From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
To:     linux-bluetooth@vger.kernel.org
Subject: [PATCH 1/2] Bluetooth: L2CAP: Fix responding with wrong PDU type
Date:   Thu,  9 Mar 2023 16:00:54 -0800
Message-Id: <20230310000055.3396026-1-luiz.dentz@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

L2CAP_ECRED_CONN_REQ shall be responded with L2CAP_ECRED_CONN_RSP not
L2CAP_LE_CONN_RSP:

L2CAP LE EATT Server - Reject - run
  Listening for connections
  New client connection with handle 0x002a
  Sending L2CAP Request from client
  Client received response code 0x15
  Unexpected L2CAP response code (expected 0x18)
L2CAP LE EATT Server - Reject - test failed

> ACL Data RX: Handle 42 flags 0x02 dlen 26
      LE L2CAP: Enhanced Credit Connection Request (0x17) ident 1 len 18
        PSM: 39 (0x0027)
        MTU: 64
        MPS: 64
        Credits: 5
        Source CID: 65
        Source CID: 66
        Source CID: 67
        Source CID: 68
        Source CID: 69
< ACL Data TX: Handle 42 flags 0x00 dlen 16
      LE L2CAP: LE Connection Response (0x15) ident 1 len 8
        invalid size
        00 00 00 00 00 00 06 00

L2CAP LE EATT Server - Reject - run
  Listening for connections
  New client connection with handle 0x002a
  Sending L2CAP Request from client
  Client received response code 0x18
L2CAP LE EATT Server - Reject - test passed

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
---
 net/bluetooth/l2cap_core.c | 133 ++++++++++++++++++++++++-------------
 1 file changed, 87 insertions(+), 46 deletions(-)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index adfc3ea06d08..49926f59cc12 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -708,6 +708,17 @@ void l2cap_chan_del(struct l2cap_chan *chan, int err)
 }
 EXPORT_SYMBOL_GPL(l2cap_chan_del);
 
+static void __l2cap_chan_list_id(struct l2cap_conn *conn, u16 id,
+				 l2cap_chan_func_t func, void *data)
+{
+	struct l2cap_chan *chan, *l;
+
+	list_for_each_entry_safe(chan, l, &conn->chan_l, list) {
+		if (chan->ident == id)
+			func(chan, data);
+	}
+}
+
 static void __l2cap_chan_list(struct l2cap_conn *conn, l2cap_chan_func_t func,
 			      void *data)
 {
@@ -775,23 +786,9 @@ static void l2cap_chan_le_connect_reject(struct l2cap_chan *chan)
 
 static void l2cap_chan_ecred_connect_reject(struct l2cap_chan *chan)
 {
-	struct l2cap_conn *conn = chan->conn;
-	struct l2cap_ecred_conn_rsp rsp;
-	u16 result;
-
-	if (test_bit(FLAG_DEFER_SETUP, &chan->flags))
-		result = L2CAP_CR_LE_AUTHORIZATION;
-	else
-		result = L2CAP_CR_LE_BAD_PSM;
-
 	l2cap_state_change(chan, BT_DISCONN);
 
-	memset(&rsp, 0, sizeof(rsp));
-
-	rsp.result  = cpu_to_le16(result);
-
-	l2cap_send_cmd(conn, chan->ident, L2CAP_LE_CONN_RSP, sizeof(rsp),
-		       &rsp);
+	__l2cap_ecred_conn_rsp_defer(chan);
 }
 
 static void l2cap_chan_connect_reject(struct l2cap_chan *chan)
@@ -846,7 +843,7 @@ void l2cap_chan_close(struct l2cap_chan *chan, int reason)
 					break;
 				case L2CAP_MODE_EXT_FLOWCTL:
 					l2cap_chan_ecred_connect_reject(chan);
-					break;
+					return;
 				}
 			}
 		}
@@ -3938,43 +3935,86 @@ void __l2cap_le_connect_rsp_defer(struct l2cap_chan *chan)
 		       &rsp);
 }
 
-void __l2cap_ecred_conn_rsp_defer(struct l2cap_chan *chan)
+static void l2cap_ecred_list_defer(struct l2cap_chan *chan, void *data)
 {
-	struct {
-		struct l2cap_ecred_conn_rsp rsp;
-		__le16 dcid[5];
-	} __packed pdu;
-	struct l2cap_conn *conn = chan->conn;
-	u16 ident = chan->ident;
-	int i = 0;
+	int *result = data;
 
