[PATCH for 4.4.y, 4.9.y, 4.14.y, 4.19.y] net: cdc_ncm: Signedness bug in cdc_ncm_set_dgram_size()

[PATCH for 4.4.y, 4.9.y, 4.14.y, 4.19.y] net: cdc_ncm: Signedness bug in cdc_ncm_set_dgram_size()

[Nobuhiro Iwamatsu]

From: Dan Carpenter <dan.carpenter@oracle.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@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
---
 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 71ef895b4dca..bab13ccfb085 100644
--- 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(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;
 	}
-- 
2.23.0

Re: [PATCH for 4.4.y, 4.9.y, 4.14.y, 4.19.y] net: cdc_ncm: Signedness bug in cdc_ncm_set_dgram_size()

[Greg KH]

On Wed, Nov 20, 2019 at 12:07:10PM +0900, Nobuhiro Iwamatsu wrote:
> From: Dan Carpenter <dan.carpenter@oracle.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@oracle.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
> ---
>  drivers/net/usb/cdc_ncm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Now queud up, thanks!

greg k-h