Revert "tty: pty: Fix race condition between release_one_tty and pty_write"
[muen/linux.git] / drivers / tty / pty.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  Copyright (C) 1991, 1992  Linus Torvalds
4  *
5  *  Added support for a Unix98-style ptmx device.
6  *    -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
7  *
8  */
9
10 #include <linux/module.h>
11 #include <linux/errno.h>
12 #include <linux/interrupt.h>
13 #include <linux/tty.h>
14 #include <linux/tty_flip.h>
15 #include <linux/fcntl.h>
16 #include <linux/sched/signal.h>
17 #include <linux/string.h>
18 #include <linux/major.h>
19 #include <linux/mm.h>
20 #include <linux/init.h>
21 #include <linux/device.h>
22 #include <linux/uaccess.h>
23 #include <linux/bitops.h>
24 #include <linux/devpts_fs.h>
25 #include <linux/slab.h>
26 #include <linux/mutex.h>
27 #include <linux/poll.h>
28 #include <linux/mount.h>
29 #include <linux/file.h>
30 #include <linux/ioctl.h>
31 #include <linux/compat.h>
32
33 #undef TTY_DEBUG_HANGUP
34 #ifdef TTY_DEBUG_HANGUP
35 # define tty_debug_hangup(tty, f, args...)      tty_debug(tty, f, ##args)
36 #else
37 # define tty_debug_hangup(tty, f, args...)      do {} while (0)
38 #endif
39
40 #ifdef CONFIG_UNIX98_PTYS
41 static struct tty_driver *ptm_driver;
42 static struct tty_driver *pts_driver;
43 static DEFINE_MUTEX(devpts_mutex);
44 #endif
45
46 static void pty_close(struct tty_struct *tty, struct file *filp)
47 {
48         BUG_ON(!tty);
49         if (tty->driver->subtype == PTY_TYPE_MASTER)
50                 WARN_ON(tty->count > 1);
51         else {
52                 if (tty_io_error(tty))
53                         return;
54                 if (tty->count > 2)
55                         return;
56         }
57         set_bit(TTY_IO_ERROR, &tty->flags);
58         wake_up_interruptible(&tty->read_wait);
59         wake_up_interruptible(&tty->write_wait);
60         spin_lock_irq(&tty->ctrl_lock);
61         tty->packet = 0;
62         spin_unlock_irq(&tty->ctrl_lock);
63         /* Review - krefs on tty_link ?? */
64         if (!tty->link)
65                 return;
66         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
67         wake_up_interruptible(&tty->link->read_wait);
68         wake_up_interruptible(&tty->link->write_wait);
69         if (tty->driver->subtype == PTY_TYPE_MASTER) {
70                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
71 #ifdef CONFIG_UNIX98_PTYS
72                 if (tty->driver == ptm_driver) {
73                         mutex_lock(&devpts_mutex);
74                         if (tty->link->driver_data)
75                                 devpts_pty_kill(tty->link->driver_data);
76                         mutex_unlock(&devpts_mutex);
77                 }
78 #endif
79                 tty_vhangup(tty->link);
80         }
81 }
82
83 /*
84  * The unthrottle routine is called by the line discipline to signal
85  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
86  * flag is always set, to force the line discipline to always call the
87  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
88  * characters in the queue.  This is necessary since each time this
89  * happens, we need to wake up any sleeping processes that could be
90  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
91  * for the pty buffer to be drained.
92  */
93 static void pty_unthrottle(struct tty_struct *tty)
94 {
95         tty_wakeup(tty->link);
96         set_bit(TTY_THROTTLED, &tty->flags);
97 }
98
99 /**
100  *      pty_write               -       write to a pty
101  *      @tty: the tty we write from
102  *      @buf: kernel buffer of data
103  *      @count: bytes to write
104  *
105  *      Our "hardware" write method. Data is coming from the ldisc which
106  *      may be in a non sleeping state. We simply throw this at the other
107  *      end of the link as if we were an IRQ handler receiving stuff for
108  *      the other side of the pty/tty pair.
