Re: [PATCH v2] watchdog: starfive-wdt: fix PM reference leak in probe error path

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] pm: desynchronize PM state by manually disabling clocks on put failure
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commit 5ff7d303ba1caba3e17ed0a2e51c79514ccbc5c5
Author: Ivy Lopez <skunkolee@gmail.com>

watchdog: starfive-wdt: fix PM reference leak in probe error path

This commit addresses a PM reference leak in the probe error path by tracking
whether a PM reference is held and whether clocks are enabled, ensuring they
are properly released on exit.

> diff --git a/drivers/watchdog/starfive-wdt.c b/drivers/watchdog/starfive-wdt.c
> index af55adc4a3c69..4ad587732bdaa 100644
> --- a/drivers/watchdog/starfive-wdt.c
> +++ b/drivers/watchdog/starfive-wdt.c

[ ... ]

> @@ -509,7 +517,12 @@ static int starfive_wdt_probe(struct platform_device *pdev)
>  err_unregister_wdt:
>  	watchdog_unregister_device(&wdt->wdd);
>  err_exit:
> -	starfive_wdt_disable_clock(wdt);
> +	if (pm_ref_held) {
> +		if (pm_runtime_put_sync(&pdev->dev))
> +			starfive_wdt_disable_clock(wdt);

[Severity: High]
Does manually disabling the clock here risk desynchronizing the PM state if
pm_runtime_put_sync() intentionally fails?

If a concurrent operation (like userspace sysfs interaction) bumps the PM
usage count during this window, pm_runtime_put_sync() in starfive_wdt_probe()
returns an error such as -EAGAIN. This indicates the PM core has decided to
keep the device active.

By manually disabling the clocks here, the hardware is turned off while the
PM core still considers the device to be RPM_ACTIVE.

If a concurrent thread or a subsequent driver reprobe accesses the peripheral
registers while unclocked (since a later pm_runtime_resume_and_get() would
find the device already active and skip the resume callback), could this lead
to a bus error or system crash?

> +	} else if (clocks_on) {
> +		starfive_wdt_disable_clock(wdt);
> +	}
>  	pm_runtime_disable(&pdev->dev);
>  
>  	return ret;

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Sashiko AI review · https://sashiko.dev/#/patchset/20260915032032.222665-1-skunkolee@gmail.com?part=1