linux/drivers/tty/pty.c
Alan Cox d155255a34 tty: Fix race in tty release
Ian Abbott found that the tty layer would explode with the right set of
parallel open and close operations. This is because we race in the
handling of tty->drivers->termios[].

Correct this by
	Making tty_ldisc_release behave like nromal code (takes the lock,
			does stuff, drops the lock)
	Drop the tty lock earlier in tty_ldisc_release
	Taking the tty mutex around the driver->termios update in all cases
	Adding a WARN_ON to catch future screwups.

I also forgot to clean up the pty resources properly. With a pty pair we
need to pull both halves out of the tables.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Tested-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-07-27 11:55:59 -07:00

737 lines
18 KiB
C

/*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* Added support for a Unix98-style ptmx device.
* -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
*
* When reading this code see also fs/devpts. In particular note that the
* driver_data field is used by the devpts side as a binding to the devpts
* inode.
*/
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/fcntl.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/major.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/uaccess.h>
#include <linux/bitops.h>
#include <linux/devpts_fs.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#ifdef CONFIG_UNIX98_PTYS
static struct tty_driver *ptm_driver;
static struct tty_driver *pts_driver;
static DEFINE_MUTEX(devpts_mutex);
#endif
static void pty_close(struct tty_struct *tty, struct file *filp)
{
BUG_ON(!tty);
if (tty->driver->subtype == PTY_TYPE_MASTER)
WARN_ON(tty->count > 1);
else {
if (tty->count > 2)
return;
}
wake_up_interruptible(&tty->read_wait);
wake_up_interruptible(&tty->write_wait);
tty->packet = 0;
if (!tty->link)
return;
tty->link->packet = 0;
set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
wake_up_interruptible(&tty->link->read_wait);
wake_up_interruptible(&tty->link->write_wait);
if (tty->driver->subtype == PTY_TYPE_MASTER) {
set_bit(TTY_OTHER_CLOSED, &tty->flags);
#ifdef CONFIG_UNIX98_PTYS
if (tty->driver == ptm_driver) {
mutex_lock(&devpts_mutex);
devpts_pty_kill(tty->link);
mutex_unlock(&devpts_mutex);
}
#endif
tty_unlock();
tty_vhangup(tty->link);
tty_lock();
}
}
/*
* The unthrottle routine is called by the line discipline to signal
* that it can receive more characters. For PTY's, the TTY_THROTTLED
* flag is always set, to force the line discipline to always call the
* unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
* characters in the queue. This is necessary since each time this
* happens, we need to wake up any sleeping processes that could be
* (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
* for the pty buffer to be drained.
*/
static void pty_unthrottle(struct tty_struct *tty)
{
tty_wakeup(tty->link);
set_bit(TTY_THROTTLED, &tty->flags);
}
/**
* pty_space - report space left for writing
* @to: tty we are writing into
*
* The tty buffers allow 64K but we sneak a peak and clip at 8K this
* allows a lot of overspill room for echo and other fun messes to
* be handled properly
*/
static int pty_space(struct tty_struct *to)
{
int n = 8192 - to->buf.memory_used;
if (n < 0)
return 0;
return n;
}
/**
* pty_write - write to a pty
* @tty: the tty we write from
* @buf: kernel buffer of data
* @count: bytes to write
*
* Our "hardware" write method. Data is coming from the ldisc which
* may be in a non sleeping state. We simply throw this at the other
* end of the link as if we were an IRQ handler receiving stuff for
* the other side of the pty/tty pair.
*/
static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
{
struct tty_struct *to = tty->link;
if (tty->stopped)
return 0;
if (c > 0) {
/* Stuff the data into the input queue of the other end */
c = tty_insert_flip_string(to, buf, c);
/* And shovel */
if (c) {
tty_flip_buffer_push(to);
tty_wakeup(tty);
}
}
return c;
}
/**
* pty_write_room - write space
* @tty: tty we are writing from
*
* Report how many bytes the ldisc can send into the queue for
* the other device.
