From: Nikolay Aleksandrov nikolay@cumulusnetworks.com
[ Upstream commit 3b2e2904deb314cc77a2192f506f2fd44e3d10d0 ]
When the commit below was introduced it changed two visible things: - the skb was no longer passed through the protocol handlers with the original device - the skb was passed up the stack with skb->dev = bridge
The first change broke af_packet sockets on bridge ports. For example we use them for hostapd which listens for ETH_P_PAE packets on the ports. We discussed two possible fixes: - create a clone and pass it through NF_HOOK(), act on the original skb based on the result - somehow signal to the caller from the okfn() that it was called, meaning the skb is ok to be passed, which this patch is trying to implement via returning 1 from the bridge link-local okfn()
Note that we rely on the fact that NF_QUEUE/STOLEN would return 0 and drop/error would return < 0 thus the okfn() is called only when the return was 1, so we signal to the caller that it was called by preserving the return value from nf_hook().
Fixes: 8626c56c8279 ("bridge: fix potential use-after-free when hook returns QUEUE or STOLEN verdict") Signed-off-by: Nikolay Aleksandrov nikolay@cumulusnetworks.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/bridge/br_input.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-)
--- a/net/bridge/br_input.c +++ b/net/bridge/br_input.c @@ -236,13 +236,10 @@ static void __br_handle_local_finish(str /* note: already called with rcu_read_lock */ static int br_handle_local_finish(struct net *net, struct sock *sk, struct sk_buff *skb) { - struct net_bridge_port *p = br_port_get_rcu(skb->dev); - __br_handle_local_finish(skb);
- BR_INPUT_SKB_CB(skb)->brdev = p->br->dev; - br_pass_frame_up(skb); - return 0; + /* return 1 to signal the okfn() was called so it's ok to use the skb */ + return 1; }
/* @@ -318,10 +315,18 @@ rx_handler_result_t br_handle_frame(stru goto forward; }
- /* Deliver packet to local host only */ - NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, dev_net(skb->dev), - NULL, skb, skb->dev, NULL, br_handle_local_finish); - return RX_HANDLER_CONSUMED; + /* The else clause should be hit when nf_hook(): + * - returns < 0 (drop/error) + * - returns = 0 (stolen/nf_queue) + * Thus return 1 from the okfn() to signal the skb is ok to pass + */ + if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, + dev_net(skb->dev), NULL, skb, skb->dev, NULL, + br_handle_local_finish) == 1) { + return RX_HANDLER_PASS; + } else { + return RX_HANDLER_CONSUMED; + } }
forward: