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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Andrew Duggan <aduggan@synaptics.com>,
        Federico Cerutti <federico@ceres-c.it>,
        Jiri Kosina <jkosina@suse.cz>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 082/191] HID: rmi: Check that the RMI_STARTED bit is set before unregistering the RMI transport device
Date:   Thu,  2 Jan 2020 23:06:04 +0100
Message-Id: <20200102215838.729753573@linuxfoundation.org>
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From: Andrew Duggan <aduggan@synaptics.com>

[ Upstream commit 8725aa4fa7ded30211ebd28bb1c9bae806eb3841 ]

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.

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

[jkosina@suse.cz: reworded changelog as agreed with Andrew]
Signed-off-by: Andrew Duggan <aduggan@synaptics.com>
Reported-by: Federico Cerutti <federico@ceres-c.it>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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