Make sure to check the serial disconnected flag before accessing port
private data after waking up.
This fixes a use after free in the ftdi_sio introduced by commit
876ae50d94b ("USB: ftdi_sio: fix race condition in TIOCMIWAIT, and abort
of TIOCMIWAIT when the device is removed").
When switching to tty ports, some lifetime assumptions where changed.
Specifically, close can now be called before the final tty reference is
dropped as part of hangup at device disconnect. Even with the ftdi
private-data refcounting this means that the port private data can be
freed while a process is sleeping on modem-status changes and thus
cannot be relied on to detect disconnects when woken up.
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Johan Hovold <jhovold@xxxxxxxxx>
---
drivers/usb/serial/ftdi_sio.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index edd162d..83dd0b9 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -71,7 +71,6 @@ struct ftdi_private {
struct async_icount icount;
wait_queue_head_t delta_msr_wait; /* Used for TIOCMIWAIT */
char prev_status; /* Used for TIOCMIWAIT */
- bool dev_gone; /* Used to abort TIOCMIWAIT */
char transmit_empty; /* If transmitter is empty or not */
__u16 interface; /* FT2232C, FT2232H or FT4232H port interface
(0 for FT232/245) */
@@ -1694,7 +1693,6 @@ static int ftdi_sio_port_probe(struct usb_serial_port *port)
init_waitqueue_head(&priv->delta_msr_wait);
priv->flags = ASYNC_LOW_LATENCY;
- priv->dev_gone = false;
if (quirk && quirk->port_probe)
quirk->port_probe(priv);
@@ -1840,7 +1838,6 @@ static int ftdi_sio_port_remove(struct usb_serial_port *port)
{
struct ftdi_private *priv = usb_get_serial_port_data(port);
- priv->dev_gone = true;
wake_up_interruptible_all(&priv->delta_msr_wait);
remove_sysfs_attrs(port);
@@ -2440,11 +2437,15 @@ static int ftdi_ioctl(struct tty_struct *tty,
*/
case TIOCMIWAIT:
cprev = priv->icount;
- while (!priv->dev_gone) {
+ for (;;) {
interruptible_sleep_on(&priv->delta_msr_wait);
/* see if a signal did it */
if (signal_pending(current))
return -ERESTARTSYS;
+
+ if (port->serial->disconnected)
+ return -EIO;
+
cnow = priv->icount;
if (((arg & TIOCM_RNG) && (cnow.rng != cprev.rng)) ||
((arg & TIOCM_DSR) && (cnow.dsr != cprev.dsr)) ||
@@ -2454,8 +2455,6 @@ static int ftdi_ioctl(struct tty_struct *tty,
}
cprev = cnow;
}
- return -EIO;
- break;
case TIOCSERGETLSR:
return get_lsr_info(port, (struct serial_struct __user *)arg);
break;
--
1.8.1.1
--
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