[PATCH 4.19 101/118] can: kvaser_usb: Fix accessing freed memory in kvaser_usb_start_xmit()

Greg Kroah-Hartman
2018-11-26T11:05:50Z

From: Jimmy Assarsson <jimmyassarsson@gmail.com>

commit e13fb9b37cc00616b90df2d620f30345b5ada6ff upstream.

The call to can_put_echo_skb() may result in the skb being freed. The skb
is later used in the call to dev->ops->dev_frame_to_cmd().

This is avoided by moving the call to can_put_echo_skb() after
dev->ops->dev_frame_to_cmd().

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jimmy Assarsson <jimmyassarsson@gmail.com>
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c
+++ b/drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c
@@ -528,7 +528,6 @@ static netdev_tx_t kvaser_usb_start_xmit
context = &priv->tx_contexts[i];

context->echo_index = i;
- can_put_echo_skb(skb, netdev, context->echo_index);
++priv->active_tx_contexts;
if (priv->active_tx_contexts >= (int)dev->max_tx_urbs)
netif_stop_queue(netdev);
@@ -553,7 +552,6 @@ static netdev_tx_t kvaser_usb_start_xmit
dev_kfree_skb(skb);
spin_lock_irqsave(&priv->tx_contexts_lock, flags);

- can_free_echo_skb(netdev, context->echo_index);
context->echo_index = dev->max_tx_urbs;
--priv->active_tx_contexts;
netif_wake_queue(netdev);
@@ -564,6 +562,8 @@ static netdev_tx_t kvaser_usb_start_xmit

context->priv = priv;

+ can_put_echo_skb(skb, netdev, context->echo_index);
+
usb_fill_bulk_urb(urb, dev->udev,
usb_sndbulkpipe(dev->udev,
dev->bulk_out->bEndpointAddress),