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From:   Sungwoo Kim <iam@sung-woo.kim>
Cc:     daveti@purdue.edu, Sungwoo Kim <iam@sung-woo.kim>,
        Marcel Holtmann <marcel@holtmann.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] Bluetooth: L2CAP: Add missing checks for invalid DCID
Date:   Sat,  3 Jun 2023 08:28:09 -0400
Message-Id: <20230603122808.1633403-1-iam@sung-woo.kim>
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When receiving a connect response we should make sure that the DCID is
within the valid range and that we don't already have another channel
allocated for the same DCID.
Missing checks may violate the specification (BLUETOOTH CORE SPECIFICATION
Version 5.4 | Vol 3, Part A, Page 1046).

Fixes: 40624183c202 ("L2CAP: Add missing checks for invalid LE DCID")
Signed-off-by: Sungwoo Kim <iam@sung-woo.kim>
---
 net/bluetooth/l2cap_core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 376b523c7..104eb0320 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -4306,6 +4306,10 @@ static int l2cap_connect_create_rsp(struct l2cap_conn *conn,
 	result = __le16_to_cpu(rsp->result);
 	status = __le16_to_cpu(rsp->status);
 
+	if (result == L2CAP_CR_SUCCESS && (dcid < L2CAP_CID_DYN_START ||
+					   dcid > L2CAP_CID_DYN_END))
+		return -EPROTO;
+
 	BT_DBG("dcid 0x%4.4x scid 0x%4.4x result 0x%2.2x status 0x%2.2x",
 	       dcid, scid, result, status);
 
@@ -4337,6 +4341,11 @@ static int l2cap_connect_create_rsp(struct l2cap_conn *conn,
 
 	switch (result) {
 	case L2CAP_CR_SUCCESS:
+		if (__l2cap_get_chan_by_dcid(conn, dcid)) {
+			err = -EBADSLT;
+			break;
+		}
+
 		l2cap_state_change(chan, BT_CONFIG);
 		chan->ident = 0;
 		chan->dcid = dcid;
-- 
2.34.1