From: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx> commit 1c1f721375989579e46741f59523e39ec9b2a9bd upstream. Adding the following warning ... WARN_ON_ONCE(msk->pm.add_addr_accepted == 0) ... before decrementing the add_addr_accepted counter helped to find a bug when running the "remove single subflow" subtest from the mptcp_join.sh selftest. Removing a 'subflow' endpoint will first trigger a RM_ADDR, then the subflow closure. Before this patch, and upon the reception of the RM_ADDR, the other peer will then try to decrement this add_addr_accepted. That's not correct because the attached subflows have not been created upon the reception of an ADD_ADDR. A way to solve that is to decrement the counter only if the attached subflow was an MP_JOIN to a remote id that was not 0, and initiated by the host receiving the RM_ADDR. Fixes: d0876b2284cf ("mptcp: add the incoming RM_ADDR support") Cc: stable@xxxxxxxxxxxxxxx Reviewed-by: Mat Martineau <martineau@xxxxxxxxxx> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx> Link: https://patch.msgid.link/20240819-net-mptcp-pm-reusing-id-v1-9-38035d40de5b@xxxxxxxxxx Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/mptcp/pm_netlink.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -834,7 +834,7 @@ static void mptcp_pm_nl_rm_addr_or_subfl mptcp_close_ssk(sk, ssk, subflow); spin_lock_bh(&msk->pm.lock); - removed = true; + removed |= subflow->request_join; if (rm_type == MPTCP_MIB_RMSUBFLOW) __MPTCP_INC_STATS(sock_net(sk), rm_type); } @@ -848,7 +848,11 @@ static void mptcp_pm_nl_rm_addr_or_subfl if (!mptcp_pm_is_kernel(msk)) continue; - if (rm_type == MPTCP_MIB_RMADDR) { + if (rm_type == MPTCP_MIB_RMADDR && rm_id && + !WARN_ON_ONCE(msk->pm.add_addr_accepted == 0)) { + /* Note: if the subflow has been closed before, this + * add_addr_accepted counter will not be decremented. + */ msk->pm.add_addr_accepted--; WRITE_ONCE(msk->pm.accept_addr, true); } else if (rm_type == MPTCP_MIB_RMSUBFLOW) { Patches currently in stable-queue which might be from matttbe@xxxxxxxxxx are queue-6.1/mptcp-pm-only-decrement-add_addr_accepted-for-mpj-req.patch queue-6.1/mptcp-pm-re-using-id-of-unused-flushed-subflows.patch queue-6.1/mptcp-pm-re-using-id-of-unused-removed-add_addr.patch queue-6.1/mptcp-pm-re-using-id-of-unused-removed-subflows.patch queue-6.1/mptcp-correct-mptcp_subflow_attr_ssn_offset-reserved.patch