linux-kernel - Re: [PATCH linux-next 3/4] macvlan: fix possible NULL pointer dereference in macvlan_dev_get

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Message-ID: <20150414152626.GJ7874@acer.localdomain>
Date:	Tue, 14 Apr 2015 16:26:27 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Honggang Li <honli@...hat.com>
Cc:	roland@...nel.org, sean.hefty@...el.com, hal.rosenstock@...il.com,
	davem@...emloft.net, alex.estrin@...el.com, dledford@...hat.com,
	edumazet@...gle.com, erezsh@...lanox.com,
	nicolas.dichtel@...nd.com, maheshb@...gle.com, jbenc@...hat.com,
	ebiederm@...ssion.com, elfring@...rs.sourceforge.net,
	f.fainelli@...il.com, linux@...ck-us.net, andrew@...n.ch,
	sfeldma@...il.com, alexander.h.duyck@...el.com,
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH linux-next 3/4] macvlan: fix possible NULL pointer
 dereference in macvlan_dev_get_iflink

On 14.04, Honggang Li wrote:
> Signed-off-by: Honggang Li <honli@...hat.com>
> ---
>  drivers/net/macvlan.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
> index b227a13..1e59f39 100644
> --- a/drivers/net/macvlan.c
> +++ b/drivers/net/macvlan.c
> @@ -998,7 +998,9 @@ static int macvlan_dev_get_iflink(const struct net_device *dev)
>  {
>  	struct macvlan_dev *vlan = netdev_priv(dev);
>  
> -	return vlan->lowerdev->ifindex;
> +	if (vlan && vlan->lowerdev)
> +		return vlan->lowerdev->ifindex;

That is completely useless. vlan (=netdev_priv) can not be NULL as
netdev_priv() never returns NULL and vlan->lowerdev is always valid
because a macvlan wouldn't make much sense otherwise.
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