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From:   Zheng Hacker <hackerzheng666@gmail.com>
Date:   Thu, 13 Apr 2023 01:18:09 +0800
Message-ID: <CAJedcCxqTr0s6dpRgqnUQXaLWzW4ZS3FCtRgF8bYh8U12=FtTA@mail.gmail.com>
Subject: Re: [PATCH] HID: intel-ish-hid: pci-ish: Fix use after free bug in
 ish_remove due to race condition
To:     Zheng Wang <zyytlz.wz@163.com>
Cc:     srinivas.pandruvada@linux.intel.com, jikos@kernel.org,
        benjamin.tissoires@redhat.com, rafael@kernel.org,
        hdegoede@redhat.com, gregkh@linuxfoundation.org,
        linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
        1395428693sheep@gmail.com, alex000young@gmail.com
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Hi,

I missed some detail in the patch. bh_hbm_work_fn will call
ishtp_hbm_dispatch and access &dev->fw_clients in it.

Best regards,
Zheng

Zheng Wang <zyytlz.wz@163.com> =E4=BA=8E2023=E5=B9=B44=E6=9C=8813=E6=97=A5=
=E5=91=A8=E5=9B=9B 01:17=E5=86=99=E9=81=93=EF=BC=9A
>
> In ish_probe, it calls ish_dev_init to init the device. In this function,
> ishtp_device_init is called and &dev->bh_hbm_work is bound with
> bh_hbm_work_fn. recv_hbm may be called to start the timer work.
>
> If we remove the module which will call ish_remove to make cleanup,
> there may be an unfinished work. The possible sequence is as follows:
>
> Fix it by canceling the work before cleanup in ishtp_bus_remove_all_clien=
ts
>
> CPU0                  CPUc1
>
>                     |bh_hbm_work_fn
> ish_remove      |
> ishtp_bus_remove_all_clients  |
> kfree(ishtp_dev->fw_clients); |
>                     |
>                     |&dev->fw_clients[...]
>                     |   //use
>
> Fixes: 3703f53b99e4 ("HID: intel_ish-hid: ISH Transport layer")
> Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> ---
>  drivers/hid/intel-ish-hid/ishtp/bus.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/hid/intel-ish-hid/ishtp/bus.c b/drivers/hid/intel-is=
h-hid/ishtp/bus.c
> index 81385ab37fa9..ada7cd08dbeb 100644
> --- a/drivers/hid/intel-ish-hid/ishtp/bus.c
> +++ b/drivers/hid/intel-ish-hid/ishtp/bus.c
> @@ -744,6 +744,7 @@ void ishtp_bus_remove_all_clients(struct ishtp_device=
 *ishtp_dev,
>                  */
>         }
>         spin_unlock_irqrestore(&ishtp_dev->cl_list_lock, flags);
> +       cancel_work_sync(&ishtp_dev->bh_hbm_work);
>
>         /* Release DMA buffers for client messages */
>         ishtp_cl_free_dma_buf(ishtp_dev);
> --
> 2.25.1
>