netdev - Re: [PATCH] net-bridge: fix unsafe dereference of potential null ptr in __vlan

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Message-ID: <a7cef78d-81fb-7de6-1f6e-a948cca1b46b@blackwall.org>
Date:   Fri, 17 Feb 2023 15:53:43 +0200
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     Alexander Sapozhnikov <alsp705@...il.com>,
        Roopa Prabhu <roopa@...dia.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        bridge@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH] net-bridge: fix unsafe dereference of potential null ptr
 in __vlan_del()

On 17/02/2023 15:16, Alexander Sapozhnikov wrote:
> After having been compared to NULL value at br_vlan.c:399,
> pointer 'p' is passed as 1st parameter in call to function
> 'nbp_vlan_set_vlan_dev_state' at br_vlan.c:420, 
> where it is dereferenced at br_vlan.c:1722.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Alexander Sapozhnikov <alsp705@...il.com>
> ---
>  net/bridge/br_vlan.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
> index bc75fa1e4666..87091e270adf 100644
> --- a/net/bridge/br_vlan.c
> +++ b/net/bridge/br_vlan.c
> @@ -417,7 +417,8 @@ static int __vlan_del(struct net_bridge_vlan *v)
>  		rhashtable_remove_fast(&vg->vlan_hash, &v->vnode,
>  				       br_vlan_rht_params);
>  		__vlan_del_list(v);
> -		nbp_vlan_set_vlan_dev_state(p, v->vid);
> +		if (p)
> +			nbp_vlan_set_vlan_dev_state(p, v->vid);
>  		br_multicast_toggle_one_vlan(v, false);
>  		br_multicast_port_ctx_deinit(&v->port_mcast_ctx);
>  		call_rcu(&v->rcu, nbp_vlan_rcu_free);

This cannot happen, read the code more carefully.
If you have a trace or have hit a bug, please provide the log.
Thanks,

Nacked-by: Nikolay Aleksandrov <razor@...ckwall.org>