can: m_can: m_can_tx_work_queue(): fix tx_skb race condition

The m_can_start_xmit() function checks if the cdev->tx_skb is NULL and
returns with NETDEV_TX_BUSY in case tx_sbk is not NULL.

There is a race condition in the m_can_tx_work_queue(), where first
the skb is send to the driver and then the case tx_sbk is set to NULL.
A TX complete IRQ might come in between and wake the queue, which
results in tx_skb not being cleared yet.

Fixes: f524f829b75a ("can: m_can: Create a m_can platform framework")
Tested-by: Torin Cooper-Bennun <torin@maxiluxsystems.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index 34073cd..3cf6de2 100644 (file)
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -1562,6 +1562,8 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
        int i;
        int putidx;
 
+       cdev->tx_skb = NULL;
+
        /* Generate ID field for TX buffer Element */
        /* Common to all supported M_CAN versions */
        if (cf->can_id & CAN_EFF_FLAG) {
@@ -1678,7 +1680,6 @@ static void m_can_tx_work_queue(struct work_struct *ws)
                                                   tx_work);
 
        m_can_tx_handler(cdev);
-       cdev->tx_skb = NULL;
 }
 
 static netdev_tx_t m_can_start_xmit(struct sk_buff *skb,