xref: /openbmc/linux/drivers/tty/pty.c (revision 95713967)
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 
pty_close(struct tty_struct * tty,struct file * filp)47 static void pty_close(struct tty_struct *tty, struct file *filp)
48 {
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->ctrl.packet = false;
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  */
pty_unthrottle(struct tty_struct * tty)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  *	@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 
pty_write(struct tty_struct * tty,const u8 * buf,size_t c)111 static ssize_t pty_write(struct tty_struct *tty, const u8 *buf, size_t c)
112 {
113 	struct tty_struct *to = tty->link;
114 
115 	if (tty->flow.stopped || !c)
116 		return 0;
117 
118 	return tty_insert_flip_string_and_push_buffer(to->port, buf, c);
119 }
120 
121 /**
122  *	pty_write_room	-	write space
123  *	@tty: tty we are writing from
124  *
125  *	Report how many bytes the ldisc can send into the queue for
126  *	the other device.
127  */
128 
pty_write_room(struct tty_struct * tty)129 static unsigned int pty_write_room(struct tty_struct *tty)
130 {
131 	if (tty->flow.stopped)
132 		return 0;
133 	return tty_buffer_space_avail(tty->link->port);
134 }
135 
136 /* Set the lock flag on a pty */
pty_set_lock(struct tty_struct * tty,int __user * arg)137 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
138 {
139 	int val;
140 
141 	if (get_user(val, arg))
142 		return -EFAULT;
143 	if (val)
144 		set_bit(TTY_PTY_LOCK, &tty->flags);
145 	else
146 		clear_bit(TTY_PTY_LOCK, &tty->flags);
147 	return 0;
148 }
149 
pty_get_lock(struct tty_struct * tty,int __user * arg)150 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
151 {
152 	int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
153 
154 	return put_user(locked, arg);
155 }
156 
157 /* Set the packet mode on a pty */
pty_set_pktmode(struct tty_struct * tty,int __user * arg)158 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
159 {
160 	int pktmode;
161 
162 	if (get_user(pktmode, arg))
163 		return -EFAULT;
164 
165 	spin_lock_irq(&tty->ctrl.lock);
166 	if (pktmode) {
167 		if (!tty->ctrl.packet) {
168 			tty->link->ctrl.pktstatus = 0;
169 			smp_mb();
170 			tty->ctrl.packet = true;
171 		}
172 	} else
173 		tty->ctrl.packet = false;
174 	spin_unlock_irq(&tty->ctrl.lock);
175 
176 	return 0;
177 }
178 
179 /* Get the packet mode of a pty */
pty_get_pktmode(struct tty_struct * tty,int __user * arg)180 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
181 {
182 	int pktmode = tty->ctrl.packet;
183 
184 	return put_user(pktmode, arg);
185 }
186 
187 /* Send a signal to the slave */
pty_signal(struct tty_struct * tty,int sig)188 static int pty_signal(struct tty_struct *tty, int sig)
189 {
190 	struct pid *pgrp;
191 
192 	if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
193 		return -EINVAL;
194 
195 	if (tty->link) {
196 		pgrp = tty_get_pgrp(tty->link);
197 		if (pgrp)
198 			kill_pgrp(pgrp, sig, 1);
199 		put_pid(pgrp);
200 	}
201 	return 0;
202 }
203 
pty_flush_buffer(struct tty_struct * tty)204 static void pty_flush_buffer(struct tty_struct *tty)
205 {
206 	struct tty_struct *to = tty->link;
207 
208 	if (!to)
209 		return;
210 
211 	tty_buffer_flush(to, NULL);
212 	if (to->ctrl.packet) {
