[PATCH] 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@xxxxxxxxxxxxxxx
Signed-off-by: Günther Noack <gnoack@xxxxxxxxxx>
---
 drivers/hid/hid-logitech-hidpp.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 9ced0e4d46ae..919ba9f50292 100644
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -4316,6 +4316,9 @@ static int hidpp_get_report_length(struct hid_device *hdev, int id)
 	if (!report)
 		return 0;
 
+	if (!report->maxfield)
+		return 0;
+
 	return report->field[0]->report_count + 1;
 }
 
-- 
2.52.0.457.g6b5491de43-goog