[PATCH 5.15 037/139] mptcp: fix race in incoming ADD_ADDR option processing

Greg Kroah-Hartman
2022-02-28T17:51:30Z

From: Paolo Abeni <pabeni@redhat.com>

commit 837cf45df163a3780bc04b555700231e95b31dc9 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/mptcp/pm_netlink.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)

--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -606,6 +606,7 @@ static void mptcp_pm_nl_add_addr_receive
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);
@@ -615,15 +616,19 @@ static void mptcp_pm_nl_add_addr_receive
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++;
@@ -636,8 +641,12 @@ static void mptcp_pm_nl_add_addr_receive
__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);
}