2019-10-10 01:02:03

by Yizhuo Zhai

Subject: [PATCH] USB: core: Fix potental Null Pointer dereference

Inside function usb_device_is_owned(), usb_hub_to_struct_hub()
could return NULL but there's no check before its dereference,
which is potentially unsafe.

Signed-off-by: Yizhuo <[email protected]>
---
drivers/usb/core/hub.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 236313f41f4a..8d628c8e0c1b 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1977,7 +1977,7 @@ bool usb_device_is_owned(struct usb_device *udev)
if (udev->state == USB_STATE_NOTATTACHED || !udev->parent)
return false;
hub = usb_hub_to_struct_hub(udev->parent);
- return !!hub->ports[udev->portnum - 1]->port_owner;
+ return hub && !!hub->ports[udev->portnum - 1]->port_owner;
}

static void recursively_mark_NOTATTACHED(struct usb_device *udev)
--
2.17.1

2019-10-10 05:23:06

by Greg Kroah-Hartman

Subject: Re: [PATCH] USB: core: Fix potental Null Pointer dereference

On Wed, Oct 09, 2019 at 06:02:02PM -0700, Yizhuo wrote:
> Inside function usb_device_is_owned(), usb_hub_to_struct_hub()
> could return NULL but there's no check before its dereference,
> which is potentially unsafe.
>
> Signed-off-by: Yizhuo <[email protected]>
> ---
> drivers/usb/core/hub.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 236313f41f4a..8d628c8e0c1b 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -1977,7 +1977,7 @@ bool usb_device_is_owned(struct usb_device *udev)
> if (udev->state == USB_STATE_NOTATTACHED || !udev->parent)
> return false;
> hub = usb_hub_to_struct_hub(udev->parent);
> - return !!hub->ports[udev->portnum - 1]->port_owner;
> + return hub && !!hub->ports[udev->portnum - 1]->port_owner;

How can hub ever not be valid?

thanks,

greg k-h