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SubjectRe: [PATCH v2 2/3] HID: logitech-hidpp: rework device validation
On Wed, Oct 16, 2019 at 9:38 PM Andrey Smirnov <andrew.smirnov@gmail.com> wrote:
>
> 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.
>

Oh, the issue is that the very long HID++ reports on the G920 are
HIDPP_REPORT_VERY_LONG_MAX_LENGTH long, which means the test will fail
for those.

Cheers,
Benjamin

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