linux-kernel - Re: linux-next: dock_link

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Message-ID: <20120218111419.GA2488@homac.suse.de>
Date:	Sat, 18 Feb 2012 12:14:19 +0100
From:	Holger Macht <holger@...ac.de>
To:	Hugh Dickins <hughd@...gle.com>
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 Fr 17. Feb - 15:49:02, Hugh Dickins wrote:
> 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.
> > 
> > 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>
> 
> Certainly won't fix it as is (well, it shifts the crash over into kfree).
> This function is expected to return a pointer, not an error or success
> code.

Oh well, too late for me yesterday...

> 
> I've little doubt that returning NULL rather than -ENODEV there would fix
> the boot crash; and if you're in a hurry to fix up booting (understandable)
> then I suppose that would do for the moment.

I really think this will basically do the trick. dock_(un)link_device()
is called by ata_acpi_(un)bind_dock(), which in turn is called by
ata_scsi_scan_host() unconditionally, thus not depending on the presence
of a dock device. And dock_(un)link_device() simply misses the check if
there is a dock/bay device.

So how about that?

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 |   19 ++++++++++++++-----
 1 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/acpi/dock.c b/drivers/acpi/dock.c
index b5e4142..0b3072c 100644
--- a/drivers/acpi/dock.c
+++ b/drivers/acpi/dock.c
@@ -281,11 +281,15 @@ EXPORT_SYMBOL_GPL(is_dock_device);
  */
 struct device **dock_link_device(acpi_handle handle)
 {
-	struct device *dev = acpi_get_physical_device(handle);
+	struct device *dev;
 	struct dock_station *dock_station;
 	int ret, dock = 0;
 	struct device **devices;
 
+	if (!dock_station_count)
+		return NULL;
+
+	dev = acpi_get_physical_device(handle);
 	devices = kmalloc(dock_station_count * sizeof(struct device *),
 			  GFP_KERNEL);
 
@@ -320,12 +324,17 @@ EXPORT_SYMBOL_GPL(dock_link_device);
  */
 struct device **dock_unlink_device(acpi_handle handle)
 {
-	struct device *dev = acpi_get_physical_device(handle);
+	struct device *dev;
 	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 NULL;
+
+	dev = acpi_get_physical_device(handle);
+	devices = kmalloc(dock_station_count * sizeof(struct device *),
+			  GFP_KERNEL);
 
 	if (!dev)
 		return NULL;
-- 
1.7.7

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