linux-kernel - Re: [PATCH v4 01/04] can: kvaser_usb: Don't dereference skb after a netif

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Message-ID: <20150111201116.GB8855@linux>
Date:	Sun, 11 Jan 2015 15:11:16 -0500
From:	"Ahmed S. Darwish" <darwish.07@...il.com>
To:	Olivier Sobrie <olivier@...rie.be>,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	Wolfgang Grandegger <wg@...ndegger.com>,
	Marc Kleine-Budde <mkl@...gutronix.de>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Linux-CAN <linux-can@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 01/04] can: kvaser_usb: Don't dereference skb after a
 netif_rx() devices

From: Ahmed S. Darwish <ahmed.darwish@...eo.com>

We should not touch the packet after a netif_rx: it might
get freed behind our back.

Suggested-by: Marc Kleine-Budde <mkl@...gutronix.de>
Signed-off-by: Ahmed S. Darwish <ahmed.darwish@...eo.com>
---
 drivers/net/can/usb/kvaser_usb.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/net/can/usb/kvaser_usb.c b/drivers/net/can/usb/kvaser_usb.c
index cc7bfc0..c32cd61 100644
--- a/drivers/net/can/usb/kvaser_usb.c
+++ b/drivers/net/can/usb/kvaser_usb.c
@@ -520,10 +520,10 @@ static void kvaser_usb_tx_acknowledge(const struct kvaser_usb *dev,
 		skb = alloc_can_err_skb(priv->netdev, &cf);
 		if (skb) {
 			cf->can_id |= CAN_ERR_RESTARTED;
-			netif_rx(skb);
 
 			stats->rx_packets++;
 			stats->rx_bytes += cf->can_dlc;
+			netif_rx(skb);
 		} else {
 			netdev_err(priv->netdev,
 				   "No memory left for err_skb\n");
@@ -770,10 +770,9 @@ static void kvaser_usb_rx_error(const struct kvaser_usb *dev,
 
 	priv->can.state = new_state;
 
-	netif_rx(skb);
-
 	stats->rx_packets++;
 	stats->rx_bytes += cf->can_dlc;
+	netif_rx(skb);
 }
 
 static void kvaser_usb_rx_can_err(const struct kvaser_usb_net_priv *priv,
@@ -805,10 +804,9 @@ static void kvaser_usb_rx_can_err(const struct kvaser_usb_net_priv *priv,
 		stats->rx_over_errors++;
 		stats->rx_errors++;
 
-		netif_rx(skb);
-
 		stats->rx_packets++;
 		stats->rx_bytes += cf->can_dlc;
+		netif_rx(skb);
 	}
 }
 
@@ -887,10 +885,9 @@ static void kvaser_usb_rx_can_msg(const struct kvaser_usb *dev,
 			       cf->can_dlc);
 	}
 
-	netif_rx(skb);
-
 	stats->rx_packets++;
 	stats->rx_bytes += cf->can_dlc;
+	netif_rx(skb);
 }
 
 static void kvaser_usb_start_chip_reply(const struct kvaser_usb *dev,
-- 
1.9.1

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