Re: [PATCH v3] platform/x86/amd/pmc: Fix RTC reference leak in amd_pmc_verify_czn_rtc()

[Mario Limonciello]

On 10/11/26 07:17, Ma Ke wrote:
> amd_pmc_verify_czn_rtc() opens the RTC with rtc_class_open(), which
> takes both a device reference and a module reference on the RTC
> driver. The matching release is rtc_class_close(), and it is never
> called. Every return path after the device has been opened, the ones
> that return 0 as well as the ones that report an error, leaves both
> references behind, so each S0i3 suspend leaks them.
>
> Release the reference with a __free() cleanup on the declaration,
> which covers every return path without adding labels.
>
> rtc_class_close() does not accept a NULL argument, so the cleanup
> helper has to guard against one: rtc_class_open() may fail and the
> declaration still has to be cleaned up.
>
> Found by code review.
>
> Fixes: 59348401ebed ("platform/x86: amd-pmc: Add special handling for timer based S0i3 wakeup")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Ma Ke <make_ruc2021@xxxxxxx>

Reviewed-by: Mario Limonciello (AMD) <superm1@xxxxxxxxxx>

> ---
> Changes in v3:
> - Define DEFINE_FREE(rtc_class_close, ...) in include/linux/rtc.h rather
>    than locally in pmc.c, since it belongs with the API it wraps.
>    Suggested by Ilpo Järvinen.
> - Guard the cleanup against a NULL rtc_device; rtc_class_close() does not
>    handle one.
> - Move the __free() declaration to the assignment, as described in the
>    comment in <linux/cleanup.h>.
> - Cc the RTC maintainer and list, since v3 touches include/linux/rtc.h.
>
> Changes in v2:
> - Replace the added goto labels with a __free() cleanup on the
>    declaration, as suggested by Mario Limonciello and Ilpo Järvinen.
> ---
>   drivers/platform/x86/amd/pmc/pmc.c | 5 +++--
>   include/linux/rtc.h                | 2 ++
>   2 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/platform/x86/amd/pmc/pmc.c b/drivers/platform/x86/amd/pmc/pmc.c
> index 6792aa2c6187..f96e8a358eb7 100644
> --- a/drivers/platform/x86/amd/pmc/pmc.c
> +++ b/drivers/platform/x86/amd/pmc/pmc.c
> @@ -14,6 +14,7 @@
>   #include <linux/array_size.h>
>   #include <linux/bitfield.h>
>   #include <linux/bits.h>
> +#include <linux/cleanup.h>
>   #include <linux/debugfs.h>
>   #include <linux/delay.h>
>   #include <linux/dmi.h>
> @@ -648,7 +649,6 @@ static int amd_pmc_wa_irq1(struct amd_pmc_dev *pdev)
>   
>   static int amd_pmc_verify_czn_rtc(struct amd_pmc_dev *pdev, u32 *arg)
>   {
> -	struct rtc_device *rtc_device;
>   	time64_t then, now, duration;
>   	struct rtc_wkalrm alarm;
>   	struct rtc_time tm;
> @@ -664,7 +664,8 @@ static int amd_pmc_verify_czn_rtc(struct amd_pmc_dev *pdev, u32 *arg)
>   	if (pdev->major < 64 || (pdev->major == 64 && pdev->minor < 53))
>   		return 0;
>   
> -	rtc_device = rtc_class_open("rtc0");
> +	struct rtc_device *rtc_device __free(rtc_class_close) =
> +		rtc_class_open("rtc0");
>   	if (!rtc_device)
>   		return 0;
>   	rc = rtc_read_next_alarm(rtc_device, &alarm);
> diff --git a/include/linux/rtc.h b/include/linux/rtc.h
> index c09fc22819d0..0f43b5027235 100644
> --- a/include/linux/rtc.h
> +++ b/include/linux/rtc.h
> @@ -13,6 +13,7 @@
>   #define _LINUX_RTC_H_
>   
>   
> +#include <linux/cleanup.h>
>   #include <linux/types.h>
>   #include <linux/interrupt.h>
>   #include <linux/nvmem-provider.h>
> @@ -201,6 +202,7 @@ extern void rtc_update_irq(struct rtc_device *rtc,
>   
>   extern struct rtc_device *rtc_class_open(const char *name);
>   extern void rtc_class_close(struct rtc_device *rtc);
> +DEFINE_FREE(rtc_class_close, struct rtc_device *, if (_T) rtc_class_close(_T));
>   
>   extern int rtc_irq_set_state(struct rtc_device *rtc, int enabled);
>   extern int rtc_irq_set_freq(struct rtc_device *rtc, int freq);