5.4-stable review patch. If anyone has any objections, please let me know.
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From: Lizhi Xu lizhi.xu@windriver.com
[ Upstream commit 420c84c330d1688b8c764479e5738bbdbf0a33de ]
The root cause of this issue are: 1. When probing the usbnet device, executing usbnet_link_change(dev, 0, 0); put the kevent work in global workqueue. However, the kevent has not yet been scheduled when the usbnet device is unregistered. Therefore, executing free_netdev() results in the "free active object (kevent)" error reported here.
2. Another factor is that when calling usbnet_disconnect()->unregister_netdev(), if the usbnet device is up, ndo_stop() is executed to cancel the kevent. However, because the device is not up, ndo_stop() is not executed.
The solution to this problem is to cancel the kevent before executing free_netdev().
Fixes: a69e617e533e ("usbnet: Fix linkwatch use-after-free on disconnect") Reported-by: Sam Sun samsun1006219@gmail.com Closes: https://syzkaller.appspot.com/bug?extid=8bfd7bcc98f7300afb84 Signed-off-by: Lizhi Xu lizhi.xu@windriver.com Link: https://patch.msgid.link/20251022024007.1831898-1-lizhi.xu@windriver.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/usb/usbnet.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c index 87c0bcfef4801..f0dd0d7b51dc1 100644 --- a/drivers/net/usb/usbnet.c +++ b/drivers/net/usb/usbnet.c @@ -1615,6 +1615,8 @@ void usbnet_disconnect (struct usb_interface *intf) net = dev->net; unregister_netdev (net);
+ cancel_work_sync(&dev->kevent); + while ((urb = usb_get_from_anchor(&dev->deferred))) { dev_kfree_skb(urb->context); kfree(urb->sg);