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[71.56.157.77]) by smtp.gmail.com with ESMTPSA id p11sm409093pjo.19.2021.06.02.16.23.55 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Jun 2021 16:23:56 -0700 (PDT) From: Luiz Augusto von Dentz To: linux-bluetooth@vger.kernel.org Subject: [RFC] Bluetooth: L2CAP: Fix general protection fault in l2cap_chan_timeout Date: Wed, 2 Jun 2021 16:23:48 -0700 Message-Id: <20210602232348.766496-1-luiz.dentz@gmail.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-bluetooth@vger.kernel.org From: Luiz Augusto von Dentz Even though l2cap_chan_del calls __clear_chan_timer that uses cancel_delayed_work which doesn't prevent the work to run as it could be already pending. So instead this check if chan->conn has been set to NULL, which indicates that l2cap_conn_del might have run, and proceed to release its reference since the channel has already been cleanup. Reported-by: syzbot+008cdbf7a9044c2c2f99@syzkaller.appspotmail.com Signed-off-by: Luiz Augusto von Dentz --- net/bluetooth/l2cap_core.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index 9ebb85df4db4..4408e07a00d1 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -414,11 +414,21 @@ static void l2cap_chan_timeout(struct work_struct *work) { struct l2cap_chan *chan = container_of(work, struct l2cap_chan, chan_timer.work); - struct l2cap_conn *conn = chan->conn; + struct l2cap_conn *conn; int reason; BT_DBG("chan %p state %s", chan, state_to_string(chan->state)); + conn = chan->conn; + if (!conn) { + /* Channel is no longer attached to a connection so + * l2cap_conn_del might have run, just release reference + * acquired via __set_chan_timer. + */ + l2cap_chan_put(chan); + return; + } + mutex_lock(&conn->chan_lock); /* __set_chan_timer() calls l2cap_chan_hold(chan) while scheduling * this work. No need to call l2cap_chan_hold(chan) here again.