drivers/tty/pty.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  Copyright (C) 1991, 1992  Linus Torvalds
   4  *
   5  *  Added support for a Unix98-style ptmx device.
   6  *    -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
   7  *
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/errno.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/tty.h>
  14 #include <linux/tty_flip.h>
  15 #include <linux/fcntl.h>
  16 #include <linux/sched/signal.h>
  17 #include <linux/string.h>
  18 #include <linux/major.h>
  19 #include <linux/mm.h>
  20 #include <linux/init.h>
  21 #include <linux/device.h>
  22 #include <linux/uaccess.h>
  23 #include <linux/bitops.h>
  24 #include <linux/devpts_fs.h>
  25 #include <linux/slab.h>
  26 #include <linux/mutex.h>
  27 #include <linux/poll.h>
  28 #include <linux/mount.h>
  29 #include <linux/file.h>
  30 #include <linux/ioctl.h>
  31 #include <linux/compat.h>
  32
  33 #undef TTY_DEBUG_HANGUP
  34 #ifdef TTY_DEBUG_HANGUP
  35 # define tty_debug_hangup(tty, f, args...)      tty_debug(tty, f, ##args)
  36 #else
  37 # define tty_debug_hangup(tty, f, args...)      do {} while (0)
  38 #endif
  39
  40 #ifdef CONFIG_UNIX98_PTYS
  41 static struct tty_driver *ptm_driver;
  42 static struct tty_driver *pts_driver;
  43 static DEFINE_MUTEX(devpts_mutex);
  44 #endif
  45
  46 static void pty_close(struct tty_struct *tty, struct file *filp)
  47 {
  48         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  *      @c: 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                 spin_unlock_irqrestore(&to->port->lock, flags);
 123                 /* And shovel */
 124                 if (c)
 125                         tty_flip_buffer_push(to->port);
 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
 163         if (get_user(val, arg))
 164                 return -EFAULT;
 165         if (val)
 166                 set_bit(TTY_PTY_LOCK, &tty->flags);
 167         else
 168                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 169         return 0;
 170 }
 171
 172 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 173 {
 174         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 175
 176         return put_user(locked, arg);
 177 }
 178
 179 /* Set the packet mode on a pty */
 180 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 181 {
 182         int pktmode;
 183
 184         if (get_user(pktmode, arg))
 185                 return -EFAULT;
 186
 187         spin_lock_irq(&tty->ctrl_lock);
 188         if (pktmode) {
 189                 if (!tty->packet) {
 190                         tty->link->ctrl_status = 0;
 191                         smp_mb();
 192                         tty->packet = 1;
 193                 }
 194         } else
 195                 tty->packet = 0;
 196         spin_unlock_irq(&tty->ctrl_lock);
 197
 198         return 0;
 199 }
 200
 201 /* Get the packet mode of a pty */
 202 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 203 {
 204         int pktmode = tty->packet;
 205
 206         return put_user(pktmode, arg);
 207 }
 208
 209 /* Send a signal to the slave */
 210 static int pty_signal(struct tty_struct *tty, int sig)
 211 {
 212         struct pid *pgrp;
 213
 214         if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
 215                 return -EINVAL;
 216
 217         if (tty->link) {
 218                 pgrp = tty_get_pgrp(tty->link);
 219                 if (pgrp)
 220                         kill_pgrp(pgrp, sig, 1);
 221                 put_pid(pgrp);
 222         }
 223         return 0;
 224 }
 225
 226 static void pty_flush_buffer(struct tty_struct *tty)
 227 {
 228         struct tty_struct *to = tty->link;
 229
 230         if (!to)
 231                 return;
 232
 233         tty_buffer_flush(to, NULL);
 234         if (to->packet) {
 235                 spin_lock_irq(&tty->ctrl_lock);
 236                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 237                 wake_up_interruptible(&to->read_wait);
 238                 spin_unlock_irq(&tty->ctrl_lock);
 239         }
 240 }
 241
 242 static int pty_open(struct tty_struct *tty, struct file *filp)
 243 {
 244         if (!tty || !tty->link)
 245                 return -ENODEV;
 246
 247         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 248                 goto out;
 249         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 250                 goto out;
 251         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 252                 goto out;
 253
 254         clear_bit(TTY_IO_ERROR, &tty->flags);
 255         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 256         set_bit(TTY_THROTTLED, &tty->flags);
 257         return 0;
 258
