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Subject: Re: [PATCH v3 1/2] xen/xenbus: reference count registered modules
To:     Paul Durrant <pdurrant@amazon.com>
Cc:     xen-devel@lists.xenproject.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Stefano Stabellini <sstabellini@kernel.org>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Juergen Gross <jgross@suse.com>
References: <20191202114117.1264-1-pdurrant@amazon.com>
 <20191202114117.1264-2-pdurrant@amazon.com>
From:   Jan Beulich <jbeulich@suse.com>
Message-ID: <c784e57a-46ea-a839-8c0c-5a299aa5a64f@suse.com>
Date:   Tue, 3 Dec 2019 10:47:55 +0100
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On 02.12.2019 12:41, Paul Durrant wrote:
> To prevent a PV driver module being removed whilst attached to its other
> end, and hence xenbus calling into potentially invalid text, take a
> reference on the module before calling the probe() method (dropping it if
> unsuccessful) and drop the reference after returning from the remove()
> method.
> 
> Suggested-by: Jan Beulich <jbeulich@suse.com>
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>
with ...

> --- a/drivers/xen/xenbus/xenbus_probe.c
> +++ b/drivers/xen/xenbus/xenbus_probe.c
> @@ -232,9 +232,16 @@ int xenbus_dev_probe(struct device *_dev)
>  		return err;
>  	}
>  
> +	if (!try_module_get(drv->driver.owner)) {
> +		dev_warn(&dev->dev, "failed to acquire module reference on '%s'.\n",
> +			 drv->driver.name);

... perhaps the full stop dropped here and ...

> +		err = -ESRCH;
> +		goto fail;
> +        }

... (definitely) indentation here changed to use a tab.

Jan