[PATCH AUTOSEL 6.15 4/9] watchdog: stm32: Fix wakeup source leaks on device unbind

Sasha Levin
2025-06-04T11:49:34Z

From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

[ Upstream commit b6f8a417e17f1929bb8e7e6ba9f4677f1f3ce364 ]

Device can be unbound or probe can fail, so driver must also release
memory for the wakeup source.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20250406203531.61322-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

**YES** Based on my comprehensive analysis of the commit and examination
of the Linux kernel repository, this commit should be backported to
stable kernel trees. ## Analysis of the Commit ### Nature of the Bug Fix
This commit addresses a **memory leak** in the STM32 watchdog driver's
wakeup source handling. The change is minimal but important: ```c //
Before: ret = device_init_wakeup(dev, true); // After: ret =
devm_device_init_wakeup(dev); ``` The original code creates a wakeup
source using `device_init_wakeup()` but never properly releases it when
the device is unbound or the driver is removed. The fix uses
`devm_device_init_wakeup()`, which automatically handles cleanup through
the device-managed resource framework. ### Strong Alignment with Similar
Backported Commits This commit follows **exactly the same pattern** as
the similar commits #1 and #2 that were marked as **"Backport Status:
YES"**: - **GPIO mpc8xxx commit**: Also changed `device_init_wakeup(dev,
true)` to `devm_device_init_wakeup(dev)` and was explicitly marked for
stable with `Cc: stable@vger.kernel.org` - **GPIO zynq commit**: Added
proper cleanup with `device_init_wakeup(&pdev->dev, 0)` in the remove
function, also marked for stable ### Key Factors Supporting Backporting
1. **Clear Bug Fix**: Fixes a definitive memory leak - each time the
device is unbound, wakeup source memory (struct wakeup_source, device
name strings, sysfs entries) is not freed 2. **Minimal Risk**: The
change is extremely low-risk: - `devm_device_init_wakeup()` is just a
wrapper that provides automatic cleanup - No functional behavior changes
during normal operation - Only adds proper resource management on device
removal 3. **Small and Contained**: Single line change with no
architectural implications 4. **Part of Systematic Cleanup**: My
analysis of the kernel repository revealed this is part of a larger
cleanup effort with 10+ similar fixes across different subsystems in
2024-2025 5. **Real Impact**: While not critical, the leak affects: -
Embedded systems with limited memory - Development environments with
frequent driver loading/unloading - Systems that dynamically bind/unbind
devices 6. **Stable Tree Criteria Compliance**: - Fixes an actual bug
affecting users - Extremely minimal regression risk - Confined to a
single driver - No new features or architectural changes ### Risk
Assessment The technical risk is **extremely low**. The
`devm_device_init_wakeup()` function is a simple wrapper around
`device_init_wakeup(dev, true)` that adds automatic cleanup via
`devm_add_action_or_reset()`. There are no functional changes to the
watchdog or power management behavior - only proper resource cleanup is
added. This commit exemplifies an ideal stable backport candidate: it
fixes a real bug with minimal code change and virtually no risk of
introducing regressions.

drivers/watchdog/stm32_iwdg.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/watchdog/stm32_iwdg.c b/drivers/watchdog/stm32_iwdg.c
index 8ad06b54c5adc..b356a272ff9a0 100644
--- a/drivers/watchdog/stm32_iwdg.c
+++ b/drivers/watchdog/stm32_iwdg.c
@@ -291,7 +291,7 @@ static int stm32_iwdg_irq_init(struct platform_device *pdev,
return 0;

if (of_property_read_bool(np, "wakeup-source")) {
- ret = device_init_wakeup(dev, true);
+ ret = devm_device_init_wakeup(dev);
if (ret)
return ret;

--
2.39.5