*/
static int pty_write_room(struct tty_struct *tty)
{
if (tty->stopped)
return 0;
return pty_space(tty->link);
}
/**
* pty_chars_in_buffer - characters currently in our tx queue
* @tty: our tty
*
* Report how much we have in the transmit queue. As everything is
* instantly at the other end this is easy to implement.
*/
static int pty_chars_in_buffer(struct tty_struct *tty)
{
return 0;
}
/* Set the lock flag on a pty */
static int pty_set_lock(struct tty_struct *tty, int __user *arg)
{
int val;
if (get_user(val, arg))
return -EFAULT;
if (val)
set_bit(TTY_PTY_LOCK, &tty->flags);
else
clear_bit(TTY_PTY_LOCK, &tty->flags);
return 0;
}
/* Send a signal to the slave */
static int pty_signal(struct tty_struct *tty, int sig)
{
unsigned long flags;
struct pid *pgrp;
if (tty->link) {
spin_lock_irqsave(&tty->link->ctrl_lock, flags);
pgrp = get_pid(tty->link->pgrp);
spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
kill_pgrp(pgrp, sig, 1);
put_pid(pgrp);
}
return 0;
}
static void pty_flush_buffer(struct tty_struct *tty)
{
struct tty_struct *to = tty->link;
unsigned long flags;
if (!to)
return;
/* tty_buffer_flush(to); FIXME */
if (to->packet) {
spin_lock_irqsave(&tty->ctrl_lock, flags);
tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
wake_up_interruptible(&to->read_wait);
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
}
}
static int pty_open(struct tty_struct *tty, struct file *filp)
{
int retval = -ENODEV;
if (!tty || !tty->link)
goto out;
retval = -EIO;
if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
goto out;
if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
goto out;
if (tty->link->count != 1)
goto out;
clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
set_bit(TTY_THROTTLED, &tty->flags);
retval = 0;
out:
return retval;
}
static void pty_set_termios(struct tty_struct *tty,
struct ktermios *old_termios)
{
tty->termios.c_cflag &= ~(CSIZE | PARENB);
tty->termios.c_cflag |= (CS8 | CREAD);
}
/**
* pty_do_resize - resize event
* @tty: tty being resized
* @ws: window size being set.
*
* Update the termios variables and send the necessary signals to
* peform a terminal resize correctly
*/
int pty_resize(struct tty_struct *tty, struct winsize *ws)
{
struct pid *pgrp, *rpgrp;
unsigned long flags;
struct tty_struct *pty = tty->link;
/* For a PTY we need to lock the tty side */
mutex_lock(&tty->termios_mutex);
if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
goto done;
/* Get the PID values and reference them so we can
avoid holding the tty ctrl lock while sending signals.
We need to lock these individually however. */
spin_lock_irqsave(&tty->ctrl_lock, flags);
pgrp = get_pid(tty->pgrp);
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
spin_lock_irqsave(&pty->ctrl_lock, flags);
rpgrp = get_pid(pty->pgrp);
spin_unlock_irqrestore(&pty->ctrl_lock, flags);
if (pgrp)
kill_pgrp(pgrp, SIGWINCH, 1);
if (rpgrp != pgrp && rpgrp)
kill_pgrp(rpgrp, SIGWINCH, 1);
put_pid(pgrp);
put_pid(rpgrp);
tty->winsize = *ws;
pty->winsize = *ws; /* Never used so will go away soon */
done:
mutex_unlock(&tty->termios_mutex);
return 0;
}
/**
* pty_common_install - set up the pty pair
* @driver: the pty driver
* @tty: the tty being instantiated
* @bool: legacy, true if this is BSD style
*
* Perform the initial set up for the tty/pty pair. Called from the
* tty layer when the port is first opened.
