[PATCH net] ptp: netc: skip PEROUT disable if channel is not enabled

[wei . fang]

From: Wei Fang <wei.fang@xxxxxxx>

When userspace calls ioctl(PTP_PEROUT_REQUEST) with period = 0 to disable
a PEROUT channel that is not enabled, the driver incorrectly enters the
disable path. Since the channel's struct netc_pp was previously zeroed,
pp->alarm_id evaluates to 0, causing priv->fs_alarm_bitmap &= ~BIT(0) to
silently revoke the alarm 0 allocation from whichever channel is actively
using it. This can cause two channels conflict over the same hardware
alarm configuration and corrupt their periodic output signals.

Therefore, guard the disable path with a check on pp->enabled and return
early if the channel is not enabled.

Fixes: 671e266835b8 ("ptp: netc: add periodic pulse output support")
Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Closes: https://sashiko.dev/#/message/20260809031908.46EBF1F00A3A%40smtp.kernel.org
Signed-off-by: Wei Fang <wei.fang@xxxxxxx>
---
 drivers/ptp/ptp_netc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/ptp/ptp_netc.c b/drivers/ptp/ptp_netc.c
index 1c20d7efab92..59db08e189e6 100644
--- a/drivers/ptp/ptp_netc.c
+++ b/drivers/ptp/ptp_netc.c
@@ -482,6 +482,9 @@ static int net_timer_enable_perout(struct netc_timer *priv,
 
 		netc_timer_enable_periodic_pulse(priv, channel);
 	} else {
+		if (!pp->enabled)
+			goto unlock_spinlock;
+
 		netc_timer_disable_periodic_pulse(priv, channel);
 		priv->fs_alarm_bitmap &= ~BIT(pp->alarm_id);
 		memset(pp, 0, sizeof(*pp));
-- 
2.34.1