Re: [PATCH] pci/aspm: Fix null pointer dereference during re-enumeration of PCI bus in pcie_aspm_init_link_state even though ASPM is off

From: Bjorn Helgaas <helgaas@kernel.org>
To: "Jan Rüth" <rueth@comsys.rwth-aachen.de>
Cc: linux-pci@vger.kernel.org
Subject: Re: [PATCH] pci/aspm: Fix null pointer dereference during re-enumeration of PCI bus in pcie_aspm_init_link_state even though ASPM is off
Date: Mon, 6 Mar 2017 18:27:34 -0600	[thread overview]
Message-ID: <20170307002734.GB21358@bhelgaas-glaptop.roam.corp.google.com> (raw)
In-Reply-To: <20170203173243.GB10291@bhelgaas-glaptop.roam.corp.google.com>

On Fri, Feb 03, 2017 at 11:32:43AM -0600, Bjorn Helgaas wrote:
> On Tue, Jan 03, 2017 at 09:09:49AM +0100, Jan Rüth wrote:
> > This patch fixes a null pointer dereference during PCI bus enumeration
> > when ASPM is off. On an IBM x3850 8664 this bug causes the kernel to
> > halt, this behavior did not appear in 3.10, so this is a regression.
> > 
> > pcie_aspm_sanity_check should only be called if ASPM is on.
> > 
> > Signed-off-by: Jan Rueth <rueth@comsys.rwth-aachen.de>
> 
> We have https://bugzilla.kernel.org/show_bug.cgi?id=187731 for this issue.
> 
> Per the dmesg attached there, you're booting with "pcie_aspm=off".
> This patch fixes the NULL pointer dereference in that case, but I'm
> concerned that we may still trip over it if you boot without
> "pcie_aspm=off".
> 
> I want to make sure we fix both cases.  Can you please try a boot
> with this patch but without "pcie_aspm=off"?

Ping?  I'd like to get this patch merged but I want to make sure we
fix the problem both with and without "pcie_aspm=off".

Is anybody in a position to test this on an IBM x3850 8664?

> > ---
> >  drivers/pci/pcie/aspm.c | +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> > index f981129..e758b56 100644
> > --- a/drivers/pci/pcie/aspm.c
> > +++ b/drivers/pci/pcie/aspm.c
> > @@ -552,11 +552,12 @@ static struct pcie_link_state
> > *alloc_pcie_link_state(struct pci_dev *pdev)
> >  void pcie_aspm_init_link_state(struct pci_dev *pdev)
> >  {
> >         struct pcie_link_state *link;
> > -       int blacklist = !!pcie_aspm_sanity_check(pdev);
> > -
> > +       int blacklist;
> >         if (!aspm_support_enabled)
> >                 return;
> > 
> > +       blacklist = !!pcie_aspm_sanity_check(pdev);
> > +
> >         if (pdev->link_state)
> >                 return;
> > --
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