linux-kernel - Re: [PATCH 4.3 34/71] vrf: fix double free and memory corruption on register

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Date:	Mon, 14 Dec 2015 21:40:04 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	David Ahern <dsa@...ulusnetworks.com>
Cc:	Ben Hutchings <ben@...adent.org.uk>, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org,
	Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 4.3 34/71] vrf: fix double free and memory corruption on
 register_netdevice failure

On Mon, Dec 14, 2015 at 11:59:15AM -0700, David Ahern wrote:
> On 12/14/15 10:45 AM, Ben Hutchings wrote:
> >On Sat, 2015-12-12 at 12:05 -0800, Greg Kroah-Hartman wrote:
> >>4.3-stable review patch.  If anyone has any objections, please let me
> >>know.
> >>
> >>------------------
> >>
> >>From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
> >>
> >>[ Upstream commit 7f109f7cc37108cba7243bc832988525b0d85909 ]
> >[...]
> >>--- a/drivers/net/vrf.c
> >>+++ b/drivers/net/vrf.c
> >>@@ -581,7 +581,6 @@ static int vrf_newlink(struct net *src_n
> >>  {
> >>  	struct net_vrf *vrf = netdev_priv(dev);
> >>  	struct net_vrf_dev *vrf_ptr;
> >>-	int err;
> >>
> >>  	if (!data || !data[IFLA_VRF_TABLE])
> >>  		return -EINVAL;
> >>@@ -590,26 +589,16 @@ static int vrf_newlink(struct net *src_n
> >>
> >>  	dev->priv_flags |= IFF_VRF_MASTER;
> >>
> >>-	err = -ENOMEM;
> >>  	vrf_ptr = kmalloc(sizeof(*dev->vrf_ptr), GFP_KERNEL);
> >>  	if (!vrf_ptr)
> >>-		goto out_fail;
> >>+		return -ENOMEM;
> >>
> >>  	vrf_ptr->ifindex = dev->ifindex;
> >>  	vrf_ptr->tb_id = vrf->tb_id;
> >>
> >>-	err = register_netdevice(dev);
> >>-	if (err < 0)
> >>-		goto out_fail;
> >>-
> >>  	rcu_assign_pointer(dev->vrf_ptr, vrf_ptr);
> >>
> >>-	return 0;
> >>-
> >>-out_fail:
> >>-	kfree(vrf_ptr);
> >>-	free_netdev(dev);
> >>-	return err;
> >>+	return register_netdev(dev);
> >>  }
> >>
> >>  static size_t vrf_nl_getsize(const struct net_device *dev)
> >
> >This leaks *dev->vrf_ptr if register_netdevice() fails.  (This bug does
> >not exist in the mainline version, as net_device::vrf_ptr no longer
> >exists there.)
> 
> Good catch. The backport just needs to drop the free_netdev call:
> 
> diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
> index 488c6f50df73..374feba02565 100644
> --- a/drivers/net/vrf.c
> +++ b/drivers/net/vrf.c
> @@ -608,7 +608,6 @@ static int vrf_newlink(struct net *src_net, struct
> net_device *dev,
> 
>  out_fail:
>         kfree(vrf_ptr);
> -       free_netdev(dev);
>         return err;
>  }

I don't understand, can someone send me a patch on top of what I have
already applied to resolve this?  This patch doesn't make much sense in
any context...

thanks,

greg k-h
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