Re: [PATCH 4.3 34/71] vrf: fix double free and memory corruption on register_netdevice failure

From: David Ahern
Date: Mon Dec 14 2015 - 13:59:24 EST


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@xxxxxxxxxxxxxxxxxxx>

[ 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;
}



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