linux-kernel - [PATCH 07/12] hrtimers: Make callback function pointer private

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Message-Id: <e82b7bc0c04158652a6bc63bd4dd131d00b488a6.1729865740.git.namcao@linutronix.de>
Date: Mon, 28 Oct 2024 08:35:51 +0100
From: Nam Cao <namcao@...utronix.de>
To: Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Frederic Weisbecker <frederic@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Kees Cook <kees@...nel.org>,
	linux-kernel@...r.kernel.org
Cc: Nam Cao <namcao@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH 07/12] 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@...utronix.de>
---
Cc: Steven Rostedt <rostedt@...dmis.org>
---
 include/linux/hrtimer.h       | 2 +-
 include/linux/hrtimer_types.h | 2 +-
 include/trace/events/timer.h  | 4 ++--
 kernel/time/hrtimer.c         | 8 ++++----
 kernel/time/timer_list.c      | 2 +-
 5 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 47103a0f6691..38983c2e1dd4 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -339,7 +339,7 @@ static inline void hrtimer_update_function(struct hrtimer *timer,
 	if (WARN_ON_ONCE(!function))
 		return;
 
-	timer->function = function;
+	ACCESS_PRIVATE(timer, function) = function;
 }
 
 /* Forward a hrtimer so it expires after now: */
diff --git a/include/linux/hrtimer_types.h b/include/linux/hrtimer_types.h
index 7c5b27daa89d..8fbbb6bdf7a1 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 1ef58a04fc57..f8c906be4cd0 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 cf362d93a323..d11697492bdb 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1276,7 +1276,7 @@ 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
@@ -1577,9 +1577,9 @@ 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;
 }
 
 /**
@@ -1691,7 +1691,7 @@ 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 1c311c46da50..958dd4194684 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: <%pK>, %ps", idx, taddr, timer->function);
+	SEQ_printf(m, " #%d: <%pK>, %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",
-- 
2.39.5