linux-kernel - Re: [PATCH linux-next 4/4] net/dsa: fix possible NULL pointer dereference in dsa_slave_get

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Date:	Tue, 14 Apr 2015 08:55:24 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Honggang Li <honli@...hat.com>
Cc:	roland@...nel.org, sean.hefty@...el.com, hal.rosenstock@...il.com,
	kaber@...sh.net, 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, 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 4/4] net/dsa: fix possible NULL pointer
 dereference in dsa_slave_get_iflink

On Tue, Apr 14, 2015 at 11:20:17PM +0800, Honggang Li wrote:
> Signed-off-by: Honggang Li <honli@...hat.com>
> ---
>  net/dsa/slave.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> index 827cda56..070b599 100644
> --- a/net/dsa/slave.c
> +++ b/net/dsa/slave.c
> @@ -59,7 +59,10 @@ static int dsa_slave_get_iflink(const struct net_device *dev)
>  {
>  	struct dsa_slave_priv *p = netdev_priv(dev);
>  
> -	return p->parent->dst->master_netdev->ifindex;
> +	if (p && p->parent && p->parent->dst && p->parent->dst->master_netdev)
> +		return p->parent->dst->master_netdev->ifindex;
> +	else
> +		return 0;
>  }
I would expect some explanation why you believe that any of those pointers
can be NULL.

Guenter
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