netdev - [PATCH net] netfilter: bridge: Don't sabotage nf

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Fri,  7 Sep 2018 15:08:13 -0700
From:   dsahern@...nel.org
To:     netdev@...r.kernel.org
Cc:     ndsouza@...na.com, idosch@...lanox.com, pablo@...filter.org,
        fw@...len.de, David Ahern <dsahern@...il.com>
Subject: [PATCH net] netfilter: bridge: Don't sabotage nf_hook calls from an l3mdev

From: David Ahern <dsahern@...il.com>

For starters, the bridge netfilter code registers operations that
are invoked any time nh_hook is called. Specifically, ip_sabotage_in
watches for nested calls for NF_INET_PRE_ROUTING when a bridge is in
the stack.

Packet wise, the bridge netfilter hook runs first. br_nf_pre_routing
allocates nf_bridge, sets in_prerouting to 1 and calls NF_HOOK for
NF_INET_PRE_ROUTING. It's finish function, br_nf_pre_routing_finish,
then resets in_prerouting flag to 0 and the packet continues up the
stack. The packet eventually makes it to the VRF driver and it invokes
nf_hook for NF_INET_PRE_ROUTING in case any rules have been added against
the vrf device.

Because of the registered operations the call to nf_hook causes
ip_sabotage_in to be invoked. That function sees the nf_bridge on the
skb and that in_prerouting is not set. Thinking it is an invalid nested
call it steals (drops) the packet.

Update ip_sabotage_in to recognize that the bridge or one of its upper
devices (e.g., vlan) can be enslaved to a VRF (L3 master device) and
allow the packet to go through the nf_hook a second time.

Fixes: 73e20b761acf ("net: vrf: Add support for PREROUTING rules on vrf device")
Reported-by: D'Souza, Nelson <ndsouza@...na.com>
Signed-off-by: David Ahern <dsahern@...il.com>
---
 net/bridge/br_netfilter_hooks.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c
index 6e0dc6bcd32a..37278dc280eb 100644
--- a/net/bridge/br_netfilter_hooks.c
+++ b/net/bridge/br_netfilter_hooks.c
@@ -835,7 +835,8 @@ static unsigned int ip_sabotage_in(void *priv,
 				   struct sk_buff *skb,
 				   const struct nf_hook_state *state)
 {
-	if (skb->nf_bridge && !skb->nf_bridge->in_prerouting) {
+	if (skb->nf_bridge && !skb->nf_bridge->in_prerouting &&
+	    !netif_is_l3_master(skb->dev)) {
 		state->okfn(state->net, state->sk, skb);
 		return NF_STOLEN;
 	}
-- 
2.11.0