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    Subject[PATCH 4.6 09/56] bridge: Fix incorrect re-injection of LLDP packets
    Date
    4.6-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Ido Schimmel <idosch@mellanox.com>

    [ Upstream commit baedbe55884c003819f5c8c063ec3d2569414296 ]

    Commit 8626c56c8279 ("bridge: fix potential use-after-free when hook
    returns QUEUE or STOLEN verdict") caused LLDP packets arriving through a
    bridge port to be re-injected to the Rx path with skb->dev set to the
    bridge device, but this breaks the lldpad daemon.

    The lldpad daemon opens a packet socket with protocol set to ETH_P_LLDP
    for any valid device on the system, which doesn't not include soft
    devices such as bridge and VLAN.

    Since packet sockets (ptype_base) are processed in the Rx path after the
    Rx handler, LLDP packets with skb->dev set to the bridge device never
    reach the lldpad daemon.

    Fix this by making the bridge's Rx handler re-inject LLDP packets with
    RX_HANDLER_PASS, which effectively restores the behaviour prior to the
    mentioned commit.

    This means netfilter will never receive LLDP packets coming through a
    bridge port, as I don't see a way in which we can have okfn() consume
    the packet without breaking existing behaviour. I've already carried out
    a similar fix for STP packets in commit 56fae404fb2c ("bridge: Fix
    incorrect re-injection of STP packets").

    Fixes: 8626c56c8279 ("bridge: fix potential use-after-free when hook returns QUEUE or STOLEN verdict")
    Signed-off-by: Ido Schimmel <idosch@mellanox.com>
    Reviewed-by: Jiri Pirko <jiri@mellanox.com>
    Cc: Florian Westphal <fw@strlen.de>
    Cc: John Fastabend <john.fastabend@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/bridge/br_input.c | 18 ++++++++++++++++++
    1 file changed, 18 insertions(+)

    --- a/net/bridge/br_input.c
    +++ b/net/bridge/br_input.c
    @@ -213,6 +213,16 @@ drop:
    }
    EXPORT_SYMBOL_GPL(br_handle_frame_finish);

    +static void __br_handle_local_finish(struct sk_buff *skb)
    +{
    + struct net_bridge_port *p = br_port_get_rcu(skb->dev);
    + u16 vid = 0;
    +
    + /* check if vlan is allowed, to avoid spoofing */
    + if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid))
    + br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
    +}
    +
    /* note: already called with rcu_read_lock */
    static int br_handle_local_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
    {
    @@ -279,6 +289,14 @@ rx_handler_result_t br_handle_frame(stru
    case 0x01: /* IEEE MAC (Pause) */
    goto drop;

    + case 0x0E: /* 802.1AB LLDP */
    + fwd_mask |= p->br->group_fwd_mask;
    + if (fwd_mask & (1u << dest[5]))
    + goto forward;
    + *pskb = skb;
    + __br_handle_local_finish(skb);
    + return RX_HANDLER_PASS;
    +
    default:
    /* Allow selective forwarding for most other protocols */
    fwd_mask |= p->br->group_fwd_mask;

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