[ No idea why I haven never sent this email before. I was just going
through all the use after free warnings again today and noticed it. ]
Hello Jake Oshins,
The patch 4daace0d8ce8: "PCI: hv: Add paravirtual PCI front-end for
Microsoft Hyper-V VMs" from Feb 16, 2016, leads to the following
static checker warning:
drivers/pci/host/pci-hyperv.c:1441 pci_devices_present_work()
error: dereferencing freed memory 'dr'
drivers/pci/host/pci-hyperv.c
1410 /* Pull this off the queue and process it if it was the last
one. */
1411 spin_lock_irqsave(&hbus->device_list_lock, flags);
1412 while (!list_empty(&hbus->dr_list)) {
1413 dr = list_first_entry(&hbus->dr_list, struct
hv_dr_state,
1414 list_entry);
1415 list_del(&dr->list_entry);
1416
1417 /* Throw this away if the list still has stuff in it. */
1418 if (!list_empty(&hbus->dr_list)) {
1419 kfree(dr);
^^^^^^^^^
We free "dr". Presumably we should set dr = NULL here?
1420 continue;
1421 }
1422 }
1423 spin_unlock_irqrestore(&hbus->device_list_lock, flags);
1424
1425 if (!dr) {
1426 up(&hbus->enum_sem);
1427 put_hvpcibus(hbus);
1428 return;
1429 }
1430
1431 /* First, mark all existing children as reported missing. */
1432 spin_lock_irqsave(&hbus->device_list_lock, flags);
1433 list_for_each(iter, &hbus->children) {
1434 hpdev = container_of(iter, struct hv_pci_dev,
1435 list_entry);
1436 hpdev->reported_missing = true;
1437 }
1438 spin_unlock_irqrestore(&hbus->device_list_lock, flags);
1439
1440 /* Next, add back any reported devices. */
1441 for (child_no = 0; child_no < dr->device_count; child_no++) {
^^^^^^^^^^^^^^^^
Use after free.
1442 found = false;
1443 new_desc = &dr->func[child_no];
1444
1445 spin_lock_irqsave(&hbus->device_list_lock, flags);
regards,
dan carpenter
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