[PATCH net-next] asix: silence log message from oversize packet

[PATCH net-next] asix: silence log message from oversize packet

[Stephen Hemminger]

Since it is possible for an external system to send oversize packets
at anytime, it is best for driver not to print a message and spam
the log (potential external DoS).

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=109471

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

--- a/drivers/net/usb/asix_common.c	2015-10-16 16:05:30.997785598 -0700
+++ b/drivers/net/usb/asix_common.c	2015-12-17 17:50:30.983973764 -0800
@@ -118,7 +118,7 @@ int asix_rx_fixup_internal(struct usbnet
 				return 0;
 			}
 			if (size > dev->net->mtu + ETH_HLEN + VLAN_HLEN) {
-				netdev_err(dev->net, "asix_rx_fixup() Bad RX Length %d\n",
+				netdev_dbg(dev->net, "asix_rx_fixup() Bad RX Length %d\n",
 					   size);
 				return 0;
 			}

Re: [PATCH net-next] asix: silence log message from oversize packet

[David Miller]

From: Stephen Hemminger <stephen@networkplumber.org>
Date: Thu, 17 Dec 2015 17:51:16 -0800

> Since it is possible for an external system to send oversize packets
> at anytime, it is best for driver not to print a message and spam
> the log (potential external DoS).
> 
> Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=109471
> 
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

Seems reasonable, applied, thanks Stephen.

Re: [PATCH net-next] asix: silence log message from oversize packet

[Stephen Hemminger]

On Fri, 18 Dec 2015 16:08:53 -0500 (EST)
David Miller <davem@davemloft.net> wrote:

> From: Stephen Hemminger <stephen@networkplumber.org>
> Date: Thu, 17 Dec 2015 17:51:16 -0800
> 
> > Since it is possible for an external system to send oversize packets
> > at anytime, it is best for driver not to print a message and spam
> > the log (potential external DoS).
> > 
> > Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=109471
> > 
> > Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> 
> Seems reasonable, applied, thanks Stephen.

It doesn't fix the bug that is generating the oversize packet, that still needs
to be root caused.

Re: [PATCH net-next] asix: silence log message from oversize packet

[David Miller]

From: Stephen Hemminger <stephen@networkplumber.org>
Date: Fri, 18 Dec 2015 16:15:03 -0800

> On Fri, 18 Dec 2015 16:08:53 -0500 (EST)
> David Miller <davem@davemloft.net> wrote:
> 
>> From: Stephen Hemminger <stephen@networkplumber.org>
>> Date: Thu, 17 Dec 2015 17:51:16 -0800
>> 
>> > Since it is possible for an external system to send oversize packets
>> > at anytime, it is best for driver not to print a message and spam
>> > the log (potential external DoS).
>> > 
>> > Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=109471
>> > 
>> > Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
>> 
>> Seems reasonable, applied, thanks Stephen.
> 
> It doesn't fix the bug that is generating the oversize packet, that still needs
> to be root caused.

Remote systems can do this easily.  It's not a bug in the driver.

Say you decrease the MTU to 500 or whatever, nothing in the hardware
prevents reception of > 500 byte frames.

It's only a software limit.