linux-kernel - [PATCH 4/4] HID: logitech-hidpp: disable io in probe error path

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Date:	Thu, 11 Dec 2014 13:51:20 +0100
From:	Peter Wu <peter@...ensteyn.nl>
To:	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Nestor Lopez Casado <nlopezcasad@...itech.com>,
	Andrew de los Reyes <adlr@...omium.org>
Cc:	Peter Hutterer <peter.hutterer@...-t.net>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 4/4] HID: logitech-hidpp: disable io in probe error path

Balance a hid_device_io_start() call with hid_device_io_stop() in the
error path. This avoids processing of HID reports when the probe fails
which possibly leads to invalid memory access in hid_device_probe() as
report_enum->report_id_hash might already be freed via
hid_close_report().

hid_set_drvdata() is called before wtp_allocate, be consistent and clear
drvdata too on the error path of wtp_allocate.

Signed-off-by: Peter Wu <peter@...ensteyn.nl>
---
Hi Andrew,

There are few users of hid_device_io_start/stop, this is the first one
to get start/stop out of sync. Should the comment of
hid_device_io_start() be updated to ensure that hid_device_io_stop()
gets called before probe() returns? Or should the hid-core be changed to
handle this out-of-sync issue:

		if (ret) {
			if (hdev->io_started))
				down(&hdev->driver_input_lock);
			hid_close_report(hdev);
			hdev->driver = NULL;
		}

Is my observation correct or not that HID reports can arrive during
hid_close_report() when io_started == true?

Kind regards,
Peter
---
 drivers/hid/hid-logitech-hidpp.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 4292cc3..2f420c0 100644
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -1121,7 +1121,7 @@ static int hidpp_probe(struct hid_device *hdev, const struct hid_device_id *id)
 	if (hidpp->quirks & HIDPP_QUIRK_CLASS_WTP) {
 		ret = wtp_allocate(hdev, id);
 		if (ret)
-			return ret;
+			goto wtp_allocate_fail;
 	}
 
 	INIT_WORK(&hidpp->work, delayed_work_cb);
@@ -1141,6 +1141,7 @@ static int hidpp_probe(struct hid_device *hdev, const struct hid_device_id *id)
 	if (id->group != HID_GROUP_LOGITECH_DJ_DEVICE) {
 		if (!connected) {
 			hid_err(hdev, "Device not connected");
+			hid_device_io_stop(hdev);
 			goto hid_parse_fail;
 		}
 
@@ -1186,6 +1187,7 @@ hid_hw_start_fail:
 hid_parse_fail:
 	cancel_work_sync(&hidpp->work);
 	mutex_destroy(&hidpp->send_mutex);
+wtp_allocate_fail:
 	hid_set_drvdata(hdev, NULL);
 	return ret;
 }
-- 
2.1.3

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