[PATCH v2] PCI: hv: Fix a use-after-free bug in hv_eject_device_work()

[Dexuan Cui]

The commit 05f151a73ec2 itself is correct, but it exposes this
use-after-free bug, which is caught by some memory debug options.

Add a Fixes tag to indicate the dependency.

Fixes: 05f151a73ec2 ("PCI: hv: Fix a memory leak in hv_eject_device_work()")
Signed-off-by: Dexuan Cui <de...@microsoft.com>
Cc: sta...@vger.kernel.org
---

In v2:
Replaced "hpdev->hbus" with "hbus", since we have the new "hbus" variable. 
[Michael Kelley]

 drivers/pci/controller/pci-hyperv.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c 
b/drivers/pci/controller/pci-hyperv.c
index 808a182830e5..5dadc964ad3b 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -1880,6 +1880,7 @@ static void hv_pci_devices_present(struct 
hv_pcibus_device *hbus,
 static void hv_eject_device_work(struct work_struct *work)
 {
        struct pci_eject_response *ejct_pkt;
+       struct hv_pcibus_device *hbus;
        struct hv_pci_dev *hpdev;
        struct pci_dev *pdev;
        unsigned long flags;
@@ -1890,6 +1891,7 @@ static void hv_eject_device_work(struct work_struct *work)
        } ctxt;
 
        hpdev = container_of(work, struct hv_pci_dev, wrk);
+       hbus = hpdev->hbus;
 
        WARN_ON(hpdev->state != hv_pcichild_ejecting);
 
@@ -1900,8 +1902,7 @@ static void hv_eject_device_work(struct work_struct *work)
         * because hbus->pci_bus may not exist yet.
         */
        wslot = wslot_to_devfn(hpdev->desc.win_slot.slot);
-       pdev = pci_get_domain_bus_and_slot(hpdev->hbus->sysdata.domain, 0,
-                                          wslot);
+       pdev = pci_get_domain_bus_and_slot(hbus->sysdata.domain, 0, wslot);
        if (pdev) {
                pci_lock_rescan_remove();
                pci_stop_and_remove_bus_device(pdev);
@@ -1909,9 +1910,9 @@ static void hv_eject_device_work(struct work_struct *work)
                pci_unlock_rescan_remove();
        }
 
-       spin_lock_irqsave(&hpdev->hbus->device_list_lock, flags);
+       spin_lock_irqsave(&hbus->device_list_lock, flags);
        list_del(&hpdev->list_entry);
-       spin_unlock_irqrestore(&hpdev->hbus->device_list_lock, flags);
+       spin_unlock_irqrestore(&hbus->device_list_lock, flags);
 
        if (hpdev->pci_slot)
                pci_destroy_slot(hpdev->pci_slot);
@@ -1920,7 +1921,7 @@ static void hv_eject_device_work(struct work_struct *work)
        ejct_pkt = (struct pci_eject_response *)&ctxt.pkt.message;
        ejct_pkt->message_type.type = PCI_EJECTION_COMPLETE;
        ejct_pkt->wslot.slot = hpdev->desc.win_slot.slot;
-       vmbus_sendpacket(hpdev->hbus->hdev->channel, ejct_pkt,
+       vmbus_sendpacket(hbus->hdev->channel, ejct_pkt,
                         sizeof(*ejct_pkt), (unsigned long)&ctxt.pkt,
                         VM_PKT_DATA_INBAND, 0);
 
@@ -1929,7 +1930,9 @@ static void hv_eject_device_work(struct work_struct *work)
        /* For the two refs got in new_pcichild_device() */
        put_pcichild(hpdev);
        put_pcichild(hpdev);
-       put_hvpcibus(hpdev->hbus);
+       /* hpdev has been freed. Do not use it any more. */
+
+       put_hvpcibus(hbus);
 }
 
 /**
-- 
2.17.1