linux-kernel - [PATCH 5.14 08/14] HID: usbhid: Fix warning caused by 0-length input reports

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Date:   Mon,  6 Sep 2021 14:55:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Alan Stern <stern@...land.harvard.edu>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Jiri Kosina <jkosina@...e.cz>,
        syzbot+9b57a46bf1801ce2a2ca@...kaller.appspotmail.com
Subject: [PATCH 5.14 08/14] HID: usbhid: Fix warning caused by 0-length input reports

From: Alan Stern <stern@...land.harvard.edu>

commit 0a824efdb724e07574bafcd2c2486b2a3de35ff6 upstream.

Syzbot found a warning caused by hid_submit_ctrl() submitting a
control request to transfer a 0-length input report:

	usb 1-1: BOGUS control dir, pipe 80000280 doesn't match bRequestType a1

(The warning message is a little difficult to understand.  It means
that the control request claims to be for an IN transfer but this
contradicts the USB spec, which requires 0-length control transfers
always to be in the OUT direction.)

Now, a zero-length report isn't good for anything and there's no
reason for a device to have one, but the fuzzer likes to pick out
these weird edge cases.  In the future, perhaps we will decide to
reject 0-length reports at probe time.  For now, the simplest approach
for avoiding these warnings is to pretend that the report actually has
length 1.

Signed-off-by: Alan Stern <stern@...land.harvard.edu>
Reported-and-tested-by: syzbot+9b57a46bf1801ce2a2ca@...kaller.appspotmail.com
Tested-by: Oleksandr Natalenko <oleksandr@...alenko.name>
Tested-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
Acked-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc: stable@...r.kernel.org
Signed-off-by: Jiri Kosina <jkosina@...e.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/hid/usbhid/hid-core.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c
@@ -389,6 +389,7 @@ static int hid_submit_ctrl(struct hid_de
 		maxpacket = usb_maxpacket(hid_to_usb_dev(hid),
 					  usbhid->urbctrl->pipe, 0);
 		if (maxpacket > 0) {
+			len += (len == 0);    /* Don't allow 0-length reports */
 			len = DIV_ROUND_UP(len, maxpacket);
 			len *= maxpacket;
 			if (len > usbhid->bufsize)