netdev - Re: [PATCH linux-next 1/4] infiniband/ipoib: fix possible NULL pointer dereference in ipoib_get

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Date:	Wed, 15 Apr 2015 13:16:40 +0800
From:	Honggang LI <honli@...hat.com>
To:	Erez Shitrit <erezsh@....mellanox.co.il>
Cc:	Roland Dreier <roland@...nel.org>, sean.hefty@...el.com,
	hal.rosenstock@...il.com, kaber@...sh.net, davem@...emloft.net,
	Alex Estrin <alex.estrin@...el.com>,
	Doug Ledford <dledford@...hat.com>, edumazet@...gle.com,
	Erez Shitrit <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-rdma@...r.kernel.org>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH linux-next 1/4] infiniband/ipoib: fix possible NULL
 pointer dereference in ipoib_get_iflink

On Tue, Apr 14, 2015 at 07:30:03PM +0300, Erez Shitrit wrote:
> > @@ -846,7 +846,10 @@ static int ipoib_get_iflink(const struct net_device *dev)
> >  {
> >         struct ipoib_dev_priv *priv = netdev_priv(dev);
> >
> > -       return priv->parent->ifindex;
> > +       if (priv && priv->parent)
> > +               return priv->parent->ifindex;
> > +       else
> > +               return 0;
> This will make parent interface to return 0 instead of its own ifindex.
> I would suggest write something like that:
> 
> +       /* parent interface */
> +       if (!test_bit(IPOIB_FLAG_SUBINTERFACE, &priv->flags))
> +               return dev->ifindex;
> +

Hi, Erez

Sorry for delay of reply. It was about 01:00 in the morning, so I
went into bed. And thank you for the suggestion. You are right. After 
insert some printk statements in the driver, I confirmed it.

---------------------- console log --------------------
ipoib_get_iflink: priv = ffff880275e487c0, priv->parent = (null), priv->flags = 0x20f, dev = ffff880275e48000, dev->name = qib_ib1
qib_ib1, test_bit(IPOIB_FLAG_SUBINTERFACE, &priv->flags) = 0
qib_ib1, idev->ifindex = 14

ipoib_get_iflink: priv = ffff8802765d27c0, priv->parent = (null), priv->flags = 0x20f, dev = ffff8802765d2000, dev->name = qib_ib2
qib_ib2, test_bit(IPOIB_FLAG_SUBINTERFACE, &priv->flags) = 0
qib_ib2, idev->ifindex = 15

ipoib_get_iflink: priv = ffff8804741a47c0, priv->parent = ffff880275e48000, priv->flags = 0x224, dev = ffff8804741a4000, dev->name = qib_ib1.8003
qib_ib1.8003, test_bit(IPOIB_FLAG_SUBINTERFACE, &priv->flags) = 1
qib_ib1.8003, idev->ifindex = 16

---------------------- console log --------------------

I will rewrite the patch.

> +       /* child/vlan interface */
> +       if (!priv->parent)
> +               return -1;
> +
>         return priv->parent->ifindex;
> 
> Thanks,
> Erez.
> 
> >  }
> >
> >  static u32 ipoib_addr_hash(struct ipoib_neigh_hash *htbl, u8 *daddr)
> > --
> > 1.8.3.1
> >
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