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

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Date:	Wed, 17 Oct 2012 07:55:42 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
Cc:	linux-acpi@...r.kernel.org, lenb@...nel.org,
	linux-kernel@...r.kernel.org, rjw@...k.pl, liuj97@...il.com
Subject: Re: [PATCH 1/2] ACPI: Fix stale pointer access to flags.lockable

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!
-Toshi


> > ---
> >   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;
> > 
> 
> 


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