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powerpc/PCI: Fix NULL dereference in sys_pciconfig_iobase() list traversal 

3bc955987f ("powerpc/PCI: Use list_for_each_entry() for bus traversal")
caused a NULL pointer dereference because the loop body set the iterator to
NULL:

  Unable to handle kernel paging request for data at address 0x00000000
  Faulting instruction address: 0xc000000000041d78
  Oops: Kernel access of bad area, sig: 11 [#1]
  ...
  NIP [c000000000041d78] .sys_pciconfig_iobase+0x68/0x1f0
  LR [c000000000041e0c] .sys_pciconfig_iobase+0xfc/0x1f0
  Call Trace:
  [c0000003b4787db0] [c000000000041e0c] .sys_pciconfig_iobase+0xfc/0x1f0 (unreliable)
  [c0000003b4787e30] [c000000000009ed8] syscall_exit+0x0/0x98

Fix it by using a temporary variable for the iterator.

[bhelgaas: changelog, drop tmp_bus initialization]
Fixes: 3bc955987f powerpc/PCI: Use list_for_each_entry() for bus traversal
Signed-off-by: Mike Qiu <qiudayu@linux.vnet.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
Mike Qiu 2014-04-14 16:12:35 -06:00 committed by Bjorn Helgaas
parent c9eaa447e7
commit 140ab6452c
1 changed files with 6 additions and 4 deletions
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10
arch/powerpc/kernel/pci_64.c
View File

@ -208,7 +208,7 @@ long sys_pciconfig_iobase(long which, unsigned long in_bus,
unsigned long in_devfn)
{
struct pci_controller* hose;
struct pci_bus *bus = NULL;
struct pci_bus *tmp_bus, *bus = NULL;
struct device_node *hose_node;
/* Argh ! Please forgive me for that hack, but that's the
@ -229,10 +229,12 @@ long sys_pciconfig_iobase(long which, unsigned long in_bus,
* used on pre-domains setup. We return the first match
*/
list_for_each_entry(bus, &pci_root_buses, node) {
if (in_bus >= bus->number && in_bus <= bus->busn_res.end)
list_for_each_entry(tmp_bus, &pci_root_buses, node) {
if (in_bus >= tmp_bus->number &&
in_bus <= tmp_bus->busn_res.end) {
bus = tmp_bus;
break;
bus = NULL;
}
}
if (bus == NULL || bus->dev.of_node == NULL)
return -ENODEV;