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 <[email protected]>
Cc: [email protected]
---
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
From: Dexuan Cui <[email protected]> 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 <[email protected]>
> Cc: [email protected]
> ---
> 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
> From: Michael Kelley <[email protected]>
> > @@ -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
Ok, let me post a v2 for this.
Thanks,
Dexuan