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