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