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Subject: Re: [PATCH 1/2] xen: fix out-of-bounds irq unbind for MSI message
 groups
To:     Amit Shah <aams@amazon.com>, xen-devel@lists.xenproject.org
Cc:     linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= <roger.pau@citrix.com>,
        David Vrabel <david.vrabel@citrix.com>,
        Eduardo Valentin <eduval@amazon.com>,
        Juergen Gross <jgross@suse.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Liu Shuo <shuo.a.liu@intel.com>,
        Anoob Soman <anoob.soman@citrix.com>
References: <1519666595-41362-1-git-send-email-aams@amazon.com>
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From:   Boris Ostrovsky <boris.ostrovsky@oracle.com>
Message-ID: <db4a0e0b-31cf-9c37-ba89-c0e7b6c99d87@oracle.com>
Date:   Mon, 26 Feb 2018 15:02:33 -0500
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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@amazon.com>
> CC: <stable@vger.kernel.org>
> CC: Roger Pau Monné <roger.pau@citrix.com>
> CC: David Vrabel <david.vrabel@citrix.com>
> CC: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> CC: Eduardo Valentin <eduval@amazon.com>
> CC: Juergen Gross <jgross@suse.com>
> CC: Thomas Gleixner <tglx@linutronix.de>
> CC: "K. Y. Srinivasan" <kys@microsoft.com>
> CC: Liu Shuo <shuo.a.liu@intel.com>
> CC: Anoob Soman <anoob.soman@citrix.com>
> Signed-off-by: Amit Shah <aams@amazon.com>
> ---
>  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