[PATCH 5.10.y] Bluetooth: L2CAP: Only accept connection responses to outstanding requests

[Sasha Levin <sashal@kernel.org>]

From: Siwei Zhang <oss@fourdim.xyz>

[ Upstream commit a518b9a9ef6ee3b18ecdf6ba5360c608aaf969e9 ]

An outgoing channel waits in BT_CONNECT until security
and the feature mask exchange complete, and only then
sends its connection request. A peer can answer it
before that with a connection response matching our
source CID. The channel then moves to BT_CONFIG,
completes configuration and becomes connected before
security has completed. If security then fails,
l2cap_security_cfm() leaves the connected channel
alone, so it stays up on a link that did not reach
the required security level.

A connection response with a zero source CID is
matched by identifier. Another channel can hold the
same identifier for a response it still has to send,
so the lookup can pick the wrong channel.

Only accept a connection response while our request
is outstanding, and only look at such channels when
matching by identifier.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Siwei Zhang <oss@fourdim.xyz>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
[ sashal: adapted the checks to chan_lock-based locking while tracking pending requests in the existing AMP create-channel path ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/bluetooth/l2cap_core.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index de97a746bb38c..564eaa1b3e24a 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -185,6 +185,29 @@ static struct l2cap_chan *l2cap_get_chan_by_ident(struct l2cap_conn *conn,
 	return c;
 }
 
+/* Our connection request has been sent and is still outstanding */
+static bool l2cap_chan_connect_pending(struct l2cap_chan *chan)
+{
+	return chan->state == BT_CONNECT &&
+	       test_bit(CONF_CONNECT_PEND, &chan->conf_state);
+}
+
+/* Other channels may hold the same ident for a response they still have
+ * to send, so only look at channels waiting for a connection response.
+ */
+static struct l2cap_chan *__l2cap_get_connect_chan_by_ident(struct l2cap_conn *conn,
+							    u8 ident)
+	__must_hold(&conn->chan_lock)
+{
+	struct l2cap_chan *c;
+
+	list_for_each_entry(c, &conn->chan_l, list) {
+		if (c->ident == ident && l2cap_chan_connect_pending(c))
+			return c;
+	}
+	return NULL;
+}
+
 static struct l2cap_chan *__l2cap_global_chan_by_addr(__le16 psm, bdaddr_t *src,
 						      u8 src_type)
 {
@@ -1355,6 +1378,8 @@ static void l2cap_send_create_chan_req(struct l2cap_chan *chan, u8 amp_id)
 
 	chan->ident = l2cap_get_ident(chan->conn);
 
+	set_bit(CONF_CONNECT_PEND, &chan->conf_state);
+
 	l2cap_send_cmd(chan->conn, chan->ident, L2CAP_CREATE_CHAN_REQ,
 		       sizeof(req), &req);
 }
@@ -4461,7 +4486,7 @@ static int l2cap_connect_create_rsp(struct l2cap_conn *conn,
 			goto unlock;
 		}
 	} else {
-		chan = __l2cap_get_chan_by_ident(conn, cmd->ident);
+		chan = __l2cap_get_connect_chan_by_ident(conn, cmd->ident);
 		if (!chan) {
 			err = -EBADSLT;
 			goto unlock;
@@ -4478,6 +4503,13 @@ static int l2cap_connect_create_rsp(struct l2cap_conn *conn,
 
 	l2cap_chan_lock(chan);
 
+	/* Only accept a response to a connection request we sent and that
+	 * is still outstanding. A channel waiting in BT_CONNECT for security
+	 * or the feature mask has not sent one yet.
+	 */
+	if (!l2cap_chan_connect_pending(chan))
+		goto done;
+
 	switch (result) {
 	case L2CAP_CR_SUCCESS:
 		if (__l2cap_get_chan_by_dcid(conn, dcid)) {
@@ -4507,6 +4539,7 @@ static int l2cap_connect_create_rsp(struct l2cap_conn *conn,
 		break;
 	}
 
+done:
 	l2cap_chan_unlock(chan);
 	l2cap_chan_put(chan);
 
-- 
2.53.0