linux-kernel - [PATCH 4.9 035/241] usb: misc: lvs: fix race condition in disconnect handling

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Message-Id: <20180319180752.635543182@linuxfoundation.org>
Date:   Mon, 19 Mar 2018 19:05:00 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Oliver Neukum <oneukum@...e.com>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.9 035/241] usb: misc: lvs: fix race condition in disconnect handling

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Oliver Neukum <oneukum@...e.com>


[ Upstream commit c4ba329cabca7c839ab48fb58b5bcc2582951a48 ]

There is a small window during which the an URB may
remain active after disconnect has returned. If in that case
already freed memory may be accessed and executed.

The fix is to poison the URB befotre the work is flushed.

Signed-off-by: Oliver Neukum <oneukum@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/usb/misc/lvstest.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/usb/misc/lvstest.c
+++ b/drivers/usb/misc/lvstest.c
@@ -433,6 +433,7 @@ static void lvs_rh_disconnect(struct usb
 	struct lvs_rh *lvs = usb_get_intfdata(intf);
 
 	sysfs_remove_group(&intf->dev.kobj, &lvs_attr_group);
+	usb_poison_urb(lvs->urb); /* used in scheduled work */
 	flush_work(&lvs->rh_work);
 	usb_free_urb(lvs->urb);
 }