnikove9aba512012-01-05 13:06:11 +0400170 opts->max = NR_UNIX98_PTY_MAX;
Domen Puncer7a673c62006-03-23 03:00:59 -0800171
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000172 /* newinstance makes sense only on initial mount */
173 if (op == PARSE_MOUNT)
174 opts->newinstance = 0;
175
Domen Puncer7a673c62006-03-23 03:00:59 -0800176 while ((p = strsep(&data, ",")) != NULL) {
177 substring_t args[MAX_OPT_ARGS];
178 int token;
179 int option;
180
181 if (!*p)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182 continue;
Domen Puncer7a673c62006-03-23 03:00:59 -0800183
184 token = match_token(p, tokens, args);
185 switch (token) {
186 case Opt_uid:
187 if (match_int(&args[0], &option))
188 return -EINVAL;
Eric W. Biedermanf04c6ce2012-02-07 16:22:56 -0800189 uid = make_kuid(current_user_ns(), option);
190 if (!uid_valid(uid))
191 return -EINVAL;
192 opts->uid = uid;
Sukadev Bhattiprolu31af0ab2009-01-02 13:41:33 +0000193 opts->setuid = 1;
Domen Puncer7a673c62006-03-23 03:00:59 -0800194 break;
195 case Opt_gid:
196 if (match_int(&args[0], &option))
197 return -EINVAL;
Eric W. Biedermanf04c6ce2012-02-07 16:22:56 -0800198 gid = make_kgid(current_user_ns(), option);
199 if (!gid_valid(gid))
200 return -EINVAL;
201 opts->gid = gid;
Sukadev Bhattiprolu31af0ab2009-01-02 13:41:33 +0000202 opts->setgid = 1;
Domen Puncer7a673c62006-03-23 03:00:59 -0800203 break;
204 case Opt_mode:
205 if (match_octal(&args[0], &option))
206 return -EINVAL;
Sukadev Bhattiprolu31af0ab2009-01-02 13:41:33 +0000207 opts->mode = option & S_IALLUGO;
Domen Puncer7a673c62006-03-23 03:00:59 -0800208 break;
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000209#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;
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000215 case Opt_newinstance:
216 /* newinstance makes sense only on initial mount */
217 if (op == PARSE_MOUNT)
218 opts->newinstance = 1;
219 break;
Konstantin Khlebnikove9aba512012-01-05 13:06:11 +0400220 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;
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000226#endif
Domen Puncer7a673c62006-03-23 03:00:59 -0800227 default:
228 printk(KERN_ERR "devpts: called with bogus options\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -0700229 return -EINVAL;
230 }
231 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700232
233 return 0;
234}
235
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000236#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
237static int mknod_ptmx(struct super_block *sb)
Sukadev Bhattiprolu53af8ee2009-01-02 13:41:47 +0000238{
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000239 int mode;
240 int rc = -ENOMEM;
241 struct dentry *dentry;
242 struct inode *inode;
243 struct dentry *root = sb->s_root;
Sukadev Bhattiprolu53af8ee2009-01-02 13:41:47 +0000244 struct pts_fs_info *fsi = DEVPTS_SB(sb);
245 struct pts_mount_opts *opts = &fsi->mount_opts;
246
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000247 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;
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000272 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;
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000281out:
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
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000307 err = parse_mount_options(data, PARSE_REMOUNT, opts);
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000308
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;
Sukadev Bhattiprolu53af8ee2009-01-02 13:41:47 +0000318}
319
Al Viro34c80b12011-12-08 21:32:45 -0500320static int devpts_show_options(struct seq_file *seq, struct dentry *root)
Miklos Szeredib87a2672008-02-08 04:21:41 -0800321{
Al Viro34c80b12011-12-08 21:32:45 -0500322 struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb);
Sukadev Bhattiprolu31af0ab2009-01-02 13:41:33 +0000323 struct pts_mount_opts *opts = &fsi->mount_opts;
324
325 if (opts->setuid)
Eric W. Biedermanf04c6ce2012-02-07 16:22:56 -0800326 seq_printf(seq, ",uid=%u", from_kuid_munged(&init_user_ns, opts->uid));
Sukadev Bhattiprolu31af0ab2009-01-02 13:41:33 +0000327 if (opts->setgid)
Eric W. Biedermanf04c6ce2012-02-07 16:22:56 -0800328 seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, opts->gid));
Sukadev Bhattiprolu31af0ab2009-01-02 13:41:33 +0000329 seq_printf(seq, ",mode=%03o", opts->mode);
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000330#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
