can: m_can: m_can_read_fifo: fix memory leak in error branch

In m_can_read_fifo(), if the second call to m_can_fifo_read() fails,
the function jump to the out_fail label and returns without calling
m_can_receive_skb(). This means that the skb previously allocated by
alloc_can_skb() is not freed. In other terms, this is a memory leak.

This patch adds a goto label to destroy the skb if an error occurs.

Issue was found with GCC -fanalyzer, please follow the link below for
details.

Fixes: e39381770ec9 ("can: m_can: Disable IRQs on FIFO bus errors")
Link: https://lore.kernel.org/all/20211107050755.70655-1-mailhol.vincent@wanadoo.fr
Cc: stable@vger.kernel.org
Cc: Matt Kline <matt@bitbashing.io>
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
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 91be87c..e330b4c 100644 (file)
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -517,7 +517,7 @@ static int m_can_read_fifo(struct net_device *dev, u32 rxfs)
                err = m_can_fifo_read(cdev, fgi, M_CAN_FIFO_DATA,
                                      cf->data, DIV_ROUND_UP(cf->len, 4));
                if (err)
-                       goto out_fail;
+                       goto out_free_skb;
        }
 
        /* acknowledge rx fifo 0 */
@@ -532,6 +532,8 @@ static int m_can_read_fifo(struct net_device *dev, u32 rxfs)
 
        return 0;
 
+out_free_skb:
+       kfree_skb(skb);
 out_fail:
        netdev_err(dev, "FIFO read returned %d\n", err);
        return err;