linux-kernel - Re: [PATCH 1/1] PCI: check return value of pci_find_ext

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Date:   Tue, 25 Apr 2017 14:31:05 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     Pan Bian <bianpan201603@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lukas Wunner <lukas@...ner.de>,
        Keith Busch <keith.busch@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pan Bian <bianpan2016@....com>
Subject: Re: [PATCH 1/1] PCI: check return value of pci_find_ext_capability

On Mon, Apr 24, 2017 at 01:36:58PM +0300, Mika Westerberg wrote:
> On Sun, Apr 23, 2017 at 10:00:20PM +0800, Pan Bian wrote:
> > From: Pan Bian <bianpan2016@....com>
> > 
> > Function pci_find_ext_capability() will returns 0 on failure, and its
> > return value should be checked before it is used. However, in function
> > pcie_port_enable_msix(), its return value is not checked. This patch
> > adds the check.
> > 
> > Signed-off-by: Pan Bian <bianpan2016@....com>
> > ---
> >  drivers/pci/pcie/portdrv_core.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
> > index cea504f..001951d 100644
> > --- a/drivers/pci/pcie/portdrv_core.c
> > +++ b/drivers/pci/pcie/portdrv_core.c
> > @@ -103,6 +103,8 @@ static int pcie_port_enable_msix(struct pci_dev *dev, int *irqs, int mask)
> >  		 * interrupt message."
> >  		 */
> >  		pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
> > +		if (!pos)
> > +			goto out_free_irqs;
> 
> I don't think this can happen because get_port_device_capability() will
> enumerate this capability and only if it exists, set PCIE_PORT_SERVICE_AER.

The path is more complicated than I'd like, but I think you're right.
We should also be able to use dev->aer_cap here instead of looking it
up again.

Bjorn