213 		spin_lock_irq(&tty->ctrl.lock);
214 		tty->ctrl.pktstatus |= TIOCPKT_FLUSHWRITE;
215 		wake_up_interruptible(&to->read_wait);
216 		spin_unlock_irq(&tty->ctrl.lock);
217 	}
218 }
219 
pty_open(struct tty_struct * tty,struct file * filp)220 static int pty_open(struct tty_struct *tty, struct file *filp)
221 {
222 	if (!tty || !tty->link)
223 		return -ENODEV;
224 
225 	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
226 		goto out;
227 	if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
228 		goto out;
229 	if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
230 		goto out;
231 
232 	clear_bit(TTY_IO_ERROR, &tty->flags);
233 	clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
234 	set_bit(TTY_THROTTLED, &tty->flags);
235 	return 0;
236 
237 out:
238 	set_bit(TTY_IO_ERROR, &tty->flags);
239 	return -EIO;
240 }
241 
pty_set_termios(struct tty_struct * tty,const struct ktermios * old_termios)242 static void pty_set_termios(struct tty_struct *tty,
243 			    const struct ktermios *old_termios)
244 {
245 	/* See if packet mode change of state. */
246 	if (tty->link && tty->link->ctrl.packet) {
247 		int extproc = (old_termios->c_lflag & EXTPROC) | L_EXTPROC(tty);
248 		int old_flow = ((old_termios->c_iflag & IXON) &&
249 				(old_termios->c_cc[VSTOP] == '\023') &&
250 				(old_termios->c_cc[VSTART] == '\021'));
251 		int new_flow = (I_IXON(tty) &&
252 				STOP_CHAR(tty) == '\023' &&
253 				START_CHAR(tty) == '\021');
254 		if ((old_flow != new_flow) || extproc) {
255 			spin_lock_irq(&tty->ctrl.lock);
256 			if (old_flow != new_flow) {
257 				tty->ctrl.pktstatus &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
258 				if (new_flow)
259 					tty->ctrl.pktstatus |= TIOCPKT_DOSTOP;
260 				else
261 					tty->ctrl.pktstatus |= TIOCPKT_NOSTOP;
262 			}
263 			if (extproc)
264 				tty->ctrl.pktstatus |= TIOCPKT_IOCTL;
265 			spin_unlock_irq(&tty->ctrl.lock);
266 			wake_up_interruptible(&tty->link->read_wait);
267 		}
268 	}
269 
270 	tty->termios.c_cflag &= ~(CSIZE | PARENB);
271 	tty->termios.c_cflag |= (CS8 | CREAD);
272 }
273 
274 /**
275  *	pty_resize		-	resize event
276  *	@tty: tty being resized
277  *	@ws: window size being set.
278  *
279  *	Update the termios variables and send the necessary signals to
280  *	peform a terminal resize correctly
281  */
282 
pty_resize(struct tty_struct * tty,struct winsize * ws)283 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
284 {
285 	struct pid *pgrp, *rpgrp;
286 	struct tty_struct *pty = tty->link;
287 
288 	/* For a PTY we need to lock the tty side */
289 	mutex_lock(&tty->winsize_mutex);
290 	if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
291 		goto done;
292 
293 	/* Signal the foreground process group of both ptys */
294 	pgrp = tty_get_pgrp(tty);
295 	rpgrp = tty_get_pgrp(pty);
296 
297 	if (pgrp)
298 		kill_pgrp(pgrp, SIGWINCH, 1);
299 	if (rpgrp != pgrp && rpgrp)
300 		kill_pgrp(rpgrp, SIGWINCH, 1);
301 
302 	put_pid(pgrp);
303 	put_pid(rpgrp);
304 
305 	tty->winsize = *ws;
306 	pty->winsize = *ws;	/* Never used so will go away soon */
307 done:
308 	mutex_unlock(&tty->winsize_mutex);
309 	return 0;
310 }
311 
312 /**
313  *	pty_start - start() handler
314  *	pty_stop  - stop() handler
315  *	@tty: tty being flow-controlled
316  *
317  *	Propagates the TIOCPKT status to the master pty.
