Re: zd1211 or mac80211: SKB invalid truesize

[Michael Buesch <mb@bu3sch.de>]

On Tuesday 25 September 2007 23:18:16 David Miller wrote:
> From: Michael Buesch <mb@bu3sch.de>
> Date: Tue, 25 Sep 2007 22:42:11 +0200
> 
> > I get dmesg spammed with the following message when
> > I connect to an open network with zd1211rw-mac80211.
> > I'm not sure if that's a bug in zd or mac80211.
> > Any idea how to debug this?
> > 
> > [  280.915811] SKB BUG: Invalid truesize (840) len=1440, sizeof(sk_buff)=168
> > 
> > The device keeps working fine while this spams dmesg.
> 
> For anyone who investigates this, the issue is that if there is a
> socket associated with an skb (ie. skb->sk is non-NULL) you cannot
> change the skb->truesize without also adjusting the memory accounted
> to the socket.
> 
> Otherwise when the SKB gets freed, the wrong amount of socket buffer
> memory allocation will be given back to the socket.
> 
> When the above message triggers, it means the skb->truesize is
> smaller than skb->len plus the size of struct sk_buff which is
> obviously completely bogus.

Yeah, well. But how can this happen? Someone assigning to skb->len?
zd1211 doesn't do this.
Any slight idea which (kind of) code could trigger this?

-- 
Greetings Michael.