netdev - [PATCH net 10/15] mptcp: pm: fix ID 0 endp usage after multiple re-creations

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Message-Id: <20240826-net-mptcp-more-pm-fix-v1-10-8cd6c87d1d6d@kernel.org>
Date: Mon, 26 Aug 2024 17:59:09 +0200
From: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
To: mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org>, 
 Geliang Tang <geliang@...nel.org>, "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Shuah Khan <shuah@...nel.org>, 
 Florian Westphal <fw@...len.de>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, 
 "Matthieu Baerts (NGI0)" <matttbe@...nel.org>, 
 Arınç ÜNAL <arinc.unal@...nc9.com>, 
 syzbot+455d38ecd5f655fc45cf@...kaller.appspotmail.com, 
 stable@...r.kernel.org
Subject: [PATCH net 10/15] mptcp: pm: fix ID 0 endp usage after multiple
 re-creations

'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@...nc9.com>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/512
Fixes: 3ad14f54bd74 ("mptcp: more accurate MPC endpoint tracking")
Reported-by: syzbot+455d38ecd5f655fc45cf@...kaller.appspotmail.com
Closes: https://lore.kernel.org/00000000000049861306209237f4@google.com
Cc: stable@...r.kernel.org
Tested-by: Arınç ÜNAL <arinc.unal@...nc9.com>
Reviewed-by: Mat Martineau <martineau@...nel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.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);

-- 
2.45.2