[PATCH 4.2.y-ckt 73/98] PCI: Allow a NULL "parent" pointer in pci_bus_assign_domain_nr()

Kamal Mostafa
2016-03-15T23:31:07Z

From: =?UTF-8?q?Krzysztof=20=3D=3Futf-8=3FQ=3FHa=3DC5=3D82asa=3F=3D?=

commit 54c6e2dd00c313d0add58e5befe62fe6f286d03b upstream.

pci_create_root_bus() passes a "parent" pointer to
pci_bus_assign_domain_nr(). When CONFIG_PCI_DOMAINS_GENERIC is defined,
pci_bus_assign_domain_nr() dereferences that pointer. Many callers of
pci_create_root_bus() supply a NULL "parent" pointer, which leads to a NULL
pointer dereference error.

7c674700098c ("PCI: Move domain assignment from arm64 to generic code")
moved the "parent" dereference from arm64 to generic code. Only arm64 used
that code (because only arm64 defined CONFIG_PCI_DOMAINS_GENERIC), and it
always supplied a valid "parent" pointer. Other arches supplied NULL
"parent" pointers but didn't defined CONFIG_PCI_DOMAINS_GENERIC, so they
used a no-op version of pci_bus_assign_domain_nr().

8c7d14746abc ("ARM/PCI: Move to generic PCI domains") defined
CONFIG_PCI_DOMAINS_GENERIC on ARM, and many ARM platforms use
pci_common_init(), which supplies a NULL "parent" pointer.
These platforms (cns3xxx, dove, footbridge, iop13xx, etc.) crash
with a NULL pointer dereference like this while probing PCI:

Unable to handle kernel NULL pointer dereference at virtual address 000000a4
PC is at pci_bus_assign_domain_nr+0x10/0x84
LR is at pci_create_root_bus+0x48/0x2e4
Kernel panic - not syncing: Attempted to kill init!

[bhelgaas: changelog, add "Reported:" and "Fixes:" tags]
Reported: http://forum.doozan.com/read.php?2,17868,22070,quote=1
Fixes: 8c7d14746abc ("ARM/PCI: Move to generic PCI domains")
Fixes: 7c674700098c ("PCI: Move domain assignment from arm64 to generic code")
Signed-off-by: Krzysztof Hałasa <khalasa@piap.pl>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
drivers/pci/pci.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 0008c95..f6f2384 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4487,8 +4487,10 @@ int pci_get_new_domain_nr(void)
void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
{
static int use_dt_domains = -1;
- int domain = of_get_pci_domain_nr(parent->of_node);
+ int domain = -1;

+ if (parent)
+ domain = of_get_pci_domain_nr(parent->of_node);
/*
* Check DT domain and use_dt_domains values.
*
--
2.7.0