*
* Locking: the caller must hold the tty_mutex
*/
static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
bool legacy)
{
struct tty_struct *o_tty;
struct tty_port *ports[2];
int idx = tty->index;
int retval = -ENOMEM;
o_tty = alloc_tty_struct();
ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
if (!o_tty || !ports[0] || !ports[1])
goto err_free_tty;
if (!try_module_get(driver->other->owner)) {
/* This cannot in fact currently happen */
goto err_free_tty;
}
initialize_tty_struct(o_tty, driver->other, idx);
if (legacy) {
/* We always use new tty termios data so we can do this
the easy way .. */
retval = tty_init_termios(tty);
if (retval)
goto err_deinit_tty;
retval = tty_init_termios(o_tty);
if (retval)
goto err_free_termios;
driver->other->ttys[idx] = o_tty;
driver->ttys[idx] = tty;
} else {
memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
tty->termios = driver->init_termios;
memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
o_tty->termios = driver->other->init_termios;
}
/*
* Everything allocated ... set up the o_tty structure.
*/
tty_driver_kref_get(driver->other);
if (driver->subtype == PTY_TYPE_MASTER)
o_tty->count++;
/* Establish the links in both directions */
tty->link = o_tty;
o_tty->link = tty;
tty_port_init(ports[0]);
tty_port_init(ports[1]);
o_tty->port = ports[0];
tty->port = ports[1];
tty_driver_kref_get(driver);
tty->count++;
return 0;
err_free_termios:
if (legacy)
tty_free_termios(tty);
err_deinit_tty:
deinitialize_tty_struct(o_tty);
module_put(o_tty->driver->owner);
err_free_tty:
kfree(ports[0]);
kfree(ports[1]);
free_tty_struct(o_tty);
return retval;
}
static void pty_cleanup(struct tty_struct *tty)
{
kfree(tty->port);
}
/* Traditional BSD devices */
#ifdef CONFIG_LEGACY_PTYS
static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
{
return pty_common_install(driver, tty, true);
}
static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
{
struct tty_struct *pair = tty->link;
driver->ttys[tty->index] = NULL;
if (pair)
pair->driver->ttys[pair->index] = NULL;
}
static int pty_bsd_ioctl(struct tty_struct *tty,
unsigned int cmd, unsigned long arg)
{
switch (cmd) {
case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
return pty_set_lock(tty, (int __user *) arg);
case TIOCSIG: /* Send signal to other side of pty */
return pty_signal(tty, (int) arg);
}
return -ENOIOCTLCMD;
}
static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
module_param(legacy_count, int, 0);
/*
* The master side of a pty can do TIOCSPTLCK and thus
* has pty_bsd_ioctl.
*/
static const struct tty_operations master_pty_ops_bsd = {
.install = pty_install,
.open = pty_open,
.close = pty_close,
.write = pty_write,
.write_room = pty_write_room,
.flush_buffer = pty_flush_buffer,
.chars_in_buffer = pty_chars_in_buffer,
.unthrottle = pty_unthrottle,
.set_termios = pty_set_termios,
.ioctl = pty_bsd_ioctl,
.cleanup = pty_cleanup,
.resize = pty_resize,
.remove = pty_remove
};
static const struct tty_operations slave_pty_ops_bsd = {
.install = pty_install,
.open = pty_open,
.close = pty_close,
.write = pty_write,
.write_room = pty_write_room,
.flush_buffer = pty_flush_buffer,
.chars_in_buffer = pty_chars_in_buffer,
.unthrottle = pty_unthrottle,
.set_termios = pty_set_termios,
.cleanup = pty_cleanup,
.resize = pty_resize,
.remove = pty_remove
};
static void __init legacy_pty_init(void)
{
struct tty_driver *pty_driver, *pty_slave_driver;
if (legacy_count <= 0)
return;
pty_driver = alloc_tty_driver(legacy_count);
if (!pty_driver)
panic("Couldn't allocate pty driver");
pty_slave_driver = alloc_tty_driver(legacy_count);
if (!pty_slave_driver)
panic("Couldn't allocate pty slave driver");
pty_driver->driver_name = "pty_master";
pty_driver->name = "pty";
pty_driver->major = PTY_MASTER_MAJOR;
pty_driver->minor_start = 0;
pty_driver->type = TTY_DRIVER_TYPE_PTY;
pty_driver->subtype = PTY_TYPE_MASTER;
