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Subject[PATCH v2 2/3] HID: logitech-hidpp: rework device validation
Date
G920 device only advertises REPORT_ID_HIDPP_LONG and
REPORT_ID_HIDPP_VERY_LONG in its HID report descriptor, so querying
for REPORT_ID_HIDPP_SHORT with optional=false will always fail and
prevent G920 to be recognized as a valid HID++ device.

To fix this and improve some other aspects, modify
hidpp_validate_device() as follows:

- Inline the code of hidpp_validate_report() to simplify
distingushing between non-present and invalid report descriptors

- Drop the check for id >= HID_MAX_IDS || id < 0 since all of our
IDs are static and known to satisfy that at compile time

- Change the algorithms to check all possible report
types (including very long report) and deem the device as a valid
HID++ device if it supports at least one

- Treat invalid report length as a hard stop for the validation
algorithm, meaning that if any of the supported reports has
invalid length we assume the worst and treat the device as a
generic HID device.

- Fold initialization of hidpp->very_long_report_length into
hidpp_validate_device() since it already fetches very long report
length and validates its value

Fixes: fe3ee1ec007b ("HID: logitech-hidpp: allow non HID++ devices to be handled by this module")
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=204191
Reported-by: Sam Bazely <sambazley@fastmail.com>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: Henrik Rydberg <rydberg@bitmath.org>
Cc: Pierre-Loup A. Griffais <pgriffais@valvesoftware.com>
Cc: Austin Palmer <austinp@valvesoftware.com>
Cc: linux-input@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org # 5.2+
---
drivers/hid/hid-logitech-hidpp.c | 54 ++++++++++++++++++--------------
1 file changed, 30 insertions(+), 24 deletions(-)

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 85911586b3b6..8c4be991f387 100644
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -3498,34 +3498,45 @@ static int hidpp_get_report_length(struct hid_device *hdev, int id)
return report->field[0]->report_count + 1;
}

-static bool hidpp_validate_report(struct hid_device *hdev, int id,
- int expected_length, bool optional)
+static bool hidpp_validate_device(struct hid_device *hdev)
{
- int report_length;
+ struct hidpp_device *hidpp = hid_get_drvdata(hdev);
+ int id, report_length, supported_reports = 0;
+
+ id = REPORT_ID_HIDPP_SHORT;
+ report_length = hidpp_get_report_length(hdev, id);
+ if (report_length) {
+ if (report_length < HIDPP_REPORT_SHORT_LENGTH)
+ goto bad_device;

- if (id >= HID_MAX_IDS || id < 0) {
- hid_err(hdev, "invalid HID report id %u\n", id);
- return false;
+ supported_reports++;
}

+ id = REPORT_ID_HIDPP_LONG;
report_length = hidpp_get_report_length(hdev, id);
- if (!report_length)
- return optional;
+ if (report_length) {
+ if (report_length < HIDPP_REPORT_LONG_LENGTH)
+ goto bad_device;

- if (report_length < expected_length) {
- hid_warn(hdev, "not enough values in hidpp report %d\n", id);
- return false;
+ supported_reports++;
}

- return true;
-}
+ id = REPORT_ID_HIDPP_VERY_LONG;
+ report_length = hidpp_get_report_length(hdev, id);
+ if (report_length) {
+ if (report_length > HIDPP_REPORT_LONG_LENGTH &&
+ report_length < HIDPP_REPORT_VERY_LONG_MAX_LENGTH)
+ goto bad_device;

-static bool hidpp_validate_device(struct hid_device *hdev)
-{
- return hidpp_validate_report(hdev, REPORT_ID_HIDPP_SHORT,
- HIDPP_REPORT_SHORT_LENGTH, false) &&
- hidpp_validate_report(hdev, REPORT_ID_HIDPP_LONG,
- HIDPP_REPORT_LONG_LENGTH, true);
+ supported_reports++;
+ hidpp->very_long_report_length = report_length;
+ }
+
+ return supported_reports;
+
+bad_device:
+ hid_warn(hdev, "not enough values in hidpp report %d\n", id);
+ return false;
}

static bool hidpp_application_equals(struct hid_device *hdev,
@@ -3572,11 +3583,6 @@ static int hidpp_probe(struct hid_device *hdev, const struct hid_device_id *id)
return hid_hw_start(hdev, HID_CONNECT_DEFAULT);
}

- hidpp->very_long_report_length =
- hidpp_get_report_length(hdev, REPORT_ID_HIDPP_VERY_LONG);
- if (hidpp->very_long_report_length > HIDPP_REPORT_VERY_LONG_MAX_LENGTH)
- hidpp->very_long_report_length = HIDPP_REPORT_VERY_LONG_MAX_LENGTH;
-
if (id->group == HID_GROUP_LOGITECH_DJ_DEVICE)
hidpp->quirks |= HIDPP_QUIRK_UNIFYING;

--
2.21.0
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