Re: [PATCH v2] memstick: rtsx_usb_ms: fix UAF

[Ulf Hansson]

On Tue, 11 May 2021 at 18:40, Tong Zhang <ztong0001@xxxxxxxxx> wrote:
>
> This patch fixes the following issues:
> 1. memstick_free_host() will free the host, so the use of ms_dev(host) after
> it will be a problem. To fix this, move memstick_free_host() after when we
> are done with ms_dev(host).
> 2. In rtsx_usb_ms_drv_remove(), pm need to be disabled before we remove
> and free host otherwise memstick_check will be called and UAF will
> happen.
>
> [   11.351173] BUG: KASAN: use-after-free in rtsx_usb_ms_drv_remove+0x94/0x140 [rtsx_usb_ms]
> [   11.357077]  rtsx_usb_ms_drv_remove+0x94/0x140 [rtsx_usb_ms]
> [   11.357376]  platform_remove+0x2a/0x50
> [   11.367531] Freed by task 298:
> [   11.368537]  kfree+0xa4/0x2a0
> [   11.368711]  device_release+0x51/0xe0
> [   11.368905]  kobject_put+0xa2/0x120
> [   11.369090]  rtsx_usb_ms_drv_remove+0x8c/0x140 [rtsx_usb_ms]
> [   11.369386]  platform_remove+0x2a/0x50
>
> [   12.038408] BUG: KASAN: use-after-free in __mutex_lock.isra.0+0x3ec/0x7c0
> [   12.045432]  mutex_lock+0xc9/0xd0
> [   12.046080]  memstick_check+0x6a/0x578 [memstick]
> [   12.046509]  process_one_work+0x46d/0x750
> [   12.052107] Freed by task 297:
> [   12.053115]  kfree+0xa4/0x2a0
> [   12.053272]  device_release+0x51/0xe0
> [   12.053463]  kobject_put+0xa2/0x120
> [   12.053647]  rtsx_usb_ms_drv_remove+0xc4/0x140 [rtsx_usb_ms]
> [   12.053939]  platform_remove+0x2a/0x50
>
> Signed-off-by: Tong Zhang <ztong0001@xxxxxxxxx>
> Co-Developed-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>

Applied for next, thanks!

Kind regards
Uffe


> ---
> v2: remove useless code in err_out label
>
>  drivers/memstick/host/rtsx_usb_ms.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/memstick/host/rtsx_usb_ms.c b/drivers/memstick/host/rtsx_usb_ms.c
> index 102dbb8080da..29271ad4728a 100644
> --- a/drivers/memstick/host/rtsx_usb_ms.c
> +++ b/drivers/memstick/host/rtsx_usb_ms.c
> @@ -799,9 +799,9 @@ static int rtsx_usb_ms_drv_probe(struct platform_device *pdev)
>
>         return 0;
>  err_out:
> -       memstick_free_host(msh);
>         pm_runtime_disable(ms_dev(host));
>         pm_runtime_put_noidle(ms_dev(host));
> +       memstick_free_host(msh);
>         return err;
>  }
>
> @@ -828,9 +828,6 @@ static int rtsx_usb_ms_drv_remove(struct platform_device *pdev)
>         }
>         mutex_unlock(&host->host_mutex);
>
> -       memstick_remove_host(msh);
> -       memstick_free_host(msh);
> -
>         /* Balance possible unbalanced usage count
>          * e.g. unconditional module removal
>          */
> @@ -838,10 +835,11 @@ static int rtsx_usb_ms_drv_remove(struct platform_device *pdev)
>                 pm_runtime_put(ms_dev(host));
>
>         pm_runtime_disable(ms_dev(host));
> -       platform_set_drvdata(pdev, NULL);
> -
> +       memstick_remove_host(msh);
>         dev_dbg(ms_dev(host),
>                 ": Realtek USB Memstick controller has been removed\n");
> +       memstick_free_host(msh);
> +       platform_set_drvdata(pdev, NULL);
>
>         return 0;
>  }
> --
> 2.25.1
>