PCI: Allow a NULL "parent" pointer in pci_bus_assign_domain_nr()

Krzysztof =?utf-8?Q?Ha=C5=82asa?= · bjorn-helgaas · commit 54c6e2dd00c3 · 2016-03-07T14:33:16.000-06:00
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. 7c67470 ("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(). 8c7d147 ("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: 8c7d147 ("ARM/PCI: Move to generic PCI domains") Fixes: 7c67470 ("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> CC: stable@vger.kernel.org # v4.0+
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
@@ -4772,8 +4772,10 @@ 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.
 	 *

Original file line number	Diff line number	Diff line change
`@@ -4772,8 +4772,10 @@ int pci_get_new_domain_nr(void)`
`4772`	`4772`	`void pci_bus_assign_domain_nr(struct pci_bus bus, struct device parent)`
`4773`	`4773`	`{`
`4774`	`4774`	`static int use_dt_domains = -1;`
`4775`		`- int domain = of_get_pci_domain_nr(parent->of_node);`
	`4775`	`+ int domain = -1;`
`4776`	`4776`
	`4777`	`+ if (parent)`
	`4778`	`+ domain = of_get_pci_domain_nr(parent->of_node);`
`4777`	`4779`	`/*`
`4778`	`4780`	`* Check DT domain and use_dt_domains values.`
`4779`	`4781`	`*`