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

[David Miller <davem@xxxxxxxxxxxxx>]

From: Paul Durrant <pdurrant@xxxxxxxxxx>
Date: Thu, 12 Dec 2019 12:37:23 +0000

> Commit 2ac061ce97f4 ("xen/netback: cleanup init and deinit code")
> introduced a problem. 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.
> 
> Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>

Please repost this with an appropriate Fixes: tag.

And then you can removed the explicit commit reference from the log message
and simply say "The commit mentioned in the Fixes tag introduced a problen ..."

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