can: m_can: m_can_receive_skb(): add missing error handling to can_rx_offload_queue_sorted() call

In commit 1be37d3b ("can: m_can: fix periph RX path: use
rx-offload to ensure skbs are sent from softirq context") the RX path
for peripherals (i.e. SPI based m_can controllers) was converted to
the rx-offload infrastructure. However, the error handling for
can_rx_offload_queue_sorted() was forgotten.
can_rx_offload_queue_sorted() will return with an error if the
internal queue is full.

This patch adds the missing error handling, by increasing the
rx_fifo_errors.

Fixes: 1be37d3b ("can: m_can: fix periph RX path: use rx-offload to ensure skbs are sent from softirq context")
Link: https://lore.kernel.org/r/20210401084515.1455013-1-mkl@pengutronix.deReported-by: coverity-bot <keescook+coverity-bot@chromium.org>
Addresses-Coverity-ID: 1503583 ("Error handling issues")
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Torin Cooper-Bennun <torin@maxiluxsystems.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/m_can/m_can.c

@@ -466,10 +466,17 @@ static void m_can_receive_skb(struct m_can_classdev *cdev,
 			      struct sk_buff *skb,
 			      u32 timestamp)
 {
-	if (cdev->is_peripheral)
-		can_rx_offload_queue_sorted(&cdev->offload, skb, timestamp);
-	else
+	if (cdev->is_peripheral) {
+		struct net_device_stats *stats = &cdev->net->stats;
+		int err;
+
+		err = can_rx_offload_queue_sorted(&cdev->offload, skb,
+						  timestamp);
+		if (err)
+			stats->rx_fifo_errors++;
+	} else {
 		netif_receive_skb(skb);
+	}
 }
 
 static void m_can_read_fifo(struct net_device *dev, u32 rxfs)