Re: [PATCH] net: usb: fix possible use-after-free in smsc75xx_bind

Greg KH
2021-06-15T07:38:36Z

On Mon, Jun 14, 2021 at 11:37:12PM +0800, Dongliang Mu wrote:
> The commit 46a8b29c6306 ("net: usb: fix memory leak in smsc75xx_bind")
> fails to clean up the work scheduled in smsc75xx_reset->
> smsc75xx_set_multicast, which leads to use-after-free if the work is
> scheduled to start after the deallocation. In addition, this patch also
> removes one dangling pointer - dev->data[0].
>
> This patch calls cancel_work_sync to cancel the schedule work and set
> the dangling pointer to NULL.
>
> Fixes: 46a8b29c6306 ("net: usb: fix memory leak in smsc75xx_bind")
> Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
> ---
> drivers/net/usb/smsc75xx.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/net/usb/smsc75xx.c b/drivers/net/usb/smsc75xx.c
> index b286993da67c..f81740fcc8d5 100644
> --- a/drivers/net/usb/smsc75xx.c
> +++ b/drivers/net/usb/smsc75xx.c
> @@ -1504,7 +1504,10 @@ static int smsc75xx_bind(struct usbnet *dev, struct usb_interface *intf)
> return 0;
>
> err:
> + cancel_work_sync(&pdata->set_multicast);
> kfree(pdata);
> + pdata = NULL;

Why do you have to set pdata to NULL afterward?

thanks,

greg k-h