[PATCH -next] rtc: synqmp: uninitialized variable error

[PATCH -next] rtc: synqmp: uninitialized variable error

[Sebin Sebastian]

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@gmail.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


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

[Michal Simek]

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@gmail.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

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