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    Subject[PATCH AUTOSEL 4.19 110/206] rtc: sa1100: fix possible race condition
    Date
    From: Alexandre Belloni <alexandre.belloni@bootlin.com>

    [ Upstream commit f2997775b111c6d660c32a18d5d44d37cb7361b1 ]

    Both RTC IRQs are requested before the struct rtc_device is allocated,
    this may lead to a NULL pointer dereference in the IRQ handler.

    To fix this issue, allocating the rtc_device struct before requesting
    the IRQs using devm_rtc_allocate_device, and use rtc_register_device
    to register the RTC device.

    Link: https://lore.kernel.org/r/20200306010146.39762-1-alexandre.belloni@bootlin.com
    Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/rtc/rtc-sa1100.c | 18 ++++++++++--------
    1 file changed, 10 insertions(+), 8 deletions(-)

    diff --git a/drivers/rtc/rtc-sa1100.c b/drivers/rtc/rtc-sa1100.c
    index 304d905cb23fd..56f625371735f 100644
    --- a/drivers/rtc/rtc-sa1100.c
    +++ b/drivers/rtc/rtc-sa1100.c
    @@ -186,7 +186,6 @@ static const struct rtc_class_ops sa1100_rtc_ops = {

    int sa1100_rtc_init(struct platform_device *pdev, struct sa1100_rtc *info)
    {
    - struct rtc_device *rtc;
    int ret;

    spin_lock_init(&info->lock);
    @@ -215,15 +214,14 @@ int sa1100_rtc_init(struct platform_device *pdev, struct sa1100_rtc *info)
    writel_relaxed(0, info->rcnr);
    }

    - rtc = devm_rtc_device_register(&pdev->dev, pdev->name, &sa1100_rtc_ops,
    - THIS_MODULE);
    - if (IS_ERR(rtc)) {
    + info->rtc->ops = &sa1100_rtc_ops;
    + info->rtc->max_user_freq = RTC_FREQ;
    +
    + ret = rtc_register_device(info->rtc);
    + if (ret) {
    clk_disable_unprepare(info->clk);
    - return PTR_ERR(rtc);
    + return ret;
    }
    - info->rtc = rtc;
    -
    - rtc->max_user_freq = RTC_FREQ;

    /* Fix for a nasty initialization problem the in SA11xx RTSR register.
    * See also the comments in sa1100_rtc_interrupt().
    @@ -272,6 +270,10 @@ static int sa1100_rtc_probe(struct platform_device *pdev)
    info->irq_1hz = irq_1hz;
    info->irq_alarm = irq_alarm;

    + info->rtc = devm_rtc_allocate_device(&pdev->dev);
    + if (IS_ERR(info->rtc))
    + return PTR_ERR(info->rtc);
    +
    ret = devm_request_irq(&pdev->dev, irq_1hz, sa1100_rtc_interrupt, 0,
    "rtc 1Hz", &pdev->dev);
    if (ret) {
    --
    2.25.1
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