-	if (!ident)
+	if (*result || test_bit(FLAG_ECRED_CONN_REQ_SENT, &chan->flags))
 		return;
 
-	BT_DBG("chan %p ident %d", chan, ident);
-
-	pdu.rsp.mtu     = cpu_to_le16(chan->imtu);
-	pdu.rsp.mps     = cpu_to_le16(chan->mps);
-	pdu.rsp.credits = cpu_to_le16(chan->rx_credits);
-	pdu.rsp.result  = cpu_to_le16(L2CAP_CR_LE_SUCCESS);
-
-	mutex_lock(&conn->chan_lock);
-
-	list_for_each_entry(chan, &conn->chan_l, list) {
-		if (chan->ident != ident)
-			continue;
-
-		/* Reset ident so only one response is sent */
-		chan->ident = 0;
-
-		/* Include all channels pending with the same ident */
-		pdu.dcid[i++] = cpu_to_le16(chan->scid);
+	switch (chan->state) {
+	case BT_CONNECT2:
+		/* If channel still pending accept add to result */
+		(*result)++;
+		return;
+	case BT_CONNECTED:
+		return;
+	default:
+		/* If not connected or pending accept it has been refused */
+		*result = -ECONNREFUSED;
+		return;
 	}
+}
 
-	mutex_unlock(&conn->chan_lock);
+struct l2cap_ecred_rsp_data {
+	struct {
+		struct l2cap_ecred_conn_rsp rsp;
+		__le16 scid[L2CAP_ECRED_MAX_CID];
+	} __packed pdu;
+	int count;
+};
 
-	l2cap_send_cmd(conn, ident, L2CAP_ECRED_CONN_RSP,
-			sizeof(pdu.rsp) + i * sizeof(__le16), &pdu);
+static void l2cap_ecred_rsp_defer(struct l2cap_chan *chan, void *data)
+{
+	struct l2cap_ecred_rsp_data *rsp = data;
+
+	if (test_bit(FLAG_ECRED_CONN_REQ_SENT, &chan->flags))
+		return;
+
+	/* Reset ident so only one response is sent */
+	chan->ident = 0;
+
+	/* Include all channels pending with the same ident */
+	if (!rsp->pdu.rsp.result)
+		rsp->pdu.rsp.dcid[rsp->count++] = cpu_to_le16(chan->scid);
+	else
+		l2cap_chan_del(chan, ECONNRESET);
+}
+
+void __l2cap_ecred_conn_rsp_defer(struct l2cap_chan *chan)
+{
+	struct l2cap_conn *conn = chan->conn;
+	struct l2cap_ecred_rsp_data data;
+	u16 id = chan->ident;
+	int result = 0;
+
+	if (!id)
+		return;
+
+	BT_DBG("chan %p id %d", chan, id);
+
+	memset(&data, 0, sizeof(data));
+
+	data.pdu.rsp.mtu     = cpu_to_le16(chan->imtu);
+	data.pdu.rsp.mps     = cpu_to_le16(chan->mps);
+	data.pdu.rsp.credits = cpu_to_le16(chan->rx_credits);
+	data.pdu.rsp.result  = cpu_to_le16(L2CAP_CR_LE_SUCCESS);
+
+	/* Verify that all channels are ready */
+	__l2cap_chan_list_id(conn, id, l2cap_ecred_list_defer, &result);
+
+	if (result > 0)
+		return;
+
+	if (result < 0)
+		data.pdu.rsp.result = cpu_to_le16(L2CAP_CR_LE_AUTHORIZATION);
+
+	/* Build response */
+	__l2cap_chan_list_id(conn, id, l2cap_ecred_rsp_defer, &data);
+
+	l2cap_send_cmd(conn, id, L2CAP_ECRED_CONN_RSP,
+		       sizeof(data.pdu.rsp) + (data.count * sizeof(__le16)),
+		       &data.pdu);
 }
 
 void __l2cap_connect_rsp_defer(struct l2cap_chan *chan)
@@ -6078,6 +6118,7 @@ static inline int l2cap_ecred_conn_req(struct l2cap_conn *conn,
 		__set_chan_timer(chan, chan->ops->get_sndtimeo(chan));
 
 		chan->ident = cmd->ident;
+		chan->mode = L2CAP_MODE_EXT_FLOWCTL;
 
 		if (test_bit(FLAG_DEFER_SETUP, &chan->flags)) {
 			l2cap_state_change(chan, BT_CONNECT2);
-- 
2.39.2