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    Subject[PATCH 5.15 026/132] rtc: sun6i: Fix time overflow handling
    Date
    From: Andre Przywara <andre.przywara@arm.com>

    [ Upstream commit 9f6cd82eca7e91a0d0311242a87c6aa3c2737968 ]

    Using "unsigned long" for UNIX timestamps is never a good idea, and
    comparing the value of such a variable against U32_MAX does not do
    anything useful on 32-bit systems.

    Use the proper time64_t type when dealing with timestamps, and avoid
    cutting down the time range unnecessarily. This also fixes the flawed
    check for the alarm time being too far into the future.

    The check for this condition is actually somewhat theoretical, as the
    RTC counts till 2033 only anyways, and 2^32 seconds from now is not
    before the year 2157 - at which point I hope nobody will be using this
    hardware anymore.

    Signed-off-by: Andre Przywara <andre.przywara@arm.com>
    Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
    Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
    Link: https://lore.kernel.org/r/20220211122643.1343315-4-andre.przywara@arm.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/rtc/rtc-sun6i.c | 14 +++++---------
    1 file changed, 5 insertions(+), 9 deletions(-)

    diff --git a/drivers/rtc/rtc-sun6i.c b/drivers/rtc/rtc-sun6i.c
    index adec1b14a8de..c551ebf0ac00 100644
    --- a/drivers/rtc/rtc-sun6i.c
    +++ b/drivers/rtc/rtc-sun6i.c
    @@ -138,7 +138,7 @@ struct sun6i_rtc_dev {
    const struct sun6i_rtc_clk_data *data;
    void __iomem *base;
    int irq;
    - unsigned long alarm;
    + time64_t alarm;

    struct clk_hw hw;
    struct clk_hw *int_osc;
    @@ -510,10 +510,8 @@ static int sun6i_rtc_setalarm(struct device *dev, struct rtc_wkalrm *wkalrm)
    struct sun6i_rtc_dev *chip = dev_get_drvdata(dev);
    struct rtc_time *alrm_tm = &wkalrm->time;
    struct rtc_time tm_now;
    - unsigned long time_now = 0;
    - unsigned long time_set = 0;
    - unsigned long time_gap = 0;
    - int ret = 0;
    + time64_t time_now, time_set;
    + int ret;

    ret = sun6i_rtc_gettime(dev, &tm_now);
    if (ret < 0) {
    @@ -528,9 +526,7 @@ static int sun6i_rtc_setalarm(struct device *dev, struct rtc_wkalrm *wkalrm)
    return -EINVAL;
    }

    - time_gap = time_set - time_now;
    -
    - if (time_gap > U32_MAX) {
    + if ((time_set - time_now) > U32_MAX) {
    dev_err(dev, "Date too far in the future\n");
    return -EINVAL;
    }
    @@ -539,7 +535,7 @@ static int sun6i_rtc_setalarm(struct device *dev, struct rtc_wkalrm *wkalrm)
    writel(0, chip->base + SUN6I_ALRM_COUNTER);
    usleep_range(100, 300);

    - writel(time_gap, chip->base + SUN6I_ALRM_COUNTER);
    + writel(time_set - time_now, chip->base + SUN6I_ALRM_COUNTER);
    chip->alarm = time_set;

    sun6i_rtc_setaie(wkalrm->enabled, chip);
    --
    2.35.1


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