[PATCH v2] Input: cyapa - fix runtime PM leak in cyapa_update_rt_suspend_scanrate()

[Wentao Liang <vulab@iscas.ac.cn>]

Hi Dmitry,

Sorry for the very late reply.

It does not have to be the "sync" variant.  I used
pm_runtime_put_sync_autosuspend() only to mirror the normal flow of the
same function and the other runtime PM call sites in cyapa.c, but there
is nothing on this path that needs a synchronous transition: no device
state has been changed yet, both put variants mark the device busy
first, and cyapa_start_runtime() sets a 2 s autosuspend delay, so either
of them would only arm the autosuspend timer before the store returns.
v2 uses pm_runtime_put_autosuspend(), the counterpart of
pm_runtime_get_sync() for devices that use autosuspend.

For the record on how the patch was produced: the candidate came from
static analysis tooling, and DeepSeek and GPT-6.1 Sol were used to audit
it and to help write the change.  I reviewed the result and I am
responsible for it.  v2 is build-tested only: it compiles cleanly on
x86-64 with CONFIG_MOUSE_CYAPA=y, including W=1, and passes checkpatch.
I have no Cypress trackpad to test it on.

Thanks,
Wentao

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Wentao Liang <vulab@iscas.ac.cn>
Date: Sun, 8 Nov 2026 06:45:47 +0000
Subject: [PATCH v2] Input: cyapa - fix runtime PM leak in cyapa_update_rt_suspend_scanrate()

pm_runtime_get_sync() unconditionally increments the runtime PM usage
counter. If mutex_lock_interruptible() is interrupted, the function
returns without dropping that reference, so the usage count stays
elevated for as long as the driver is bound and the device can no longer
be autosuspended. Drop the reference on the error path.

Use pm_runtime_put_autosuspend() rather than the synchronous variant
there: nothing has been done to the device on this path, so there is
nothing to wait for, and with the 2 s autosuspend delay the driver
configures the put only arms the autosuspend timer instead of suspending
the device.

Fixes: 672865080a8f ("Input: cyapa - add runtime power management support")
Cc: stable@vger.kernel.org
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
---
Changes in v2:
- Apologies for the late reply.
- Use pm_runtime_put_autosuspend() instead of
  pm_runtime_put_sync_autosuspend() on the error path: the synchronous
  variant was only there to mirror the normal flow, and with the 2 s
  autosuspend delay the put only arms the timer, so there is nothing to
  wait for.
- Link to v1: https://lore.kernel.org/all/20260916185015.2093520-1-vulab@iscas.ac.cn/
- Link to the June posting of the same change:
  https://lore.kernel.org/all/20260609004617.175476-1-vulab@iscas.ac.cn/
---
 drivers/input/mouse/cyapa.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/input/mouse/cyapa.c b/drivers/input/mouse/cyapa.c
index a8e9b9ab9f84..737fc54539d9 100644
--- a/drivers/input/mouse/cyapa.c
+++ b/drivers/input/mouse/cyapa.c
@@ -900,8 +900,10 @@ static ssize_t cyapa_update_rt_suspend_scanrate(struct device *dev,
 	pm_runtime_get_sync(dev);
 
 	error = mutex_lock_interruptible(&cyapa->state_sync_lock);
-	if (error)
+	if (error) {
+		pm_runtime_put_autosuspend(dev);
 		return error;
+	}
 
 	cyapa->runtime_suspend_sleep_time = min_t(u16, time, 1000);
 	cyapa->runtime_suspend_power_mode =
-- 
2.34.1