109  */
110
111 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
112 {
113         struct tty_struct *to = tty->link;
114         unsigned long flags;
115
116         if (tty->stopped)
117                 return 0;
118
119         if (c > 0) {
120                 spin_lock_irqsave(&to->port->lock, flags);
121                 /* Stuff the data into the input queue of the other end */
122                 c = tty_insert_flip_string(to->port, buf, c);
123                 /* And shovel */
124                 if (c)
125                         tty_flip_buffer_push(to->port);
126                 spin_unlock_irqrestore(&to->port->lock, flags);
127         }
128         return c;
129 }
130
131 /**
132  *      pty_write_room  -       write space
133  *      @tty: tty we are writing from
134  *
135  *      Report how many bytes the ldisc can send into the queue for
136  *      the other device.
137  */
138
139 static int pty_write_room(struct tty_struct *tty)
140 {
141         if (tty->stopped)
142                 return 0;
143         return tty_buffer_space_avail(tty->link->port);
144 }
145
146 /**
147  *      pty_chars_in_buffer     -       characters currently in our tx queue
148  *      @tty: our tty
149  *
150  *      Report how much we have in the transmit queue. As everything is
151  *      instantly at the other end this is easy to implement.
152  */
153
154 static int pty_chars_in_buffer(struct tty_struct *tty)
155 {
156         return 0;
157 }
158
159 /* Set the lock flag on a pty */
160 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
161 {
162         int val;
163         if (get_user(val, arg))
164                 return -EFAULT;
165         if (val)
166                 set_bit(TTY_PTY_LOCK, &tty->flags);
167         else
168                 clear_bit(TTY_PTY_LOCK, &tty->flags);
169         return 0;
170 }
171
172 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
173 {
174         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
175         return put_user(locked, arg);
176 }
177
178 /* Set the packet mode on a pty */
179 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
180 {
181         int pktmode;
182
183         if (get_user(pktmode, arg))
184                 return -EFAULT;
185
186         spin_lock_irq(&tty->ctrl_lock);
187         if (pktmode) {
188                 if (!tty->packet) {
189                         tty->link->ctrl_status = 0;
190                         smp_mb();
191                         tty->packet = 1;
192                 }
193         } else
194                 tty->packet = 0;
195         spin_unlock_irq(&tty->ctrl_lock);
196
197         return 0;
198 }
199
200 /* Get the packet mode of a pty */
201 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
202 {
203         int pktmode = tty->packet;
204         return put_user(pktmode, arg);
205 }
206
207 /* Send a signal to the slave */
208 static int pty_signal(struct tty_struct *tty, int sig)
209 {
210         struct pid *pgrp;
211
212         if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
213                 return -EINVAL;
214
215         if (tty->link) {
216                 pgrp = tty_get_pgrp(tty->link);
217                 if (pgrp)
218                         kill_pgrp(pgrp, sig, 1);
219                 put_pid(pgrp);
220         }
221         return 0;
222 }
223
224 static void pty_flush_buffer(struct tty_struct *tty)
225 {
226         struct tty_struct *to = tty->link;
227
228         if (!to)
229                 return;
230
231         tty_buffer_flush(to, NULL);
232         if (to->packet) {
233                 spin_lock_irq(&tty->ctrl_lock);
234                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
235                 wake_up_interruptible(&to->read_wait);
236                 spin_unlock_irq(&tty->ctrl_lock);
237         }
238 }
239
240 static int pty_open(struct tty_struct *tty, struct file *filp)
241 {
242         if (!tty || !tty->link)
243                 return -ENODEV;
244
245         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
246                 goto out;
247         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
248                 goto out;
249         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
250                 goto out;
251
252         clear_bit(TTY_IO_ERROR, &tty->flags);
253         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
254         set_bit(TTY_THROTTLED, &tty->flags);
255         return 0;
256
257 out:
258         set_bit(TTY_IO_ERROR, &tty->flags);
259         return -EIO;
