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tty: Fix tty_send_xchar() lock order inversion

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commit ee0c1a65cf upstream.

The correct lock order is atomic_write_lock => termios_rwsem, as
established by tty_write() => n_tty_write().

Fixes: c274f6ef1c ("tty: Hold termios_rwsem for tcflow(TCIxxx)")
Reported-and-Tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley
2015-11-11 08:03:54 -05:00
committed by Greg Kroah-Hartman
parent b7861b3137
commit 0163804569
2 changed files with 4 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/tty/tty_io.c
View File

@@ -1279,18 +1279,22 @@ int tty_send_xchar(struct tty_struct *tty, char ch)
int was_stopped = tty->stopped; int was_stopped = tty->stopped;
if (tty->ops->send_xchar) { if (tty->ops->send_xchar) {
down_read(&tty->termios_rwsem);
tty->ops->send_xchar(tty, ch); tty->ops->send_xchar(tty, ch);
up_read(&tty->termios_rwsem);
return 0; return 0;
} }
if (tty_write_lock(tty, 0) < 0) if (tty_write_lock(tty, 0) < 0)
return -ERESTARTSYS; return -ERESTARTSYS;
down_read(&tty->termios_rwsem);
if (was_stopped) if (was_stopped)
start_tty(tty); start_tty(tty);
tty->ops->write(tty, &ch, 1); tty->ops->write(tty, &ch, 1);
if (was_stopped) if (was_stopped)
stop_tty(tty); stop_tty(tty);
up_read(&tty->termios_rwsem);
tty_write_unlock(tty); tty_write_unlock(tty);
return 0; return 0;
} }

4
drivers/tty/tty_ioctl.c
View File

@@ -1142,16 +1142,12 @@ int n_tty_ioctl_helper(struct tty_struct *tty, struct file *file,
spin_unlock_irq(&tty->flow_lock); spin_unlock_irq(&tty->flow_lock);
break; break;
case TCIOFF: case TCIOFF:
down_read(&tty->termios_rwsem);
if (STOP_CHAR(tty) != __DISABLED_CHAR) if (STOP_CHAR(tty) != __DISABLED_CHAR)
retval = tty_send_xchar(tty, STOP_CHAR(tty)); retval = tty_send_xchar(tty, STOP_CHAR(tty));
up_read(&tty->termios_rwsem);
break; break;
case TCION: case TCION:
down_read(&tty->termios_rwsem);
if (START_CHAR(tty) != __DISABLED_CHAR) if (START_CHAR(tty) != __DISABLED_CHAR)
retval = tty_send_xchar(tty, START_CHAR(tty)); retval = tty_send_xchar(tty, START_CHAR(tty));
up_read(&tty->termios_rwsem);
break; break;
default: default:
return -EINVAL; return -EINVAL;