318  *
319  *	NB: only the master pty can be in packet mode so only the slave
320  *	    needs start()/stop() handlers
321  */
pty_start(struct tty_struct * tty)322 static void pty_start(struct tty_struct *tty)
323 {
324 	unsigned long flags;
325 
326 	if (tty->link && tty->link->ctrl.packet) {
327 		spin_lock_irqsave(&tty->ctrl.lock, flags);
328 		tty->ctrl.pktstatus &= ~TIOCPKT_STOP;
329 		tty->ctrl.pktstatus |= TIOCPKT_START;
330 		spin_unlock_irqrestore(&tty->ctrl.lock, flags);
331 		wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
332 	}
333 }
334 
pty_stop(struct tty_struct * tty)335 static void pty_stop(struct tty_struct *tty)
336 {
337 	unsigned long flags;
338 
339 	if (tty->link && tty->link->ctrl.packet) {
340 		spin_lock_irqsave(&tty->ctrl.lock, flags);
341 		tty->ctrl.pktstatus &= ~TIOCPKT_START;
342 		tty->ctrl.pktstatus |= TIOCPKT_STOP;
343 		spin_unlock_irqrestore(&tty->ctrl.lock, flags);
344 		wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
345 	}
346 }
347 
348 /**
349  *	pty_common_install		-	set up the pty pair
350  *	@driver: the pty driver
351  *	@tty: the tty being instantiated
352  *	@legacy: true if this is BSD style
353  *
354  *	Perform the initial set up for the tty/pty pair. Called from the
355  *	tty layer when the port is first opened.
356  *
357  *	Locking: the caller must hold the tty_mutex
358  */
pty_common_install(struct tty_driver * driver,struct tty_struct * tty,bool legacy)359 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
360 		bool legacy)
361 {
362 	struct tty_struct *o_tty;
363 	struct tty_port *ports[2];
364 	int idx = tty->index;
365 	int retval = -ENOMEM;
366 
367 	/* Opening the slave first has always returned -EIO */
368 	if (driver->subtype != PTY_TYPE_MASTER)
369 		return -EIO;
370 
371 	ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
372 	ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
373 	if (!ports[0] || !ports[1])
374 		goto err;
375 	if (!try_module_get(driver->other->owner)) {
376 		/* This cannot in fact currently happen */
377 		goto err;
378 	}
379 	o_tty = alloc_tty_struct(driver->other, idx);
380 	if (!o_tty)
381 		goto err_put_module;
382 
383 	tty_set_lock_subclass(o_tty);
384 	lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
385 
386 	if (legacy) {
387 		/* We always use new tty termios data so we can do this
388 		   the easy way .. */
389 		tty_init_termios(tty);
390 		tty_init_termios(o_tty);
391 
392 		driver->other->ttys[idx] = o_tty;
393 		driver->ttys[idx] = tty;
394 	} else {
395 		memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
396 		tty->termios = driver->init_termios;
397 		memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
398 		o_tty->termios = driver->other->init_termios;
399 	}
400 
401 	/*
402 	 * Everything allocated ... set up the o_tty structure.