260 }
261
262 static void pty_set_termios(struct tty_struct *tty,
263                                         struct ktermios *old_termios)
264 {
265         /* See if packet mode change of state. */
266         if (tty->link && tty->link->packet) {
267                 int extproc = (old_termios->c_lflag & EXTPROC) | L_EXTPROC(tty);
268                 int old_flow = ((old_termios->c_iflag & IXON) &&
269                                 (old_termios->c_cc[VSTOP] == '\023') &&
270                                 (old_termios->c_cc[VSTART] == '\021'));
271                 int new_flow = (I_IXON(tty) &&
272                                 STOP_CHAR(tty) == '\023' &&
273                                 START_CHAR(tty) == '\021');
274                 if ((old_flow != new_flow) || extproc) {
275                         spin_lock_irq(&tty->ctrl_lock);
276                         if (old_flow != new_flow) {
277                                 tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
278                                 if (new_flow)
279                                         tty->ctrl_status |= TIOCPKT_DOSTOP;
280                                 else
281                                         tty->ctrl_status |= TIOCPKT_NOSTOP;
282                         }
283                         if (extproc)
284                                 tty->ctrl_status |= TIOCPKT_IOCTL;
285                         spin_unlock_irq(&tty->ctrl_lock);
286                         wake_up_interruptible(&tty->link->read_wait);
287                 }
288         }
289
290         tty->termios.c_cflag &= ~(CSIZE | PARENB);
291         tty->termios.c_cflag |= (CS8 | CREAD);
292 }
293
294 /**
295  *      pty_do_resize           -       resize event
296  *      @tty: tty being resized
297  *      @ws: window size being set.
298  *
299  *      Update the termios variables and send the necessary signals to
300  *      peform a terminal resize correctly
301  */
302
303 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
304 {
305         struct pid *pgrp, *rpgrp;
306         struct tty_struct *pty = tty->link;
307
308         /* For a PTY we need to lock the tty side */
309         mutex_lock(&tty->winsize_mutex);
310         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
311                 goto done;
312
313         /* Signal the foreground process group of both ptys */
314         pgrp = tty_get_pgrp(tty);
315         rpgrp = tty_get_pgrp(pty);
316
317         if (pgrp)
318                 kill_pgrp(pgrp, SIGWINCH, 1);
319         if (rpgrp != pgrp && rpgrp)
320                 kill_pgrp(rpgrp, SIGWINCH, 1);
321
322         put_pid(pgrp);
323         put_pid(rpgrp);
324
325         tty->winsize = *ws;
326         pty->winsize = *ws;     /* Never used so will go away soon */
327 done:
328         mutex_unlock(&tty->winsize_mutex);
329         return 0;
330 }
331
332 /**
333  *      pty_start - start() handler
334  *      pty_stop  - stop() handler
335  *      @tty: tty being flow-controlled
336  *
337  *      Propagates the TIOCPKT status to the master pty.
338  *
339  *      NB: only the master pty can be in packet mode so only the slave
340  *          needs start()/stop() handlers
341  */
342 static void pty_start(struct tty_struct *tty)
343 {
344         unsigned long flags;
345
346         if (tty->link && tty->link->packet) {
347                 spin_lock_irqsave(&tty->ctrl_lock, flags);
348                 tty->ctrl_status &= ~TIOCPKT_STOP;
349                 tty->ctrl_status |= TIOCPKT_START;
350                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
351                 wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
352         }
353 }
354
355 static void pty_stop(struct tty_struct *tty)
356 {
357         unsigned long flags;
358
359         if (tty->link && tty->link->packet) {
360                 spin_lock_irqsave(&tty->ctrl_lock, flags);
361                 tty->ctrl_status &= ~TIOCPKT_START;
362                 tty->ctrl_status |= TIOCPKT_STOP;
363                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
364                 wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
365         }
366 }
367
368 /**
369  *      pty_common_install              -       set up the pty pair
370  *      @driver: the pty driver
371  *      @tty: the tty being instantiated
372  *      @legacy: true if this is BSD style
373  *
374  *      Perform the initial set up for the tty/pty pair. Called from the
375  *      tty layer when the port is first opened.
