Subject: Re: [net-next PATCH] bpf: cpumap fix potential lost wake-up problem

From: Jesper Dangaard Brouer <[email-masked]>
Date: Tue, 24 Oct 2017 06:46:32 +0200

On Mon, 23 Oct 2017 22:34:37 +0200
Daniel Borkmann <[email-masked]> wrote:

> On 10/23/2017 07:39 PM, Jesper Dangaard Brouer wrote:
> > As pointed out by Michael, commit 1c601d829ab0 ("bpf: cpumap xdp_buff
> > to skb conversion and allocation") contains a classical example of the
> > potential lost wake-up problem.
> >
> > We need to recheck the condition __ptr_ring_empty() after changing
> > current->state to TASK_INTERRUPTIBLE, this avoids a race between
> > wake_up_process() and schedule(). After this, a race with
> > wake_up_process() will simply change the state to TASK_RUNNING, and
> > the schedule() call not really put us to sleep.
> >
> > Fixes: 1c601d829ab0 ("bpf: cpumap xdp_buff to skb conversion and allocation")
> > Reported-by: "Michael S. Tsirkin" <[email-masked]>  
> 
> SOB missing ...

Signed-off-by: Jesper Dangaard Brouer <[email-masked]>

Damn... DaveM do I need to resubmit? Or will patchwork pickup above SOB?

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer