linux-kernel - Re: [PATCH 1/2] ACPI: Fix stale pointer access to flags.lockable

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Date:	Thu, 25 Oct 2012 00:08:26 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Toshi Kani <toshi.kani@...com>
Cc:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	linux-acpi@...r.kernel.org, lenb@...nel.org,
	linux-kernel@...r.kernel.org, liuj97@...il.com
Subject: Re: [PATCH 1/2] ACPI: Fix stale pointer access to flags.lockable

On Wednesday 17 of October 2012 07:55:42 Toshi Kani wrote:
> On Wed, 2012-10-17 at 10:25 +0900, Yasuaki Ishimatsu wrote:
> > 2012/10/16 1:34, Toshi Kani wrote:
> > > During hot-remove, acpi_bus_hot_remove_device() calls ACPI _LCK
> > > method when device->flags.lockable is set. However, this device
> > > pointer is stale since the target acpi_device object has been
> > > already kfree'd by acpi_bus_trim().
> > > 
> > > The flags.lockable indicates whether or not this ACPI object
> > > implements _LCK method. Fix the stable pointer access by replacing
> > > it with acpi_get_handle() to check if _LCK is implemented.
> > > 
> > > Signed-off-by: Toshi Kani <toshi.kani@...com>
> > 
> > Looks good to me.
> > Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
> 
> Thanks Yasuaki for reviewing!

Applied to linux-pm.git/linux-next as v3.8 material.

Thanks,
Rafael


> > > ---
> > >   drivers/acpi/scan.c | 6 +++++-
> > >   1 file changed, 5 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> > > index 1fcb867..ed87f43 100644
> > > --- a/drivers/acpi/scan.c
> > > +++ b/drivers/acpi/scan.c
> > > @@ -97,6 +97,7 @@ void acpi_bus_hot_remove_device(void *context)
> > >   	struct acpi_eject_event *ej_event = (struct acpi_eject_event *) context;
> > >   	struct acpi_device *device;
> > >   	acpi_handle handle = ej_event->handle;
> > > +	acpi_handle temp;
> > >   	struct acpi_object_list arg_list;
> > >   	union acpi_object arg;
> > >   	acpi_status status = AE_OK;
> > > @@ -117,13 +118,16 @@ void acpi_bus_hot_remove_device(void *context)
> > >   		goto err_out;
> > >   	}
> > >   
> > > +	/* device has been freed */
> > > +	device = NULL;
> > > +
> > >   	/* power off device */
> > >   	status = acpi_evaluate_object(handle, "_PS3", NULL, NULL);
> > >   	if (ACPI_FAILURE(status) && status != AE_NOT_FOUND)
> > >   		printk(KERN_WARNING PREFIX
> > >   				"Power-off device failed\n");
> > >   
> > > -	if (device->flags.lockable) {
> > > +	if (ACPI_SUCCESS(acpi_get_handle(handle, "_LCK", &temp))) {
> > >   		arg_list.count = 1;
> > >   		arg_list.pointer = &arg;
> > >   		arg.type = ACPI_TYPE_INTEGER;
> > > 
> > 
> > 
> 
> 
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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