403 	 */
404 	tty_driver_kref_get(driver->other);
405 	/* Establish the links in both directions */
406 	tty->link   = o_tty;
407 	o_tty->link = tty;
408 	tty_port_init(ports[0]);
409 	tty_port_init(ports[1]);
410 	tty_buffer_set_limit(ports[0], 8192);
411 	tty_buffer_set_limit(ports[1], 8192);
412 	o_tty->port = ports[0];
413 	tty->port = ports[1];
414 	o_tty->port->itty = o_tty;
415 
416 	tty_buffer_set_lock_subclass(o_tty->port);
417 
418 	tty_driver_kref_get(driver);
419 	tty->count++;
420 	o_tty->count++;
421 	return 0;
422 
423 err_put_module:
424 	module_put(driver->other->owner);
425 err:
426 	kfree(ports[0]);
427 	kfree(ports[1]);
428 	return retval;
429 }
430 
pty_cleanup(struct tty_struct * tty)431 static void pty_cleanup(struct tty_struct *tty)
432 {
433 	tty_port_put(tty->port);
434 }
435 
436 /* Traditional BSD devices */
437 #ifdef CONFIG_LEGACY_PTYS
438 
pty_install(struct tty_driver * driver,struct tty_struct * tty)439 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
440 {
441 	return pty_common_install(driver, tty, true);
442 }
443 
pty_remove(struct tty_driver * driver,struct tty_struct * tty)444 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
445 {
446 	struct tty_struct *pair = tty->link;
447 
448 	driver->ttys[tty->index] = NULL;
449 	if (pair)
450 		pair->driver->ttys[pair->index] = NULL;
451 }
452 
pty_bsd_ioctl(struct tty_struct * tty,unsigned int cmd,unsigned long arg)453 static int pty_bsd_ioctl(struct tty_struct *tty,
454 			 unsigned int cmd, unsigned long arg)
455 {
456 	switch (cmd) {
457 	case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
458 		return pty_set_lock(tty, (int __user *) arg);
459 	case TIOCGPTLCK: /* Get PT Lock status */
460 		return pty_get_lock(tty, (int __user *)arg);
461 	case TIOCPKT: /* Set PT packet mode */
462 		return pty_set_pktmode(tty, (int __user *)arg);
463 	case TIOCGPKT: /* Get PT packet mode */
464 		return pty_get_pktmode(tty, (int __user *)arg);
465 	case TIOCSIG:    /* Send signal to other side of pty */
466 		return pty_signal(tty, (int) arg);
467 	case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
468 		return -EINVAL;
469 	}
470 	return -ENOIOCTLCMD;
471 }
472 
473 #ifdef CONFIG_COMPAT
pty_bsd_compat_ioctl(struct tty_struct * tty,unsigned int cmd,unsigned long arg)474 static long pty_bsd_compat_ioctl(struct tty_struct *tty,
475 				 unsigned int cmd, unsigned long arg)
476 {
477 	/*
478 	 * PTY ioctls don't require any special translation between 32-bit and
479 	 * 64-bit userspace, they are already compatible.
480 	 */
481 	return pty_bsd_ioctl(tty, cmd, (unsigned long)compat_ptr(arg));
482 }
483 #else
484 #define pty_bsd_compat_ioctl NULL
485 #endif
486 
487 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
488 /*
489  * not really modular, but the easiest way to keep compat with existing
490  * bootargs behaviour is to continue using module_param here.
491  */
492 module_param(legacy_count, int, 0);
493 
494 /*
495  * The master side of a pty can do TIOCSPTLCK and thus
496  * has pty_bsd_ioctl.
497  */
498 static const struct tty_operations master_pty_ops_bsd = {
499 	.install = pty_install,
500 	.open = pty_open,
501 	.close = pty_close,
502 	.write = pty_write,
503 	.write_room = pty_write_room,
504 	.flush_buffer = pty_flush_buffer,
505 	.unthrottle = pty_unthrottle,