376  *
377  *      Locking: the caller must hold the tty_mutex
378  */
379 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
380                 bool legacy)
381 {
382         struct tty_struct *o_tty;
383         struct tty_port *ports[2];
384         int idx = tty->index;
385         int retval = -ENOMEM;
386
387         /* Opening the slave first has always returned -EIO */
388         if (driver->subtype != PTY_TYPE_MASTER)
389                 return -EIO;
390
391         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
392         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
393         if (!ports[0] || !ports[1])
394                 goto err;
395         if (!try_module_get(driver->other->owner)) {
396                 /* This cannot in fact currently happen */
397                 goto err;
398         }
399         o_tty = alloc_tty_struct(driver->other, idx);
400         if (!o_tty)
401                 goto err_put_module;
402
403         tty_set_lock_subclass(o_tty);
404         lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
405
406         if (legacy) {
407                 /* We always use new tty termios data so we can do this
408                    the easy way .. */
409                 tty_init_termios(tty);
410                 tty_init_termios(o_tty);
411
412                 driver->other->ttys[idx] = o_tty;
413                 driver->ttys[idx] = tty;
414         } else {
415                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
416                 tty->termios = driver->init_termios;
417                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
418                 o_tty->termios = driver->other->init_termios;
419         }
420
421         /*
422          * Everything allocated ... set up the o_tty structure.
423          */
424         tty_driver_kref_get(driver->other);
425         /* Establish the links in both directions */
426         tty->link   = o_tty;
427         o_tty->link = tty;
428         tty_port_init(ports[0]);
429         tty_port_init(ports[1]);
430         tty_buffer_set_limit(ports[0], 8192);
431         tty_buffer_set_limit(ports[1], 8192);
432         o_tty->port = ports[0];
433         tty->port = ports[1];
434         o_tty->port->itty = o_tty;
435
436         tty_buffer_set_lock_subclass(o_tty->port);
437
438         tty_driver_kref_get(driver);
439         tty->count++;
440         o_tty->count++;
441         return 0;
442
443 err_put_module:
444         module_put(driver->other->owner);
445 err:
446         kfree(ports[0]);
447         kfree(ports[1]);
448         return retval;
449 }
450
451 static void pty_cleanup(struct tty_struct *tty)
452 {
453         tty_port_put(tty->port);
454 }
455
456 /* Traditional BSD devices */
457 #ifdef CONFIG_LEGACY_PTYS
458
459 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
460 {
461         return pty_common_install(driver, tty, true);
462 }
463
464 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
465 {
466         struct tty_struct *pair = tty->link;
467         driver->ttys[tty->index] = NULL;
468         if (pair)
469                 pair->driver->ttys[pair->index] = NULL;
470 }
471
472 static int pty_bsd_ioctl(struct tty_struct *tty,
473                          unsigned int cmd, unsigned long arg)
474 {
475         switch (cmd) {
476         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
477                 return pty_set_lock(tty, (int __user *) arg);
478         case TIOCGPTLCK: /* Get PT Lock status */
479                 return pty_get_lock(tty, (int __user *)arg);
480         case TIOCPKT: /* Set PT packet mode */
481                 return pty_set_pktmode(tty, (int __user *)arg);
482         case TIOCGPKT: /* Get PT packet mode */
483                 return pty_get_pktmode(tty, (int __user *)arg);
484         case TIOCSIG:    /* Send signal to other side of pty */
485                 return pty_signal(tty, (int) arg);
486         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
487                 return -EINVAL;
488         }
489         return -ENOIOCTLCMD;
490 }
491
492 #ifdef CONFIG_COMPAT
493 static long pty_bsd_compat_ioctl(struct tty_struct *tty,
494                                  unsigned int cmd, unsigned long arg)
495 {
496         /*
497          * PTY ioctls don't require any special translation between 32-bit and
498          * 64-bit userspace, they are already compatible.
499          */
500         return pty_bsd_ioctl(tty, cmd, (unsigned long)compat_ptr(arg));
501 }
502 #else
503 #define pty_bsd_compat_ioctl NULL
504 #endif
505
506 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
507 /*
508  * not really modular, but the easiest way to keep compat with existing
509  * bootargs behaviour is to continue using module_param here.