 259 out:
 260         set_bit(TTY_IO_ERROR, &tty->flags);
 261         return -EIO;
 262 }
 263
 264 static void pty_set_termios(struct tty_struct *tty,
 265                                         struct ktermios *old_termios)
 266 {
 267         /* See if packet mode change of state. */
 268         if (tty->link && tty->link->packet) {
 269                 int extproc = (old_termios->c_lflag & EXTPROC) | L_EXTPROC(tty);
 270                 int old_flow = ((old_termios->c_iflag & IXON) &&
 271                                 (old_termios->c_cc[VSTOP] == '\023') &&
 272                                 (old_termios->c_cc[VSTART] == '\021'));
 273                 int new_flow = (I_IXON(tty) &&
 274                                 STOP_CHAR(tty) == '\023' &&
 275                                 START_CHAR(tty) == '\021');
 276                 if ((old_flow != new_flow) || extproc) {
 277                         spin_lock_irq(&tty->ctrl_lock);
 278                         if (old_flow != new_flow) {
 279                                 tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
 280                                 if (new_flow)
 281                                         tty->ctrl_status |= TIOCPKT_DOSTOP;
 282                                 else
 283                                         tty->ctrl_status |= TIOCPKT_NOSTOP;
 284                         }
 285                         if (extproc)
 286                                 tty->ctrl_status |= TIOCPKT_IOCTL;
 287                         spin_unlock_irq(&tty->ctrl_lock);
 288                         wake_up_interruptible(&tty->link->read_wait);
 289                 }
 290         }
 291
 292         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 293         tty->termios.c_cflag |= (CS8 | CREAD);
 294 }
 295
 296 /**
 297  *      pty_do_resize           -       resize event
 298  *      @tty: tty being resized
 299  *      @ws: window size being set.
 300  *
 301  *      Update the termios variables and send the necessary signals to
 302  *      peform a terminal resize correctly
 303  */
 304
 305 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 306 {
 307         struct pid *pgrp, *rpgrp;
 308         struct tty_struct *pty = tty->link;
 309
 310         /* For a PTY we need to lock the tty side */
 311         mutex_lock(&tty->winsize_mutex);
 312         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 313                 goto done;
 314
 315         /* Signal the foreground process group of both ptys */
 316         pgrp = tty_get_pgrp(tty);
 317         rpgrp = tty_get_pgrp(pty);
 318
 319         if (pgrp)
 320                 kill_pgrp(pgrp, SIGWINCH, 1);
 321         if (rpgrp != pgrp && rpgrp)
 322                 kill_pgrp(rpgrp, SIGWINCH, 1);
 323
 324         put_pid(pgrp);
 325         put_pid(rpgrp);
 326
 327         tty->winsize = *ws;
 328         pty->winsize = *ws;     /* Never used so will go away soon */
 329 done:
 330         mutex_unlock(&tty->winsize_mutex);
 331         return 0;
 332 }
 333
 334 /**
 335  *      pty_start - start() handler
 336  *      pty_stop  - stop() handler
 337  *      @tty: tty being flow-controlled
 338  *
 339  *      Propagates the TIOCPKT status to the master pty.
 340  *
 341  *      NB: only the master pty can be in packet mode so only the slave
 342  *          needs start()/stop() handlers
 343  */
 344 static void pty_start(struct tty_struct *tty)
 345 {
 346         unsigned long flags;
 347
 348         if (tty->link && tty->link->packet) {
 349                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 350                 tty->ctrl_status &= ~TIOCPKT_STOP;
 351                 tty->ctrl_status |= TIOCPKT_START;
 352                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 353                 wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
 354         }
 355 }
 356
 357 static void pty_stop(struct tty_struct *tty)
 358 {
 359         unsigned long flags;
 360
 361         if (tty->link && tty->link->packet) {
 362                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 363                 tty->ctrl_status &= ~TIOCPKT_START;
 364                 tty->ctrl_status |= TIOCPKT_STOP;
 365                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 366                 wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
 367         }
 368 }
 369
 370 /**
 371  *      pty_common_install              -       set up the pty pair
 372  *      @driver: the pty driver
 373  *      @tty: the tty being instantiated
 374  *      @legacy: true if this is BSD style
 375  *
 376  *      Perform the initial set up for the tty/pty pair. Called from the
 377  *      tty layer when the port is first opened.
