alarm_timer_forward() passes arguments to alarm_forward() in the
wrong order:
  alarm_forward(alarm, timr->it_interval, now);

However, alarm_forward() is defined as:
  u64 alarm_forward(struct alarm *alarm, ktime_t now, ktime_t interval);

and uses the second argument as the current time:
  delta = ktime_sub(now, alarm->node.expires);

Passing the interval as "now" results in incorrect delta computation,
which can lead to missed expirations or incorrect overrun accounting.

Fix this by swapping the arguments.

This issue has been present since the introduction of
alarm_timer_forward().

Fixes: e7561f1633ac ("alarmtimer: Implement forward callback")
Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
---
 kernel/time/alarmtimer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index 069d93bfb0c7..b64db405ba5c 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -540,7 +540,7 @@ static s64 alarm_timer_forward(struct k_itimer *timr, ktime_t now)
 {
 	struct alarm *alarm = &timr->it.alarm.alarmtimer;
 
-	return alarm_forward(alarm, timr->it_interval, now);
+	return alarm_forward(alarm, now, timr->it_interval);
 }
 
 /**
-- 
2.43.0

The following commit has been merged into the timers/urgent branch of tip:

Commit-ID:     5d16467ae56343b9205caedf85e3a131e0914ad8
Gitweb:        https://git.kernel.org/tip/5d16467ae56343b9205caedf85e3a131e0914ad8
Author:        Zhan Xusheng <zhanxusheng1024@gmail.com>
AuthorDate:    Mon, 23 Mar 2026 14:11:30 +08:00
Committer:     Thomas Gleixner <tglx@kernel.org>
CommitterDate: Tue, 24 Mar 2026 23:17:14 +01:00

alarmtimer: Fix argument order in alarm_timer_forward()

alarm_timer_forward() passes arguments to alarm_forward() in the wrong
order:

  alarm_forward(alarm, timr->it_interval, now);

However, alarm_forward() is defined as:

  u64 alarm_forward(struct alarm *alarm, ktime_t now, ktime_t interval);

and uses the second argument as the current time:

  delta = ktime_sub(now, alarm->node.expires);

Passing the interval as "now" results in incorrect delta computation,
which can lead to missed expirations or incorrect overrun accounting.

This issue has been present since the introduction of
alarm_timer_forward().

Fix this by swapping the arguments.

Fixes: e7561f1633ac ("alarmtimer: Implement forward callback")
Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260323061130.29991-1-zhanxusheng@xiaomi.com
---
 kernel/time/alarmtimer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index 069d93b..b64db40 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -540,7 +540,7 @@ static s64 alarm_timer_forward(struct k_itimer *timr, ktime_t now)
 {
 	struct alarm *alarm = &timr->it.alarm.alarmtimer;
 
-	return alarm_forward(alarm, timr->it_interval, now);
+	return alarm_forward(alarm, now, timr->it_interval);
 }
 
 /**