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    Subject[PATCH 34/76] tty: Termios locking - sort out real_tty confusions and lock reads
    Date
    This moves us towards sanity and should mean our termios locking is now
    complete and comprehensive.
    ---

    drivers/char/tty_io.c | 2 +-
    drivers/char/tty_ioctl.c | 58 ++++++++++++++++++++++++++++++----------------
    2 files changed, 39 insertions(+), 21 deletions(-)

    diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
    index fa162c9..ac53d7f 100644
    --- a/drivers/char/tty_io.c
    +++ b/drivers/char/tty_io.c
    @@ -2605,7 +2605,7 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
    case TIOCSTI:
    return tiocsti(tty, p);
    case TIOCGWINSZ:
    - return tiocgwinsz(tty, p);
    + return tiocgwinsz(real_tty, p);
    case TIOCSWINSZ:
    return tiocswinsz(tty, real_tty, p);
    case TIOCCONS:
    diff --git a/drivers/char/tty_ioctl.c b/drivers/char/tty_ioctl.c
    index 93bfa1d..3067085 100644
    --- a/drivers/char/tty_ioctl.c
    +++ b/drivers/char/tty_ioctl.c
    @@ -893,6 +893,7 @@ int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
    {
    struct tty_struct *real_tty;
    void __user *p = (void __user *)arg;
    + int ret = 0;

    if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
    tty->driver->subtype == PTY_TYPE_MASTER)
    @@ -928,18 +929,24 @@ int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
    return set_termios(real_tty, p, TERMIOS_OLD);
    #ifndef TCGETS2
    case TCGETS:
    + mutex_lock(&real_tty->termios_mutex);
    if (kernel_termios_to_user_termios((struct termios __user *)arg, real_tty->termios))
    - return -EFAULT;
    - return 0;
    + ret = -EFAULT;
    + mutex_unlock(&real_tty->termios_mutex);
    + return ret;
    #else
    case TCGETS:
    + mutex_lock(&real_tty->termios_mutex);
    if (kernel_termios_to_user_termios_1((struct termios __user *)arg, real_tty->termios))
    - return -EFAULT;
    - return 0;
    + ret = -EFAULT;
    + mutex_unlock(&real_tty->termios_mutex);
    + return ret;
    case TCGETS2:
    + mutex_lock(&real_tty->termios_mutex);
    if (kernel_termios_to_user_termios((struct termios2 __user *)arg, real_tty->termios))
    - return -EFAULT;
    - return 0;
    + ret = -EFAULT;
    + mutex_unlock(&real_tty->termios_mutex);
    + return ret;
    case TCSETSF2:
    return set_termios(real_tty, p, TERMIOS_FLUSH | TERMIOS_WAIT);
    case TCSETSW2:
    @@ -957,36 +964,46 @@ int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
    return set_termios(real_tty, p, TERMIOS_TERMIO);
    #ifndef TCGETS2
    case TIOCGLCKTRMIOS:
    + mutex_lock(&real_tty->termios_mutex);
    if (kernel_termios_to_user_termios((struct termios __user *)arg, real_tty->termios_locked))
    - return -EFAULT;
    - return 0;
    + ret = -EFAULT;
    + mutex_unlock(&real_tty->termios_mutex);
    + return ret;
    case TIOCSLCKTRMIOS:
    if (!capable(CAP_SYS_ADMIN))
    return -EPERM;
    + mutex_lock(&real_tty->termios_mutex);
    if (user_termios_to_kernel_termios(real_tty->termios_locked,
    (struct termios __user *) arg))
    - return -EFAULT;
    - return 0;
    + ret = -EFAULT;
    + mutex_unlock(&real_tty->termios_mutex);
    + return ret;
    #else
    case TIOCGLCKTRMIOS:
    + mutex_lock(&real_tty->termios_mutex);
    if (kernel_termios_to_user_termios_1((struct termios __user *)arg, real_tty->termios_locked))
    - return -EFAULT;
    - return 0;
    + ret = -EFAULT;
    + mutex_unlock(&real_tty->termios_mutex);
    + return ret;
    case TIOCSLCKTRMIOS:
    if (!capable(CAP_SYS_ADMIN))
    - return -EPERM;
    + ret = -EPERM;
    + mutex_lock(&real_tty->termios_mutex);
    if (user_termios_to_kernel_termios_1(real_tty->termios_locked,
    (struct termios __user *) arg))
    - return -EFAULT;
    - return 0;
    + ret = -EFAULT;
    + mutex_unlock(&real_tty->termios_mutex);
    + return ret;
    #endif
    #ifdef TCGETX
    case TCGETX:
    if (real_tty->termiox == NULL)
    return -EINVAL;
    + mutex_lock(&real_tty->termios_mutex);
    if (copy_to_user(p, real_tty->termiox, sizeof(struct termiox)))
    - return -EFAULT;
    - return 0;
    + ret = -EFAULT;
    + mutex_unlock(&real_tty->termios_mutex);
    + return ret;
    case TCSETX:
    return set_termiox(real_tty, p, 0);
    case TCSETXW:
    @@ -995,10 +1012,11 @@ int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
    return set_termiox(real_tty, p, TERMIOS_FLUSH);
    #endif
    case TIOCGSOFTCAR:
    - /* FIXME: for correctness we may need to take the termios
    - lock here - review */
    - return put_user(C_CLOCAL(real_tty) ? 1 : 0,
    + mutex_lock(&real_tty->termios_mutex);
    + ret = put_user(C_CLOCAL(real_tty) ? 1 : 0,
    (int __user *)arg);
    + mutex_unlock(&real_tty->termios_mutex);
    + return ret;
    case TIOCSSOFTCAR:
    if (get_user(arg, (unsigned int __user *) arg))
    return -EFAULT;


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