linux-kernel - [PATCH 4.4 09/23] Bluetooth: fix the erroneous flush

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Date:   Tue,  8 Jun 2021 20:27:01 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, 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>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
        Lin Ma <linma@....edu.cn>, Hao Xiong <mart1n@....edu.cn>
Subject: [PATCH 4.4 09/23] Bluetooth: fix the erroneous flush_work() order

From: Lin Ma <linma@....edu.cn>

commit 6a137caec23aeb9e036cdfd8a46dd8a366460e5d upstream.

In the cleanup routine for failed initialization of HCI device,
the flush_work(&hdev->rx_work) need to be finished before the
flush_work(&hdev->cmd_work). Otherwise, the hci_rx_work() can
possibly invoke new cmd_work and cause a bug, like double free,
in late processings.

This was assigned CVE-2021-3564.

This patch reorder the flush_work() to fix this bug.

Cc: Marcel Holtmann <marcel@...tmann.org>
Cc: Johan Hedberg <johan.hedberg@...il.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: linux-bluetooth@...r.kernel.org
Cc: netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Lin Ma <linma@....edu.cn>
Signed-off-by: Hao Xiong <mart1n@....edu.cn>
Cc: stable <stable@...r.kernel.org>
Signed-off-by: Marcel Holtmann <marcel@...tmann.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/bluetooth/hci_core.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -1555,8 +1555,13 @@ static int hci_dev_do_open(struct hci_de
 	} else {
 		/* Init failed, cleanup */
 		flush_work(&hdev->tx_work);
-		flush_work(&hdev->cmd_work);
+
+		/* Since hci_rx_work() is possible to awake new cmd_work
+		 * it should be flushed first to avoid unexpected call of
+		 * hci_cmd_work()
+		 */
 		flush_work(&hdev->rx_work);
+		flush_work(&hdev->cmd_work);
 
 		skb_queue_purge(&hdev->cmd_q);
 		skb_queue_purge(&hdev->rx_q);