506 	.ioctl = pty_bsd_ioctl,
507 	.compat_ioctl = pty_bsd_compat_ioctl,
508 	.cleanup = pty_cleanup,
509 	.resize = pty_resize,
510 	.remove = pty_remove
511 };
512 
513 static const struct tty_operations slave_pty_ops_bsd = {
514 	.install = pty_install,
515 	.open = pty_open,
516 	.close = pty_close,
517 	.write = pty_write,
518 	.write_room = pty_write_room,
519 	.flush_buffer = pty_flush_buffer,
520 	.unthrottle = pty_unthrottle,
521 	.set_termios = pty_set_termios,
522 	.cleanup = pty_cleanup,
523 	.resize = pty_resize,
524 	.start = pty_start,
525 	.stop = pty_stop,
526 	.remove = pty_remove
527 };
528 
legacy_pty_init(void)529 static void __init legacy_pty_init(void)
530 {
531 	struct tty_driver *pty_driver, *pty_slave_driver;
532 
533 	if (legacy_count <= 0)
534 		return;
535 
536 	pty_driver = tty_alloc_driver(legacy_count,
537 			TTY_DRIVER_RESET_TERMIOS |
538 			TTY_DRIVER_REAL_RAW |
539 			TTY_DRIVER_DYNAMIC_ALLOC);
540 	if (IS_ERR(pty_driver))
541 		panic("Couldn't allocate pty driver");
542 
543 	pty_slave_driver = tty_alloc_driver(legacy_count,
544 			TTY_DRIVER_RESET_TERMIOS |
545 			TTY_DRIVER_REAL_RAW |
546 			TTY_DRIVER_DYNAMIC_ALLOC);
547 	if (IS_ERR(pty_slave_driver))
548 		panic("Couldn't allocate pty slave driver");
549 
550 	pty_driver->driver_name = "pty_master";
551 	pty_driver->name = "pty";
552 	pty_driver->major = PTY_MASTER_MAJOR;
553 	pty_driver->minor_start = 0;
554 	pty_driver->type = TTY_DRIVER_TYPE_PTY;
555 	pty_driver->subtype = PTY_TYPE_MASTER;
556 	pty_driver->init_termios = tty_std_termios;
557 	pty_driver->init_termios.c_iflag = 0;
558 	pty_driver->init_termios.c_oflag = 0;
559 	pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
560 	pty_driver->init_termios.c_lflag = 0;
561 	pty_driver->init_termios.c_ispeed = 38400;
562 	pty_driver->init_termios.c_ospeed = 38400;
563 	pty_driver->other = pty_slave_driver;
564 	tty_set_operations(pty_driver, &master_pty_ops_bsd);
565 
566 	pty_slave_driver->driver_name = "pty_slave";
567 	pty_slave_driver->name = "ttyp";
568 	pty_slave_driver->major = PTY_SLAVE_MAJOR;
569 	pty_slave_driver->minor_start = 0;
570 	pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
571 	pty_slave_driver->subtype = PTY_TYPE_SLAVE;
572 	pty_slave_driver->init_termios = tty_std_termios;
573 	pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
574 	pty_slave_driver->init_termios.c_ispeed = 38400;
575 	pty_slave_driver->init_termios.c_ospeed = 38400;
576 	pty_slave_driver->other = pty_driver;
577 	tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
578 
579 	if (tty_register_driver(pty_driver))
580 		panic("Couldn't register pty driver");
581 	if (tty_register_driver(pty_slave_driver))
582 		panic("Couldn't register pty slave driver");
583 }
584 #else
legacy_pty_init(void)585 static inline void legacy_pty_init(void) { }
586 #endif
587 
588 /* Unix98 devices */
589 #ifdef CONFIG_UNIX98_PTYS
590 static struct cdev ptmx_cdev;
591 
592 /**
593  *	ptm_open_peer - open the peer of a pty
594  *	@master: the open struct file of the ptmx device node
595  *	@tty: the master of the pty being opened
596  *	@flags: the flags for open
597  *
598  *	Provide a race free way for userspace to open the slave end of a pty
599  *	(where they have the master fd and cannot access or trust the mount
600  *	namespace /dev/pts was mounted inside).
