netdev - Re: [PATCH 6/7] : tehuti Fix possible causing oops of net_rx

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Date:	Wed, 12 Dec 2007 07:20:34 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	shemminger@...ux-foundation.org
Cc:	joonwpark81@...il.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, jgarzik@...ox.com,
	baum@...utinetworks.net, andy@...yhouse.net
Subject: Re: [PATCH 6/7] : tehuti Fix possible causing oops of
 net_rx_action

From: Stephen Hemminger <shemminger@...ux-foundation.org>
Date: Tue, 11 Dec 2007 21:39:39 -0800

> On Wed, 12 Dec 2007 13:01:27 +0900
> "Joonwoo Park" <joonwpark81@...il.com> wrote:
> 
> > [NETDEV]: tehuti Fix possible causing oops of net_rx_action
> > 
> > Signed-off-by: Joonwoo Park <joonwpark81@...il.com>
> > ---
> >  drivers/net/tehuti.c |    2 ++
> >  1 files changed, 2 insertions(+), 0 deletions(-)
> > 
> > diff --git a/drivers/net/tehuti.c b/drivers/net/tehuti.c
> > index 21230c9..955e749 100644
> > --- a/drivers/net/tehuti.c
> > +++ b/drivers/net/tehuti.c
> > @@ -305,6 +305,8 @@ static int bdx_poll(struct napi_struct *napi, int budget)
> >  
> >  		netif_rx_complete(dev, napi);
> >  		bdx_enable_interrupts(priv);
> > +		if (unlikely(work_done == napi->weight))
> > +			return work_done - 1;
> >  	}
> >  	return work_done;
> >  }
> 
> A better fix would be not going over budget in the first place.

That's not the problem.

They are not going over the budget, rather, they are hitting
the budget yet doing netif_rx_complete() as well which is
illegal.

Unless you strictly process less than "weight" packets, you must
not netif_rx_complete() and re-enable chip interrupts.

I can't believe people are trying to fix this bug like this.
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