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Message-ID: <BYAPR21MB13524CDAAD1F9A19935E5F9BD7E70@BYAPR21MB1352.namprd21.prod.outlook.com>
Date: Fri, 21 Jun 2019 23:24:51 +0000
From: Michael Kelley <mikelley@...rosoft.com>
To: Dexuan Cui <decui@...rosoft.com>,
"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>
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: RE: [PATCH] PCI: hv: Fix a use-after-free bug in
hv_eject_device_work()
From: Dexuan Cui <decui@...rosoft.com> Sent: Friday, June 21, 2019 12:02 PM
>
> 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;
In the lines of code following this new assignment, there are four uses of
hpdev->hbus besides the one at the bottom of the function that causes the
use-after-free error. With 'hbus' now available as a local variable, it looks
rather strange to have those other places still using hpdev->hbus. I'm thinking
they should be shortened to just 'hbus' for consistency, even though such
changes aren't directly related to fixing the bug.
Michael
>
> 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
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