[PATCH part4 04/11] PCI: Fix an access-after-free issue in function pci_stop_and_remove_bus()

[Yinghai Lu <yinghai@kernel.org>]

From: Jiang Liu <jiang.liu@huawei.com>

If pci_stop_and_remove_bus() is called to remove a pci root bus,
the host_bridge structure may have already been freed after returning
from pci_remove_bus(). To avoid that, hold an extra reference count
to the root bus before calling pci_remove_bus(), so we can safely
access the pci_host_bridge structure after returning from function
pci_remove_bus().

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
---
 drivers/pci/remove.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
index 94407d4..40f8148 100644
--- a/drivers/pci/remove.c
+++ b/drivers/pci/remove.c
@@ -154,6 +154,7 @@ void pci_stop_and_remove_bus(struct pci_bus *bus)
 
 	if (pci_is_root_bus(bus)) {
 		host_bridge = to_pci_host_bridge(bus->bridge);
+		get_device(&host_bridge->dev);
 		pci_stop_host_bridge(host_bridge);
 	} else
 		pci_bridge = bus->self;
@@ -162,8 +163,10 @@ void pci_stop_and_remove_bus(struct pci_bus *bus)
 
 	pci_remove_bus(bus);
 
-	if (host_bridge)
+	if (host_bridge) {
 		host_bridge->bus = NULL;
+		put_device(&host_bridge->dev);
+	}
 
 	if (pci_bridge)
 		pci_bridge->subordinate = NULL;
-- 
1.7.7