netdev - [PATCH 12/12] can: pcan_usb: don't touch skb after netif

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Date:	Wed, 15 Jul 2015 09:09:49 +0200
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	netdev@...r.kernel.org
Cc:	davem@...emloft.net, linux-can@...r.kernel.org,
	kernel@...gutronix.de, Marc Kleine-Budde <mkl@...gutronix.de>,
	Stephane Grosjean <s.grosjean@...k-system.com>
Subject: [PATCH 12/12] can: pcan_usb: don't touch skb after netif_rx()

There is no guarantee that the skb is in the same state after calling
net_receive_skb() or netif_rx(). It might be freed or reused. Not really
harmful as its a read access, except you turn on the proper debugging options
which catch a use after free.

Cc: Stephane Grosjean <s.grosjean@...k-system.com>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 drivers/net/can/usb/peak_usb/pcan_usb.c     | 7 +++----
 drivers/net/can/usb/peak_usb/pcan_usb_pro.c | 4 ++--
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/net/can/usb/peak_usb/pcan_usb.c b/drivers/net/can/usb/peak_usb/pcan_usb.c
index 72427f21edff..6b94007ae052 100644
--- a/drivers/net/can/usb/peak_usb/pcan_usb.c
+++ b/drivers/net/can/usb/peak_usb/pcan_usb.c
@@ -526,9 +526,9 @@ static int pcan_usb_decode_error(struct pcan_usb_msg_context *mc, u8 n,
 		hwts->hwtstamp = timeval_to_ktime(tv);
 	}
 
-	netif_rx(skb);
 	mc->netdev->stats.rx_packets++;
 	mc->netdev->stats.rx_bytes += cf->can_dlc;
+	netif_rx(skb);
 
 	return 0;
 }
@@ -659,12 +659,11 @@ static int pcan_usb_decode_data(struct pcan_usb_msg_context *mc, u8 status_len)
 	hwts = skb_hwtstamps(skb);
 	hwts->hwtstamp = timeval_to_ktime(tv);
 
-	/* push the skb */
-	netif_rx(skb);
-
 	/* update statistics */
 	mc->netdev->stats.rx_packets++;
 	mc->netdev->stats.rx_bytes += cf->can_dlc;
+	/* push the skb */
+	netif_rx(skb);
 
 	return 0;
 
diff --git a/drivers/net/can/usb/peak_usb/pcan_usb_pro.c b/drivers/net/can/usb/peak_usb/pcan_usb_pro.c
index dec51717635e..7d61b3279798 100644
--- a/drivers/net/can/usb/peak_usb/pcan_usb_pro.c
+++ b/drivers/net/can/usb/peak_usb/pcan_usb_pro.c
@@ -553,9 +553,9 @@ static int pcan_usb_pro_handle_canmsg(struct pcan_usb_pro_interface *usb_if,
 	hwts = skb_hwtstamps(skb);
 	hwts->hwtstamp = timeval_to_ktime(tv);
 
-	netif_rx(skb);
 	netdev->stats.rx_packets++;
 	netdev->stats.rx_bytes += can_frame->can_dlc;
+	netif_rx(skb);
 
 	return 0;
 }
@@ -670,9 +670,9 @@ static int pcan_usb_pro_handle_error(struct pcan_usb_pro_interface *usb_if,
 	peak_usb_get_ts_tv(&usb_if->time_ref, le32_to_cpu(er->ts32), &tv);
 	hwts = skb_hwtstamps(skb);
 	hwts->hwtstamp = timeval_to_ktime(tv);
-	netif_rx(skb);
 	netdev->stats.rx_packets++;
 	netdev->stats.rx_bytes += can_frame->can_dlc;
+	netif_rx(skb);
 
 	return 0;
 }
-- 
2.1.4

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