pty_driver->init_termios = tty_std_termios;
pty_driver->init_termios.c_iflag = 0;
pty_driver->init_termios.c_oflag = 0;
pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
pty_driver->init_termios.c_lflag = 0;
pty_driver->init_termios.c_ispeed = 38400;
pty_driver->init_termios.c_ospeed = 38400;
pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
pty_driver->other = pty_slave_driver;
tty_set_operations(pty_driver, &master_pty_ops_bsd);
pty_slave_driver->driver_name = "pty_slave";
pty_slave_driver->name = "ttyp";
pty_slave_driver->major = PTY_SLAVE_MAJOR;
pty_slave_driver->minor_start = 0;
pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
pty_slave_driver->subtype = PTY_TYPE_SLAVE;
pty_slave_driver->init_termios = tty_std_termios;
pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
pty_slave_driver->init_termios.c_ispeed = 38400;
pty_slave_driver->init_termios.c_ospeed = 38400;
pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
TTY_DRIVER_REAL_RAW;
pty_slave_driver->other = pty_driver;
tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
if (tty_register_driver(pty_driver))
panic("Couldn't register pty driver");
if (tty_register_driver(pty_slave_driver))
panic("Couldn't register pty slave driver");
}
#else
static inline void legacy_pty_init(void) { }
#endif
/* Unix98 devices */
#ifdef CONFIG_UNIX98_PTYS
static struct cdev ptmx_cdev;
static int pty_unix98_ioctl(struct tty_struct *tty,
unsigned int cmd, unsigned long arg)
{
switch (cmd) {
case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
return pty_set_lock(tty, (int __user *)arg);
case TIOCGPTN: /* Get PT Number */
return put_user(tty->index, (unsigned int __user *)arg);
case TIOCSIG: /* Send signal to other side of pty */
return pty_signal(tty, (int) arg);
}
return -ENOIOCTLCMD;
}
/**
* ptm_unix98_lookup - find a pty master
* @driver: ptm driver
* @idx: tty index
*
* Look up a pty master device. Called under the tty_mutex for now.
* This provides our locking.
*/
static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
struct inode *ptm_inode, int idx)
{
/* Master must be open via /dev/ptmx */
return ERR_PTR(-EIO);
}
/**
* pts_unix98_lookup - find a pty slave
* @driver: pts driver
* @idx: tty index
*
* Look up a pty master device. Called under the tty_mutex for now.
* This provides our locking for the tty pointer.
*/
static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
struct inode *pts_inode, int idx)
{
struct tty_struct *tty;
mutex_lock(&devpts_mutex);
tty = devpts_get_tty(pts_inode, idx);
mutex_unlock(&devpts_mutex);
/* Master must be open before slave */
if (!tty)
return ERR_PTR(-EIO);
return tty;
}
/* We have no need to install and remove our tty objects as devpts does all
the work for us */
static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
{
return pty_common_install(driver, tty, false);
}
static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
{
}
static const struct tty_operations ptm_unix98_ops = {
.lookup = ptm_unix98_lookup,
.install = pty_unix98_install,
.remove = pty_unix98_remove,
.open = pty_open,
.close = pty_close,
.write = pty_write,
.write_room = pty_write_room,
.flush_buffer = pty_flush_buffer,
.chars_in_buffer = pty_chars_in_buffer,
.unthrottle = pty_unthrottle,
.set_termios = pty_set_termios,
.ioctl = pty_unix98_ioctl,
.resize = pty_resize,
.cleanup = pty_cleanup
};
static const struct tty_operations pty_unix98_ops = {
.lookup = pts_unix98_lookup,
.install = pty_unix98_install,
.remove = pty_unix98_remove,
.open = pty_open,
.close = pty_close,
.write = pty_write,
.write_room = pty_write_room,
.flush_buffer = pty_flush_buffer,
.chars_in_buffer = pty_chars_in_buffer,
.unthrottle = pty_unthrottle,
.set_termios = pty_set_termios,
.cleanup = pty_cleanup,
};
/**
* ptmx_open - open a unix 98 pty master
* @inode: inode of device file
* @filp: file pointer to tty
*
* Allocate a unix98 pty master device from the ptmx driver.
