Re: [PATCH net v2] xen-netback: avoid race that can lead to NULL pointer dereference

From: Jakub Kicinski
Date: Sun Dec 15 2019 - 14:43:59 EST

On Fri, 13 Dec 2019 13:20:40 +0000, Paul Durrant wrote:
> In function xenvif_disconnect_queue(), the value of queue->rx_irq is
> zeroed *before* queue->task is stopped. Unfortunately that task may call
> notify_remote_via_irq(queue->rx_irq) and calling that function with a
> zero value results in a NULL pointer dereference in evtchn_from_irq().
> This patch simply re-orders things, stopping all tasks before zero-ing the
> irq values, thereby avoiding the possibility of the race.
> Fixes: 2ac061ce97f4 ("xen/netback: cleanup init and deinit code")
> Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>

> v2:
> - Add 'Fixes' tag and re-work commit comment

I've added Wei's Ack from v1, if the code doesn't change substantially
please keep people's Acks.

Applied, thanks.