Hello,
as a consequence of hitting a NULL dereference bug[1] while downstream
aspm is setting up link_state, I started to wonder why is the code
skipping its parent bus in favour of grandparent's link_state.[2]
Is this right? (I have no device to test on ...)
Thanks.
---
1: https://bugzilla.redhat.com/show_bug.cgi?id=972381
The bug is hit because "pdev->bus->parent" has NULL "->parent" and thus
NULL "->self".
2: "pdev = bus->self", so "pdev->bus->parent == bus->parent->parent"
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 403a443..d58e282 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -527,7 +527,7 @@ static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
link->pdev = pdev;
if (pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM) {
struct pcie_link_state *parent;
- parent = pdev->bus->parent->self->link_state;
+ parent = pdev->bus->self->link_state;
if (!parent) {
kfree(link);
return NULL;
[+cc linux-pci, Myron, Joe]
On Wed, Jun 12, 2013 at 11:21 AM, Radim Krčmář <[email protected]> wrote:
> Hello,
>
> as a consequence of hitting a NULL dereference bug[1] while downstream
> aspm is setting up link_state, I started to wonder why is the code
> skipping its parent bus in favour of grandparent's link_state.[2]
>
> Is this right? (I have no device to test on ...)
>
> Thanks.
>
> ---
> 1: https://bugzilla.redhat.com/show_bug.cgi?id=972381
> The bug is hit because "pdev->bus->parent" has NULL "->parent" and thus
> NULL "->self".
> 2: "pdev = bus->self", so "pdev->bus->parent == bus->parent->parent"
>
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 403a443..d58e282 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -527,7 +527,7 @@ static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
> link->pdev = pdev;
> if (pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM) {
> struct pcie_link_state *parent;
> - parent = pdev->bus->parent->self->link_state;
> + parent = pdev->bus->self->link_state;
> if (!parent) {
> kfree(link);
> return NULL;
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
2013-06-12 15:54-0600, Bjorn Helgaas:
> [+cc linux-pci, Myron, Joe]
I'll remember it.
> On Wed, Jun 12, 2013 at 11:21 AM, Radim Krčmář <[email protected]> wrote:
> > Hello,
> >
> > as a consequence of hitting a NULL dereference bug[1] while downstream
> > aspm is setting up link_state, I started to wonder why is the code
> > skipping its parent bus in favour of grandparent's link_state.[2]
> >
> > Is this right? (I have no device to test on ...)
No,
pcie_link_state covers both upstream and downstream port, so we skip
upstream port of current device.
Must the "parent device" (grandparent) have valid "->self"?
(qemu allows even topologies without the upstream port, so it does not
count for much ...)
> > Thanks.
> >
> > ---
> > 1: https://bugzilla.redhat.com/show_bug.cgi?id=972381
> > The bug is hit because "pdev->bus->parent" has NULL "->parent" and thus
> > NULL "->self".
> > 2: "pdev = bus->self", so "pdev->bus->parent == bus->parent->parent"
> >
> >
> > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> > index 403a443..d58e282 100644
> > --- a/drivers/pci/pcie/aspm.c
> > +++ b/drivers/pci/pcie/aspm.c
> > @@ -527,7 +527,7 @@ static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
> > link->pdev = pdev;
> > if (pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM) {
> > struct pcie_link_state *parent;
> > - parent = pdev->bus->parent->self->link_state;
> > + parent = pdev->bus->self->link_state;
> > if (!parent) {
> > kfree(link);
> > return NULL;