PM: QoS: Fix misc device registration unwind

[PATCH v1] PM: QoS: Fix misc device registration unwind

Posted by Yuho Choi 2 weeks, 2 days ago

cpu_latency_qos_init() registers cpu_dma_latency first and, when
CONFIG_PM_QOS_CPU_SYSTEM_WAKEUP is enabled, registers cpu_wakeup_latency
afterwards. The second registration overwrites the first return value.

As a result, a failure to register cpu_dma_latency can be masked if the
second registration succeeds. Conversely, if cpu_dma_latency succeeds and
cpu_wakeup_latency fails, the function returns an error while leaving the
first misc device registered.

Return immediately on the first registration failure and deregister
cpu_dma_latency if the second registration fails.

Fixes: a4e6512a79d8 ("PM: QoS: Introduce a CPU system wakeup QoS limit")
Signed-off-by: Yuho Choi <dbgh9129@gmail.com>
---
 kernel/power/qos.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/kernel/power/qos.c b/kernel/power/qos.c
index 398b994b73aa..1944dbeb0d4c 100644
--- a/kernel/power/qos.c
+++ b/kernel/power/qos.c
@@ -519,18 +519,23 @@ static int __init cpu_latency_qos_init(void)
 	int ret;
 
 	ret = misc_register(&cpu_latency_qos_miscdev);
-	if (ret < 0)
+	if (ret < 0) {
 		pr_err("%s: %s setup failed\n", __func__,
 		       cpu_latency_qos_miscdev.name);
+		return ret;
+	}
 
 #ifdef CONFIG_PM_QOS_CPU_SYSTEM_WAKEUP
 	ret = misc_register(&cpu_wakeup_latency_qos_miscdev);
-	if (ret < 0)
+	if (ret < 0) {
 		pr_err("%s: %s setup failed\n", __func__,
 		       cpu_wakeup_latency_qos_miscdev.name);
+		misc_deregister(&cpu_latency_qos_miscdev);
+		return ret;
+	}
 #endif
 
-	return ret;
+	return 0;
 }
 late_initcall(cpu_latency_qos_init);
 #endif /* CONFIG_CPU_IDLE */
-- 
2.43.0

Re: [PATCH v1] PM: QoS: Fix misc device registration unwind

Posted by Rafael J. Wysocki 2 weeks, 1 day ago

On Mon, Jun 8, 2026 at 7:08 PM Yuho Choi <dbgh9129@gmail.com> wrote:
>
> cpu_latency_qos_init() registers cpu_dma_latency first and, when
> CONFIG_PM_QOS_CPU_SYSTEM_WAKEUP is enabled, registers cpu_wakeup_latency
> afterwards. The second registration overwrites the first return value.
>
> As a result, a failure to register cpu_dma_latency can be masked if the
> second registration succeeds. Conversely, if cpu_dma_latency succeeds and
> cpu_wakeup_latency fails, the function returns an error while leaving the
> first misc device registered.
>
> Return immediately on the first registration failure and deregister
> cpu_dma_latency if the second registration fails.
>
> Fixes: a4e6512a79d8 ("PM: QoS: Introduce a CPU system wakeup QoS limit")
> Signed-off-by: Yuho Choi <dbgh9129@gmail.com>
> ---
>  kernel/power/qos.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/power/qos.c b/kernel/power/qos.c
> index 398b994b73aa..1944dbeb0d4c 100644
> --- a/kernel/power/qos.c
> +++ b/kernel/power/qos.c
> @@ -519,18 +519,23 @@ static int __init cpu_latency_qos_init(void)
>         int ret;
>
>         ret = misc_register(&cpu_latency_qos_miscdev);
> -       if (ret < 0)
> +       if (ret < 0) {
>                 pr_err("%s: %s setup failed\n", __func__,
>                        cpu_latency_qos_miscdev.name);
> +               return ret;
> +       }
>
>  #ifdef CONFIG_PM_QOS_CPU_SYSTEM_WAKEUP
>         ret = misc_register(&cpu_wakeup_latency_qos_miscdev);
> -       if (ret < 0)
> +       if (ret < 0) {
>                 pr_err("%s: %s setup failed\n", __func__,
>                        cpu_wakeup_latency_qos_miscdev.name);
> +               misc_deregister(&cpu_latency_qos_miscdev);
> +               return ret;
> +       }
>  #endif
>
> -       return ret;
> +       return 0;
>  }
>  late_initcall(cpu_latency_qos_init);
>  #endif /* CONFIG_CPU_IDLE */
> --

Applied as 7.2 material, thanks!