From: Taehee Yoo ap420073@gmail.com
[ Upstream commit ba61539c6ae57f4146284a5cb4f7b7ed8d42bf45 ]
In the datapath, the ip_tunnel_lookup() is used and it internally uses fallback tunnel device pointer, which is fb_tunnel_dev. This pointer variable should be set to NULL when a fb interface is deleted. But there is no routine to set fb_tunnel_dev pointer to NULL. So, this pointer will be still used after interface is deleted and it eventually results in the use-after-free problem.
Test commands: ip netns add A ip netns add B ip link add eth0 type veth peer name eth1 ip link set eth0 netns A ip link set eth1 netns B
ip netns exec A ip link set lo up ip netns exec A ip link set eth0 up ip netns exec A ip link add gre1 type gre local 10.0.0.1 \ remote 10.0.0.2 ip netns exec A ip link set gre1 up ip netns exec A ip a a 10.0.100.1/24 dev gre1 ip netns exec A ip a a 10.0.0.1/24 dev eth0
ip netns exec B ip link set lo up ip netns exec B ip link set eth1 up ip netns exec B ip link add gre1 type gre local 10.0.0.2 \ remote 10.0.0.1 ip netns exec B ip link set gre1 up ip netns exec B ip a a 10.0.100.2/24 dev gre1 ip netns exec B ip a a 10.0.0.2/24 dev eth1 ip netns exec A hping3 10.0.100.2 -2 --flood -d 60000 & ip netns del B
Splat looks like: [ 77.793450][ C3] ================================================================== [ 77.794702][ C3] BUG: KASAN: use-after-free in ip_tunnel_lookup+0xcc4/0xf30 [ 77.795573][ C3] Read of size 4 at addr ffff888060bd9c84 by task hping3/2905 [ 77.796398][ C3] [ 77.796664][ C3] CPU: 3 PID: 2905 Comm: hping3 Not tainted 5.8.0-rc1+ #616 [ 77.797474][ C3] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006 [ 77.798453][ C3] Call Trace: [ 77.798815][ C3] <IRQ> [ 77.799142][ C3] dump_stack+0x9d/0xdb [ 77.799605][ C3] print_address_description.constprop.7+0x2cc/0x450 [ 77.800365][ C3] ? ip_tunnel_lookup+0xcc4/0xf30 [ 77.800908][ C3] ? ip_tunnel_lookup+0xcc4/0xf30 [ 77.801517][ C3] ? ip_tunnel_lookup+0xcc4/0xf30 [ 77.802145][ C3] kasan_report+0x154/0x190 [ 77.802821][ C3] ? ip_tunnel_lookup+0xcc4/0xf30 [ 77.803503][ C3] ip_tunnel_lookup+0xcc4/0xf30 [ 77.804165][ C3] __ipgre_rcv+0x1ab/0xaa0 [ip_gre] [ 77.804862][ C3] ? rcu_read_lock_sched_held+0xc0/0xc0 [ 77.805621][ C3] gre_rcv+0x304/0x1910 [ip_gre] [ 77.806293][ C3] ? lock_acquire+0x1a9/0x870 [ 77.806925][ C3] ? gre_rcv+0xfe/0x354 [gre] [ 77.807559][ C3] ? erspan_xmit+0x2e60/0x2e60 [ip_gre] [ 77.808305][ C3] ? rcu_read_lock_sched_held+0xc0/0xc0 [ 77.809032][ C3] ? rcu_read_lock_held+0x90/0xa0 [ 77.809713][ C3] gre_rcv+0x1b8/0x354 [gre] [ ... ]
Suggested-by: Eric Dumazet eric.dumazet@gmail.com Fixes: c54419321455 ("GRE: Refactor GRE tunneling code.") Signed-off-by: Taehee Yoo ap420073@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/ip_tunnel.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c index dd5db4cc7d066..5f2e3334cccec 100644 --- a/net/ipv4/ip_tunnel.c +++ b/net/ipv4/ip_tunnel.c @@ -98,9 +98,10 @@ struct ip_tunnel *ip_tunnel_lookup(struct ip_tunnel_net *itn, __be32 remote, __be32 local, __be32 key) { - unsigned int hash; struct ip_tunnel *t, *cand = NULL; struct hlist_head *head; + struct net_device *ndev; + unsigned int hash;
hash = ip_tunnel_hash(key, remote); head = &itn->tunnels[hash]; @@ -175,8 +176,9 @@ struct ip_tunnel *ip_tunnel_lookup(struct ip_tunnel_net *itn, if (t) return t;
- if (itn->fb_tunnel_dev && itn->fb_tunnel_dev->flags & IFF_UP) - return netdev_priv(itn->fb_tunnel_dev); + ndev = READ_ONCE(itn->fb_tunnel_dev); + if (ndev && ndev->flags & IFF_UP) + return netdev_priv(ndev);
return NULL; } @@ -1193,9 +1195,9 @@ void ip_tunnel_uninit(struct net_device *dev) struct ip_tunnel_net *itn;
itn = net_generic(net, tunnel->ip_tnl_net_id); - /* fb_tunnel_dev will be unregisted in net-exit call. */ - if (itn->fb_tunnel_dev != dev) - ip_tunnel_del(itn, netdev_priv(dev)); + ip_tunnel_del(itn, netdev_priv(dev)); + if (itn->fb_tunnel_dev == dev) + WRITE_ONCE(itn->fb_tunnel_dev, NULL);
dst_cache_reset(&tunnel->dst_cache); }