linux-kernel - Re: linux-next: dock_link

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Date:	Fri, 17 Feb 2012 23:52:15 -0800 (PST)
From:	Hugh Dickins <hughd@...gle.com>
To:	Holger Macht <holger@...ac.de>
cc:	Matthew Garrett <mjg@...hat.com>, Jeff Garzik <jgarzik@...hat.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: linux-next: dock_link_device is oopsy

On Sat, 18 Feb 2012, Holger Macht wrote:
> On Fr 17. Feb - 14:42:31, Hugh Dickins wrote:
> > On Fri, 17 Feb 2012, Holger Macht wrote:
> > > On Fr 17. Feb - 13:46:04, Hugh Dickins wrote:
> > > > Matthew,
> > > > 
> > > > A linux-next oops at bootup in dock_link_device() tells me that you
> > > > were not feeling well when you wrote that and dock_unlink_device():
> > > > I hope you're feeling better now and can rewrite them soon.
> > > 
> > > Andrew Morton experienced a similar problem. What system are you using?
> > > I didn't encounter this problem with the systems I tested with.
> > 
> > The two systems I got that on were both 4-year-old Core2 Duo systems,
> > one an HP quad desktop, one a Fujitsu-Siemens laptop.
> 
> Thanks for the information I think this is really independent from the
> fact if a laptop, or more precicely if a system with dock station/bay is
> used.
> 
> > 
> > > 
> > > Do you actually have a /sys/devices/platform/dock.?/ directory with a
> > > file 'type' that contains 'dock_station'?
> > 
> > I'll have to report back on that this evening, I'm away from them now.
> 
> I actually guess that those systems don't have a
> /sys/devices/platform/dock.? directory at all, which is fine.

You are correct, no /sys/devices/platform/dock.? directory on those.

> 
> I also think this will fix it, would be great if you could confirm this:
> 
> acpi: Bail out when linking devices and there are no dock stations
> 
> If dock_station_count is zero, we allocate zero memory and don't check
> this at future references. So bail out if there are actually no dock
> stations.
> 
> Signed-off-by: Holger Macht <holger@...ac.de>
> ---
>  drivers/acpi/dock.c |   13 ++++++++++---
>  1 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/acpi/dock.c b/drivers/acpi/dock.c
> index b5e4142..8641912 100644
> --- a/drivers/acpi/dock.c
> +++ b/drivers/acpi/dock.c
> @@ -286,6 +286,9 @@ struct device **dock_link_device(acpi_handle handle)
>  	int ret, dock = 0;
>  	struct device **devices;
>  
> +	if (!dock_station_count)
> +		return -ENODEV;

If I change your -ENODEV to NULL (here and in unlink, though I didn't
check if that gets called), yes, that "fixes" the crash at boot.

But note that in each case you already did an acpi_get_physical_device:
if the existing code was correct in this regard, then you ought to be
doing a put_device(dev) before returning.

Or better reorder it all.

Hugh

> +
>  	devices = kmalloc(dock_station_count * sizeof(struct device *),
>  			  GFP_KERNEL);
>  
> @@ -323,9 +326,13 @@ struct device **dock_unlink_device(acpi_handle handle)
>  	struct device *dev = acpi_get_physical_device(handle);
>  	struct dock_station *dock_station;
>  	int dock = 0;
> -	struct device **devices =
> -		kmalloc(dock_station_count * sizeof(struct device *),
> -			GFP_KERNEL);
> +	struct device **devices;
> +
> +	if (!dock_station_count)
> +		return -ENODEV;
> +
> +	devices = kmalloc(dock_station_count * sizeof(struct device *),
> +			  GFP_KERNEL);
>  
>  	if (!dev)
>  		return NULL;
> -- 
> 1.7.7
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