 378  *
 379  *      Locking: the caller must hold the tty_mutex
 380  */
 381 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 382                 bool legacy)
 383 {
 384         struct tty_struct *o_tty;
 385         struct tty_port *ports[2];
 386         int idx = tty->index;
 387         int retval = -ENOMEM;
 388
 389         /* Opening the slave first has always returned -EIO */
 390         if (driver->subtype != PTY_TYPE_MASTER)
 391                 return -EIO;
 392
 393         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 394         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 395         if (!ports[0] || !ports[1])
 396                 goto err;
 397         if (!try_module_get(driver->other->owner)) {
 398                 /* This cannot in fact currently happen */
 399                 goto err;
 400         }
 401         o_tty = alloc_tty_struct(driver->other, idx);
 402         if (!o_tty)
 403                 goto err_put_module;
 404
 405         tty_set_lock_subclass(o_tty);
 406         lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
 407
 408         if (legacy) {
 409                 /* We always use new tty termios data so we can do this
 410                    the easy way .. */
 411                 tty_init_termios(tty);
 412                 tty_init_termios(o_tty);
 413
 414                 driver->other->ttys[idx] = o_tty;
 415                 driver->ttys[idx] = tty;
 416         } else {
 417                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 418                 tty->termios = driver->init_termios;
 419                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 420                 o_tty->termios = driver->other->init_termios;
 421         }
 422
 423         /*
 424          * Everything allocated ... set up the o_tty structure.
 425          */
 426         tty_driver_kref_get(driver->other);
 427         /* Establish the links in both directions */
 428         tty->link   = o_tty;
 429         o_tty->link = tty;
 430         tty_port_init(ports[0]);
 431         tty_port_init(ports[1]);
 432         tty_buffer_set_limit(ports[0], 8192);
 433         tty_buffer_set_limit(ports[1], 8192);
 434         o_tty->port = ports[0];
 435         tty->port = ports[1];
 436         o_tty->port->itty = o_tty;
 437
 438         tty_buffer_set_lock_subclass(o_tty->port);
 439
 440         tty_driver_kref_get(driver);
 441         tty->count++;
 442         o_tty->count++;
 443         return 0;
 444
 445 err_put_module:
 446         module_put(driver->other->owner);
 447 err:
 448         kfree(ports[0]);
 449         kfree(ports[1]);
 450         return retval;
 451 }
 452
 453 static void pty_cleanup(struct tty_struct *tty)
 454 {
 455         tty_port_put(tty->port);
 456 }
 457
 458 /* Traditional BSD devices */
 459 #ifdef CONFIG_LEGACY_PTYS
 460
 461 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 462 {
 463         return pty_common_install(driver, tty, true);
 464 }
 465
 466 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 467 {
 468         struct tty_struct *pair = tty->link;
 469
 470         driver->ttys[tty->index] = NULL;
 471         if (pair)
 472                 pair->driver->ttys[pair->index] = NULL;
 473 }
 474
 475 static int pty_bsd_ioctl(struct tty_struct *tty,
 476                          unsigned int cmd, unsigned long arg)
 477 {
 478         switch (cmd) {
 479         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 480                 return pty_set_lock(tty, (int __user *) arg);
 481         case TIOCGPTLCK: /* Get PT Lock status */
 482                 return pty_get_lock(tty, (int __user *)arg);
 483         case TIOCPKT: /* Set PT packet mode */
 484                 return pty_set_pktmode(tty, (int __user *)arg);
 485         case TIOCGPKT: /* Get PT packet mode */
 486                 return pty_get_pktmode(tty, (int __user *)arg);
 487         case TIOCSIG:    /* Send signal to other side of pty */
 488                 return pty_signal(tty, (int) arg);
 489         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 490                 return -EINVAL;
 491         }
 492         return -ENOIOCTLCMD;
 493 }
 494
 495 #ifdef CONFIG_COMPAT
 496 static long pty_bsd_compat_ioctl(struct tty_struct *tty,
 497                                  unsigned int cmd, unsigned long arg)
 498 {
 499         /*
 500          * PTY ioctls don't require any special translation between 32-bit and
 501          * 64-bit userspace, they are already compatible.
