linux-kernel - Re: [PATCH 2/2] ACPI / bind: Use (put|get)

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Date:	Thu, 14 Nov 2013 15:20:09 +0800
From:	Lan Tianyu <tianyu.lan@...el.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Aaron Lu <aaron.lu@...el.com>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	"Luck, Tony" <tony.luck@...el.com>
Subject: Re: [PATCH 2/2] ACPI / bind: Use (put|get)_device() on ACPI device
 objects too

On 2013年11月14日 07:26, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> When associating a "physical" device with an ACPI device object
> acpi_bind_one() only uses get_device() to increment the reference
> counter of the former, but there is no reason not to do that with
> the latter too.  Among other things, that may help to avoid
> use-after-free when an ACPI device object is freed without calling
> acpi_unbind_one() for all "physical" devices associated with it
> (that only can happen in buggy code, but then it's better if the
> kernel doesn't crash as a result of a bug).
> 
> For this reason, modify acpi_bind_one() to apply get_device() to
> the ACPI device object too and update acpi_unbind_one() to drop
> that reference using put_device() as appropriate.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/acpi/glue.c |    6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> Index: linux-pm/drivers/acpi/glue.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/glue.c
> +++ linux-pm/drivers/acpi/glue.c
> @@ -217,6 +217,7 @@ int acpi_bind_one(struct device *dev, ac
>  	if (!acpi_dev)
>  		return -EINVAL;
>  
> +	get_device(&acpi_dev->dev);
>  	get_device(dev);
>  	physical_node = kzalloc(sizeof(*physical_node), GFP_KERNEL);
>  	if (!physical_node) {
> @@ -243,6 +244,7 @@ int acpi_bind_one(struct device *dev, ac
>  				goto err;
>  
>  			put_device(dev);
> +			put_device(&acpi_dev->dev);
>  			return 0;
>  		}
>  		if (pn->node_id == node_id) {
> @@ -282,6 +284,7 @@ int acpi_bind_one(struct device *dev, ac
>   err:
>  	ACPI_COMPANION_SET(dev, NULL);
>  	put_device(dev);
> +	put_device(&acpi_dev->dev);
>  	return retval;
>  }
>  EXPORT_SYMBOL_GPL(acpi_bind_one);
> @@ -307,8 +310,9 @@ int acpi_unbind_one(struct device *dev)
>  			sysfs_remove_link(&acpi_dev->dev.kobj, physnode_name);
>  			sysfs_remove_link(&dev->kobj, "firmware_node");
>  			ACPI_COMPANION_SET(dev, NULL);
> -			/* acpi_bind_one() increase refcnt by one. */
> +			/* Drop references taken by acpi_bind_one(). */
>  			put_device(dev);
> +			put_device(&acpi_dev->dev);
>  			kfree(entry);
>  			break;
>  		}
> 

Reviewed-by: Lan Tianyu <tianyu.lan@...el.com>

-- 
Best regards
Tianyu Lan
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