linux-kernel - [PATCH AUTOSEL 4.19 17/25] net: cdc_ncm: Signedness bug in cdc_ncm_set_dgram

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Message-Id: <20191122194859.24508-17-sashal@kernel.org>
Date:   Fri, 22 Nov 2019 14:48:50 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, linux-usb@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 17/25] net: cdc_ncm: Signedness bug in cdc_ncm_set_dgram_size()

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

[ Upstream commit a56dcc6b455830776899ce3686735f1172e12243 ]

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: Sasha Levin <sashal@...nel.org>
---
 drivers/net/usb/cdc_ncm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index a57d82ef0f810..1f57a6a2b8a25 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -579,7 +579,7 @@ static void cdc_ncm_set_dgram_size(struct usbnet *dev, int new_size)
 	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;
 	}
-- 
2.20.1