netfilter: br_netfilter: disable sabotage_in hook after first suppression

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2189550
Upstream Status: commit 2b272bb

commit 2b272bb
Author: Florian Westphal <[email protected]>
Date:   Mon Jan 30 11:39:29 2023 +0100

    netfilter: br_netfilter: disable sabotage_in hook after first suppression

    When using a xfrm interface in a bridged setup (the outgoing device is
    bridged), the incoming packets in the xfrm interface are only tracked
    in the outgoing direction.

    $ brctl show
    bridge name     interfaces
    br_eth1         eth1

    $ conntrack -L
    tcp 115 SYN_SENT src=192... dst=192... [UNREPLIED] ...

    If br_netfilter is enabled, the first (encrypted) packet is received onR
    eth1, conntrack hooks are called from br_netfilter emulation which
    allocates nf_bridge info for this skb.

    If the packet is for local machine, skb gets passed up the ip stack.
    The skb passes through ip prerouting a second time. br_netfilter
    ip_sabotage_in supresses the re-invocation of the hooks.

    After this, skb gets decrypted in xfrm layer and appears in
    network stack a second time (after decryption).

    Then, ip_sabotage_in is called again and suppresses netfilter
    hook invocation, even though the bridge layer never called them
    for the plaintext incarnation of the packet.

    Free the bridge info after the first suppression to avoid this.

    I was unable to figure out where the regression comes from, as far as i
    can see br_netfilter always had this problem; i did not expect that skb
    is looped again with different headers.

    Fixes: c4b0e77 ("netfilter: avoid using skb->nf_bridge directly")
    Reported-and-tested-by: Wolfgang Nothdurft <[email protected]>
    Signed-off-by: Florian Westphal <[email protected]>
    Signed-off-by: Pablo Neira Ayuso <[email protected]>

Signed-off-by: Florian Westphal <[email protected]>

Author: fw-strlen

net/bridge/br_netfilter_hooks.c

@@ -871,6 +871,7 @@ static unsigned int ip_sabotage_in(void *priv,
 	if (nf_bridge && !nf_bridge->in_prerouting &&
 	    !netif_is_l3_master(skb->dev) &&
 	    !netif_is_l3_slave(skb->dev)) {
+		nf_bridge_info_free(skb);
 		state->okfn(state->net, state->sk, skb);
 		return NF_STOLEN;
 	}