331 seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
Konstantin Khlebnikove9aba512012-01-05 13:06:11 +0400332 if (opts->max < NR_UNIX98_PTY_MAX)
333 seq_printf(seq, ",max=%d", opts->max);
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000334#endif
Miklos Szeredib87a2672008-02-08 04:21:41 -0800335
336 return 0;
337}
338
Josef 'Jeff' Sipekee9b6d62007-02-12 00:55:41 -0800339static const struct super_operations devpts_sops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700340 .statfs = simple_statfs,
341 .remount_fs = devpts_remount,
Miklos Szeredib87a2672008-02-08 04:21:41 -0800342 .show_options = devpts_show_options,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700343};
344
Sukadev Bhattiprolue76b7c02009-01-02 13:41:21 +0000345static 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);
Sukadev Bhattiprolu31af0ab2009-01-02 13:41:33 +0000354 fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000355 fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
Sukadev Bhattiprolue76b7c02009-01-02 13:41:21 +0000356
357 return fsi;
358}
359
Linus Torvalds1da177e2005-04-16 15:20:36 -0700360static int
361devpts_fill_super(struct super_block *s, void *data, int silent)
362{
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000363 struct inode *inode;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700364
365 s->s_blocksize = 1024;
366 s->s_blocksize_bits = 10;
367 s->s_magic = DEVPTS_SUPER_MAGIC;
368 s->s_op = &devpts_sops;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700369 s->s_time_gran = 1;
370
Sukadev Bhattiprolue76b7c02009-01-02 13:41:21 +0000371 s->s_fs_info = new_pts_fs_info();
372 if (!s->s_fs_info)
373 goto fail;
374
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375 inode = new_inode(s);
376 if (!inode)
Al Viro3850aba2012-01-08 19:40:27 -0500377 goto fail;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700378 inode->i_ino = 1;
379 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700380 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;
Miklos Szeredibfe86842011-10-28 14:13:29 +0200383 set_nlink(inode, 2);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384
Al Viro48fde702012-01-08 22:15:13 -0500385 s->s_root = d_make_root(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700386 if (s->s_root)
387 return 0;
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000388
Alan Cox835aa442009-01-02 13:42:48 +0000389 printk(KERN_ERR "devpts: get root dentry failed\n");
Sukadev Bhattiprolue76b7c02009-01-02 13:41:21 +0000390
Linus Torvalds1da177e2005-04-16 15:20:36 -0700391fail:
392 return -ENOMEM;
393}
394
Andrew Morton8c056e52009-01-02 13:44:12 +0000395#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
Sukadev Bhattiprolud4076ac2009-01-02 13:42:19 +0000396static int compare_init_pts_sb(struct super_block *s, void *p)
397{
398 if (devpts_mnt)
399 return devpts_mnt->mnt_sb == s;
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000400 return 0;
401}
402
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000403/*
Al Virofc14f2f2010-07-25 01:48:30 +0400404 * devpts_mount()
Sukadev Bhattiprolu289f00e2009-03-07 10:12:06 -0800405 *
Sukadev Bhattiprolu1bd79032009-03-07 10:12:32 -0800406 * 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.
Sukadev Bhattiprolud4076ac2009-01-02 13:42:19 +0000409 *
Sukadev Bhattiprolu1bd79032009-03-07 10:12:32 -0800410 * 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.
Sukadev Bhattiprolud4076ac2009-01-02 13:42:19 +0000413 *
Sukadev Bhattiprolu1bd79032009-03-07 10:12:32 -0800414 * 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
Al Virofc14f2f2010-07-25 01:48:30 +0400418 * kernel mount, like mount_single().
Sukadev Bhattiprolud4076ac2009-01-02 13:42:19 +0000419 *
Sukadev Bhattiprolu1bd79032009-03-07 10:12:32 -0800420 * Mounts with 'newinstance' option create a new, private namespace.
421 *
422 * NOTE:
423 *
Al Virofc14f2f2010-07-25 01:48:30 +0400424 * For single-mount semantics, devpts cannot use mount_single(),
425 * because mount_single()/sget() find and use the super-block from
Sukadev Bhattiprolud4076ac2009-01-02 13:42:19 +0000426 * the most recent mount of devpts. But that recent mount may be a
Al Virofc14f2f2010-07-25 01:48:30 +0400427 * 'newinstance' mount and mount_single() would pick the newinstance
Sukadev Bhattiprolud4076ac2009-01-02 13:42:19 +0000428 * super-block instead of the initial super-block.
Sukadev Bhattiprolud4076ac2009-01-02 13:42:19 +0000429 */
Al Virofc14f2f2010-07-25 01:48:30 +0400430static struct dentry *devpts_mount(struct file_system_type *fs_type,
431 int flags, const char *dev_name, void *data)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700432{
Sukadev Bhattiprolu482984f2009-03-07 10:14:41 -0800433 int error;
434 struct pts_mount_opts opts;
Sukadev Bhattiprolu1bd79032009-03-07 10:12:32 -0800435 struct super_block *s;
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000436
Sukadev Bhattiprolu1f71ebe2009-05-14 19:38:24 -0700437 error = parse_mount_options(data, PARSE_MOUNT, &opts);
438 if (error)
Al Virofc14f2f2010-07-25 01:48:30 +0400439 return ERR_PTR(error);
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000440
Sukadev Bhattiprolu482984f2009-03-07 10:14:41 -0800441 if (opts.newinstance)
David Howells9249e172012-06-25 12:55:37 +0100442 s = sget(fs_type, NULL, set_anon_super, flags, NULL);
Sukadev Bhattiprolu482984f2009-03-07 10:14:41 -0800443 else
David Howells9249e172012-06-25 12:55:37 +0100444 s = sget(fs_type, compare_init_pts_sb, set_anon_super, flags,
445 NULL);
Sukadev Bhattiprolu945cf2c2009-03-07 10:11:41 -0800446
Sukadev Bhattiprolu1bd79032009-03-07 10:12:32 -0800447 if (IS_ERR(s))
Al Virofc14f2f2010-07-25 01:48:30 +0400448 return ERR_CAST(s);
Sukadev Bhattiprolu945cf2c2009-03-07 10:11:41 -0800449
Sukadev Bhattiprolu1bd79032009-03-07 10:12:32 -0800450 if (!s->s_root) {
Sukadev Bhattiprolu1bd79032009-03-07 10:12:32 -0800451 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
Sukadev Bhattiprolu1bd79032009-03-07 10:12:32 -0800457 memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
458
459 error = mknod_ptmx(s);
Sukadev Bhattiprolu945cf2c2009-03-07 10:11:41 -0800460 if (error)
Al Viro89468072010-03-20 21:57:43 -0400461 goto out_undo_sget;
462
Al Virofc14f2f2010-07-25 01:48:30 +0400463 return dget(s->s_root);
Sukadev Bhattiprolu945cf2c2009-03-07 10:11:41 -0800464
Sukadev Bhattiprolu1bd79032009-03-07 10:12:32 -0800465out_undo_sget:
Al Viro6f5bbff2009-05-06 01:34:22 -0400466 deactivate_locked_super(s);
Al Virofc14f2f2010-07-25 01:48:30 +0400467 return ERR_PTR(error);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700468}
Sukadev Bhattiprolu482984f2009-03-07 10:14:41 -0800469
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000470#else
471/*
472 * This supports only the legacy single-instance semantics (no
473 * multiple-instance semantics)
474 */
Al Virofc14f2f2010-07-25 01:48:30 +0400475static struct dentry *devpts_mount(struct file_system_type *fs_type, int flags,
476 const char *dev_name, void *data)
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000477{
Al Virofc14f2f2010-07-25 01:48:30 +0400478 return mount_single(fs_type, flags, data, devpts_fill_super);
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000479}
480#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700481
Sukadev Bhattiprolue76b7c02009-01-02 13:41:21 +0000482static void devpts_kill_sb(struct super_block *sb)
483{
484 struct pts_fs_info *fsi = DEVPTS_SB(sb);
485
486 kfree(fsi);
Sukadev Bhattiprolu1f8f1e22009-01-02 13:42:02 +0000487 kill_litter_super(sb);
Sukadev Bhattiprolue76b7c02009-01-02 13:41:21 +0000488}
489
Linus Torvalds1da177e2005-04-16 15:20:36 -0700490static struct file_system_type devpts_fs_type = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700491 .name = "devpts",
Al Virofc14f2f2010-07-25 01:48:30 +0400492 .mount = devpts_mount,
Sukadev Bhattiprolue76b7c02009-01-02 13:41:21 +0000493 .kill_sb = devpts_kill_sb,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700494};
495
496/*
497 * The normal naming convention is simply /dev/pts/<number>; this conforms
498 * to the System V naming convention
499 */
500
Sukadev Bhattiprolu15f1a632008-10-13 10:42:59 +0100501int devpts_new_index(struct inode *ptmx_inode)
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -0700502{
Sukadev Bhattiprolue76b7c02009-01-02 13:41:21 +0000503 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
504 struct pts_fs_info *fsi = DEVPTS_SB(sb);
