PCI: hv: Fix a memory leak in hv_eject_device_work()

[ Upstream commit 05f151a7 ]

When a device is created in new_pcichild_device(), hpdev->refs is set
to 2 (i.e. the initial value of 1 plus the get_pcichild()).

When we hot remove the device from the host, in a Linux VM we first call
hv_pci_eject_device(), which increases hpdev->refs by get_pcichild() and
then schedules a work of hv_eject_device_work(), so hpdev->refs becomes
3 (let's ignore the paired get/put_pcichild() in other places). But in
hv_eject_device_work(), currently we only call put_pcichild() twice,
meaning the 'hpdev' struct can't be freed in put_pcichild().

Add one put_pcichild() to fix the memory leak.

The device can also be removed when we run "rmmod pci-hyperv". On this
path (hv_pci_remove() -> hv_pci_bus_exit() -> hv_pci_devices_present()),
hpdev->refs is 2, and we do correctly call put_pcichild() twice in
pci_devices_present_work().

Fixes: 4daace0d ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
[lorenzo.pieralisi@arm.com: commit log rework]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/pci/host/pci-hyperv.c

@@ -1620,6 +1620,7 @@ static void hv_eject_device_work(struct work_struct *work)
 	spin_unlock_irqrestore(&hpdev->hbus->device_list_lock, flags);
 
 	put_pcichild(hpdev, hv_pcidev_ref_childlist);
+	put_pcichild(hpdev, hv_pcidev_ref_initial);
 	put_pcichild(hpdev, hv_pcidev_ref_pnp);
 	put_hvpcibus(hpdev->hbus);
 }