From: Xin Long lucien.xin@gmail.com
commit c3bcde026684c62d7a2b6f626dc7cf763833875c upstream.
udp_tunnel(6)_xmit_skb() called by tipc_udp_xmit() expects a tunnel device to count packets on dev->tstats, a perpcu variable. However, TIPC is using udp tunnel with no tunnel device, and pass the lower dev, like veth device that only initializes dev->lstats(a perpcu variable) when creating it.
Later iptunnel_xmit_stats() called by ip(6)tunnel_xmit() thinks the dev as a tunnel device, and uses dev->tstats instead of dev->lstats. tstats' each pointer points to a bigger struct than lstats, so when tstats->tx_bytes is increased, other percpu variable's members could be overwritten.
syzbot has reported quite a few crashes due to fib_nh_common percpu member 'nhc_pcpu_rth_output' overwritten, call traces are like:
BUG: KASAN: slab-out-of-bounds in rt_cache_valid+0x158/0x190 net/ipv4/route.c:1556 rt_cache_valid+0x158/0x190 net/ipv4/route.c:1556 __mkroute_output net/ipv4/route.c:2332 [inline] ip_route_output_key_hash_rcu+0x819/0x2d50 net/ipv4/route.c:2564 ip_route_output_key_hash+0x1ef/0x360 net/ipv4/route.c:2393 __ip_route_output_key include/net/route.h:125 [inline] ip_route_output_flow+0x28/0xc0 net/ipv4/route.c:2651 ip_route_output_key include/net/route.h:135 [inline] ...
or:
kasan: GPF could be caused by NULL-ptr deref or user memory access RIP: 0010:dst_dev_put+0x24/0x290 net/core/dst.c:168 <IRQ> rt_fibinfo_free_cpus net/ipv4/fib_semantics.c:200 [inline] free_fib_info_rcu+0x2e1/0x490 net/ipv4/fib_semantics.c:217 __rcu_reclaim kernel/rcu/rcu.h:240 [inline] rcu_do_batch kernel/rcu/tree.c:2437 [inline] invoke_rcu_callbacks kernel/rcu/tree.c:2716 [inline] rcu_process_callbacks+0x100a/0x1ac0 kernel/rcu/tree.c:2697 ...
The issue exists since tunnel stats update is moved to iptunnel_xmit by Commit 039f50629b7f ("ip_tunnel: Move stats update to iptunnel_xmit()"), and here to fix it by passing a NULL tunnel dev to udp_tunnel(6)_xmit_skb so that the packets counting won't happen on dev->tstats.
Reported-by: syzbot+9d4c12bfd45a58738d0a@syzkaller.appspotmail.com Reported-by: syzbot+a9e23ea2aa21044c2798@syzkaller.appspotmail.com Reported-by: syzbot+c4c4b2bb358bb936ad7e@syzkaller.appspotmail.com Reported-by: syzbot+0290d2290a607e035ba1@syzkaller.appspotmail.com Reported-by: syzbot+a43d8d4e7e8a7a9e149e@syzkaller.appspotmail.com Reported-by: syzbot+a47c5f4c6c00fc1ed16e@syzkaller.appspotmail.com Fixes: 039f50629b7f ("ip_tunnel: Move stats update to iptunnel_xmit()") Signed-off-by: Xin Long lucien.xin@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/tipc/udp_media.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)
--- a/net/tipc/udp_media.c +++ b/net/tipc/udp_media.c @@ -176,7 +176,6 @@ static int tipc_udp_xmit(struct net *net goto tx_error; }
- skb->dev = rt->dst.dev; ttl = ip4_dst_hoplimit(&rt->dst); udp_tunnel_xmit_skb(rt, ub->ubsock->sk, skb, src->ipv4.s_addr, dst->ipv4.s_addr, 0, ttl, 0, src->port, @@ -195,10 +194,9 @@ static int tipc_udp_xmit(struct net *net if (err) goto tx_error; ttl = ip6_dst_hoplimit(ndst); - err = udp_tunnel6_xmit_skb(ndst, ub->ubsock->sk, skb, - ndst->dev, &src->ipv6, - &dst->ipv6, 0, ttl, 0, src->port, - dst->port, false); + err = udp_tunnel6_xmit_skb(ndst, ub->ubsock->sk, skb, NULL, + &src->ipv6, &dst->ipv6, 0, ttl, 0, + src->port, dst->port, false); #endif } return err;