From 03f16c5075b22c8902d2af739969e878b0879c94 Mon Sep 17 00:00:00 2001
From: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Date: Wed, 20 Jan 2021 20:41:35 +0900
Subject: [PATCH] can: dev: can_restart: fix use after free bug
Git-commit: 03f16c5075b22c8902d2af739969e878b0879c94
References: git-fixes
Patch-mainline: v5.11-rc5

After calling netif_rx_ni(skb), dereferencing skb is unsafe.
Especially, the can_frame cf which aliases skb memory is accessed
after the netif_rx_ni() in:
      stats->rx_bytes += cf->len;

Reordering the lines solves the issue.

Fixes: 39549eef3587 ("can: CAN Network device driver and Netlink interface")
Link: https://lore.kernel.org/r/20210120114137.200019-2-mailhol.vincent@wanadoo.fr
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/net/can/dev.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -568,11 +568,11 @@ static void can_restart(struct net_devic
 	}
 	cf->can_id |= CAN_ERR_RESTARTED;
 
-	netif_rx_ni(skb);
-
 	stats->rx_packets++;
 	stats->rx_bytes += cf->can_dlc;
 
+	netif_rx_ni(skb);
+
 restart:
 	netdev_dbg(dev, "restarted\n");
 	priv->can_stats.restarts++;