601  */
ptm_open_peer(struct file * master,struct tty_struct * tty,int flags)602 int ptm_open_peer(struct file *master, struct tty_struct *tty, int flags)
603 {
604 	int fd;
605 	struct file *filp;
606 	int retval = -EINVAL;
607 	struct path path;
608 
609 	if (tty->driver != ptm_driver)
610 		return -EIO;
611 
612 	fd = get_unused_fd_flags(flags);
613 	if (fd < 0) {
614 		retval = fd;
615 		goto err;
616 	}
617 
618 	/* Compute the slave's path */
619 	path.mnt = devpts_mntget(master, tty->driver_data);
620 	if (IS_ERR(path.mnt)) {
621 		retval = PTR_ERR(path.mnt);
622 		goto err_put;
623 	}
624 	path.dentry = tty->link->driver_data;
625 
626 	filp = dentry_open(&path, flags, current_cred());
627 	mntput(path.mnt);
628 	if (IS_ERR(filp)) {
629 		retval = PTR_ERR(filp);
630 		goto err_put;
631 	}
632 
633 	fd_install(fd, filp);
634 	return fd;
635 
636 err_put:
637 	put_unused_fd(fd);
638 err:
639 	return retval;
640 }
641 
pty_unix98_ioctl(struct tty_struct * tty,unsigned int cmd,unsigned long arg)642 static int pty_unix98_ioctl(struct tty_struct *tty,
643 			    unsigned int cmd, unsigned long arg)
644 {
645 	switch (cmd) {
646 	case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
647 		return pty_set_lock(tty, (int __user *)arg);
648 	case TIOCGPTLCK: /* Get PT Lock status */
649 		return pty_get_lock(tty, (int __user *)arg);
650 	case TIOCPKT: /* Set PT packet mode */
651 		return pty_set_pktmode(tty, (int __user *)arg);
652 	case TIOCGPKT: /* Get PT packet mode */
653 		return pty_get_pktmode(tty, (int __user *)arg);
654 	case TIOCGPTN: /* Get PT Number */
655 		return put_user(tty->index, (unsigned int __user *)arg);
656 	case TIOCSIG:    /* Send signal to other side of pty */
657 		return pty_signal(tty, (int) arg);
658 	}
659 
660 	return -ENOIOCTLCMD;
661 }
662 
663 #ifdef CONFIG_COMPAT
pty_unix98_compat_ioctl(struct tty_struct * tty,unsigned int cmd,unsigned long arg)664 static long pty_unix98_compat_ioctl(struct tty_struct *tty,
665 				 unsigned int cmd, unsigned long arg)
666 {
667 	/*
668 	 * PTY ioctls don't require any special translation between 32-bit and
669 	 * 64-bit userspace, they are already compatible.
670 	 */
671 	return pty_unix98_ioctl(tty, cmd,
672 		cmd == TIOCSIG ? arg : (unsigned long)compat_ptr(arg));
673 }
674 #else
675 #define pty_unix98_compat_ioctl NULL
676 #endif
677 
678 /**
679  *	ptm_unix98_lookup	-	find a pty master
680  *	@driver: ptm driver
681  *	@file: unused
682  *	@idx: tty index
683  *
684  *	Look up a pty master device. Called under the tty_mutex for now.
685  *	This provides our locking.
686  */
687 
ptm_unix98_lookup(struct tty_driver * driver,struct file * file,int idx)688 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
689 		struct file *file, int idx)
690 {
691 	/* Master must be open via /dev/ptmx */
692 	return ERR_PTR(-EIO);
693 }
694 
695 /**
696  *	pts_unix98_lookup	-	find a pty slave
697  *	@driver: pts driver
698  *	@file: file pointer to tty
699  *	@idx: tty index
700  *
701  *	Look up a pty master device. Called under the tty_mutex for now.
702  *	This provides our locking for the tty pointer.
703  */
704 
pts_unix98_lookup(struct tty_driver * driver,struct file * file,int idx)705 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
706 		struct file *file, int idx)
707 {
708 	struct tty_struct *tty;
709 
710 	mutex_lock(&devpts_mutex);
711 	tty = devpts_get_priv(file->f_path.dentry);
712 	mutex_unlock(&devpts_mutex);
713 	/* Master must be open before slave */
714 	if (!tty)
715 		return ERR_PTR(-EIO);
716 	return tty;
717 }
718 
