[PATCH v2 03/12] USB: serial: io_edgeport: fix potential NULL-deref at open

[Johan Hovold]

Do not mark the port as open until after the write FIFO has been
allocated and initialised to prevent a racing interrupt completion from
attempting to send stale data and dereference the FIFO buffer pointer.

Note that the open flag defaults to false and is cleared on close() so
there is no need to reinitialise it on every open().

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
---
 drivers/usb/serial/io_edgeport.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
index a5011fa91ee7..e8e641e9a197 100644
--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -885,9 +885,7 @@ static int edge_open(struct tty_struct *tty, struct usb_serial_port *port)
 
 	/* send a open port command */
 	edge_port->openPending = true;
-	edge_port->open        = false;
 	response = send_iosp_ext_cmd(edge_port, IOSP_CMD_OPEN_PORT, 0);
-
 	if (response < 0) {
 		dev_err(dev, "%s - error sending open port command\n", __func__);
 		edge_port->openPending = false;
@@ -897,8 +895,7 @@ static int edge_open(struct tty_struct *tty, struct usb_serial_port *port)
 	/* now wait for the port to be completely opened */
 	wait_event_timeout(edge_port->wait_open, !edge_port->openPending,
 								OPEN_TIMEOUT);
-
-	if (!edge_port->open) {
+	if (edge_port->openPending) {
 		/* open timed out */
 		dev_dbg(dev, "%s - open timeout\n", __func__);
 		edge_port->openPending = false;
@@ -926,6 +923,10 @@ static int edge_open(struct tty_struct *tty, struct usb_serial_port *port)
 		return -ENOMEM;
 	}
 
+	spin_lock_irq(&edge_port->ep_lock);
+	edge_port->open = true;
+	spin_unlock_irq(&edge_port->ep_lock);
+
 	dev_dbg(dev, "%s - Initialize TX fifo to %d bytes\n",
 		__func__, edge_port->maxTxCredits);
 
@@ -1818,7 +1819,6 @@ static void process_rcvd_status(struct edgeport_serial *edge_serial,
 
 		/* we have completed the open */
 		edge_port->openPending = false;
-		edge_port->open = true;
 		wake_up(&edge_port->wait_open);
 		return;
 	}
-- 
2.55.0