linux-kernel - [PATCH] PCI: hv: Fix a use-after-free bug in hv_eject_device

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Message-ID: <PU1P153MB01691036654142C7972F3ACDBFE70@PU1P153MB0169.APCP153.PROD.OUTLOOK.COM>
Date:   Fri, 21 Jun 2019 19:02:26 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        vkuznets <vkuznets@...hat.com>,
        "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>,
        Michael Kelley <mikelley@...rosoft.com>
CC:     "Lili Deng (Wicresoft North America Ltd)" <v-lide@...rosoft.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "driverdev-devel@...uxdriverproject.org" 
        <driverdev-devel@...uxdriverproject.org>
Subject: [PATCH] PCI: hv: Fix a use-after-free bug in hv_eject_device_work()


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 <decui@...rosoft.com>
Cc: stable@...r.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