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -0700505 int index;
Alexey Dobriyan7ee7c122008-07-26 11:42:16 +0400506 int ida_ret;
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -0700507
508retry:
Alan Cox835aa442009-01-02 13:42:48 +0000509 if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -0700510 return -ENOMEM;
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -0700511
512 mutex_lock(&allocated_ptys_lock);
Konstantin Khlebnikove9aba512012-01-05 13:06:11 +0400513 if (pty_count >= pty_limit -
514 (fsi->mount_opts.newinstance ? pty_reserve : 0)) {
515 mutex_unlock(&allocated_ptys_lock);
516 return -ENOSPC;
517 }
518
Sukadev Bhattiprolue76b7c02009-01-02 13:41:21 +0000519 ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
Alexey Dobriyan7ee7c122008-07-26 11:42:16 +0400520 if (ida_ret < 0) {
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -0700521 mutex_unlock(&allocated_ptys_lock);
Alexey Dobriyan7ee7c122008-07-26 11:42:16 +0400522 if (ida_ret == -EAGAIN)
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -0700523 goto retry;
524 return -EIO;
525 }
526
Konstantin Khlebnikove9aba512012-01-05 13:06:11 +0400527 if (index >= fsi->mount_opts.max) {
Sukadev Bhattiprolue76b7c02009-01-02 13:41:21 +0000528 ida_remove(&fsi->allocated_ptys, index);
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -0700529 mutex_unlock(&allocated_ptys_lock);
Konstantin Khlebnikove9aba512012-01-05 13:06:11 +0400530 return -ENOSPC;
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -0700531 }
Konstantin Khlebnikova4834c12012-01-05 13:06:02 +0400532 pty_count++;
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -0700533 mutex_unlock(&allocated_ptys_lock);
534 return index;
535}
536
Sukadev Bhattiprolu15f1a632008-10-13 10:42:59 +0100537void devpts_kill_index(struct inode *ptmx_inode, int idx)
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -0700538{
Sukadev Bhattiprolue76b7c02009-01-02 13:41:21 +0000539 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
540 struct pts_fs_info *fsi = DEVPTS_SB(sb);
541
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -0700542 mutex_lock(&allocated_ptys_lock);
Sukadev Bhattiprolue76b7c02009-01-02 13:41:21 +0000543 ida_remove(&fsi->allocated_ptys, idx);
Konstantin Khlebnikova4834c12012-01-05 13:06:02 +0400544 pty_count--;
Sukadev Bhattiprolu718a9162008-04-30 00:54:21 -0700545 mutex_unlock(&allocated_ptys_lock);
546}
547
Sukadev Bhattiprolu15f1a632008-10-13 10:42:59 +0100548int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700549{
Alan Cox835aa442009-01-02 13:42:48 +0000550 /* tty layer puts index from devpts_new_index() in here */
551 int number = tty->index;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700552 struct tty_driver *driver = tty->driver;
553 dev_t device = MKDEV(driver->major, driver->minor_start+number);
554 struct dentry *dentry;
Sukadev Bhattiprolu59e55e62009-01-02 13:41:11 +0000555 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
556 struct inode *inode = new_inode(sb);
557 struct dentry *root = sb->s_root;
Sukadev Bhattiprolu31af0ab2009-01-02 13:41:33 +0000558 struct pts_fs_info *fsi = DEVPTS_SB(sb);
559 struct pts_mount_opts *opts = &fsi->mount_opts;
Andrey Vaginaa597bc2011-02-08 00:14:52 +0300560 int ret = 0;
Sukadev Bhattiprolu89a52e102008-10-13 10:43:18 +0100561 char s[12];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700562
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
David Howellsd0eafc72009-01-02 13:44:49 +0000570 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();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700573 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
Sukadev Bhattiprolu31af0ab2009-01-02 13:41:33 +0000574 init_special_inode(inode, S_IFCHR|opts->mode, device);
Theodore Ts'o8e18e292006-09-27 01:50:46 -0700575 inode->i_private = tty;
Sukadev Bhattiprolua6f37da2008-10-13 10:43:27 +0100576 tty->driver_data = inode;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700577
Sukadev Bhattiprolu89a52e102008-10-13 10:43:18 +0100578 sprintf(s, "%d", number);
