'local_addr_used' and 'add_addr_accepted' are decremented for addresses not related to the initial subflow (ID0), because the source and destination addresses of the initial subflows are known from the beginning: they don't count as "additional local address being used" or "ADD_ADDR being accepted".
It is then required not to increment them when the entrypoint used by the initial subflow is removed and re-added during a connection. Without this modification, this entrypoint cannot be removed and re-added more than once.
Reported-by: Arınç ÜNAL arinc.unal@arinc9.com Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/512 Fixes: 3ad14f54bd74 ("mptcp: more accurate MPC endpoint tracking") Reported-by: syzbot+455d38ecd5f655fc45cf@syzkaller.appspotmail.com Closes: https://lore.kernel.org/00000000000049861306209237f4@google.com Cc: stable@vger.kernel.org Tested-by: Arınç ÜNAL arinc.unal@arinc9.com Reviewed-by: Mat Martineau martineau@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- net/mptcp/pm_netlink.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c index 90b7c8b45027..591ae2ffb4dd 100644 --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -615,12 +615,13 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
fullmesh = !!(local.flags & MPTCP_PM_ADDR_FLAG_FULLMESH);
- msk->pm.local_addr_used++; __clear_bit(local.addr.id, msk->pm.id_avail_bitmap);
/* Special case for ID0: set the correct ID */ if (local.addr.id == msk->mpc_endpoint_id) local.addr.id = 0; + else /* local_addr_used is not decr for ID 0 */ + msk->pm.local_addr_used++;
nr = fill_remote_addresses_vec(msk, &local.addr, fullmesh, addrs); if (nr == 0) @@ -750,7 +751,9 @@ static void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk) spin_lock_bh(&msk->pm.lock);
if (sf_created) { - msk->pm.add_addr_accepted++; + /* add_addr_accepted is not decr for ID 0 */ + if (remote.id) + msk->pm.add_addr_accepted++; if (msk->pm.add_addr_accepted >= add_addr_accept_max || msk->pm.subflows >= subflows_max) WRITE_ONCE(msk->pm.accept_addr, false);