510  */
511 module_param(legacy_count, int, 0);
512
513 /*
514  * The master side of a pty can do TIOCSPTLCK and thus
515  * has pty_bsd_ioctl.
516  */
517 static const struct tty_operations master_pty_ops_bsd = {
518         .install = pty_install,
519         .open = pty_open,
520         .close = pty_close,
521         .write = pty_write,
522         .write_room = pty_write_room,
523         .flush_buffer = pty_flush_buffer,
524         .chars_in_buffer = pty_chars_in_buffer,
525         .unthrottle = pty_unthrottle,
526         .ioctl = pty_bsd_ioctl,
527         .compat_ioctl = pty_bsd_compat_ioctl,
528         .cleanup = pty_cleanup,
529         .resize = pty_resize,
530         .remove = pty_remove
531 };
532
533 static const struct tty_operations slave_pty_ops_bsd = {
534         .install = pty_install,
535         .open = pty_open,
536         .close = pty_close,
537         .write = pty_write,
538         .write_room = pty_write_room,
539         .flush_buffer = pty_flush_buffer,
540         .chars_in_buffer = pty_chars_in_buffer,
541         .unthrottle = pty_unthrottle,
542         .set_termios = pty_set_termios,
543         .cleanup = pty_cleanup,
544         .resize = pty_resize,
545         .start = pty_start,
546         .stop = pty_stop,
547         .remove = pty_remove
548 };
549
550 static void __init legacy_pty_init(void)
551 {
552         struct tty_driver *pty_driver, *pty_slave_driver;
553
554         if (legacy_count <= 0)
555                 return;
556
557         pty_driver = tty_alloc_driver(legacy_count,
558                         TTY_DRIVER_RESET_TERMIOS |
559                         TTY_DRIVER_REAL_RAW |
560                         TTY_DRIVER_DYNAMIC_ALLOC);
561         if (IS_ERR(pty_driver))
562                 panic("Couldn't allocate pty driver");
563
564         pty_slave_driver = tty_alloc_driver(legacy_count,
565                         TTY_DRIVER_RESET_TERMIOS |
566                         TTY_DRIVER_REAL_RAW |
567                         TTY_DRIVER_DYNAMIC_ALLOC);
568         if (IS_ERR(pty_slave_driver))
569                 panic("Couldn't allocate pty slave driver");
570
571         pty_driver->driver_name = "pty_master";
572         pty_driver->name = "pty";
573         pty_driver->major = PTY_MASTER_MAJOR;
574         pty_driver->minor_start = 0;
575         pty_driver->type = TTY_DRIVER_TYPE_PTY;
576         pty_driver->subtype = PTY_TYPE_MASTER;
577         pty_driver->init_termios = tty_std_termios;
578         pty_driver->init_termios.c_iflag = 0;
579         pty_driver->init_termios.c_oflag = 0;
580         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
581         pty_driver->init_termios.c_lflag = 0;
582         pty_driver->init_termios.c_ispeed = 38400;
583         pty_driver->init_termios.c_ospeed = 38400;
584         pty_driver->other = pty_slave_driver;
585         tty_set_operations(pty_driver, &master_pty_ops_bsd);
586
587         pty_slave_driver->driver_name = "pty_slave";
588         pty_slave_driver->name = "ttyp";
589         pty_slave_driver->major = PTY_SLAVE_MAJOR;
590         pty_slave_driver->minor_start = 0;
591         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
592         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
593         pty_slave_driver->init_termios = tty_std_termios;
594         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
595         pty_slave_driver->init_termios.c_ispeed = 38400;
596         pty_slave_driver->init_termios.c_ospeed = 38400;
597         pty_slave_driver->other = pty_driver;
598         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
599
600         if (tty_register_driver(pty_driver))
601                 panic("Couldn't register pty driver");
602         if (tty_register_driver(pty_slave_driver))
603                 panic("Couldn't register pty slave driver");
604 }
605 #else
606 static inline void legacy_pty_init(void) { }
607 #endif
608
609 /* Unix98 devices */
610 #ifdef CONFIG_UNIX98_PTYS
611 static struct cdev ptmx_cdev;
612
613 /**
614  *      ptm_open_peer - open the peer of a pty
615  *      @master: the open struct file of the ptmx device node
616  *      @tty: the master of the pty being opened
617  *      @flags: the flags for open
618  *
619  *      Provide a race free way for userspace to open the slave end of a pty
620  *      (where they have the master fd and cannot access or trust the mount
621  *      namespace /dev/pts was mounted inside).