pty_unix98_install(struct tty_driver * driver,struct tty_struct * tty)719 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
720 {
721 	return pty_common_install(driver, tty, false);
722 }
723 
724 /* this is called once with whichever end is closed last */
pty_unix98_remove(struct tty_driver * driver,struct tty_struct * tty)725 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
726 {
727 	struct pts_fs_info *fsi;
728 
729 	if (tty->driver->subtype == PTY_TYPE_MASTER)
730 		fsi = tty->driver_data;
731 	else
732 		fsi = tty->link->driver_data;
733 
734 	if (fsi) {
735 		devpts_kill_index(fsi, tty->index);
736 		devpts_release(fsi);
737 	}
738 }
739 
pty_show_fdinfo(struct tty_struct * tty,struct seq_file * m)740 static void pty_show_fdinfo(struct tty_struct *tty, struct seq_file *m)
741 {
742 	seq_printf(m, "tty-index:\t%d\n", tty->index);
743 }
744 
745 static const struct tty_operations ptm_unix98_ops = {
746 	.lookup = ptm_unix98_lookup,
747 	.install = pty_unix98_install,
748 	.remove = pty_unix98_remove,
749 	.open = pty_open,
750 	.close = pty_close,
751 	.write = pty_write,
752 	.write_room = pty_write_room,
753 	.flush_buffer = pty_flush_buffer,
754 	.unthrottle = pty_unthrottle,
755 	.ioctl = pty_unix98_ioctl,
756 	.compat_ioctl = pty_unix98_compat_ioctl,
757 	.resize = pty_resize,
758 	.cleanup = pty_cleanup,
759 	.show_fdinfo = pty_show_fdinfo,
760 };
761 
762 static const struct tty_operations pty_unix98_ops = {
763 	.lookup = pts_unix98_lookup,
764 	.install = pty_unix98_install,
765 	.remove = pty_unix98_remove,
766 	.open = pty_open,
767 	.close = pty_close,
768 	.write = pty_write,
769 	.write_room = pty_write_room,
770 	.flush_buffer = pty_flush_buffer,
771 	.unthrottle = pty_unthrottle,
772 	.set_termios = pty_set_termios,
773 	.start = pty_start,
774 	.stop = pty_stop,
775 	.cleanup = pty_cleanup,
776 };
777 
778 /**
779  *	ptmx_open		-	open a unix 98 pty master
780  *	@inode: inode of device file
781  *	@filp: file pointer to tty
782  *
783  *	Allocate a unix98 pty master device from the ptmx driver.
784  *
785  *	Locking: tty_mutex protects the init_dev work. tty->count should
786  *		protect the rest.
787  *		allocated_ptys_lock handles the list of free pty numbers
788  */
789 
ptmx_open(struct inode * inode,struct file * filp)790 static int ptmx_open(struct inode *inode, struct file *filp)
791 {
792 	struct pts_fs_info *fsi;
793 	struct tty_struct *tty;
794 	struct dentry *dentry;
795 	int retval;
796 	int index;
797 
798 	nonseekable_open(inode, filp);
799 
800 	/* We refuse fsnotify events on ptmx, since it's a shared resource */
801 	filp->f_mode |= FMODE_NONOTIFY;
802 
803 	retval = tty_alloc_file(filp);
804 	if (retval)
805 		return retval;
806 
807 	fsi = devpts_acquire(filp);
808 	if (IS_ERR(fsi)) {
809 		retval = PTR_ERR(fsi);
810 		goto out_free_file;
811 	}
812 
813 	/* find a device that is not in use. */
814 	mutex_lock(&devpts_mutex);
815 	index = devpts_new_index(fsi);
816 	mutex_unlock(&devpts_mutex);
817 
818 	retval = index;
819 	if (index < 0)
820 		goto out_put_fsi;
821 
822 
823 	mutex_lock(&tty_mutex);
824 	tty = tty_init_dev(ptm_driver, index);
825 	/* The tty returned here is locked so we can safely
826 	   drop the mutex */
827 	mutex_unlock(&tty_mutex);
828 
829 	retval = PTR_ERR(tty);
830 	if (IS_ERR(tty))
831 		goto out;
832 
833 	/*
834 	 * From here on out, the tty is "live", and the index and
835 	 * fsi will be killed/put by the tty_release()
836 	 */
837 	set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
838 	tty->driver_data = fsi;
839 
