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    Subject[PATCH 4.16 157/161] rtc: rk808: fix possible race condition
    Date
    4.16-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Alexandre Belloni <alexandre.belloni@bootlin.com>

    [ Upstream commit 201fac95e799c3d0304ec724d555e1251b9f6e84 ]

    The probe function is not allowed to fail after registering the RTC because
    the following may happen:

    CPU0: CPU1:
    sys_load_module()
    do_init_module()
    do_one_initcall()
    cmos_do_probe()
    rtc_device_register()
    __register_chrdev()
    cdev->owner = struct module*
    open("/dev/rtc0")
    rtc_device_unregister()
    module_put()
    free_module()
    module_free(mod->module_core)
    /* struct module *module is now
    freed */
    chrdev_open()
    spin_lock(cdev_lock)
    cdev_get()
    try_module_get()
    module_is_live()
    /* dereferences already
    freed struct module* */

    Switch to devm_rtc_allocate_device/rtc_register_device to register the rtc
    as late as possible.

    Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/rtc/rtc-rk808.c | 14 +++++++-------
    1 file changed, 7 insertions(+), 7 deletions(-)

    --- a/drivers/rtc/rtc-rk808.c
    +++ b/drivers/rtc/rtc-rk808.c
    @@ -416,12 +416,11 @@ static int rk808_rtc_probe(struct platfo

    device_init_wakeup(&pdev->dev, 1);

    - rk808_rtc->rtc = devm_rtc_device_register(&pdev->dev, "rk808-rtc",
    - &rk808_rtc_ops, THIS_MODULE);
    - if (IS_ERR(rk808_rtc->rtc)) {
    - ret = PTR_ERR(rk808_rtc->rtc);
    - return ret;
    - }
    + rk808_rtc->rtc = devm_rtc_allocate_device(&pdev->dev);
    + if (IS_ERR(rk808_rtc->rtc))
    + return PTR_ERR(rk808_rtc->rtc);
    +
    + rk808_rtc->rtc->ops = &rk808_rtc_ops;

    rk808_rtc->irq = platform_get_irq(pdev, 0);
    if (rk808_rtc->irq < 0) {
    @@ -438,9 +437,10 @@ static int rk808_rtc_probe(struct platfo
    if (ret) {
    dev_err(&pdev->dev, "Failed to request alarm IRQ %d: %d\n",
    rk808_rtc->irq, ret);
    + return ret;
    }

    - return ret;
    + return rtc_register_device(rk808_rtc->rtc);
    }

    static struct platform_driver rk808_rtc_driver = {

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