PCI: hv: Lock PCI bus on device eject

A PCI_EJECT message can arrive at the same time we are calling
pci_scan_child_bus() in the workqueue for the previous PCI_BUS_RELATIONS
message or in create_root_hv_pci_bus().  In this case we could potentially
modify the bus from multiple places.

Properly lock the bus access.

Thanks Dexuan Cui <decui@microsoft.com> for pointing out the race condition
in create_root_hv_pci_bus().

Reported-by: Xiaofeng Wang <xiaofwan@redhat.com>
Signed-off-by: Long Li <longli@microsoft.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: K. Y. Srinivasan <kys@microsoft.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index 39fafda4deff..a1b3c1957d43 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -1209,9 +1209,11 @@ static int create_root_hv_pci_bus(struct hv_pcibus_device *hbus)
         hbus->pci_bus->msi = &hbus->msi_chip;
         hbus->pci_bus->msi->dev = &hbus->hdev->device;
 
+        pci_lock_rescan_remove();
         pci_scan_child_bus(hbus->pci_bus);
         pci_bus_assign_resources(hbus->pci_bus);
         pci_bus_add_devices(hbus->pci_bus);
+        pci_unlock_rescan_remove();
         hbus->state = hv_pcibus_installed;
         return 0;
 }
@@ -1612,8 +1614,10 @@ static void hv_eject_device_work(struct work_struct *work)
         pdev = pci_get_domain_bus_and_slot(hpdev->hbus->sysdata.domain, 0,
                                            wslot);
         if (pdev) {
+                pci_lock_rescan_remove();
                 pci_stop_and_remove_bus_device(pdev);
                 pci_dev_put(pdev);
+                pci_unlock_rescan_remove();
         }
 
         spin_lock_irqsave(&hpdev->hbus->device_list_lock, flags);