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:
[ 133.319668][ C3] BUG: KASAN: use-after-free in
ip_tunnel_lookup+0x9d6/0xde0
[ 133.343852][ C3] Read of size 4 at addr ffff8880b1701c84 by task
hping3/1222
[ 133.344724][ C3]
[ 133.345002][ C3] CPU: 3 PID: 1222 Comm: hping3 Not tainted 5.7.0+ #591
[ 133.345814][ C3] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS
VirtualBox 12/01/2006
[ 133.373336][ C3] Call Trace:
[ 133.374792][ C3] <IRQ>
[ 133.375205][ C3] dump_stack+0x96/0xdb
[ 133.375789][ C3] print_address_description.constprop.6+0x2cc/0x450
[ 133.376720][ C3] ? ip_tunnel_lookup+0x9d6/0xde0
[ 133.377431][ C3] ? ip_tunnel_lookup+0x9d6/0xde0
[ 133.378130][ C3] ? ip_tunnel_lookup+0x9d6/0xde0
[ 133.378851][ C3] kasan_report+0x154/0x190
[ 133.379494][ C3] ? ip_tunnel_lookup+0x9d6/0xde0
[ 133.380200][ C3] ip_tunnel_lookup+0x9d6/0xde0
[ 133.380894][ C3] __ipgre_rcv+0x1ab/0xaa0 [ip_gre]
[ 133.381630][ C3] ? rcu_read_lock_sched_held+0xc0/0xc0
[ 133.382429][ C3] gre_rcv+0x304/0x1910 [ip_gre]
[ ... ]
Suggested-by: Eric Dumazet <eric.duma...@gmail.com>
Fixes: c54419321455 ("GRE: Refactor GRE tunneling code.")
Signed-off-by: Taehee Yoo <ap420...@gmail.com>
---
v1 -> v2:
- Do not add a new variable.
net/ipv4/ip_tunnel.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index f4f1d11eab50..701f150f11e1 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -85,9 +85,10 @@ 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];
@@ -162,8 +163,9 @@ struct ip_tunnel *ip_tunnel_lookup(struct ip_tunnel_net
*itn,
if (t && t->dev->flags & IFF_UP)
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;
}
@@ -1260,8 +1262,9 @@ void ip_tunnel_uninit(struct net_device *dev)
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);
}
--
2.17.1
