linux-kernel - Re: [PATCH] workqueue: Fix UAF report by KASAN in pwq_release

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Message-ID: <CALm+0cUytR3-0mcW3t24gcyP27UW3rpP5_+vpLVC3w70+0n6oQ@mail.gmail.com>
Date:   Thu, 7 Sep 2023 10:13:23 +0800
From:   Z qiang <qiang.zhang1211@...il.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     jiangshanlai@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] workqueue: Fix UAF report by KASAN in pwq_release_workfn()

>
> On Wed, Sep 06, 2023 at 10:12:34AM +0800, Z qiang wrote:
> > Flush the pwq_release_worker is insufficient, the call_rcu() is
> > invoked to release wq
> > in pwq_release_workfn(), this is also asynchronous.
>
> But rcu_free_pwq() doesn't access wq or anything. The last access is from
> the work function.

The rcu_free_wq() will access wq->cpu_pwq or unbound_attrs,
but  at this time, the kfree(wq) may have been called in alloc_workqueue().

Thanks
Zqiang


>
> Thanks.
>
> --
> tejun