Re: [PATCH 1/2] xen: fix out-of-bounds irq unbind for MSI message groups

[Boris Ostrovsky]

On 02/26/2018 12:36 PM, Amit Shah wrote:
> When an MSI descriptor was not available, the error path would try to
> unbind an irq that was never acquired - potentially unbinding an
> unrelated irq.
>
> Fixes: 4892c9b4ada9f9 ("xen: add support for MSI message groups")
> Reported-by: Hooman Mirhadi <mirhadih@xxxxxxxxxx>
> CC: <stable@xxxxxxxxxxxxxxx>
> CC: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
> CC: David Vrabel <david.vrabel@xxxxxxxxxx>
> CC: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> CC: Eduardo Valentin <eduval@xxxxxxxxxx>
> CC: Juergen Gross <jgross@xxxxxxxx>
> CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> CC: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
> CC: Liu Shuo <shuo.a.liu@xxxxxxxxx>
> CC: Anoob Soman <anoob.soman@xxxxxxxxxx>
> Signed-off-by: Amit Shah <aams@xxxxxxxxxx>
> ---
>  drivers/xen/events/events_base.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
> index 1ab4bd1..b6b8b29 100644
> --- a/drivers/xen/events/events_base.c
> +++ b/drivers/xen/events/events_base.c
> @@ -749,6 +749,7 @@ int xen_bind_pirq_msi_to_irq(struct pci_dev *dev, struct msi_desc *msidesc,
>  	}
>  
>  	ret = irq_set_msi_desc(irq, msidesc);
> +	i--;
>  	if (ret < 0)
>  		goto error_irq;

We really only need to do this in case of an error.

(And this patch needs to go to stable trees as well.)

Thanks
-boris