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

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

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
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created.  Hopefully you will not take offence and will fix the problem
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