[PATCH 5.10 070/103] net: sit: Unregister catch-all devices

[Greg Kroah-Hartman]

From: Hristo Venev <hri...@venev.name>

commit 610f8c0fc8d46e0933955ce13af3d64484a4630a upstream.

A sit interface created without a local or a remote address is linked
into the `sit_net::tunnels_wc` list of its original namespace. When
deleting a network namespace, delete the devices that have been moved.

The following script triggers a null pointer dereference if devices
linked in a deleted `sit_net` remain:

    for i in `seq 1 30`; do
        ip netns add ns-test
        ip netns exec ns-test ip link add dev veth0 type veth peer veth1
        ip netns exec ns-test ip link add dev sit$i type sit dev veth0
        ip netns exec ns-test ip link set dev sit$i netns $$
        ip netns del ns-test
    done
    for i in `seq 1 30`; do
        ip link del dev sit$i
    done

Fixes: 5e6700b3bf98f ("sit: add support of x-netns")
Signed-off-by: Hristo Venev <hri...@venev.name>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/ipv6/sit.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -1867,9 +1867,9 @@ static void __net_exit sit_destroy_tunne
                if (dev->rtnl_link_ops == &sit_link_ops)
                        unregister_netdevice_queue(dev, head);
 
-       for (prio = 1; prio < 4; prio++) {
+       for (prio = 0; prio < 4; prio++) {
                int h;
-               for (h = 0; h < IP6_SIT_HASH_SIZE; h++) {
+               for (h = 0; h < (prio ? IP6_SIT_HASH_SIZE : 1); h++) {
                        struct ip_tunnel *t;
 
                        t = rtnl_dereference(sitn->tunnels[prio][h]);