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Date:   Fri, 28 Oct 2022 09:33:39 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Zhengchao Shao <shaozhengchao@...wei.com>
Cc:     linux-can@...r.kernel.org, netdev@...r.kernel.org,
        socketcan@...tkopp.net, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, linux@...pel-privat.de,
        weiyongjun1@...wei.com, yuehaibing@...wei.com
Subject: Re: [PATCH net] can: af_can: fix NULL pointer dereference in
 can_rx_register()

On 28.10.2022 11:33:42, Zhengchao Shao wrote:
> 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:
> <TASK>
> raw_enable_filters+0x8d/0x120
> raw_enable_allfilters+0x3b/0x130
> raw_bind+0x118/0x4f0
> __sys_bind+0x163/0x1a0
> __x64_sys_bind+0x1e/0x30
> do_syscall_64+0x35/0x80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
> </TASK>
> 
> Fixes: 4e096a18867a ("net: introduce CAN specific pointer in the struct net_device")
> Signed-off-by: Zhengchao Shao <shaozhengchao@...wei.com>
> ---
>  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..ef2697f3ebcb 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 || dev->ml_priv_type != ML_PRIV_CAN))

You can use the helper function: can_get_ml_priv() instead of open
coding the check.

Reviewed-by: Marc Kleine-Budde <mkl@...gutronix.de>

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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