[PATCH 5.10 068/130] net: mpls: Fix notifications when deleting a device

Greg Kroah-Hartman
2021-12-06T15:31:22Z

From: Benjamin Poirier <bpoirier@nvidia.com>

commit 7d4741eacdefa5f0475431645b56baf00784df1f upstream.

There are various problems related to netlink notifications for mpls route
changes in response to interfaces being deleted:
* delete interface of only nexthop
DELROUTE notification is missing RTA_OIF attribute
* delete interface of non-last nexthop
NEWROUTE notification is missing entirely
* delete interface of last nexthop
DELROUTE notification is missing nexthop

All of these problems stem from the fact that existing routes are modified
in-place before sending a notification. Restructure mpls_ifdown() to avoid
changing the route in the DELROUTE cases and to create a copy in the
NEWROUTE case.

Fixes: f8efb73c97e2 ("mpls: multipath route support")
Signed-off-by: Benjamin Poirier <bpoirier@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/mpls/af_mpls.c | 68 ++++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 52 insertions(+), 16 deletions(-)

--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -1490,22 +1490,52 @@ static void mpls_dev_destroy_rcu(struct
kfree(mdev);
}

-static void mpls_ifdown(struct net_device *dev, int event)
+static int mpls_ifdown(struct net_device *dev, int event)
{
struct mpls_route __rcu **platform_label;
struct net *net = dev_net(dev);
- u8 alive, deleted;
unsigned index;

platform_label = rtnl_dereference(net->mpls.platform_label);
for (index = 0; index < net->mpls.platform_labels; index++) {
struct mpls_route *rt = rtnl_dereference(platform_label[index]);
+ bool nh_del = false;
+ u8 alive = 0;

if (!rt)
continue;

- alive = 0;
- deleted = 0;
+ if (event == NETDEV_UNREGISTER) {
+ u8 deleted = 0;
+
+ for_nexthops(rt) {
+ struct net_device *nh_dev =
+ rtnl_dereference(nh->nh_dev);
+
+ if (!nh_dev || nh_dev == dev)
+ deleted++;
+ if (nh_dev == dev)
+ nh_del = true;
+ } endfor_nexthops(rt);
+
+ /* if there are no more nexthops, delete the route */
+ if (deleted == rt->rt_nhn) {
+ mpls_route_update(net, index, NULL, NULL);
+ continue;
+ }
+
+ if (nh_del) {
+ size_t size = sizeof(*rt) + rt->rt_nhn *
+ rt->rt_nh_size;
+ struct mpls_route *orig = rt;
+
+ rt = kmalloc(size, GFP_KERNEL);
+ if (!rt)
+ return -ENOMEM;
+ memcpy(rt, orig, size);
+ }
+ }
+
change_nexthops(rt) {
unsigned int nh_flags = nh->nh_flags;

@@ -1529,16 +1559,15 @@ static void mpls_ifdown(struct net_devic
next:
if (!(nh_flags & (RTNH_F_DEAD | RTNH_F_LINKDOWN)))
alive++;
- if (!rtnl_dereference(nh->nh_dev))
- deleted++;
} endfor_nexthops(rt);

WRITE_ONCE(rt->rt_nhn_alive, alive);

- /* if there are no more nexthops, delete the route */
- if (event == NETDEV_UNREGISTER && deleted == rt->rt_nhn)
- mpls_route_update(net, index, NULL, NULL);
+ if (nh_del)
+ mpls_route_update(net, index, rt, NULL);
}
+
+ return 0;
}

static void mpls_ifup(struct net_device *dev, unsigned int flags)
@@ -1596,8 +1625,12 @@ static int mpls_dev_notify(struct notifi
return NOTIFY_OK;

switch (event) {
+ int err;
+
case NETDEV_DOWN:
- mpls_ifdown(dev, event);
+ err = mpls_ifdown(dev, event);
+ if (err)
+ return notifier_from_errno(err);
break;
case NETDEV_UP:
flags = dev_get_flags(dev);
@@ -1608,13 +1641,18 @@ static int mpls_dev_notify(struct notifi
break;
case NETDEV_CHANGE:
flags = dev_get_flags(dev);
- if (flags & (IFF_RUNNING | IFF_LOWER_UP))
+ if (flags & (IFF_RUNNING | IFF_LOWER_UP)) {
mpls_ifup(dev, RTNH_F_DEAD | RTNH_F_LINKDOWN);
- else
- mpls_ifdown(dev, event);
+ } else {
+ err = mpls_ifdown(dev, event);
+ if (err)
+ return notifier_from_errno(err);
+ }
break;
case NETDEV_UNREGISTER:
- mpls_ifdown(dev, event);
+ err = mpls_ifdown(dev, event);
+ if (err)
+ return notifier_from_errno(err);
mdev = mpls_dev_get(dev);
if (mdev) {
mpls_dev_sysctl_unregister(dev, mdev);
@@ -1625,8 +1663,6 @@ static int mpls_dev_notify(struct notifi
case NETDEV_CHANGENAME:
mdev = mpls_dev_get(dev);
if (mdev) {
- int err;
-
mpls_dev_sysctl_unregister(dev, mdev);
err = mpls_dev_sysctl_register(dev, mdev);
if (err)