Re: [PATCH] net: usb: fix possible use-after-free in smsc75xx_bind
From: Pavel Skripkin <hidden>
Date: 2021-06-14 16:02:11
Also in:
linux-usb, lkml
On Mon, 14 Jun 2021 23:37:12 +0800 Dongliang Mu [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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; + dev->data[0] = 0; return ret; }
Hi, Dongliang! Just my thougth about this patch: INIT_WORK(&pdata->set_multicast, smsc75xx_deferred_multicast_write); does not queue anything, it just initalizes list structure and assigns callback function. The actual work sheduling happens in smsc75xx_set_multicast() which is smsc75xx_netdev_ops member. In case of any error in smsc75xx_bind() the device registration fails and smsc75xx_netdev_ops won't be registered, so, i guess, there is no chance of UAF. Am I missing something? :) With regards, Pavel Skripkin