Re: [PATCH] rtc: mpfs: fix unchecked devm_clk_get() error pointer in probe()

[Conor Dooley <conor@kernel.org>]

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On Sun, Sep 06, 2026 at 04:44:09PM +0530, Manush Prajwal wrote:
> devm_clk_get(&pdev->dev, "rtcref")'s return value was passed straight
> into clk_get_rate() without checking it for an error first, unlike the
> "rtc" clock a few lines above which is correctly checked with
> IS_ERR(). clk_get_rate() only guards against a NULL clk, not an error
> pointer:
> 
> 	if (!clk)
> 		return 0;
> 	...
> 	rate = clk_core_get_rate_recalc(clk->core);
> 
> so if devm_clk_get() ever returns an error pointer here (for example
> ERR_PTR(-EPROBE_DEFER), which is the normal, expected outcome if the
> clkcfg clock-provider this RTC depends on has not registered its
> clocks yet by the time this driver probes), clk_get_rate() dereferences
> that error pointer instead of returning 0, crashing instead of letting
> probe defer.
> 
> Capture the clock in the existing 'clk' local and check it with
> IS_ERR() before calling clk_get_rate(), matching the handling already
> used for the "rtc" clock in this same function.
> 
> Signed-off-by: Manush Prajwal <manushprajwal555@gmail.com>

Fixes: 0b31d703598d ("rtc: Add driver for Microchip PolarFire SoC")
CC: stable@vger.kernel.org
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>

> ---
>  drivers/rtc/rtc-mpfs.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/rtc/rtc-mpfs.c b/drivers/rtc/rtc-mpfs.c
> index ece6de4a6..60596b0ea 100644
> --- a/drivers/rtc/rtc-mpfs.c
> +++ b/drivers/rtc/rtc-mpfs.c
> @@ -256,8 +256,12 @@ static int mpfs_rtc_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> +	clk = devm_clk_get(&pdev->dev, "rtcref");
> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +
>  	/* prescaler hardware adds 1 to reg value */
> -	prescaler = clk_get_rate(devm_clk_get(&pdev->dev, "rtcref")) - 1;
> +	prescaler = clk_get_rate(clk) - 1;
>  	if (prescaler > MAX_PRESCALER_COUNT) {
>  		dev_dbg(&pdev->dev, "invalid prescaler %lu\n", prescaler);
>  		return -EINVAL;
> -- 
> 2.46.2.windows.1
> 
> 

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