linux-kernel - [PATCH v2] HID: logitech-hidpp: Check maxfield in hidpp_get_report

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Message-ID: <20260109122557.3166556-3-gnoack@google.com>
Date: Fri,  9 Jan 2026 13:25:58 +0100
From: "Günther Noack" <gnoack@...gle.com>
To: "Filipe Laíns" <lains@...eup.net>, Bastien Nocera <hadess@...ess.net>, Jiri Kosina <jikos@...nel.org>, 
	Benjamin Tissoires <bentiss@...nel.org>
Cc: Greg KH <gregkh@...uxfoundation.org>, 
	"Günther Noack" <gnoack@...gle.com>, stable@...r.kernel.org, linux-input@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] HID: logitech-hidpp: Check maxfield in hidpp_get_report_length()

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@...r.kernel.org
Signed-off-by: Günther Noack <gnoack@...gle.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