[patch] PCI: hv: potential use after free

[Dan Carpenter]

If we throw away the very last item on the list, then we could end up
with a use after free of "dr".

Fixes: 15ca17645f19 ('PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs')
Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index 9391dee..9b66ffe 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -1397,6 +1397,7 @@ static void pci_devices_present_work(struct work_struct *work)
 		/* Throw this away if the list still has stuff in it. */
 		if (!list_empty(&hbus->dr_list)) {
 			kfree(dr);
+			dr = NULL;
 			continue;
 		}
 	}