linux-kernel - Re: [PATCH] acpi: pci_root: fix NULL pointer deref after resume from suspend

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Date:	Wed, 30 Sep 2009 01:31:14 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Alex Chiang <achiang@...com>
Cc:	Danny Feng <dfeng@...hat.com>, lenb@...nel.org,
	bjorn.helgaas@...com, andrew.patterson@...com,
	jbarnes@...tuousgeek.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] acpi: pci_root: fix NULL pointer deref after resume from suspend

On Tuesday 29 September 2009, Alex Chiang wrote:
> * Rafael J. Wysocki <rjw@...k.pl>:
> > On Tuesday 29 September 2009, Danny Feng wrote:
> > > Is there any cases that pdev->subordinate is NULL while pdev is bridge 
> > > device?
> > >  From pci_slot.c::walk_p2p_bridge, there's code like following:
> > > 
> > >          dev = pci_get_slot(pci_bus, PCI_DEVFN(device, function));
> > >          if (!dev || !dev->subordinate)
> > >                  goto out;
> > > 
> > > It looks like dev->subordinate can be NULL even if in p2p
> > > bridge, right?
> 
> In the code you post above, that results from doing an ACPI
> namespace walk, which will definitely find non-bridge devices.
>  
> > Right, in general, but in this particular case each device we
> > inspect is supposed to be a parent of another device, which
> > implies that there's a bus below it (given that it's a PCI
> > device).
> 
> Right, that's why I'm surprised that my assumption broke. But now
> that I see that a dock device is involved, maybe that's not so
> surprising.

Yeah.  Still, I'd like to know the root cause.

Thanks,
Rafael
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