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Subject[PATCH 4.17 41/66] vxlan: fix default fdb entry netlink notify ordering during netdev create
Date
4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Roopa Prabhu <roopa@cumulusnetworks.com>

[ Upstream commit e99465b952861533d9ba748fdbecc96d9a36da3e ]

Problem:
In vxlan_newlink, a default fdb entry is added before register_netdev.
The default fdb creation function also notifies user-space of the
fdb entry on the vxlan device which user-space does not know about yet.
(RTM_NEWNEIGH goes before RTM_NEWLINK for the same ifindex).

This patch fixes the user-space netlink notification ordering issue
with the following changes:
- decouple fdb notify from fdb create.
- Move fdb notify after register_netdev.
- Call rtnl_configure_link in vxlan newlink handler to notify
userspace about the newlink before fdb notify and
hence avoiding the user-space race.

Fixes: afbd8bae9c79 ("vxlan: add implicit fdb entry for default destination")
Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/vxlan.c | 29 +++++++++++++++++++++--------
1 file changed, 21 insertions(+), 8 deletions(-)

--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -3190,6 +3190,7 @@ static int __vxlan_dev_create(struct net
{
struct vxlan_net *vn = net_generic(net, vxlan_net_id);
struct vxlan_dev *vxlan = netdev_priv(dev);
+ struct vxlan_fdb *f = NULL;
int err;

err = vxlan_dev_configure(net, dev, conf, false, extack);
@@ -3200,27 +3201,38 @@ static int __vxlan_dev_create(struct net

/* create an fdb entry for a valid default destination */
if (!vxlan_addr_any(&vxlan->default_dst.remote_ip)) {
- err = vxlan_fdb_update(vxlan, all_zeros_mac,
+ err = vxlan_fdb_create(vxlan, all_zeros_mac,
&vxlan->default_dst.remote_ip,
NUD_REACHABLE | NUD_PERMANENT,
- NLM_F_EXCL | NLM_F_CREATE,
vxlan->cfg.dst_port,
vxlan->default_dst.remote_vni,
vxlan->default_dst.remote_vni,
vxlan->default_dst.remote_ifindex,
- NTF_SELF);
+ NTF_SELF, &f);
if (err)
return err;
}

err = register_netdevice(dev);
+ if (err)
+ goto errout;
+
+ err = rtnl_configure_link(dev, NULL);
if (err) {
- vxlan_fdb_delete_default(vxlan, vxlan->default_dst.remote_vni);
- return err;
+ unregister_netdevice(dev);
+ goto errout;
}

+ /* notify default fdb entry */
+ if (f)
+ vxlan_fdb_notify(vxlan, f, first_remote_rtnl(f), RTM_NEWNEIGH);
+
list_add(&vxlan->next, &vn->vxlan_list);
return 0;
+errout:
+ if (f)
+ vxlan_fdb_destroy(vxlan, f, false);
+ return err;
}

static int vxlan_nl2conf(struct nlattr *tb[], struct nlattr *data[],
@@ -3449,6 +3461,7 @@ static int vxlan_changelink(struct net_d
struct vxlan_rdst *dst = &vxlan->default_dst;
struct vxlan_rdst old_dst;
struct vxlan_config conf;
+ struct vxlan_fdb *f = NULL;
int err;

err = vxlan_nl2conf(tb, data,
@@ -3474,19 +3487,19 @@ static int vxlan_changelink(struct net_d
old_dst.remote_ifindex, 0);

if (!vxlan_addr_any(&dst->remote_ip)) {
- err = vxlan_fdb_update(vxlan, all_zeros_mac,
+ err = vxlan_fdb_create(vxlan, all_zeros_mac,
&dst->remote_ip,
NUD_REACHABLE | NUD_PERMANENT,
- NLM_F_CREATE | NLM_F_APPEND,
vxlan->cfg.dst_port,
dst->remote_vni,
dst->remote_vni,
dst->remote_ifindex,
- NTF_SELF);
+ NTF_SELF, &f);
if (err) {
spin_unlock_bh(&vxlan->hash_lock);
return err;
}
+ vxlan_fdb_notify(vxlan, f, first_remote_rtnl(f), RTM_NEWNEIGH);
}
spin_unlock_bh(&vxlan->hash_lock);
}

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