From: Taehee Yoo ap420073@gmail.com
[ Upstream commit dafabb6590cb15f300b77c095d50312e2c7c8e0f ]
In the datapath, the ip6gre_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 ip6gre1 type ip6gre local fc:0::1 \ remote fc:0::2 ip netns exec A ip -6 a a fc:100::1/64 dev ip6gre1 ip netns exec A ip link set ip6gre1 up ip netns exec A ip -6 a a fc:0::1/64 dev eth0 ip netns exec A ip link set ip6gre0 up
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 ip6gre1 type ip6gre local fc:0::2 \ remote fc:0::1 ip netns exec B ip -6 a a fc:100::2/64 dev ip6gre1 ip netns exec B ip link set ip6gre1 up ip netns exec B ip -6 a a fc:0::2/64 dev eth1 ip netns exec B ip link set ip6gre0 up ip netns exec A ping fc:100::2 -s 60000 & ip netns del B
Splat looks like: [ 73.087285][ C1] BUG: KASAN: use-after-free in ip6gre_tunnel_lookup+0x1064/0x13f0 [ip6_gre] [ 73.088361][ C1] Read of size 4 at addr ffff888040559218 by task ping/1429 [ 73.089317][ C1] [ 73.089638][ C1] CPU: 1 PID: 1429 Comm: ping Not tainted 5.7.0+ #602 [ 73.090531][ C1] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006 [ 73.091725][ C1] Call Trace: [ 73.092160][ C1] <IRQ> [ 73.092556][ C1] dump_stack+0x96/0xdb [ 73.093122][ C1] print_address_description.constprop.6+0x2cc/0x450 [ 73.094016][ C1] ? ip6gre_tunnel_lookup+0x1064/0x13f0 [ip6_gre] [ 73.094894][ C1] ? ip6gre_tunnel_lookup+0x1064/0x13f0 [ip6_gre] [ 73.095767][ C1] ? ip6gre_tunnel_lookup+0x1064/0x13f0 [ip6_gre] [ 73.096619][ C1] kasan_report+0x154/0x190 [ 73.097209][ C1] ? ip6gre_tunnel_lookup+0x1064/0x13f0 [ip6_gre] [ 73.097989][ C1] ip6gre_tunnel_lookup+0x1064/0x13f0 [ip6_gre] [ 73.098750][ C1] ? gre_del_protocol+0x60/0x60 [gre] [ 73.099500][ C1] gre_rcv+0x1c5/0x1450 [ip6_gre] [ 73.100199][ C1] ? ip6gre_header+0xf00/0xf00 [ip6_gre] [ 73.100985][ C1] ? rcu_read_lock_sched_held+0xc0/0xc0 [ 73.101830][ C1] ? ip6_input_finish+0x5/0xf0 [ 73.102483][ C1] ip6_protocol_deliver_rcu+0xcbb/0x1510 [ 73.103296][ C1] ip6_input_finish+0x5b/0xf0 [ 73.103920][ C1] ip6_input+0xcd/0x2c0 [ 73.104473][ C1] ? ip6_input_finish+0xf0/0xf0 [ 73.105115][ C1] ? rcu_read_lock_held+0x90/0xa0 [ 73.105783][ C1] ? rcu_read_lock_sched_held+0xc0/0xc0 [ 73.106548][ C1] ipv6_rcv+0x1f1/0x300 [ ... ]
Suggested-by: Eric Dumazet eric.dumazet@gmail.com Fixes: c12b395a4664 ("gre: Support GRE over IPv6") 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/ipv6/ip6_gre.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index 726ba41133a36..e07cc2cfc1a63 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -124,6 +124,7 @@ static struct ip6_tnl *ip6gre_tunnel_lookup(struct net_device *dev, int dev_type = (gre_proto == htons(ETH_P_TEB)) ? ARPHRD_ETHER : ARPHRD_IP6GRE; int score, cand_score = 4; + struct net_device *ndev;
for_each_ip_tunnel_rcu(t, ign->tunnels_r_l[h0 ^ h1]) { if (!ipv6_addr_equal(local, &t->parms.laddr) || @@ -226,9 +227,9 @@ static struct ip6_tnl *ip6gre_tunnel_lookup(struct net_device *dev, if (cand) return cand;
- dev = ign->fb_tunnel_dev; - if (dev->flags & IFF_UP) - return netdev_priv(dev); + ndev = READ_ONCE(ign->fb_tunnel_dev); + if (ndev && ndev->flags & IFF_UP) + return netdev_priv(ndev);
return NULL; } @@ -364,6 +365,8 @@ static void ip6gre_tunnel_uninit(struct net_device *dev) struct ip6gre_net *ign = net_generic(t->net, ip6gre_net_id);
ip6gre_tunnel_unlink(ign, t); + if (ign->fb_tunnel_dev == dev) + WRITE_ONCE(ign->fb_tunnel_dev, NULL); dst_cache_reset(&t->dst_cache); dev_put(dev); }