 502          */
 503         return pty_bsd_ioctl(tty, cmd, (unsigned long)compat_ptr(arg));
 504 }
 505 #else
 506 #define pty_bsd_compat_ioctl NULL
 507 #endif
 508
 509 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 510 /*
 511  * not really modular, but the easiest way to keep compat with existing
 512  * bootargs behaviour is to continue using module_param here.
 513  */
 514 module_param(legacy_count, int, 0);
 515
 516 /*
 517  * The master side of a pty can do TIOCSPTLCK and thus
 518  * has pty_bsd_ioctl.
 519  */
 520 static const struct tty_operations master_pty_ops_bsd = {
 521         .install = pty_install,
 522         .open = pty_open,
 523         .close = pty_close,
 524         .write = pty_write,
 525         .write_room = pty_write_room,
 526         .flush_buffer = pty_flush_buffer,
 527         .chars_in_buffer = pty_chars_in_buffer,
 528         .unthrottle = pty_unthrottle,
 529         .ioctl = pty_bsd_ioctl,
 530         .compat_ioctl = pty_bsd_compat_ioctl,
 531         .cleanup = pty_cleanup,
 532         .resize = pty_resize,
 533         .remove = pty_remove
 534 };
 535
 536 static const struct tty_operations slave_pty_ops_bsd = {
 537         .install = pty_install,
 538         .open = pty_open,
 539         .close = pty_close,
 540         .write = pty_write,
 541         .write_room = pty_write_room,
 542         .flush_buffer = pty_flush_buffer,
 543         .chars_in_buffer = pty_chars_in_buffer,
 544         .unthrottle = pty_unthrottle,
 545         .set_termios = pty_set_termios,
 546         .cleanup = pty_cleanup,
 547         .resize = pty_resize,
 548         .start = pty_start,
 549         .stop = pty_stop,
 550         .remove = pty_remove
 551 };
 552
 553 static void __init legacy_pty_init(void)
 554 {
 555         struct tty_driver *pty_driver, *pty_slave_driver;
 556
 557         if (legacy_count <= 0)
 558                 return;
 559
 560         pty_driver = tty_alloc_driver(legacy_count,
 561                         TTY_DRIVER_RESET_TERMIOS |
 562                         TTY_DRIVER_REAL_RAW |
 563                         TTY_DRIVER_DYNAMIC_ALLOC);
 564         if (IS_ERR(pty_driver))
 565                 panic("Couldn't allocate pty driver");
 566
 567         pty_slave_driver = tty_alloc_driver(legacy_count,
 568                         TTY_DRIVER_RESET_TERMIOS |
 569                         TTY_DRIVER_REAL_RAW |
 570                         TTY_DRIVER_DYNAMIC_ALLOC);
 571         if (IS_ERR(pty_slave_driver))
 572                 panic("Couldn't allocate pty slave driver");
 573
 574         pty_driver->driver_name = "pty_master";
 575         pty_driver->name = "pty";
 576         pty_driver->major = PTY_MASTER_MAJOR;
 577         pty_driver->minor_start = 0;
 578         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 579         pty_driver->subtype = PTY_TYPE_MASTER;
 580         pty_driver->init_termios = tty_std_termios;
 581         pty_driver->init_termios.c_iflag = 0;
 582         pty_driver->init_termios.c_oflag = 0;
 583         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 584         pty_driver->init_termios.c_lflag = 0;
 585         pty_driver->init_termios.c_ispeed = 38400;
 586         pty_driver->init_termios.c_ospeed = 38400;
 587         pty_driver->other = pty_slave_driver;
 588         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 589
 590         pty_slave_driver->driver_name = "pty_slave";
 591         pty_slave_driver->name = "ttyp";
 592         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 593         pty_slave_driver->minor_start = 0;
 594         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 595         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 596         pty_slave_driver->init_termios = tty_std_termios;
 597         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 598         pty_slave_driver->init_termios.c_ispeed = 38400;
 599         pty_slave_driver->init_termios.c_ospeed = 38400;
 600         pty_slave_driver->other = pty_driver;
 601         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 602
 603         if (tty_register_driver(pty_driver))
 604                 panic("Couldn't register pty driver");
 605         if (tty_register_driver(pty_slave_driver))
 606                 panic("Couldn't register pty slave driver");
 607 }
 608 #else
 609 static inline void legacy_pty_init(void) { }
 610 #endif
 611
 612 /* Unix98 devices */
 613 #ifdef CONFIG_UNIX98_PTYS
 614 static struct cdev ptmx_cdev;
 615
 616 /**
 617  *      ptm_open_peer - open the peer of a pty
 618  *      @master: the open struct file of the ptmx device node
 619  *      @tty: the master of the pty being opened
 620  *      @flags: the flags for open
 621  *
 622  *      Provide a race free way for userspace to open the slave end of a pty
 623  *      (where they have the master fd and cannot access or trust the mount
 624  *      namespace /dev/pts was mounted inside).