*
* Locking: tty_mutex protects the init_dev work. tty->count should
* protect the rest.
* allocated_ptys_lock handles the list of free pty numbers
*/
static int ptmx_open(struct inode *inode, struct file *filp)
{
struct tty_struct *tty;
int retval;
int index;
nonseekable_open(inode, filp);
retval = tty_alloc_file(filp);
if (retval)
return retval;
/* find a device that is not in use. */
tty_lock();
index = devpts_new_index(inode);
tty_unlock();
if (index < 0) {
retval = index;
goto err_file;
}
mutex_lock(&tty_mutex);
mutex_lock(&devpts_mutex);
tty = tty_init_dev(ptm_driver, index);
mutex_unlock(&devpts_mutex);
tty_lock();
mutex_unlock(&tty_mutex);
if (IS_ERR(tty)) {
retval = PTR_ERR(tty);
goto out;
}
set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
tty_add_file(tty, filp);
retval = devpts_pty_new(inode, tty->link);
if (retval)
goto err_release;
retval = ptm_driver->ops->open(tty, filp);
if (retval)
goto err_release;
tty_unlock();
return 0;
err_release:
tty_unlock();
tty_release(inode, filp);
return retval;
out:
devpts_kill_index(inode, index);
tty_unlock();
err_file:
tty_free_file(filp);
return retval;
}
static struct file_operations ptmx_fops;
static void __init unix98_pty_init(void)
{
ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
if (!ptm_driver)
panic("Couldn't allocate Unix98 ptm driver");
pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
if (!pts_driver)
panic("Couldn't allocate Unix98 pts driver");
ptm_driver->driver_name = "pty_master";
ptm_driver->name = "ptm";
ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
ptm_driver->minor_start = 0;
ptm_driver->type = TTY_DRIVER_TYPE_PTY;
ptm_driver->subtype = PTY_TYPE_MASTER;
ptm_driver->init_termios = tty_std_termios;
ptm_driver->init_termios.c_iflag = 0;
ptm_driver->init_termios.c_oflag = 0;
ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
ptm_driver->init_termios.c_lflag = 0;
ptm_driver->init_termios.c_ispeed = 38400;
ptm_driver->init_termios.c_ospeed = 38400;
ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
ptm_driver->other = pts_driver;
tty_set_operations(ptm_driver, &ptm_unix98_ops);
pts_driver->driver_name = "pty_slave";
pts_driver->name = "pts";
pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
pts_driver->minor_start = 0;
pts_driver->type = TTY_DRIVER_TYPE_PTY;
pts_driver->subtype = PTY_TYPE_SLAVE;
pts_driver->init_termios = tty_std_termios;
pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
pts_driver->init_termios.c_ispeed = 38400;
pts_driver->init_termios.c_ospeed = 38400;
pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
pts_driver->other = ptm_driver;
tty_set_operations(pts_driver, &pty_unix98_ops);
if (tty_register_driver(ptm_driver))
panic("Couldn't register Unix98 ptm driver");
if (tty_register_driver(pts_driver))
panic("Couldn't register Unix98 pts driver");
/* Now create the /dev/ptmx special device */
tty_default_fops(&ptmx_fops);
ptmx_fops.open = ptmx_open;
cdev_init(&ptmx_cdev, &ptmx_fops);
if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
panic("Couldn't register /dev/ptmx driver\n");
device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
}
#else
static inline void unix98_pty_init(void) { }
#endif
static int __init pty_init(void)
{
legacy_pty_init();
unix98_pty_init();
return 0;
}
module_init(pty_init);