622  */
623 int ptm_open_peer(struct file *master, struct tty_struct *tty, int flags)
624 {
625         int fd = -1;
626         struct file *filp;
627         int retval = -EINVAL;
628         struct path path;
629
630         if (tty->driver != ptm_driver)
631                 return -EIO;
632
633         fd = get_unused_fd_flags(flags);
634         if (fd < 0) {
635                 retval = fd;
636                 goto err;
637         }
638
639         /* Compute the slave's path */
640         path.mnt = devpts_mntget(master, tty->driver_data);
641         if (IS_ERR(path.mnt)) {
642                 retval = PTR_ERR(path.mnt);
643                 goto err_put;
644         }
645         path.dentry = tty->link->driver_data;
646
647         filp = dentry_open(&path, flags, current_cred());
648         mntput(path.mnt);
649         if (IS_ERR(filp)) {
650                 retval = PTR_ERR(filp);
651                 goto err_put;
652         }
653
654         fd_install(fd, filp);
655         return fd;
656
657 err_put:
658         put_unused_fd(fd);
659 err:
660         return retval;
661 }
662
663 static int pty_unix98_ioctl(struct tty_struct *tty,
664                             unsigned int cmd, unsigned long arg)
665 {
666         switch (cmd) {
667         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
668                 return pty_set_lock(tty, (int __user *)arg);
669         case TIOCGPTLCK: /* Get PT Lock status */
670                 return pty_get_lock(tty, (int __user *)arg);
671         case TIOCPKT: /* Set PT packet mode */
672                 return pty_set_pktmode(tty, (int __user *)arg);
673         case TIOCGPKT: /* Get PT packet mode */
674                 return pty_get_pktmode(tty, (int __user *)arg);
675         case TIOCGPTN: /* Get PT Number */
676                 return put_user(tty->index, (unsigned int __user *)arg);
677         case TIOCSIG:    /* Send signal to other side of pty */
678                 return pty_signal(tty, (int) arg);
679         }
680
681         return -ENOIOCTLCMD;
682 }
683
684 #ifdef CONFIG_COMPAT
685 static long pty_unix98_compat_ioctl(struct tty_struct *tty,
686                                  unsigned int cmd, unsigned long arg)
687 {
688         /*
689          * PTY ioctls don't require any special translation between 32-bit and
690          * 64-bit userspace, they are already compatible.
691          */
692         return pty_unix98_ioctl(tty, cmd,
693                 cmd == TIOCSIG ? arg : (unsigned long)compat_ptr(arg));
694 }
695 #else
696 #define pty_unix98_compat_ioctl NULL
697 #endif
698
699 /**
700  *      ptm_unix98_lookup       -       find a pty master
701  *      @driver: ptm driver
702  *      @idx: tty index
703  *
704  *      Look up a pty master device. Called under the tty_mutex for now.
705  *      This provides our locking.
706  */
707
708 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
709                 struct file *file, int idx)
710 {
711         /* Master must be open via /dev/ptmx */
712         return ERR_PTR(-EIO);
713 }
714
715 /**
716  *      pts_unix98_lookup       -       find a pty slave
717  *      @driver: pts driver
718  *      @idx: tty index
719  *
720  *      Look up a pty master device. Called under the tty_mutex for now.
721  *      This provides our locking for the tty pointer.