 625  */
 626 int ptm_open_peer(struct file *master, struct tty_struct *tty, int flags)
 627 {
 628         int fd = -1;
 629         struct file *filp;
 630         int retval = -EINVAL;
 631         struct path path;
 632
 633         if (tty->driver != ptm_driver)
 634                 return -EIO;
 635
 636         fd = get_unused_fd_flags(flags);
 637         if (fd < 0) {
 638                 retval = fd;
 639                 goto err;
 640         }
 641
 642         /* Compute the slave's path */
 643         path.mnt = devpts_mntget(master, tty->driver_data);
 644         if (IS_ERR(path.mnt)) {
 645                 retval = PTR_ERR(path.mnt);
 646                 goto err_put;
 647         }
 648         path.dentry = tty->link->driver_data;
 649
 650         filp = dentry_open(&path, flags, current_cred());
 651         mntput(path.mnt);
 652         if (IS_ERR(filp)) {
 653                 retval = PTR_ERR(filp);
 654                 goto err_put;
 655         }
 656
 657         fd_install(fd, filp);
 658         return fd;
 659
 660 err_put:
 661         put_unused_fd(fd);
 662 err:
 663         return retval;
 664 }
 665
 666 static int pty_unix98_ioctl(struct tty_struct *tty,
 667                             unsigned int cmd, unsigned long arg)
 668 {
 669         switch (cmd) {
 670         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 671                 return pty_set_lock(tty, (int __user *)arg);
 672         case TIOCGPTLCK: /* Get PT Lock status */
 673                 return pty_get_lock(tty, (int __user *)arg);
 674         case TIOCPKT: /* Set PT packet mode */
 675                 return pty_set_pktmode(tty, (int __user *)arg);
 676         case TIOCGPKT: /* Get PT packet mode */
 677                 return pty_get_pktmode(tty, (int __user *)arg);
 678         case TIOCGPTN: /* Get PT Number */
 679                 return put_user(tty->index, (unsigned int __user *)arg);
 680         case TIOCSIG:    /* Send signal to other side of pty */
 681                 return pty_signal(tty, (int) arg);
 682         }
 683
 684         return -ENOIOCTLCMD;
 685 }
 686
 687 #ifdef CONFIG_COMPAT
 688 static long pty_unix98_compat_ioctl(struct tty_struct *tty,
 689                                  unsigned int cmd, unsigned long arg)
 690 {
 691         /*
 692          * PTY ioctls don't require any special translation between 32-bit and
 693          * 64-bit userspace, they are already compatible.
 694          */
 695         return pty_unix98_ioctl(tty, cmd,
 696                 cmd == TIOCSIG ? arg : (unsigned long)compat_ptr(arg));
 697 }
 698 #else
 699 #define pty_unix98_compat_ioctl NULL
 700 #endif
 701
 702 /**
 703  *      ptm_unix98_lookup       -       find a pty master
 704  *      @driver: ptm driver
 705  *      @file: unused
 706  *      @idx: tty index
 707  *
 708  *      Look up a pty master device. Called under the tty_mutex for now.
 709  *      This provides our locking.
 710  */
 711
 712 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 713                 struct file *file, int idx)
 714 {
 715         /* Master must be open via /dev/ptmx */
 716         return ERR_PTR(-EIO);
 717 }
 718
 719 /**
 720  *      pts_unix98_lookup       -       find a pty slave
 721  *      @driver: pts driver
 722  *      @file: file pointer to tty
 723  *      @idx: tty index
 724  *
 725  *      Look up a pty master device. Called under the tty_mutex for now.
