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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Hristo Venev <hristo@venev.name>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.9 20/37] net: sit: Unregister catch-all devices
Date:   Mon, 26 Apr 2021 09:29:21 +0200
Message-Id: <20210426072817.942653452@linuxfoundation.org>
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From: Hristo Venev <hristo@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 <hristo@venev.name>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv6/sit.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -1799,9 +1799,9 @@ 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]);