linux-kernel - [PATCH] HID: rmi: Check that the RMI_STARTED bit is set before unregistering the RMI transport device

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Message-ID: <20191023012344.20998-1-aduggan@synaptics.com>
Date:   Wed, 23 Oct 2019 01:24:03 +0000
From:   Andrew Duggan <aduggan@...aptics.com>
To:     "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Andrew Duggan <aduggan@...aptics.com>,
        Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Federico Cerutti <federico@...es-c.it>,
        Christopher Heiny <Cheiny@...aptics.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>
Subject: [PATCH] HID: rmi: Check that the RMI_STARTED bit is set before
 unregistering the RMI transport device

In the event that the RMI device is unreachable, the calls to
rmi_set_mode() or rmi_set_page() will fail before registering the RMI
transport device. When the device is removed, rmi_remove() will call
rmi_unregister_transport_device() which will attempt to access the
rmi_dev pointer which was not set. This patch adds a check of the
RMI_STARTED bit before calling rmi_unregister_transport_device().
The RMI_STARTED bit is only set after rmi_register_transport_device()
completes successfully. A subsequent patch in the RMI core will add
checks to validate the pointers before accessing them.

The kernel oops was reported in this message:
https://www.spinics.net/lists/linux-input/msg58433.html

Signed-off-by: Andrew Duggan <aduggan@...aptics.com>
Reported-by: Federico Cerutti <federico@...es-c.it>
---
 drivers/hid/hid-rmi.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-rmi.c b/drivers/hid/hid-rmi.c
index 7c6abd7e0979..9ce22acdfaca 100644
--- a/drivers/hid/hid-rmi.c
+++ b/drivers/hid/hid-rmi.c
@@ -744,7 +744,8 @@ static void rmi_remove(struct hid_device *hdev)
 {
 	struct rmi_data *hdata = hid_get_drvdata(hdev);
 
-	if (hdata->device_flags & RMI_DEVICE) {
+	if ((hdata->device_flags & RMI_DEVICE)
+	    && test_bit(RMI_STARTED, &hdata->flags)) {
 		clear_bit(RMI_STARTED, &hdata->flags);
 		cancel_work_sync(&hdata->reset_work);
 		rmi_unregister_transport_device(&hdata->xport);
-- 
2.20.1