linux-kernel - Re: [PATCH v9 04/11] HID: asus: fortify keyboard handshake

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Message-ID: 
 <CAGwozwF6wegwHy=W1zaTEVksQYaw4L7V27w2aaZBMMoDjUjRYg@mail.gmail.com>
Date: Thu, 20 Nov 2025 15:28:52 +0100
From: Antheas Kapenekakis <lkml@...heas.dev>
To: Denis Benato <benato.denis96@...il.com>
Cc: platform-driver-x86@...r.kernel.org, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, Jiri Kosina <jikos@...nel.org>,
	Benjamin Tissoires <bentiss@...nel.org>,
 Corentin Chary <corentin.chary@...il.com>,
	"Luke D . Jones" <luke@...nes.dev>, Hans de Goede <hansg@...nel.org>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: Re: [PATCH v9 04/11] HID: asus: fortify keyboard handshake

On Thu, 20 Nov 2025 at 15:15, Denis Benato <benato.denis96@...il.com> wrote:
>
>
> On 11/20/25 10:46, Antheas Kapenekakis wrote:
> > Handshaking with an Asus device involves sending it a feature report
> > with the string "ASUS Tech.Inc." and then reading it back to verify the
> > handshake was successful, under the feature ID the interaction will
> > take place.
> >
> > Currently, the driver only does the first part. Add the readback to
> > verify the handshake was successful. As this could cause breakages,
> > allow the verification to fail with a dmesg error until we verify
> > all devices work with it (they seem to).
> >
> > Since the response is more than 16 bytes, increase the buffer size
> > to 64 as well to avoid overflow errors.
> >
> > Signed-off-by: Antheas Kapenekakis <lkml@...heas.dev>
> > ---
> >  drivers/hid/hid-asus.c | 32 +++++++++++++++++++++++++++++---
> >  1 file changed, 29 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/hid/hid-asus.c b/drivers/hid/hid-asus.c
> > index 6de402d215d0..5149dc7edfc5 100644
> > --- a/drivers/hid/hid-asus.c
> > +++ b/drivers/hid/hid-asus.c
> > @@ -48,7 +48,7 @@ MODULE_DESCRIPTION("Asus HID Keyboard and TouchPad");
> >  #define FEATURE_REPORT_ID 0x0d
> >  #define INPUT_REPORT_ID 0x5d
> >  #define FEATURE_KBD_REPORT_ID 0x5a
> > -#define FEATURE_KBD_REPORT_SIZE 16
> > +#define FEATURE_KBD_REPORT_SIZE 64
> >  #define FEATURE_KBD_LED_REPORT_ID1 0x5d
> >  #define FEATURE_KBD_LED_REPORT_ID2 0x5e
> >
> > @@ -394,14 +394,40 @@ static int asus_kbd_set_report(struct hid_device *hdev, const u8 *buf, size_t bu
> >
> >  static int asus_kbd_init(struct hid_device *hdev, u8 report_id)
> >  {
> > +     /*
> > +      * The handshake is first sent as a set_report, then retrieved
> > +      * from a get_report. They should be equal.
> > +      */
> >       const u8 buf[] = { report_id, 0x41, 0x53, 0x55, 0x53, 0x20, 0x54,
> >                    0x65, 0x63, 0x68, 0x2e, 0x49, 0x6e, 0x63, 0x2e, 0x00 };
> > +     u8 *readbuf;
> >       int ret;
> >
> >       ret = asus_kbd_set_report(hdev, buf, sizeof(buf));
> > -     if (ret < 0)
> > -             hid_err(hdev, "Asus failed to send init command: %d\n", ret);
> > +     if (ret < 0) {
> > +             hid_err(hdev, "Asus failed to send handshake: %d\n", ret);
> > +             return ret;
> > +     }
> > +
> > +     readbuf = kzalloc(FEATURE_KBD_REPORT_SIZE, GFP_KERNEL);
> I see my suggestion to use __free here didn't materialize in code using
> it even after Ilpo kindly wrote how to correctly use it.
>
> I think you can move the readbuf assignment right below buf and
> take into account what Ilpo said.
>
> I don't expect new variables will be added here ever again,
> but I agree with Ilpo that it's a good idea here to write code
> accounting for that possibility.
>
> It is my understanding that who proposes patches is expected to
> resolve discussions when changes are proposed or to take into
> account requested changes and submit a modified version.

It was ambiguous. I interpreted Ilpo's email as a dismissal

I will try to incorporate it if I do another revision. Although I do
not think it improves things in this case as the function does not
have multiple return statements.

> > +     if (!readbuf)
> > +             return -ENOMEM;
> > +
> > +     ret = hid_hw_raw_request(hdev, report_id, readbuf,
> > +                              FEATURE_KBD_REPORT_SIZE, HID_FEATURE_REPORT,
> > +                              HID_REQ_GET_REPORT);
> > +     if (ret < 0) {
> > +             hid_err(hdev, "Asus failed to receive handshake ack: %d\n", ret);
> > +     } else if (memcmp(readbuf, buf, sizeof(buf)) != 0) {
> > +             hid_warn(hdev, "Asus handshake returned invalid response: %*ph\n",
> > +                     FEATURE_KBD_REPORT_SIZE, readbuf);
> > +             /*
> > +              * Do not return error if handshake is wrong until this is
> > +              * verified to work for all devices.
> > +              */
> > +     }
> >
> > +     kfree(readbuf);
> >       return ret;
> >  }
> >
>