 726  *      This provides our locking for the tty pointer.
 727  */
 728
 729 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 730                 struct file *file, int idx)
 731 {
 732         struct tty_struct *tty;
 733
 734         mutex_lock(&devpts_mutex);
 735         tty = devpts_get_priv(file->f_path.dentry);
 736         mutex_unlock(&devpts_mutex);
 737         /* Master must be open before slave */
 738         if (!tty)
 739                 return ERR_PTR(-EIO);
 740         return tty;
 741 }
 742
 743 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 744 {
 745         return pty_common_install(driver, tty, false);
 746 }
 747
 748 /* this is called once with whichever end is closed last */
 749 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 750 {
 751         struct pts_fs_info *fsi;
 752
 753         if (tty->driver->subtype == PTY_TYPE_MASTER)
 754                 fsi = tty->driver_data;
 755         else
 756                 fsi = tty->link->driver_data;
 757
 758         if (fsi) {
 759                 devpts_kill_index(fsi, tty->index);
 760                 devpts_release(fsi);
 761         }
 762 }
 763
 764 static void pty_show_fdinfo(struct tty_struct *tty, struct seq_file *m)
 765 {
 766         seq_printf(m, "tty-index:\t%d\n", tty->index);
 767 }
 768
 769 static const struct tty_operations ptm_unix98_ops = {
 770         .lookup = ptm_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         .ioctl = pty_unix98_ioctl,
 781         .compat_ioctl = pty_unix98_compat_ioctl,
 782         .resize = pty_resize,
 783         .cleanup = pty_cleanup,
 784         .show_fdinfo = pty_show_fdinfo,
 785 };
 786
 787 static const struct tty_operations pty_unix98_ops = {
 788         .lookup = pts_unix98_lookup,
 789         .install = pty_unix98_install,
 790         .remove = pty_unix98_remove,
 791         .open = pty_open,
 792         .close = pty_close,
 793         .write = pty_write,
 794         .write_room = pty_write_room,
 795         .flush_buffer = pty_flush_buffer,
 796         .chars_in_buffer = pty_chars_in_buffer,
 797         .unthrottle = pty_unthrottle,
 798         .set_termios = pty_set_termios,
 799         .start = pty_start,
 800         .stop = pty_stop,
 801         .cleanup = pty_cleanup,
 802 };
 803
 804 /**
 805  *      ptmx_open               -       open a unix 98 pty master
 806  *      @inode: inode of device file
 807  *      @filp: file pointer to tty
 808  *
 809  *      Allocate a unix98 pty master device from the ptmx driver.
 810  *
 811  *      Locking: tty_mutex protects the init_dev work. tty->count should
 812  *              protect the rest.
 813  *              allocated_ptys_lock handles the list of free pty numbers
 814  */
 815
 816 static int ptmx_open(struct inode *inode, struct file *filp)
 817 {
 818         struct pts_fs_info *fsi;
 819         struct tty_struct *tty;
 820         struct dentry *dentry;
 821         int retval;
 822         int index;
 823
 824         nonseekable_open(inode, filp);
 825
 826         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 827         filp->f_mode |= FMODE_NONOTIFY;
 828
 829         retval = tty_alloc_file(filp);
 830         if (retval)
 831                 return retval;
 832
 833         fsi = devpts_acquire(filp);
 834         if (IS_ERR(fsi)) {
 835                 retval = PTR_ERR(fsi);
 836                 goto out_free_file;
 837         }
 838
 839         /* find a device that is not in use. */
 840         mutex_lock(&devpts_mutex);
 841         index = devpts_new_index(fsi);
 842         mutex_unlock(&devpts_mutex);
 843
 844         retval = index;
 845         if (index < 0)
 846                 goto out_put_fsi;
 847
 848
 849         mutex_lock(&tty_mutex);
 850         tty = tty_init_dev(ptm_driver, index);
 851         /* The tty returned here is locked so we can safely
 852            drop the mutex */
 853         mutex_unlock(&tty_mutex);
 854
 855         retval = PTR_ERR(tty);
 856         if (IS_ERR(tty))
 857                 goto out;
 858
 859         /*
 860          * From here on out, the tty is "live", and the index and
 861          * fsi will be killed/put by the tty_release()
 862          */
 863         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 864         tty->driver_data = fsi;
 865
