[PATCH] 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 the 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
---
Sorry for not spotting the bug when sending 05f151a73ec2. 

Now I have enabled the mm debug options to help catch such mistakes in future.

 drivers/pci/controller/pci-hyperv.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pci-hyperv.c 
b/drivers/pci/controller/pci-hyperv.c
index 808a182830e5..42ace1a690f9 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);
 
@@ -1929,7 +1931,9 @@ 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