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From:   Sungwoo Kim <iam@sung-woo.kim>
Date:   Fri, 4 Nov 2022 12:11:08 -0400
Message-ID: <CAJNyHpJ7hbmDK-Tq==L1D3gWB2ac4MTVYynf57JM0GmEN9-i7Q@mail.gmail.com>
Subject: L2CAP: Spec violation
To:     marcel@holtmann.org
Cc:     johan.hedberg@gmail.com, luiz.dentz@gmail.com, davem@davemloft.net,
        edumazet@google.com, kuba@kernel.org, pabeni@redhat.com,
        linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
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Hello,

Our fuzzer found a BT spec violation, illegal state transition on L2cap.
Specifically, l2cap_chan::state is transitioned from BT_CONFIG to
BT_DISCONN by CONFIG_RSP by following trace:

l2cap_config_rsp l2cap_core.c:4498
l2cap_send_disconn_req l2cap_core.c:4585
l2cap_state_change l2cap_core.c:1618

According to the spec 5.3 vol.3 part A 6.1.4, CONFIG_RSP cannot cause
that transition, i.e., CONFIG -> DISCONN by CONFIG_RSP is illegal.
It'd be great if we could discuss.

Thanks,
Sungwoo.