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