[PATCH v2] HID: logitech-hidpp: Check maxfield in hidpp_get_report_length()

[PATCH v2] HID: logitech-hidpp: Check maxfield in hidpp_get_report_length()

[Günther Noack]

Do not crash when a report has no fields.

Fake USB gadgets can send their own HID report descriptors and can define report
structures without valid fields.  This can be used to crash the kernel over USB.

Cc: stable@vger.kernel.org
Signed-off-by: Günther Noack <gnoack@google.com>
---
 drivers/hid/hid-logitech-hidpp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 9ced0e4d46ae..c5e132a6c085 100644
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -4313,7 +4313,7 @@ static int hidpp_get_report_length(struct hid_device *hdev, int id)
 
 	re = &(hdev->report_enum[HID_OUTPUT_REPORT]);
 	report = re->report_id_hash[id];
-	if (!report)
+	if (!report || !report->maxfield)
 		return 0;
 
 	return report->field[0]->report_count + 1;
-- 
2.52.0.457.g6b5491de43-goog

Re: [PATCH v2] HID: logitech-hidpp: Check maxfield in hidpp_get_report_length()

[Greg KH]

On Fri, Jan 09, 2026 at 01:25:58PM +0100, Günther Noack wrote:
> Do not crash when a report has no fields.
> 
> Fake USB gadgets can send their own HID report descriptors and can define report
> structures without valid fields.  This can be used to crash the kernel over USB.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Günther Noack <gnoack@google.com>
> ---
>  drivers/hid/hid-logitech-hidpp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
> index 9ced0e4d46ae..c5e132a6c085 100644
> --- a/drivers/hid/hid-logitech-hidpp.c
> +++ b/drivers/hid/hid-logitech-hidpp.c
> @@ -4313,7 +4313,7 @@ static int hidpp_get_report_length(struct hid_device *hdev, int id)
>  
>  	re = &(hdev->report_enum[HID_OUTPUT_REPORT]);
>  	report = re->report_id_hash[id];
> -	if (!report)
> +	if (!report || !report->maxfield)
>  		return 0;
>  
>  	return report->field[0]->report_count + 1;
> -- 
> 2.52.0.457.g6b5491de43-goog
> 


Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- This looks like a new version of a previously submitted patch, but you
  did not list below the --- line any changes from the previous version.
  Please read the section entitled "The canonical patch format" in the
  kernel file, Documentation/process/submitting-patches.rst for what
  needs to be done here to properly describe this.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.

thanks,

greg k-h's patch email bot

Re: [PATCH v2] HID: logitech-hidpp: Check maxfield in hidpp_get_report_length()

[Jiri Kosina]

On Fri, 9 Jan 2026, Günther Noack wrote:

> Do not crash when a report has no fields.
> 
> Fake USB gadgets can send their own HID report descriptors and can define r=
> eport
> structures without valid fields.  This can be used to crash the kernel over=
>  USB.

Applied, thanks.

-- 
Jiri Kosina
SUSE Labs