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Date:   Fri, 28 Oct 2022 16:56:50 +0800
From:   Zhengchao Shao <>
To:     <>, <>,
        <>, <>,
        <>, <>, <>,
CC:     <>, <>,
        <>, <>
Subject: [PATCH net,v2] can: af_can: fix NULL pointer dereference in can_rx_register()

It causes NULL pointer dereference when testing as following:
(a) use syscall(__NR_socket, 0x10ul, 3ul, 0) to create netlink socket.
(b) use syscall(__NR_sendmsg, ...) to create bond link device and vxcan
    link device, and bind vxcan device to bond device (can also use
    ifenslave command to bind vxcan device to bond device).
(c) use syscall(__NR_socket, 0x1dul, 3ul, 1) to create CAN socket.
(d) use syscall(__NR_bind, ...) to bind the bond device to CAN socket.

The bond device invokes the can-raw protocol registration interface to
receive CAN packets. However, ml_priv is not allocated to the dev,
dev_rcv_lists is assigned to NULL in can_rx_register(). In this case,
it will occur the NULL pointer dereference issue.

The following is the stack information:
BUG: kernel NULL pointer dereference, address: 0000000000000008
PGD 122a4067 P4D 122a4067 PUD 1223c067 PMD 0
Oops: 0000 [#1] PREEMPT SMP
RIP: 0010:can_rx_register+0x12d/0x1e0
Call Trace:

Fixes: 4e096a18867a ("net: introduce CAN specific pointer in the struct net_device")
Signed-off-by: Zhengchao Shao <>
Reviewed-by: Marc Kleine-Budde <>
v2: use can_get_ml_priv() instead of open code
 net/can/af_can.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/can/af_can.c b/net/can/af_can.c
index 9503ab10f9b8..98973846f89e 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -450,7 +450,7 @@ int can_rx_register(struct net *net, struct net_device *dev, canid_t can_id,
 	/* insert new receiver  (dev,canid,mask) -> (func,data) */
-	if (dev && dev->type != ARPHRD_CAN)
+	if (dev && (dev->type != ARPHRD_CAN || !can_get_ml_priv(dev)))
 		return -ENODEV;
 	if (dev && !net_eq(net, dev_net(dev)))

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