From 36f6ee22d2d66046e369757ec6bbe1c482957ba6 Mon Sep 17 00:00:00 2001 From: Alexey Kodanev Date: Tue, 26 Sep 2017 15:14:29 +0300 Subject: vti: fix use after free in vti_tunnel_xmit/vti6_tnl_xmit When running LTP IPsec tests, KASan might report: BUG: KASAN: use-after-free in vti_tunnel_xmit+0xeee/0xff0 [ip_vti] Read of size 4 at addr ffff880dc6ad1980 by task swapper/0/0 ... Call Trace: dump_stack+0x63/0x89 print_address_description+0x7c/0x290 kasan_report+0x28d/0x370 ? vti_tunnel_xmit+0xeee/0xff0 [ip_vti] __asan_report_load4_noabort+0x19/0x20 vti_tunnel_xmit+0xeee/0xff0 [ip_vti] ? vti_init_net+0x190/0x190 [ip_vti] ? save_stack_trace+0x1b/0x20 ? save_stack+0x46/0xd0 dev_hard_start_xmit+0x147/0x510 ? icmp_echo.part.24+0x1f0/0x210 __dev_queue_xmit+0x1394/0x1c60 ... Freed by task 0: save_stack_trace+0x1b/0x20 save_stack+0x46/0xd0 kasan_slab_free+0x70/0xc0 kmem_cache_free+0x81/0x1e0 kfree_skbmem+0xb1/0xe0 kfree_skb+0x75/0x170 kfree_skb_list+0x3e/0x60 __dev_queue_xmit+0x1298/0x1c60 dev_queue_xmit+0x10/0x20 neigh_resolve_output+0x3a8/0x740 ip_finish_output2+0x5c0/0xe70 ip_finish_output+0x4ba/0x680 ip_output+0x1c1/0x3a0 xfrm_output_resume+0xc65/0x13d0 xfrm_output+0x1e4/0x380 xfrm4_output_finish+0x5c/0x70 Can be fixed if we get skb->len before dst_output(). Fixes: b9959fd3b0fa ("vti: switch to new ip tunnel code") Fixes: 22e1b23dafa8 ("vti6: Support inter address family tunneling.") Signed-off-by: Alexey Kodanev Signed-off-by: David S. Miller --- net/ipv4/ip_vti.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'net/ipv4/ip_vti.c') diff --git a/net/ipv4/ip_vti.c b/net/ipv4/ip_vti.c index 5ed63d250950..89453cf62158 100644 --- a/net/ipv4/ip_vti.c +++ b/net/ipv4/ip_vti.c @@ -168,6 +168,7 @@ static netdev_tx_t vti_xmit(struct sk_buff *skb, struct net_device *dev, struct ip_tunnel_parm *parms = &tunnel->parms; struct dst_entry *dst = skb_dst(skb); struct net_device *tdev; /* Device to other host */ + int pkt_len = skb->len; int err; int mtu; @@ -229,7 +230,7 @@ static netdev_tx_t vti_xmit(struct sk_buff *skb, struct net_device *dev, err = dst_output(tunnel->net, skb->sk, skb); if (net_xmit_eval(err) == 0) - err = skb->len; + err = pkt_len; iptunnel_xmit_stats(dev, err); return NETDEV_TX_OK; -- cgit v1.2.3-59-g8ed1b