722  */
723
724 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
725                 struct file *file, int idx)
726 {
727         struct tty_struct *tty;
728
729         mutex_lock(&devpts_mutex);
730         tty = devpts_get_priv(file->f_path.dentry);
731         mutex_unlock(&devpts_mutex);
732         /* Master must be open before slave */
733         if (!tty)
734                 return ERR_PTR(-EIO);
735         return tty;
736 }
737
738 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
739 {
740         return pty_common_install(driver, tty, false);
741 }
742
743 /* this is called once with whichever end is closed last */
744 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
745 {
746         struct pts_fs_info *fsi;
747
748         if (tty->driver->subtype == PTY_TYPE_MASTER)
749                 fsi = tty->driver_data;
750         else
751                 fsi = tty->link->driver_data;
752
753         if (fsi) {
754                 devpts_kill_index(fsi, tty->index);
755                 devpts_release(fsi);
756         }
757 }
758
759 static void pty_show_fdinfo(struct tty_struct *tty, struct seq_file *m)
760 {
761         seq_printf(m, "tty-index:\t%d\n", tty->index);
762 }
763
764 static const struct tty_operations ptm_unix98_ops = {
765         .lookup = ptm_unix98_lookup,
766         .install = pty_unix98_install,
767         .remove = pty_unix98_remove,
768         .open = pty_open,
769         .close = pty_close,
770         .write = pty_write,
771         .write_room = pty_write_room,
772         .flush_buffer = pty_flush_buffer,
773         .chars_in_buffer = pty_chars_in_buffer,
774         .unthrottle = pty_unthrottle,
775         .ioctl = pty_unix98_ioctl,
776         .compat_ioctl = pty_unix98_compat_ioctl,
777         .resize = pty_resize,
778         .cleanup = pty_cleanup,
779         .show_fdinfo = pty_show_fdinfo,
780 };
781
782 static const struct tty_operations pty_unix98_ops = {
783         .lookup = pts_unix98_lookup,
784         .install = pty_unix98_install,
785         .remove = pty_unix98_remove,
786         .open = pty_open,
787         .close = pty_close,
788         .write = pty_write,
789         .write_room = pty_write_room,
790         .flush_buffer = pty_flush_buffer,
791         .chars_in_buffer = pty_chars_in_buffer,
792         .unthrottle = pty_unthrottle,
793         .set_termios = pty_set_termios,
794         .start = pty_start,
795         .stop = pty_stop,
796         .cleanup = pty_cleanup,
797 };
798
799 /**
800  *      ptmx_open               -       open a unix 98 pty master
801  *      @inode: inode of device file
802  *      @filp: file pointer to tty
803  *
804  *      Allocate a unix98 pty master device from the ptmx driver.
805  *
806  *      Locking: tty_mutex protects the init_dev work. tty->count should
807  *              protect the rest.
808  *              allocated_ptys_lock handles the list of free pty numbers
809  */
810
811 static int ptmx_open(struct inode *inode, struct file *filp)
812 {
813         struct pts_fs_info *fsi;
814         struct tty_struct *tty;
815         struct dentry *dentry;
816         int retval;
817         int index;
818
819         nonseekable_open(inode, filp);
820
821         /* We refuse fsnotify events on ptmx, since it's a shared resource */
822         filp->f_mode |= FMODE_NONOTIFY;
823
824         retval = tty_alloc_file(filp);
825         if (retval)
826                 return retval;
827
828         fsi = devpts_acquire(filp);
829         if (IS_ERR(fsi)) {
830                 retval = PTR_ERR(fsi);
831                 goto out_free_file;
832         }
833
834         /* find a device that is not in use. */
835         mutex_lock(&devpts_mutex);
836         index = devpts_new_index(fsi);
837         mutex_unlock(&devpts_mutex);
838
839         retval = index;
840         if (index < 0)
841                 goto out_put_fsi;
842
843
844         mutex_lock(&tty_mutex);
845         tty = tty_init_dev(ptm_driver, index);
846         /* The tty returned here is locked so we can safely
847            drop the mutex */
848         mutex_unlock(&tty_mutex);
849
850         retval = PTR_ERR(tty);
851         if (IS_ERR(tty))
852                 goto out;
853
854         /*
855          * From here on out, the tty is "live", and the index and
856          * fsi will be killed/put by the tty_release()
