linux-kernel - Re: [PATCH -next] rtc: synqmp: uninitialized variable error

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Date:   Wed, 3 Aug 2022 07:46:42 +0200
From:   Michal Simek <michal.simek@....com>
To:     Sebin Sebastian <mailmesebin00@...il.com>
CC:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Michal Simek <michal.simek@...inx.com>,
        <linux-rtc@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] rtc: synqmp: uninitialized variable error

Hi,

On 8/3/22 03:31, Sebin Sebastian wrote:
> 
> fract_tick is uninitialized and can lead to uninitialized read which can
> result in any arbitrary value from previous computations. If the code
> flow doesnt execute the `if (fract_offset > (tick_mult /
> RTC_FR_MAX_TICKS)) { ` block, fract_tick is left uninitialized.
> Initializing with zero fixes the issue.
> 
> Signed-off-by: Sebin Sebastian <mailmesebin00@...il.com>
> ---
>   drivers/rtc/rtc-zynqmp.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/rtc/rtc-zynqmp.c b/drivers/rtc/rtc-zynqmp.c
> index 1dd389b891fe..c9b85c838ebe 100644
> --- a/drivers/rtc/rtc-zynqmp.c
> +++ b/drivers/rtc/rtc-zynqmp.c
> @@ -203,7 +203,7 @@ static int xlnx_rtc_set_offset(struct device *dev, long offset)
>          struct xlnx_rtc_dev *xrtcdev = dev_get_drvdata(dev);
>          unsigned long long rtc_ppb = RTC_PPB;
>          unsigned int tick_mult = do_div(rtc_ppb, xrtcdev->freq);
> -       unsigned char fract_tick;
> +       unsigned char fract_tick = 0;
>          unsigned int calibval;
>          short int  max_tick;
>          int fract_offset;
> --
> 2.34.1
> 

Alexandre already send the patch for it here.

https://lore.kernel.org/r/20220727100018.3301470-1-alexandre.belloni@bootlin.com

Thanks,
Michal