tty: Termios locking - sort out real_tty confusions and lock reads

This moves us towards sanity and should mean our termios locking is now
complete and comprehensive.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 38 insertions, 20 deletions

diff --git a/drivers/char/tty_ioctl.c b/drivers/char/tty_ioctl.c
index 93bfa1d6cc92..30670851e51a 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;