[PATCH] hwrng: cctrng - Fix runtime PM usage counter leak

[PATCH] hwrng: cctrng - Fix runtime PM usage counter leak

[Ruoyu Wang]

pm_runtime_get_sync() increments the device usage counter even when
runtime resume fails. cctrng_read() propagates errors from
cc_trng_pm_get() without scheduling the work that later drops the
counter, so a clock or reset-completion failure in cctrng_resume()
leaves the counter elevated.

Use pm_runtime_resume_and_get(), which drops the usage counter when
resume fails and returns zero on success. This preserves the existing
success path while balancing the error path.

This issue was found by a static analysis checker and confirmed by
manual source review.

Fixes: a583ed310bb6 ("hwrng: cctrng - introduce Arm CryptoCell driver")
Signed-off-by: Ruoyu Wang <ruoyuw560@gmail.com>
---
 drivers/char/hw_random/cctrng.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/char/hw_random/cctrng.c b/drivers/char/hw_random/cctrng.c
index a5be9258037f8..41c338a768ce9 100644
--- a/drivers/char/hw_random/cctrng.c
+++ b/drivers/char/hw_random/cctrng.c
@@ -86,12 +86,7 @@ static inline u32 cc_ioread(struct cctrng_drvdata *drvdata, u32 reg)
 
 static int cc_trng_pm_get(struct device *dev)
 {
-	int rc = 0;
-
-	rc = pm_runtime_get_sync(dev);
-
-	/* pm_runtime_get_sync() can return 1 as a valid return code */
-	return (rc == 1 ? 0 : rc);
+	return pm_runtime_resume_and_get(dev);
 }
 
 static void cc_trng_pm_put_suspend(struct device *dev)
-- 
2.51.0

Re: [PATCH] hwrng: cctrng - Fix runtime PM usage counter leak

[Herbert Xu]

On Fri, Aug 14, 2026 at 09:39:33PM +0800, Ruoyu Wang wrote:
> pm_runtime_get_sync() increments the device usage counter even when
> runtime resume fails. cctrng_read() propagates errors from
> cc_trng_pm_get() without scheduling the work that later drops the
> counter, so a clock or reset-completion failure in cctrng_resume()
> leaves the counter elevated.
> 
> Use pm_runtime_resume_and_get(), which drops the usage counter when
> resume fails and returns zero on success. This preserves the existing
> success path while balancing the error path.
> 
> This issue was found by a static analysis checker and confirmed by
> manual source review.
> 
> Fixes: a583ed310bb6 ("hwrng: cctrng - introduce Arm CryptoCell driver")
> Signed-off-by: Ruoyu Wang <ruoyuw560@gmail.com>
> ---
>  drivers/char/hw_random/cctrng.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt