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SubjectRe: [PATCH] ALSA: hda/hdmi - Fix duplicate unref of pci_dev
On Tue, Dec 10, 2019 at 03:34:27PM +0000, Deucher, Alexander wrote:
> > Nicholas Johnson reports a null pointer deref as well as a refcount underflow
> > upon hot-removal of a Thunderbolt-attached AMD eGPU.
> > He's bisected the issue down to commit 586bc4aab878 ("ALSA: hda/hdmi - fix
> > vgaswitcheroo detection for AMD").
> >
> > The commit iterates over PCI devices using pci_get_class() and unreferences
> > each device found, even though pci_get_class() subsequently unreferences
> > the device as well. Fix it.
>
> The pci_dev_put() a few lines above should probably be dropped as well.

That one looks fine to me. The refcount is already increased in the
caller get_bound_vga() via pci_get_domain_bus_and_slot() and it's
increased again in atpx_present() via pci_get_class(). It needs to
be decremented in atpx_present() to avoid leaking a ref.

Thanks,

Lukas

> > diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c index
> > 35b4526f0d28..b856b89378ac 100644
> > --- a/sound/pci/hda/hda_intel.c
> > +++ b/sound/pci/hda/hda_intel.c
> > @@ -1419,7 +1419,6 @@ static bool atpx_present(void)
> > return true;
> > }
> > }
> > - pci_dev_put(pdev);
> > }
> > return false;
> > }
> > --
> > 2.24.0

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