Re: network packet corruption in v3.6.0-rc1 (and also in v3.5)

Eric Dumazet
2012-08-19T11:02:19Z

On Sat, 2012-08-18 at 16:40 +1000, Andrew Worsley wrote:
> Some times I get a burst of errors and dropped tcp connections with
> this warning. I had a similar issue with v3.5 (in fact v3.5 was
> unusable for https connections which would give bad MAC code messages
> at the application level)..
>
> The issue seems better under v3.6-rc1 where as it was very bad under
> v3.5. Let me know if there is something I can do to avoid this
> problem. I am using the USB r8712u wireless NIC if that is relevant as
> I haven't been able to get the native wireless working under the MAC
> book yet (requires proprietary firmware extraction which I am not
> familiar with)
>
> Much obliged if there is anything I can do to avoid it as it is rather
> annoying. Doesn't happen at all with my Debian wheezy 3.2.0-2-amd64
> kernel.

OK, this seems to be related to r8712u, still in staging tree.

At first glance, its using a buggy skb_clone(), or kind of a 'reuse skb'
trick I have no time to investigate.

I suspect that some memory area are overwritten by this driver, and this
was not noticed with older kernels. With new kernels, its triggering a
WARN_ON() in tcp stack.

Any chance you can try to reproduce the bug with another adapter ?