mptcp: fix race in incoming ADD_ADDR option processing

If an MPTCP endpoint received multiple consecutive incoming
ADD_ADDR options, mptcp_pm_add_addr_received() can overwrite
the current remote address value after the PM lock is released
in mptcp_pm_nl_add_addr_received() and before such address
is echoed.

Fix the issue caching the remote address value a little earlier
and always using the cached value after releasing the PM lock.

Fixes: f7efc7771eac ("mptcp: drop argument port from mptcp_pm_announce_addr")
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 82f82a5..4b5d795 100644 (file)
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -660,6 +660,7 @@ static void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
        unsigned int add_addr_accept_max;
        struct mptcp_addr_info remote;
        unsigned int subflows_max;
+       bool reset_port = false;
        int i, nr;
 
        add_addr_accept_max = mptcp_pm_get_add_addr_accept_max(msk);
@@ -669,15 +670,19 @@ static void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
                 msk->pm.add_addr_accepted, add_addr_accept_max,
                 msk->pm.remote.family);
 
-       if (lookup_subflow_by_daddr(&msk->conn_list, &msk->pm.remote))
+       remote = msk->pm.remote;
+       if (lookup_subflow_by_daddr(&msk->conn_list, &remote))
                goto add_addr_echo;
 
+       /* pick id 0 port, if none is provided the remote address */
+       if (!remote.port) {
+               reset_port = true;
+               remote.port = sk->sk_dport;
+       }
+
        /* connect to the specified remote address, using whatever
         * local address the routing configuration will pick.
         */
-       remote = msk->pm.remote;
-       if (!remote.port)
-               remote.port = sk->sk_dport;
        nr = fill_local_addresses_vec(msk, addrs);
 
        msk->pm.add_addr_accepted++;
@@ -690,8 +695,12 @@ static void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
                __mptcp_subflow_connect(sk, &addrs[i], &remote);
        spin_lock_bh(&msk->pm.lock);
 
+       /* be sure to echo exactly the received address */
+       if (reset_port)
+               remote.port = 0;
+
 add_addr_echo:
-       mptcp_pm_announce_addr(msk, &msk->pm.remote, true);
+       mptcp_pm_announce_addr(msk, &remote, true);
        mptcp_pm_nl_addr_send_ack(msk);
 }