netdev - Re: [PATCH] net: bridge: fix a memory leak in __vlan

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Date:   Sun, 14 Oct 2018 18:33:42 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     Li RongQing <lirongqing@...du.com>, netdev@...r.kernel.org
Cc:     bridge@...ts.linux-foundation.org,
        Roopa Prabhu <roopa@...ulusnetworks.com>
Subject: Re: [PATCH] net: bridge: fix a memory leak in __vlan_add

On 14/10/2018 06:21, Li RongQing wrote:
> After per-port vlan stats, vlan stats should be released
> when fail to add vlan
> 
> Fixes: 9163a0fc1f0c0 ("net: bridge: add support for per-port vlan stats")
> cc: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
> Signed-off-by: Zhang Yu <zhangyu31@...du.com>
> Signed-off-by: Li RongQing <lirongqing@...du.com>
> ---
>  net/bridge/br_vlan.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
> index 9b707234e4ae..e08e269041dd 100644
> --- a/net/bridge/br_vlan.c
> +++ b/net/bridge/br_vlan.c
> @@ -305,6 +305,10 @@ static int __vlan_add(struct net_bridge_vlan *v, u16 flags)
>  		if (masterv) {
>  			br_vlan_put_master(masterv);
>  			v->brvlan = NULL;
> +
> +			if (masterv->stats != v->stats && v->stats)
> +				free_percpu(v->stats);
> +			v->stats = NULL;
>  		}
>  	} else {
>  		br_switchdev_port_vlan_del(dev, v->vid);
> 

Hi,
Good catch, but the patch doesn't fix the bug entirely. The problem is that masterv can be
created just for this vlan and the br_vlan_put_master() above can free it, so we can
check a pointer that's not really up-to-date (and thus again leak memory).
You should move the new code above the br_vlan_put_master() call.

Also please tag the proper branch, this is for net-next, and CC all bridge
maintainers (added Roopa).

Thank you,
 Nik