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authorWillem de Bruijn <willemb@google.com>2013-11-13 21:27:38 -0500
committerDavid S. Miller <davem@davemloft.net>2013-11-14 16:42:17 -0500
commit9434266f2c645d4fcf62a03a8e36ad8075e37943 (patch)
tree830a0e8d211043841184ace3430867193ff1b80b
parentd842a31f121eccaba639ff26a1757649abd7d58e (diff)
downloadblackbird-op-linux-9434266f2c645d4fcf62a03a8e36ad8075e37943.tar.gz
blackbird-op-linux-9434266f2c645d4fcf62a03a8e36ad8075e37943.zip
sit: fix use after free of fb_tunnel_dev
Bug: The fallback device is created in sit_init_net and assumed to be freed in sit_exit_net. First, it is dereferenced in that function, in sit_destroy_tunnels: struct net *net = dev_net(sitn->fb_tunnel_dev); Prior to this, rtnl_unlink_register has removed all devices that match rtnl_link_ops == sit_link_ops. Commit 205983c43700 added the line + sitn->fb_tunnel_dev->rtnl_link_ops = &sit_link_ops; which cases the fallback device to match here and be freed before it is last dereferenced. Fix: This commit adds an explicit .delllink callback to sit_link_ops that skips deallocation at rtnl_unlink_register for the fallback device. This mechanism is comparable to the one in ip_tunnel. It also modifies sit_destroy_tunnels and its only caller sit_exit_net to avoid the offending dereference in the first place. That double lookup is more complicated than required. Test: The bug is only triggered when CONFIG_NET_NS is enabled. It causes a GPF only when CONFIG_DEBUG_SLAB is enabled. Verified that this bug exists at the mentioned commit, at davem-net HEAD and at 3.11.y HEAD. Verified that it went away after applying this patch. Fixes: 205983c43700 ("sit: allow to use rtnl ops on fb tunnel") Signed-off-by: Willem de Bruijn <willemb@google.com> Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv6/sit.c18
1 files changed, 14 insertions, 4 deletions
diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 3a9038dd818d..5a57f38a50d5 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -1604,6 +1604,15 @@ static const struct nla_policy ipip6_policy[IFLA_IPTUN_MAX + 1] = {
#endif
};
+static void ipip6_dellink(struct net_device *dev, struct list_head *head)
+{
+ struct net *net = dev_net(dev);
+ struct sit_net *sitn = net_generic(net, sit_net_id);
+
+ if (dev != sitn->fb_tunnel_dev)
+ unregister_netdevice_queue(dev, head);
+}
+
static struct rtnl_link_ops sit_link_ops __read_mostly = {
.kind = "sit",
.maxtype = IFLA_IPTUN_MAX,
@@ -1615,6 +1624,7 @@ static struct rtnl_link_ops sit_link_ops __read_mostly = {
.changelink = ipip6_changelink,
.get_size = ipip6_get_size,
.fill_info = ipip6_fill_info,
+ .dellink = ipip6_dellink,
};
static struct xfrm_tunnel sit_handler __read_mostly = {
@@ -1629,9 +1639,10 @@ static struct xfrm_tunnel ipip_handler __read_mostly = {
.priority = 2,
};
-static void __net_exit sit_destroy_tunnels(struct sit_net *sitn, struct list_head *head)
+static void __net_exit sit_destroy_tunnels(struct net *net,
+ struct list_head *head)
{
- struct net *net = dev_net(sitn->fb_tunnel_dev);
+ struct sit_net *sitn = net_generic(net, sit_net_id);
struct net_device *dev, *aux;
int prio;
@@ -1706,11 +1717,10 @@ err_alloc_dev:
static void __net_exit sit_exit_net(struct net *net)
{
- struct sit_net *sitn = net_generic(net, sit_net_id);
LIST_HEAD(list);
rtnl_lock();
- sit_destroy_tunnels(sitn, &list);
+ sit_destroy_tunnels(net, &list);
unregister_netdevice_many(&list);
rtnl_unlock();
}
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