[PATCH AUTOSEL 4.14 052/127] vxlan: Fix error path in __vxlan_dev_create()

Sasha Levin
2019-11-22T06:10:47Z

From: Petr Machata <petrm@mellanox.com>

[ Upstream commit 6db9246871394b3a136cd52001a0763676563840 ]

When a failure occurs in rtnl_configure_link(), the current code
calls unregister_netdevice() to roll back the earlier call to
register_netdevice(), and jumps to errout, which calls
vxlan_fdb_destroy().

However unregister_netdevice() calls transitively ndo_uninit, which is
vxlan_uninit(), and that already takes care of deleting the default FDB
entry by calling vxlan_fdb_delete_default(). Since the entry added
earlier in __vxlan_dev_create() is exactly the default entry, the
cleanup code in the errout block always leads to double free and thus a
panic.

Besides, since vxlan_fdb_delete_default() always destroys the FDB entry
with notification enabled, the deletion of the default entry is notified
even before the addition was notified.

Instead, move the unregister_netdevice() call after the manual destroy,
which solves both problems.

Fixes: 0241b836732f ("vxlan: fix default fdb entry netlink notify ordering during netdev create")
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/vxlan.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 6d26bbd190dd6..153a81ece9fe4 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -3217,6 +3217,7 @@ static int __vxlan_dev_create(struct net *net, struct net_device *dev,
struct vxlan_net *vn = net_generic(net, vxlan_net_id);
struct vxlan_dev *vxlan = netdev_priv(dev);
struct vxlan_fdb *f = NULL;
+ bool unregister = false;
int err;

err = vxlan_dev_configure(net, dev, conf, false, extack);
@@ -3242,12 +3243,11 @@ static int __vxlan_dev_create(struct net *net, struct net_device *dev,
err = register_netdevice(dev);
if (err)
goto errout;
+ unregister = true;

err = rtnl_configure_link(dev, NULL);
- if (err) {
- unregister_netdevice(dev);
+ if (err)
goto errout;
- }

/* notify default fdb entry */
if (f)
@@ -3255,9 +3255,16 @@ static int __vxlan_dev_create(struct net *net, struct net_device *dev,

list_add(&vxlan->next, &vn->vxlan_list);
return 0;
+
errout:
+ /* unregister_netdevice() destroys the default FDB entry with deletion
+ * notification. But the addition notification was not sent yet, so
+ * destroy the entry by hand here.
+ */
if (f)
vxlan_fdb_destroy(vxlan, f, false);
+ if (unregister)
+ unregister_netdevice(dev);
return err;
}

--
2.20.1