netdev - [PATCH v4 3/3] can: peak_usb: fix use after free bugs

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Date:   Wed, 20 Jan 2021 20:41:37 +0900
From:   Vincent Mailhol <mailhol.vincent@...adoo.fr>
To:     Marc Kleine-Budde <mkl@...gutronix.de>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        linux-can@...r.kernel.org
Cc:     netdev@...r.kernel.org, Wolfgang Grandegger <wg@...ndegger.com>,
        Stephane Grosjean <s.grosjean@...k-system.com>,
        Loris Fauster <loris.fauster@...ontrol.com>,
        Alejandro Concepcion Rodriguez <alejandro@...ro.eu>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Vincent Mailhol <mailhol.vincent@...adoo.fr>
Subject: [PATCH v4 3/3] can: peak_usb: fix use after free bugs

After calling peak_usb_netif_rx_ni(skb), dereferencing skb is unsafe.
Especially, the can_frame cf which aliases skb memory is accessed
after the peak_usb_netif_rx_ni().

Reordering the lines solves the issue.

Fixes: 0a25e1f4f185 ("can: peak_usb: add support for PEAK new CANFD USB adapters")
Signed-off-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>
---
 drivers/net/can/usb/peak_usb/pcan_usb_fd.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/can/usb/peak_usb/pcan_usb_fd.c b/drivers/net/can/usb/peak_usb/pcan_usb_fd.c
index 61631f4fd92a..f347ecc79aef 100644
--- a/drivers/net/can/usb/peak_usb/pcan_usb_fd.c
+++ b/drivers/net/can/usb/peak_usb/pcan_usb_fd.c
@@ -514,11 +514,11 @@ static int pcan_usb_fd_decode_canmsg(struct pcan_usb_fd_if *usb_if,
 	else
 		memcpy(cfd->data, rm->d, cfd->len);
 
-	peak_usb_netif_rx(skb, &usb_if->time_ref, le32_to_cpu(rm->ts_low));
-
 	netdev->stats.rx_packets++;
 	netdev->stats.rx_bytes += cfd->len;
 
+	peak_usb_netif_rx(skb, &usb_if->time_ref, le32_to_cpu(rm->ts_low));
+
 	return 0;
 }
 
@@ -580,11 +580,11 @@ static int pcan_usb_fd_decode_status(struct pcan_usb_fd_if *usb_if,
 	if (!skb)
 		return -ENOMEM;
 
-	peak_usb_netif_rx(skb, &usb_if->time_ref, le32_to_cpu(sm->ts_low));
-
 	netdev->stats.rx_packets++;
 	netdev->stats.rx_bytes += cf->len;
 
+	peak_usb_netif_rx(skb, &usb_if->time_ref, le32_to_cpu(sm->ts_low));
+
 	return 0;
 }
 
-- 
2.26.2