[PATCH 5.4 082/191] HID: rmi: Check that the RMI_STARTED bit is set before unregistering the RMI transport device

From: Greg Kroah-Hartman
Date: Thu Jan 02 2020 - 17:59:36 EST

From: Andrew Duggan <aduggan@xxxxxxxxxxxxx>

[ 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:

[jkosina@xxxxxxx: reworded changelog as agreed with Andrew]
Signed-off-by: Andrew Duggan <aduggan@xxxxxxxxxxxxx>
Reported-by: Federico Cerutti <federico@xxxxxxxxxx>
Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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);