linux-kernel - Re: [PATCH] hv_netvsc: Fix a memory leak bug

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Date:   Wed, 14 Aug 2019 13:37:17 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Wenwen Wang <wenwen@...uga.edu>
Cc:     "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-hyperv@...r.kernel.org (open list:Hyper-V CORE AND DRIVERS),
        netdev@...r.kernel.org (open list:NETWORKING DRIVERS),
        linux-kernel@...r.kernel.org (open list)
Subject: Re: [PATCH] hv_netvsc: Fix a memory leak bug

On Wed, 14 Aug 2019 15:16:11 -0500
Wenwen Wang <wenwen@...uga.edu> wrote:

> In rndis_filter_device_add(), 'rndis_device' is allocated through kzalloc()
> by invoking get_rndis_device(). In the following execution, if an error
> occurs, the execution will go to the 'err_dev_remv' label. However, the
> allocated 'rndis_device' is not deallocated, leading to a memory leak bug.
> 
> Signed-off-by: Wenwen Wang <wenwen@...uga.edu>
> ---
>  drivers/net/hyperv/rndis_filter.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
> index 317dbe9..ed35085 100644
> --- a/drivers/net/hyperv/rndis_filter.c
> +++ b/drivers/net/hyperv/rndis_filter.c
> @@ -1420,6 +1420,7 @@ struct netvsc_device *rndis_filter_device_add(struct hv_device *dev,
>  
>  err_dev_remv:
>  	rndis_filter_device_remove(dev, net_device);
> +	kfree(rndis_device);
>  	return ERR_PTR(ret);
>  }
>  

The rndis_device is already freed by:

rndis_filter_device_remove
	netvsc_device_remove
		free_netvsc_device_rcu

free_netvsc_device called by rcu

static void free_netvsc_device(struct rcu_head *head)
{
	struct netvsc_device *nvdev
		= container_of(head, struct netvsc_device, rcu);
	int i;

	kfree(nvdev->extension);  << here