Subject: Re: [PATCH net] bridge: Fix crash with vlan filtering and tcpdump

From: Sergei Shtylyov <[email-masked]>
Date: Fri, 03 Jan 2014 21:06:37 +0300

Hello.

On 01/03/2014 07:12 PM, Vlad Yasevich wrote:

> When the vlan filtering is enabled on the bridge, but
> the filter is not configured on the bridge device itself,
> running tcpdump on the bridge device will result in a
> an Ooops with NULL pointer dereference.  The reason
> is that br_pass_frame_up() will bypass the vlan
> check because promisc flag is set.  It will then try
> to get the table pointer and process the packet based
> on the table.  Since the table pointer is NULL, we oops.
> Catch this special condition in br_handle_vlan().

> Reported-by: Toshiaki Makita <[email-masked]>
> CC: Toshiaki Makita <[email-masked]>
> Signed-off-by: Vlad Yasevich <[email-masked]>
[...]

> diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
> index af5ebd1..ea0c29b 100644
> --- a/net/bridge/br_vlan.c
> +++ b/net/bridge/br_vlan.c
> @@ -144,6 +144,18 @@ struct sk_buff *br_handle_vlan(struct net_bridge *br,
>   	if (!br->vlan_enabled)
>   		goto out;
>
> +	/* Vlan filter table must be configrured at this point.  The

    Only "configured".

> +	 * only exception is the bridge is set in promisc mode and the
> +	 * packet is destined for the bridge device.  In this case
> +	 * pass the packet as is.
> +	 */
> +	if (!pv) {
> +       		if ((br->dev->flags & IFF_PROMISC) && skb->dev == br->dev)

    You've indented this *if* too much.

> +			goto out;
> +		else
> +			BUG();
> +	}
> +

WBR, Sergei