From 7ab69426e7ecbd18a222ee2ec87ca612d30197d7 Mon Sep 17 00:00:00 2001 From: Oleh Konko Date: Tue, 31 Mar 2026 11:52:12 +0000 Subject: [PATCH] Bluetooth: SMP: force responder MITM requirements before building the pairing response commit d05111bfe37bfd8bd4d2dfe6675d6bdeef43f7c7 upstream. smp_cmd_pairing_req() currently builds the pairing response from the initiator auth_req before enforcing the local BT_SECURITY_HIGH requirement. If the initiator omits SMP_AUTH_MITM, the response can also omit it even though the local side still requires MITM. tk_request() then sees an auth value without SMP_AUTH_MITM and may select JUST_CFM, making method selection inconsistent with the pairing policy the responder already enforces. When the local side requires HIGH security, first verify that MITM can be achieved from the IO capabilities and then force SMP_AUTH_MITM in the response in both rsp.auth_req and auth. This keeps the responder auth bits and later method selection aligned. Fixes: 2b64d153a0cc ("Bluetooth: Add MITM mechanism to LE-SMP") Cc: stable@vger.kernel.org Suggested-by: Luiz Augusto von Dentz Signed-off-by: Oleh Konko Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Greg Kroah-Hartman --- net/bluetooth/smp.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c index 77659e69663f..b77984905124 100644 --- a/net/bluetooth/smp.c +++ b/net/bluetooth/smp.c @@ -1817,7 +1817,7 @@ static u8 smp_cmd_pairing_req(struct l2cap_conn *conn, struct sk_buff *skb) if (sec_level > conn->hcon->pending_sec_level) conn->hcon->pending_sec_level = sec_level; - /* If we need MITM check that it can be achieved */ + /* If we need MITM check that it can be achieved. */ if (conn->hcon->pending_sec_level >= BT_SECURITY_HIGH) { u8 method; @@ -1825,6 +1825,10 @@ static u8 smp_cmd_pairing_req(struct l2cap_conn *conn, struct sk_buff *skb) req->io_capability); if (method == JUST_WORKS || method == JUST_CFM) return SMP_AUTH_REQUIREMENTS; + + /* Force MITM bit if it isn't set by the initiator. */ + auth |= SMP_AUTH_MITM; + rsp.auth_req |= SMP_AUTH_MITM; } key_size = min(req->max_key_size, rsp.max_key_size);