579
Sukadev Bhattiprolu59e55e62009-01-02 13:41:11 +0000580 mutex_lock(&root->d_inode->i_mutex);
Sukadev Bhattiprolu89a52e102008-10-13 10:43:18 +0100581
Sukadev Bhattiprolu59e55e62009-01-02 13:41:11 +0000582 dentry = d_alloc_name(root, s);
Andrey Vaginb12d1252011-03-22 16:35:11 -0700583 if (dentry) {
Sukadev Bhattiprolu89a52e102008-10-13 10:43:18 +0100584 d_add(dentry, inode);
Sukadev Bhattiprolu59e55e62009-01-02 13:41:11 +0000585 fsnotify_create(root->d_inode, dentry);
Andrey Vaginaa597bc2011-02-08 00:14:52 +0300586 } else {
587 iput(inode);
588 ret = -ENOMEM;
Florin Malita3972b7f2007-05-08 00:24:18 -0700589 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700590
Sukadev Bhattiprolu59e55e62009-01-02 13:41:11 +0000591 mutex_unlock(&root->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700592
Andrey Vaginaa597bc2011-02-08 00:14:52 +0300593 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700594}
595
Sukadev Bhattiprolu15f1a632008-10-13 10:42:59 +0100596struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700597{
Sukadev Bhattiproluedfacdd2009-11-17 18:35:43 -0800598 struct dentry *dentry;
599 struct tty_struct *tty;
600
Sukadev Bhattiprolu527b3e42008-10-13 10:43:08 +0100601 BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700602
Sukadev Bhattiproluedfacdd2009-11-17 18:35:43 -0800603 /* 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;
Sukadev Bhattiprolu527b3e42008-10-13 10:43:08 +0100609 if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
Sukadev Bhattiproluedfacdd2009-11-17 18:35:43 -0800610 tty = (struct tty_struct *)pts_inode->i_private;
611
612 dput(dentry);
613
614 return tty;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700615}
616
Sukadev Bhattiprolu15f1a632008-10-13 10:42:59 +0100617void devpts_pty_kill(struct tty_struct *tty)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700618{
Sukadev Bhattiprolua6f37da2008-10-13 10:43:27 +0100619 struct inode *inode = tty->driver_data;
Sukadev Bhattiprolu59e55e62009-01-02 13:41:11 +0000620 struct super_block *sb = pts_sb_from_inode(inode);
621 struct dentry *root = sb->s_root;
Sukadev Bhattiprolua6f37da2008-10-13 10:43:27 +0100622 struct dentry *dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700623
Sukadev Bhattiprolua6f37da2008-10-13 10:43:27 +0100624 BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
625
Sukadev Bhattiprolu59e55e62009-01-02 13:41:11 +0000626 mutex_lock(&root->d_inode->i_mutex);
Sukadev Bhattiprolua6f37da2008-10-13 10:43:27 +0100627
628 dentry = d_find_alias(inode);
Sukadev Bhattiprolu2a1b2dc2009-01-02 13:42:27 +0000629
Miklos Szeredi6d6b77f2011-10-28 14:13:28 +0200630 drop_nlink(inode);
Andrey Vaginaa597bc2011-02-08 00:14:52 +0300631 d_delete(dentry);
632 dput(dentry); /* d_alloc_name() in devpts_pty_new() */
Alan Cox835aa442009-01-02 13:42:48 +0000633 dput(dentry); /* d_find_alias above */
Andrey Vaginaa597bc2011-02-08 00:14:52 +0300634
Sukadev Bhattiprolu59e55e62009-01-02 13:41:11 +0000635 mutex_unlock(&root->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700636}
637
638static int __init init_devpts_fs(void)
639{
640 int err = register_filesystem(&devpts_fs_type);
Konstantin Khlebnikova4834c12012-01-05 13:06:02 +0400641 struct ctl_table_header *table;
642
Linus Torvalds1da177e2005-04-16 15:20:36 -0700643 if (!err) {
Konstantin Khlebnikova4834c12012-01-05 13:06:02 +0400644 table = register_sysctl_table(pty_root_table);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700645 devpts_mnt = kern_mount(&devpts_fs_type);
Alan Cox93d55812009-06-11 14:03:55 +0100646 if (IS_ERR(devpts_mnt)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700647 err = PTR_ERR(devpts_mnt);
Alan Cox93d55812009-06-11 14:03:55 +0100648 unregister_filesystem(&devpts_fs_type);
Konstantin Khlebnikova4834c12012-01-05 13:06:02 +0400649 unregister_sysctl_table(table);
Alan Cox93d55812009-06-11 14:03:55 +0100650 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700651 }
652 return err;
653}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700654module_init(init_devpts_fs)