linux-kernel - [PATCH 4.19 111/113] PCI: hv: Fix a memory leak in hv_eject_device

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Date:   Wed, 15 May 2019 12:56:42 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dexuan Cui <decui@...rosoft.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Michael Kelley <mikelley@...rosoft.com>
Subject: [PATCH 4.19 111/113] PCI: hv: Fix a memory leak in hv_eject_device_work()

From: Dexuan Cui <decui@...rosoft.com>

commit 05f151a73ec2b23ffbff706e5203e729a995cdc2 upstream.

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: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs")
Signed-off-by: Dexuan Cui <decui@...rosoft.com>
[lorenzo.pieralisi@....com: commit log rework]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Reviewed-by: Stephen Hemminger <stephen@...workplumber.org>
Reviewed-by:  Michael Kelley <mikelley@...rosoft.com>
Cc: stable@...r.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/pci/controller/pci-hyperv.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -1905,6 +1905,9 @@ static void hv_eject_device_work(struct
 			 sizeof(*ejct_pkt), (unsigned long)&ctxt.pkt,
 			 VM_PKT_DATA_INBAND, 0);

+	/* For the get_pcichild() in hv_pci_eject_device() */
+	put_pcichild(hpdev);
+	/* For the two refs got in new_pcichild_device() */
 	put_pcichild(hpdev);
 	put_pcichild(hpdev);
 	put_hvpcibus(hpdev->hbus);