linux-kernel - Re: [PATCH V2] usbnet: Prevents free active kevent

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Message-ID: <20251018025432.3076176-1-lizhi.xu@windriver.com>
Date: Sat, 18 Oct 2025 10:54:32 +0800
From: Lizhi Xu <lizhi.xu@...driver.com>
To: <kuba@...nel.org>
CC: <ahmed.zaki@...el.com>, <aleksander.lobakin@...el.com>,
        <davem@...emloft.net>, <edumazet@...gle.com>, <horms@...nel.org>,
        <kuniyu@...zon.com>, <linux-kernel@...r.kernel.org>,
        <lizhi.xu@...driver.com>, <netdev@...r.kernel.org>,
        <pabeni@...hat.com>, <samsun1006219@...il.com>, <sdf@...ichev.me>,
        <syzkaller-bugs@...glegroups.com>, <syzkaller@...glegroups.com>
Subject: Re: [PATCH V2] usbnet: Prevents free active kevent

On Fri, 17 Oct 2025 15:27:31 -0700, Jakub Kicinski wrote:
> On Fri, 17 Oct 2025 17:05:41 +0800 Lizhi Xu wrote:
> > 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(), which also deletes the delay timer.
> 
> Please add a fixes tag, and repost.
Fixes: a69e617e533e ("usbnet: Fix linkwatch use-after-free on disconnect")

Later, I will repost new version patch in a new thread
and at the correct time.

BR,
Lizhi