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    Subject[PATCH 4.19 084/276] rtc: 88pm860x: prevent use-after-free on device remove
    Date
    [ Upstream commit f22b1ba15ee5785aa028384ebf77dd39e8e47b70 ]

    The device's remove() attempts to shut down the delayed_work scheduled
    on the kernel-global workqueue by calling flush_scheduled_work().

    Unfortunately, flush_scheduled_work() does not prevent the delayed_work
    from re-scheduling itself. The delayed_work might run after the device
    has been removed, and touch the already de-allocated info structure.
    This is a potential use-after-free.

    Fix by calling cancel_delayed_work_sync() during remove(): this ensures
    that the delayed work is properly cancelled, is no longer running, and
    is not able to re-schedule itself.

    This issue was detected with the help of Coccinelle.

    Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>
    Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/rtc/rtc-88pm860x.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/drivers/rtc/rtc-88pm860x.c b/drivers/rtc/rtc-88pm860x.c
    index 01ffc0ef8033f..fbcf13bbbd8d1 100644
    --- a/drivers/rtc/rtc-88pm860x.c
    +++ b/drivers/rtc/rtc-88pm860x.c
    @@ -414,7 +414,7 @@ static int pm860x_rtc_remove(struct platform_device *pdev)
    struct pm860x_rtc_info *info = platform_get_drvdata(pdev);

    #ifdef VRTC_CALIBRATION
    - flush_scheduled_work();
    + cancel_delayed_work_sync(&info->calib_work);
    /* disable measurement */
    pm860x_set_bits(info->i2c, PM8607_MEAS_EN2, MEAS2_VRTC, 0);
    #endif /* VRTC_CALIBRATION */
    --
    2.20.1


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