840 	tty_add_file(tty, filp);
841 
842 	dentry = devpts_pty_new(fsi, index, tty->link);
843 	if (IS_ERR(dentry)) {
844 		retval = PTR_ERR(dentry);
845 		goto err_release;
846 	}
847 	tty->link->driver_data = dentry;
848 
849 	retval = ptm_driver->ops->open(tty, filp);
850 	if (retval)
851 		goto err_release;
852 
853 	tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
854 
855 	tty_unlock(tty);
856 	return 0;
857 err_release:
858 	tty_unlock(tty);
859 	// This will also put-ref the fsi
860 	tty_release(inode, filp);
861 	return retval;
862 out:
863 	devpts_kill_index(fsi, index);
864 out_put_fsi:
865 	devpts_release(fsi);
866 out_free_file:
867 	tty_free_file(filp);
868 	return retval;
869 }
870 
871 static struct file_operations ptmx_fops __ro_after_init;
872 
unix98_pty_init(void)873 static void __init unix98_pty_init(void)
874 {
875 	ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
876 			TTY_DRIVER_RESET_TERMIOS |
877 			TTY_DRIVER_REAL_RAW |
878 			TTY_DRIVER_DYNAMIC_DEV |
879 			TTY_DRIVER_DEVPTS_MEM |
880 			TTY_DRIVER_DYNAMIC_ALLOC);
881 	if (IS_ERR(ptm_driver))
882 		panic("Couldn't allocate Unix98 ptm driver");
883 	pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
884 			TTY_DRIVER_RESET_TERMIOS |
885 			TTY_DRIVER_REAL_RAW |
886 			TTY_DRIVER_DYNAMIC_DEV |
887 			TTY_DRIVER_DEVPTS_MEM |
888 			TTY_DRIVER_DYNAMIC_ALLOC);
889 	if (IS_ERR(pts_driver))
890 		panic("Couldn't allocate Unix98 pts driver");
891 
892 	ptm_driver->driver_name = "pty_master";
893 	ptm_driver->name = "ptm";
894 	ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
895 	ptm_driver->minor_start = 0;
896 	ptm_driver->type = TTY_DRIVER_TYPE_PTY;
897 	ptm_driver->subtype = PTY_TYPE_MASTER;
898 	ptm_driver->init_termios = tty_std_termios;
899 	ptm_driver->init_termios.c_iflag = 0;
900 	ptm_driver->init_termios.c_oflag = 0;
901 	ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
902 	ptm_driver->init_termios.c_lflag = 0;
903 	ptm_driver->init_termios.c_ispeed = 38400;
904 	ptm_driver->init_termios.c_ospeed = 38400;
905 	ptm_driver->other = pts_driver;
906 	tty_set_operations(ptm_driver, &ptm_unix98_ops);
907 
908 	pts_driver->driver_name = "pty_slave";
909 	pts_driver->name = "pts";
910 	pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
911 	pts_driver->minor_start = 0;
912 	pts_driver->type = TTY_DRIVER_TYPE_PTY;
913 	pts_driver->subtype = PTY_TYPE_SLAVE;
914 	pts_driver->init_termios = tty_std_termios;
915 	pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
916 	pts_driver->init_termios.c_ispeed = 38400;
917 	pts_driver->init_termios.c_ospeed = 38400;
918 	pts_driver->other = ptm_driver;
919 	tty_set_operations(pts_driver, &pty_unix98_ops);
920 
921 	if (tty_register_driver(ptm_driver))
922 		panic("Couldn't register Unix98 ptm driver");
923 	if (tty_register_driver(pts_driver))
924 		panic("Couldn't register Unix98 pts driver");
925 
926 	/* Now create the /dev/ptmx special device */
927 	tty_default_fops(&ptmx_fops);
928 	ptmx_fops.open = ptmx_open;
929 
930 	cdev_init(&ptmx_cdev, &ptmx_fops);
931 	if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
932 	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
933 		panic("Couldn't register /dev/ptmx driver");
934 	device_create(&tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
935 }
936 
937 #else
unix98_pty_init(void)938 static inline void unix98_pty_init(void) { }
939 #endif
940 
pty_init(void)941 static int __init pty_init(void)
942 {
943 	legacy_pty_init();
944 	unix98_pty_init();
945 	return 0;
946 }
947 device_initcall(pty_init);
948