RE: [PATCH v3] HID: intel-thc-hid: intel-quickspi: bound GET_REPORT response to the caller buffer

[Xu, Even]

> -----Original Message-----
> From: HyeongJun An <sammiee5311@xxxxxxxxx>
> Sent: Thursday, August 6, 2026 10:56 PM
> To: Jiri Kosina <jikos@xxxxxxxxxx>; Xu, Even <even.xu@xxxxxxxxx>; Sun, Xinpeng
> <xinpeng.sun@xxxxxxxxx>
> Cc: Benjamin Tissoires <bentiss@xxxxxxxxxx>; linux-input@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx; HyeongJun An
> <sammiee5311@xxxxxxxxx>; Sashiko AI <sashiko-bot@xxxxxxxxxx>
> Subject: [PATCH v3] HID: intel-thc-hid: intel-quickspi: bound GET_REPORT
> response to the caller buffer
> 
> quickspi_hid_raw_request() receives the caller's buffer length in len, but
> quickspi_get_report() never sees it and copies the whole device-supplied
> response into buf regardless:
> 
>     memcpy(buf, qsdev->report_buf, qsdev->report_len);
> 
> qsdev->report_len comes from the input report the touch controller
> qsdev->returns,
> while buf is sized to whatever the caller asked hidraw for through
> HIDIOCGFEATURE or HIDIOCGINPUT.  A response larger than that overflows buf
> with device-controlled content.
> 
> The intel-quicki2c sibling already passes the caller length down to
> quicki2c_get_report() and validates the response against it before the copy.  Do
> the same here.
> 
> Fixes: 4138f21115ae ("HID: intel-thc-hid: intel-quickspi: Complete THC QuickSPI
> driver")
> Suggested-by: Sashiko AI <sashiko-bot@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: HyeongJun An <sammiee5311@xxxxxxxxx>
> ---
> v3: added READ_ONCE() around the qsdev->report_len read the v2 bound uses -
>     quickspi_handle_input_data() writes this field from IRQ context with no
>     locking, so per kernel convention for a lockless shared read it needs
>     READ_ONCE() regardless of how many times the value is used afterward.
>     Raised by the Sashiko AI review of v2.  No other change.
> 
> v2: fixed a Time-of-Check-to-Time-of-Use race the Sashiko AI review of v1
>     pointed out - the new bound read qsdev->report_len once for the check
>     and again for the memcpy, so a concurrent update between the two could
>     have overflowed buf with the checked-against-a-smaller-value length.
>     Read it once into a local and use that for both.
> 
> v1: https://lore.kernel.org/all/20260806133838.3378362-1-
> sammiee5311@xxxxxxxxx/
> 
>  .../intel-thc-hid/intel-quickspi/quickspi-hid.c  |  2 +-
>  .../intel-quickspi/quickspi-protocol.c           | 16 +++++++++++++---
>  .../intel-quickspi/quickspi-protocol.h           |  2 +-
>  3 files changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-hid.c
> b/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-hid.c
> index 91d5807b4a83..a60a0a7f16aa 100644
> --- a/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-hid.c
> +++ b/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-hid.c
> @@ -61,7 +61,7 @@ static int quickspi_hid_raw_request(struct hid_device *hid,
> 
>  	switch (reqtype) {
>  	case HID_REQ_GET_REPORT:
> -		ret = quickspi_get_report(qsdev, rtype, reportnum, buf);
> +		ret = quickspi_get_report(qsdev, rtype, reportnum, buf, len);
>  		break;
>  	case HID_REQ_SET_REPORT:
>  		ret = quickspi_set_report(qsdev, rtype, reportnum, buf, len); diff -
> -git a/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-protocol.c
> b/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-protocol.c
> index cb19057f1191..9dacfdf7aff6 100644
> --- a/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-protocol.c
> +++ b/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-protocol.c
> @@ -342,10 +342,12 @@ int reset_tic(struct quickspi_device *qsdev)  }
> 
>  int quickspi_get_report(struct quickspi_device *qsdev,
> -			u8 report_type, unsigned int report_id, void *buf)
> +			u8 report_type, unsigned int report_id, void *buf,
> +			u32 buf_len)
>  {
>  	int rep_type;
>  	int ret;
> +	u32 report_len;
> 
>  	if (report_type == HID_INPUT_REPORT) {
>  		rep_type = GET_INPUT_REPORT;
> @@ -372,9 +374,17 @@ int quickspi_get_report(struct quickspi_device *qsdev,
>  	}
>  	qsdev->get_report_cmpl = false;
> 
> -	memcpy(buf, qsdev->report_buf, qsdev->report_len);
> +	/* quickspi_handle_input_data() updates this from IRQ context. */
> +	report_len = READ_ONCE(qsdev->report_len);
> +	if (report_len > buf_len) {
> +		dev_err_once(qsdev->dev, "Get report response too big, %u
> vs %u\n",
> +			     report_len, buf_len);
> +		return -EINVAL;
> +	}
> +
> +	memcpy(buf, qsdev->report_buf, report_len);
> 
> -	return qsdev->report_len;
> +	return report_len;
>  }
> 
>  int quickspi_set_report(struct quickspi_device *qsdev, diff --git
> a/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-protocol.h b/drivers/hid/intel-
> thc-hid/intel-quickspi/quickspi-protocol.h
> index 775e29c1ed13..8a2338bee808 100644
> --- a/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-protocol.h
> +++ b/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-protocol.h
> @@ -12,7 +12,7 @@ struct quickspi_device;
> 
>  void quickspi_handle_input_data(struct quickspi_device *qsdev, u32 buf_len);
> int quickspi_get_report(struct quickspi_device *qsdev, u8 report_type,
> -			unsigned int report_id, void *buf);
> +			unsigned int report_id, void *buf, u32 buf_len);
>  int quickspi_set_report(struct quickspi_device *qsdev, u8 report_type,
>  			unsigned int report_id, void *buf, u32 buf_len);  int
> quickspi_get_report_descriptor(struct quickspi_device *qsdev);

Thanks for the patch!
This is a good error handling for unexpected big receive buffer.

Reviewed-by: Even Xu <even.xu@xxxxxxxxx>

> --
> 2.43.0