linux-kernel - [PATCH 4.4 100/159] net: cdc_ncm: Signedness bug in cdc_ncm_set_dgram

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Date:   Fri, 22 Nov 2019 11:28:11 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@...hiba.co.jp>
Subject: [PATCH 4.4 100/159] net: cdc_ncm: Signedness bug in cdc_ncm_set_dgram_size()

From: Dan Carpenter <dan.carpenter@...cle.com>

commit a56dcc6b455830776899ce3686735f1172e12243 upstream.

This code is supposed to test for negative error codes and partial
reads, but because sizeof() is size_t (unsigned) type then negative
error codes are type promoted to high positive values and the condition
doesn't work as expected.

Fixes: 332f989a3b00 ("CDC-NCM: handle incomplete transfer of MTU")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@...hiba.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/net/usb/cdc_ncm.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -534,7 +534,7 @@ static void cdc_ncm_set_dgram_size(struc
 	err = usbnet_read_cmd(dev, USB_CDC_GET_MAX_DATAGRAM_SIZE,
 			      USB_TYPE_CLASS | USB_DIR_IN | USB_RECIP_INTERFACE,
 			      0, iface_no, &max_datagram_size, sizeof(max_datagram_size));
-	if (err < sizeof(max_datagram_size)) {
+	if (err != sizeof(max_datagram_size)) {
 		dev_dbg(&dev->intf->dev, "GET_MAX_DATAGRAM_SIZE failed\n");
 		goto out;
 	}