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SubjectRe: [PATCH v2 2/3] HID: logitech-hidpp: rework device validation
On Wed, Oct 16, 2019 at 12:24 PM Benjamin Tissoires
<benjamin.tissoires@redhat.com> wrote:
>
> Hi Andrey,
>
> On Wed, Oct 16, 2019 at 8:30 PM Andrey Smirnov <andrew.smirnov@gmail.com> wrote:
> >
> > 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)
>
> Can you double check the conditions here?
> It's late, but I think you inverted the tests as we expect the report
> length to be between HIDPP_REPORT_LONG_LENGTH and
> HIDPP_REPORT_VERY_LONG_MAX_LENGTH inclusive, while here this creates a
> bad_device.

Hmm, I think you are right. Not sure why I didn't catch it on G920
since it support very long reports AFAIR. Will re-spin and double
check in v3. Sorry about that.

Thanks,
Andrey Smirnov

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