 866         tty_add_file(tty, filp);
 867
 868         dentry = devpts_pty_new(fsi, index, tty->link);
 869         if (IS_ERR(dentry)) {
 870                 retval = PTR_ERR(dentry);
 871                 goto err_release;
 872         }
 873         tty->link->driver_data = dentry;
 874
 875         retval = ptm_driver->ops->open(tty, filp);
 876         if (retval)
 877                 goto err_release;
 878
 879         tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
 880
 881         tty_unlock(tty);
 882         return 0;
 883 err_release:
 884         tty_unlock(tty);
 885         // This will also put-ref the fsi
 886         tty_release(inode, filp);
 887         return retval;
 888 out:
 889         devpts_kill_index(fsi, index);
 890 out_put_fsi:
 891         devpts_release(fsi);
 892 out_free_file:
 893         tty_free_file(filp);
 894         return retval;
 895 }
 896
 897 static struct file_operations ptmx_fops __ro_after_init;
 898
 899 static void __init unix98_pty_init(void)
 900 {
 901         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 902                         TTY_DRIVER_RESET_TERMIOS |
 903                         TTY_DRIVER_REAL_RAW |
 904                         TTY_DRIVER_DYNAMIC_DEV |
 905                         TTY_DRIVER_DEVPTS_MEM |
 906                         TTY_DRIVER_DYNAMIC_ALLOC);
 907         if (IS_ERR(ptm_driver))
 908                 panic("Couldn't allocate Unix98 ptm driver");
 909         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 910                         TTY_DRIVER_RESET_TERMIOS |
 911                         TTY_DRIVER_REAL_RAW |
 912                         TTY_DRIVER_DYNAMIC_DEV |
 913                         TTY_DRIVER_DEVPTS_MEM |
 914                         TTY_DRIVER_DYNAMIC_ALLOC);
 915         if (IS_ERR(pts_driver))
 916                 panic("Couldn't allocate Unix98 pts driver");
 917
 918         ptm_driver->driver_name = "pty_master";
 919         ptm_driver->name = "ptm";
 920         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 921         ptm_driver->minor_start = 0;
 922         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 923         ptm_driver->subtype = PTY_TYPE_MASTER;
 924         ptm_driver->init_termios = tty_std_termios;
 925         ptm_driver->init_termios.c_iflag = 0;
 926         ptm_driver->init_termios.c_oflag = 0;
 927         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 928         ptm_driver->init_termios.c_lflag = 0;
 929         ptm_driver->init_termios.c_ispeed = 38400;
 930         ptm_driver->init_termios.c_ospeed = 38400;
 931         ptm_driver->other = pts_driver;
 932         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 933
 934         pts_driver->driver_name = "pty_slave";
 935         pts_driver->name = "pts";
 936         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 937         pts_driver->minor_start = 0;
 938         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 939         pts_driver->subtype = PTY_TYPE_SLAVE;
 940         pts_driver->init_termios = tty_std_termios;
 941         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 942         pts_driver->init_termios.c_ispeed = 38400;
 943         pts_driver->init_termios.c_ospeed = 38400;
 944         pts_driver->other = ptm_driver;
 945         tty_set_operations(pts_driver, &pty_unix98_ops);
 946
 947         if (tty_register_driver(ptm_driver))
 948                 panic("Couldn't register Unix98 ptm driver");
 949         if (tty_register_driver(pts_driver))
 950                 panic("Couldn't register Unix98 pts driver");
 951
 952         /* Now create the /dev/ptmx special device */
 953         tty_default_fops(&ptmx_fops);
 954         ptmx_fops.open = ptmx_open;
 955
 956         cdev_init(&ptmx_cdev, &ptmx_fops);
 957         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 958             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 959                 panic("Couldn't register /dev/ptmx driver");
 960         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 961 }
 962
 963 #else
 964 static inline void unix98_pty_init(void) { }
 965 #endif
 966
 967 static int __init pty_init(void)
 968 {
 969         legacy_pty_init();
 970         unix98_pty_init();
 971         return 0;
 972 }
 973 device_initcall(pty_init);