857          */
858         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
859         tty->driver_data = fsi;
860
861         tty_add_file(tty, filp);
862
863         dentry = devpts_pty_new(fsi, index, tty->link);
864         if (IS_ERR(dentry)) {
865                 retval = PTR_ERR(dentry);
866                 goto err_release;
867         }
868         tty->link->driver_data = dentry;
869
870         retval = ptm_driver->ops->open(tty, filp);
871         if (retval)
872                 goto err_release;
873
874         tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
875
876         tty_unlock(tty);
877         return 0;
878 err_release:
879         tty_unlock(tty);
880         // This will also put-ref the fsi
881         tty_release(inode, filp);
882         return retval;
883 out:
884         devpts_kill_index(fsi, index);
885 out_put_fsi:
886         devpts_release(fsi);
887 out_free_file:
888         tty_free_file(filp);
889         return retval;
890 }
891
892 static struct file_operations ptmx_fops __ro_after_init;
893
894 static void __init unix98_pty_init(void)
895 {
896         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
897                         TTY_DRIVER_RESET_TERMIOS |
898                         TTY_DRIVER_REAL_RAW |
899                         TTY_DRIVER_DYNAMIC_DEV |
900                         TTY_DRIVER_DEVPTS_MEM |
901                         TTY_DRIVER_DYNAMIC_ALLOC);
902         if (IS_ERR(ptm_driver))
903                 panic("Couldn't allocate Unix98 ptm driver");
904         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
905                         TTY_DRIVER_RESET_TERMIOS |
906                         TTY_DRIVER_REAL_RAW |
907                         TTY_DRIVER_DYNAMIC_DEV |
908                         TTY_DRIVER_DEVPTS_MEM |
909                         TTY_DRIVER_DYNAMIC_ALLOC);
910         if (IS_ERR(pts_driver))
911                 panic("Couldn't allocate Unix98 pts driver");
912
913         ptm_driver->driver_name = "pty_master";
914         ptm_driver->name = "ptm";
915         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
916         ptm_driver->minor_start = 0;
917         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
918         ptm_driver->subtype = PTY_TYPE_MASTER;
919         ptm_driver->init_termios = tty_std_termios;
920         ptm_driver->init_termios.c_iflag = 0;
921         ptm_driver->init_termios.c_oflag = 0;
922         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
923         ptm_driver->init_termios.c_lflag = 0;
924         ptm_driver->init_termios.c_ispeed = 38400;
925         ptm_driver->init_termios.c_ospeed = 38400;
926         ptm_driver->other = pts_driver;
927         tty_set_operations(ptm_driver, &ptm_unix98_ops);
928
929         pts_driver->driver_name = "pty_slave";
930         pts_driver->name = "pts";
931         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
932         pts_driver->minor_start = 0;
933         pts_driver->type = TTY_DRIVER_TYPE_PTY;
934         pts_driver->subtype = PTY_TYPE_SLAVE;
935         pts_driver->init_termios = tty_std_termios;
936         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
937         pts_driver->init_termios.c_ispeed = 38400;
938         pts_driver->init_termios.c_ospeed = 38400;
939         pts_driver->other = ptm_driver;
940         tty_set_operations(pts_driver, &pty_unix98_ops);
941
942         if (tty_register_driver(ptm_driver))
943                 panic("Couldn't register Unix98 ptm driver");
944         if (tty_register_driver(pts_driver))
945                 panic("Couldn't register Unix98 pts driver");
946
947         /* Now create the /dev/ptmx special device */
948         tty_default_fops(&ptmx_fops);
949         ptmx_fops.open = ptmx_open;
950
951         cdev_init(&ptmx_cdev, &ptmx_fops);
952         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
953             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
954                 panic("Couldn't register /dev/ptmx driver");
955         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
956 }
957
958 #else
959 static inline void unix98_pty_init(void) { }
960 #endif
961
962 static int __init pty_init(void)
963 {
964         legacy_pty_init();
965         unix98_pty_init();
966         return 0;
967 }
968 device_initcall(pty_init);