linux-kernel - [PATCH] Bluetooth: L2CAP: fix an illegal state transition from BT

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Message-Id: <20220926204657.3147968-1-iam@sung-woo.kim>
Date:   Mon, 26 Sep 2022 16:46:58 -0400
From:   Sungwoo Kim <iam@...g-woo.kim>
To:     unlisted-recipients:; (no To-header on input)
Cc:     syzkaller@...glegroups.com, Sungwoo Kim <iam@...g-woo.kim>,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] Bluetooth: L2CAP: fix an illegal state transition from BT_DISCONN

Prevent an illegal state transition from BT_DISCONN to BT_CONFIG.
L2CAP_CONN_RSP and L2CAP_CREATE_CHAN_RSP events should be ignored
for BT_DISCONN state according to the Bluetooth Core v5.3 p.1096.
It is found by BTFuzz, a modified version of syzkaller.

Signed-off-by: Sungwoo Kim <iam@...g-woo.kim>
---
 net/bluetooth/l2cap_core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 2c9de67da..a15d64b13 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -4307,6 +4307,9 @@ static int l2cap_connect_create_rsp(struct l2cap_conn *conn,
 		}
 	}
 
+	if (chan->state == BT_DISCONN)
+		goto unlock;
+
 	err = 0;
 
 	l2cap_chan_lock(chan);
-- 
2.25.1