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From:   Zheng Hacker <hackerzheng666@gmail.com>
Date:   Sat, 11 Mar 2023 00:20:57 +0800
Message-ID: <CAJedcCxrXuDjj_hGz7wizmfu1A9PNguNRNT85YVmkAHCG7ynYQ@mail.gmail.com>
Subject: Re: [PATCH] memstick: r592: Fix UAF bug in r592_remove due to race condition
To:     Ulf Hansson <ulf.hansson@linaro.org>
Cc:     Zheng Wang <zyytlz.wz@163.com>, maximlevitsky@gmail.com,
        oakad@yahoo.com, linux-mmc@vger.kernel.org,
        linux-kernel@vger.kernel.org, 1395428693sheep@gmail.com,
        alex000young@gmail.com
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Ulf Hansson <ulf.hansson@linaro.org> =E4=BA=8E2023=E5=B9=B43=E6=9C=889=E6=
=97=A5=E5=91=A8=E5=9B=9B 23:02=E5=86=99=E9=81=93=EF=BC=9A
>
> On Tue, 7 Mar 2023 at 17:44, Zheng Wang <zyytlz.wz@163.com> wrote:
> >
> > In r592_probe, dev->detect_timer was bound with r592_detect_timer.
> > In r592_irq function, the timer function will be invoked by mod_timer.
> >
> > If we remove the module which will call hantro_release to make cleanup,
> > there may be a unfinished work. The possible sequence is as follows,
> > which will cause a typical UAF bug.
> >
> > Fix it by canceling the work before cleanup in r592_remove.
> >
> > CPU0                  CPU1
> >
> >                     |r592_detect_timer
> > r592_remove         |
> >   memstick_free_host|
> >   put_device;       |
> >   kfree(host);      |
> >                     |
> >                     | queue_work
> >                     |   &host->media_checker //use
> >
> > Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
>
> Applied for next, thanks!
>
Sorry for my late reply and thanks for your effort!

Best regards,
Zheng
>
>
> > ---
> >  drivers/memstick/host/r592.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/memstick/host/r592.c b/drivers/memstick/host/r592.=
c
> > index 1d35d147552d..2bfa7eaae80a 100644
> > --- a/drivers/memstick/host/r592.c
> > +++ b/drivers/memstick/host/r592.c
> > @@ -829,7 +829,7 @@ static void r592_remove(struct pci_dev *pdev)
> >         /* Stop the processing thread.
> >         That ensures that we won't take any more requests */
> >         kthread_stop(dev->io_thread);
> > -
> > +       del_timer_sync(&dev->detect_timer);
> >         r592_enable_device(dev, false);
> >
> >         while (!error && dev->req) {
> > --
> > 2.25.1
> >