[tip: timers/cleanups] hrtimers: Make callback function pointer private

[tip-bot2 for Nam Cao]

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

Commit-ID:     96d6ac8afcdede3f80230992d587a17000357c28
Gitweb:        https://git.kernel.org/tip/96d6ac8afcdede3f80230992d587a17000357c28
Author:        Nam Cao <namcao@xxxxxxxxxxxxx>
AuthorDate:    Wed, 05 Feb 2025 11:55:16 +01:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Fri, 04 Apr 2025 19:26:44 +02:00

hrtimers: Make callback function pointer private

Make the field 'function' of struct hrtimer private, to prevent users from
changing this field in an unsafe way. hrtimer_update_function() should be
used if the callback function needs to be changed.

Signed-off-by: Nam Cao <namcao@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/all/7d0e6e0c5c59a64a9bea940051aac05d750bc0c2.1738746927.git.namcao@xxxxxxxxxxxxx

---
 include/linux/hrtimer_types.h | 2 +-
 include/trace/events/timer.h  | 4 ++--
 kernel/time/hrtimer.c         | 8 ++++----
 kernel/time/timer_list.c      | 2 +-
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/linux/hrtimer_types.h b/include/linux/hrtimer_types.h
index 7c5b27d..8fbbb6b 100644
--- a/include/linux/hrtimer_types.h
+++ b/include/linux/hrtimer_types.h
@@ -39,7 +39,7 @@ enum hrtimer_restart {
 struct hrtimer {
 	struct timerqueue_node		node;
 	ktime_t				_softexpires;
-	enum hrtimer_restart		(*function)(struct hrtimer *);
+	enum hrtimer_restart		(*__private function)(struct hrtimer *);
 	struct hrtimer_clock_base	*base;
 	u8				state;
 	u8				is_rel;
diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index 1ef58a0..f8c906b 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -235,7 +235,7 @@ TRACE_EVENT(hrtimer_start,
 
 	TP_fast_assign(
 		__entry->hrtimer	= hrtimer;
-		__entry->function	= hrtimer->function;
+		__entry->function	= ACCESS_PRIVATE(hrtimer, function);
 		__entry->expires	= hrtimer_get_expires(hrtimer);
 		__entry->softexpires	= hrtimer_get_softexpires(hrtimer);
 		__entry->mode		= mode;
@@ -271,7 +271,7 @@ TRACE_EVENT(hrtimer_expire_entry,
 	TP_fast_assign(
 		__entry->hrtimer	= hrtimer;
 		__entry->now		= *now;
-		__entry->function	= hrtimer->function;
+		__entry->function	= ACCESS_PRIVATE(hrtimer, function);
 	),
 
 	TP_printk("hrtimer=%p function=%ps now=%llu",
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 163cde3..88ea4bb 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1316,7 +1316,7 @@ void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
 	struct hrtimer_clock_base *base;
 	unsigned long flags;
 
-	if (WARN_ON_ONCE(!timer->function))
+	if (WARN_ON_ONCE(!ACCESS_PRIVATE(timer, function)))
 		return;
 	/*
 	 * Check whether the HRTIMER_MODE_SOFT bit and hrtimer.is_soft
@@ -1629,9 +1629,9 @@ static void __hrtimer_setup(struct hrtimer *timer,
 	timerqueue_init(&timer->node);
 
 	if (WARN_ON_ONCE(!function))
-		timer->function = hrtimer_dummy_timeout;
+		ACCESS_PRIVATE(timer, function) = hrtimer_dummy_timeout;
 	else
-		timer->function = function;
+		ACCESS_PRIVATE(timer, function) = function;
 }
 
 /**
@@ -1743,7 +1743,7 @@ static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base,
 	raw_write_seqcount_barrier(&base->seq);
 
 	__remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE, 0);
-	fn = timer->function;
+	fn = ACCESS_PRIVATE(timer, function);
 
 	/*
 	 * Clear the 'is relative' flag for the TIME_LOW_RES case. If the
diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
index cfbb46c..51fa7ae 100644
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -46,7 +46,7 @@ static void
 print_timer(struct seq_file *m, struct hrtimer *taddr, struct hrtimer *timer,
 	    int idx, u64 now)
 {
-	SEQ_printf(m, " #%d: <%p>, %ps", idx, taddr, timer->function);
+	SEQ_printf(m, " #%d: <%p>, %ps", idx, taddr, ACCESS_PRIVATE(timer->function));
 	SEQ_printf(m, ", S:%02x", timer->state);
 	SEQ_printf(m, "\n");
 	SEQ_printf(m, " # expires at %Lu-%Lu nsecs [in %Ld to %Ld nsecs]\n",