RE: [PATCH v2] PCI: hv: Fix a use-after-free bug in hv_eject_device_work()

[Michael Kelley]

From: Dexuan Cui <decui@xxxxxxxxxxxxx> Sent: Friday, June 21, 2019 4:45 PM
> 
> The commit 05f151a73ec2 itself is correct, but it exposes this
> use-after-free bug, which is caught by some memory debug options.
> 
> Add a 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@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> 
> In v2:
> Replaced "hpdev->hbus" with "hbus", since we have the new "hbus" variable. [Michael
> Kelley]
> 
>  drivers/pci/controller/pci-hyperv.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index 808a182830e5..5dadc964ad3b 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);
> 
> @@ -1900,8 +1902,7 @@ static void hv_eject_device_work(struct work_struct *work)
>  	 * because hbus->pci_bus may not exist yet.
>  	 */
>  	wslot = wslot_to_devfn(hpdev->desc.win_slot.slot);
> -	pdev = pci_get_domain_bus_and_slot(hpdev->hbus->sysdata.domain, 0,
> -					   wslot);
> +	pdev = pci_get_domain_bus_and_slot(hbus->sysdata.domain, 0, wslot);
>  	if (pdev) {
>  		pci_lock_rescan_remove();
>  		pci_stop_and_remove_bus_device(pdev);
> @@ -1909,9 +1910,9 @@ static void hv_eject_device_work(struct work_struct *work)
>  		pci_unlock_rescan_remove();
>  	}
> 
> -	spin_lock_irqsave(&hpdev->hbus->device_list_lock, flags);
> +	spin_lock_irqsave(&hbus->device_list_lock, flags);
>  	list_del(&hpdev->list_entry);
> -	spin_unlock_irqrestore(&hpdev->hbus->device_list_lock, flags);
> +	spin_unlock_irqrestore(&hbus->device_list_lock, flags);
> 
>  	if (hpdev->pci_slot)
>  		pci_destroy_slot(hpdev->pci_slot);
> @@ -1920,7 +1921,7 @@ static void hv_eject_device_work(struct work_struct *work)
>  	ejct_pkt = (struct pci_eject_response *)&ctxt.pkt.message;
>  	ejct_pkt->message_type.type = PCI_EJECTION_COMPLETE;
>  	ejct_pkt->wslot.slot = hpdev->desc.win_slot.slot;
> -	vmbus_sendpacket(hpdev->hbus->hdev->channel, ejct_pkt,
> +	vmbus_sendpacket(hbus->hdev->channel, ejct_pkt,
>  			 sizeof(*ejct_pkt), (unsigned long)&ctxt.pkt,
>  			 VM_PKT_DATA_INBAND, 0);
> 
> @@ -1929,7 +1930,9 @@ 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

Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>