[PATCH] hwrng: npcm: fix usage_count leak when autosuspend_delay is negative

[PATCH] hwrng: npcm: fix usage_count leak when autosuspend_delay is negative

[Guangshuo Li]

npcm_rng_probe() calls pm_runtime_use_autosuspend(), but neither the
probe failure path nor npcm_rng_remove() calls the matching
pm_runtime_dont_use_autosuspend() before disabling runtime PM.

If the autosuspend delay is set to a negative value while autosuspend
is enabled, the runtime PM core increments usage_count to prevent
runtime suspend. Without calling pm_runtime_dont_use_autosuspend()
during teardown, this reference is not dropped and usage_count remains
unbalanced.

Add the missing pm_runtime_dont_use_autosuspend() calls to both the
probe failure and remove paths before disabling runtime PM.

This issue was found by manual code inspection.

Fixes: c98429297d8b ("hwrng: npcm - add NPCM RNG driver")
Cc: stable@vger.kernel.org
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
---
 drivers/char/hw_random/npcm-rng.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/char/hw_random/npcm-rng.c b/drivers/char/hw_random/npcm-rng.c
index 40d6e29dea03..43f96abee753 100644
--- a/drivers/char/hw_random/npcm-rng.c
+++ b/drivers/char/hw_random/npcm-rng.c
@@ -118,6 +118,7 @@ static int npcm_rng_probe(struct platform_device *pdev)
 	if (ret) {
 		dev_err(&pdev->dev, "Failed to register rng device: %d\n",
 			ret);
+		pm_runtime_dont_use_autosuspend(&pdev->dev);
 		pm_runtime_disable(&pdev->dev);
 		pm_runtime_set_suspended(&pdev->dev);
 		return ret;
@@ -131,6 +132,7 @@ static void npcm_rng_remove(struct platform_device *pdev)
 	struct npcm_rng *priv = platform_get_drvdata(pdev);
 
 	devm_hwrng_unregister(&pdev->dev, &priv->rng);
+	pm_runtime_dont_use_autosuspend(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
 	pm_runtime_set_suspended(&pdev->dev);
 }
-- 
2.43.0

Re: [PATCH] hwrng: npcm: fix usage_count leak when autosuspend_delay is negative

[Krzysztof Kozlowski]

On 08/08/2026 09:37, Guangshuo Li wrote:
> npcm_rng_probe() calls pm_runtime_use_autosuspend(), but neither the
> probe failure path nor npcm_rng_remove() calls the matching
> pm_runtime_dont_use_autosuspend() before disabling runtime PM.
> 
> If the autosuspend delay is set to a negative value while autosuspend
> is enabled, the runtime PM core increments usage_count to prevent
> runtime suspend. Without calling pm_runtime_dont_use_autosuspend()
> during teardown, this reference is not dropped and usage_count remains
> unbalanced.
> 
> Add the missing pm_runtime_dont_use_autosuspend() calls to both the
> probe failure and remove paths before disabling runtime PM.
> 
> This issue was found by manual code inspection.
> 
> Fixes: c98429297d8b ("hwrng: npcm - add NPCM RNG driver")
> Cc: stable@vger.kernel.org
> Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>

You sent vast amount of patches, all separate, making it very difficult
to track and respond in efficient way. Do not do that.

Group your work per subsystem.

You were asked to clarify and respond to incorrect fixes statement. I do
not see how you clarified and responded at all.

Best regards,
Krzysztof